Appendix D

Characteristics of the Binational Region

Sustainability partnerships in the U.S.–Mexico binational region are products of, and aim at responding to, their regional context. While the report addresses partnerships, this appendix seeks to set the stage by describing the region’s biophysical environment—its water, climate, land, and ecology—and by identifying the most salient socioeconomic forces, such as population, migration, urban growth, and various economic sectors. The concept of sustainability is a critical undercurrent when describing the binational region’s diversity and evolving priorities; it provides a rich contextual background for researchers on the breadth and depth of its emerging and persistent challenges. Partnerships for sustainability, therefore, are called to consider the amplitude, complexity, and critical importance of the U.S.–Mexico region. This appendix is also intended to serve as a primer for current and future stakeholders to have a resource for understanding the complexity, and the critical importance of the context, of this region.

OVERVIEW OF THE REGION

The U.S.–Mexico border is one of the world’s longest borders, spanning an estimated 1,933 miles east to west (Beaver, 2007) and 62.5 miles north to south of the international boundary.¹ Despite containing several economic asymmetries, this region, home to approximately 15 million people,

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¹ As defined by the La Paz Agreement U.S. Department of Health and Human Services [HHS], 2017).

is also one that contains shared history, culture, environmental, and security relationships (HHS, 2017; Giner et al., 2019).

According to 2019 U.S. Census Bureau data, 7.5 million people live in the four border states (California, New Mexico, Arizona, and Texas), and 7.1 million live in the 37 Mexican municipios spanning the border. By 2025, it is expected that the border region’s population will double, mostly in urban regions (HHS, 2017; Wilder et al., 2013).

The vast majority (approximately 90%) of border region populations inhabit metro areas (HHS, 2017). The majority of the border’s urban centers are sister or “mirror” cities, having a counterpart directly across the border. These mirror cities (e.g., San Diego, California, and Tijuana, Baja California, San Luis, Arizona, and San Luis Rio Colorado, Sonora) are the focal point of most of the border’s economic and social activities.² Although the cities on each side of the border have obvious similarities to those on the opposite side due to common climate and natural resources, they differ greatly in their infrastructure, resource management, legislation, culture, and language. The sprawling urbanization has been incentivized by cheap available land adjacent to existing cities, as well as the low costs of transportation and development (Giner et al., 2019).

Many of the communities on either side of the border are among the poorest and most under-resourced of any region within their respective countries, and rampant and unplanned urbanization has put great pressure on the infrastructure and natural resources supporting these communities (Giner et al., 2019). The region’s mutual social, economic, and environmental priorities underscore the need for binational cooperation.

Much of the binational region is characterized by high aridity and high temperatures (Wilder et al., 2013). About half of its precipitation tends to fall in summer months (except in California), in brief, but high-intensity heavy-rain events. However, there is significant inter-annual and multidecadal variability in precipitation patterns, which adds complexity to managing the region’s scarce water resources (Giner et al., 2019; Wilder et al., 2013). Most of the arid and semi-arid regions receive well below 500 millimeters (20 inches) of rain annually, with some hyper-arid areas, such as the desert region adjacent to Yuma, Arizona, receiving less than 75 millimeters (3 inches) annually. Water scarcity across much of the region has been exacerbated by large increases in population, agricultural intensification, growth in the industrial sector, and climate change (Díaz-Caravantes and Wilder, 2014). Over time, the numbers and intensity of extreme events, such as flooding, have increased, due to climate change. These events have

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² For an example of growth since 1990 in mirror cities located in Texas, Chihuahua, Coahuila, and Tamaulipas, see: https://www.tceq.texas.gov/border/population.html.

been costly in terms of damages and have been exacerbated by insufficient and poorly planned infrastructure (Giner et al., 2019).

In 1994, several binational initiatives went into effect, in concert with the North American Free Trade Agreement (NAFTA),³ to provide financing and resources for the planning, development, and implementation of environmental infrastructure intended to protect and improve the shared environment and well-being of the residents in the border region. These efforts, financed by the North American Development Bank (NADB), have been developed in their technical, environmental, and social aspects by the Border Environment Cooperation Commission (BECC) (Congressional Research Service [CRS], 2020). The BECC’s authority spans approximately 60 miles north and 185 miles south of the border through a region encompassing 13.9 million and 26.1 million residents in the United States and Mexico, respectively (Giner et al., 2019). Binational cooperation through these initiatives, in partnership with Mexico’s National Water Commission, Comisión Nacional del Agua (CONAGUA), Mexico’s Ministry of the Environment, Secretaría del Medio Ambiente y Recursos Naturales (SEMARNAT), and the U.S. Environmental Protection Agency (EPA), has yielded projects that have improved basic infrastructure, including improved access to drinking water, treatment of wastewater flows, and improved management of air quality, and solid waste (Giner et al., 2019).

SOCIAL SYSTEMS

The binational region is characterized by the ebb and flow of human and ecological processes across what is now the U.S.–Mexico border. Many interactions predate the border itself, though there has been a historical hardening of the border line, resulting from national policies on immigration, trade, health, and other binational exchanges.

Indigenous Communities

Along the U.S.–Mexico border there are approximately 60 tribal nations and Indigenous communities with more than 40,000 inhabitants, occupying territories in California, Arizona, and Texas in the United States, and in the Mexican areas of Baja California, Sonora, and Coahuila, respectively (Southwest Center for Environmental Research and Policy [SCERP], 2004). Though the border has split the communities in two, many of the tribal nations still maintain close cross-border relations. The Kikapú (“Kickapoo” in the United States), Kumiai (Kumeyaay), Papago (Tohono O’odham),

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³ More information is available at: https://www.cbp.gov/trade/nafta.

Cucapá (Cocopah), and other mobile populations, such as the Yaquis, Pima, Paipai, and Kiliwa, still maintain cultural, economic, and political ties with their cross-border counterparts (SCERP, 2004). In addition to maintaining cultural and family ties, groups such as the Kikapú engage in commerce on both sides of the border such as livestock and agricultural ranches, and some tribes also operate casinos (SCERP, 2004).

Over time, the Indigenous presence in the border area has undergone substantial changes. In the northern states of Mexico, the Indigenous population increased substantially between 1970 and 2000, a situation that modified the landscape of the region by incorporating new languages and transforming socio-cultural dynamics both within each Indigenous migrant group and between the groups and existing local populations (Rodríguez, 2016). Waves of Indigenous groups from southern Mexico migrated to form communities along the border, concentrating heavily in areas such as Chihuahua and Baja, California, and bringing with them their southern Mexican dialects; two of the most widely spoken Indigenous languages in the border region are Mixteco and Nahuatl.

Migration

The region is also populated by a large number of people seeking passage to the United States from Mexico and elsewhere in Central and South America. Because it often takes a migrant time to attempt to raise the necessary resources to pay for an illegal border crossing (without sufficient documentation), these northward migrants form a substantial “floating population” (Peña Muñoz, 2018). Floating populations also include deported individuals who are having difficulty returning to the United States or their places of origin in Mexico (Peña Muñoz, 2018), as well as migrants residing in temporary shelters or provisional encampments under the Migrant Protection Protocols.⁴

According to data from the National Institute of Statistics and Geography, Instituto Nacional de Estadística, Geografía e Informática (INEGI), the floating population in 2015 accounted for a significant fraction of the population in several border urban centers: 33 percent in Nuevo Laredo, 23 percent in Tijuana, and 27 percent in Nogales (Peña Muñoz, 2018, p. 88). Large-scale temporary migration directly impacts the local economies of those cities, enlarging the labor force by temporarily integrating into the maquiladora workforce, as well as becoming consumers of services such as lodging, food, and transport. Since early 2019, a significant number of migrants have resided in temporary shelters or provisional encampments

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⁴ More information is available at: https://fas.org/sgp/crs/row/R41576.pdf.

in Mexico’s northern border states of Baja California, Chihuahua, and Tamaulipas under the Migrant Protection Protocols.⁵

Migration rates of Mexican-born individuals into the United States grew exponentially between 1980 and 2010 (Israel and Batalova, 2020). In 2010, 30 percent of all legal migrants into the United States were of Mexican origin. Between 2010 and 2019, the number of Mexican emigrants in the United States decreased by almost 780,000 and now comprises just under one-quarter of the foreign-born population. This decrease was due in part to changes in U.S. immigration policy and increased enforcement and in part to a strengthening Mexican economy (Israel and Batalova, 2020). Between 2012 and 2016, 53 percent of migrants who were undocumented in the United States were of Mexican origin; by comparison, El Salvador, Honduras, China, and Guatemala together accounted for 14 percent (Batalova et al., 2020). Most of these migrants crossed by land.

Border movements in both directions can generate temporary or permanent economic opportunities for residents in the area. These movements also translate into an increased exchange of materials and products between the two countries. In this regard, it is worth noting the importance of the urban corridors, which operate as axes along which countless cross-border interactions occur, generating economic interdependence (National Academies of Sciences, Engineering, and Medicine [NASEM], 2018). Tourism flowing from both countries to the border region has also been important in the development of the region and the service industry on both sides: according to the Border Governors Conference, an estimated 64.5 million tourists visited Mexico by car or by foot in 2019 (Secretaría de Turismo, 2019). Total vehicular movement across the U.S.–Mexico border neared 530 million in 2019.

Safety and Security

A lack of adequate human security characterizes the region. These inadequacies plague economic, food, health, environmental, community, political, and personal security (NASEM, 2018), all of which are needed as basic protections in the face of growing violence, child labor, poverty, and other social stresses. The inconsistent availability of these forms of securities and protection adds to the complexity of the border region’s social, political, economic, and ecological landscape. In this context, illegal economic activities at the border, such as drug production, transfer, and sale, become a significant and pervasive issue, fostering informal economies and money laundering through the acquisition of land, hotels, and a

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⁵ More information is available at: https://fas.org/sgp/crs/row/R41576.pdf.

range of real estate. For example, in 2014 in the Benjamin Hill municipality, located south of the border in Sonora, Mexico, 12 of every 1,000 inhabitants had been convicted of drug trafficking offenses (Piña Osuna and Poom Medina, 2019). Six of Sonora’s municipalities were included on Mexico’s top ten list of areas nationwide with the highest rates of residents convicted of such crimes (Piña Osuna and Poom Medina, 2019). In 2018 and 2019, Ciudad Juárez and Tijuana recorded Mexico’s highest incidence of violent crimes, with 1,281 murders and 2,000 homicides, respectively (Beittel, 2020). Most of the recorded homicides in Tijuana and Ciudad Juárez were connected to drug gangs, which could point to drug trafficking as playing a significant role in the social dynamic of the border region (Beittel, 2020).

Illegal trafficking of drugs from Latin America through Mexico to supply a large demand in the United States, as well as weapons and smuggled goods moving from the United States into Mexico, are persistent problems in the region. Illicit activity in the region has generated violence, corruption, and political tensions, highlighting deeper problems in both urban and rural areas, such as marginalization, poverty, and labor and social inequalities. Campbell (2007) notes that drug trafficking is socially perceived as a way to overcome poverty. For women, it presents itself as an opportunity to leave their marginalized social position (Santamaría, 2012).

Public Health Challenges

One of the main difficulties in characterizing public health conditions in the border region stems from a lack of basic data, which makes it difficult to develop comparative diagnoses and to coordinate actions based on shared health indicators (Carrillo et al., 2017). However, some binational efforts have focused on public health, such as the 2000 Mexico–U.S. Border Health Commission Strategic Plan, while binational groups, such as the Border Health Consortium of California, have focused on public health in the border region. The latter consortium meets frequently to explore opportunities for collaboration between California and Baja California. This region in particular shows some peculiarities, such as a high incidence of tuberculosis infections in both countries (Pelozzi et al., 2014).

The border region also has high rates of people without access to health insurance: while the U.S. national average is 8 percent uninsured, in Texas the rate is 25 percent, and the rate in Mexico at the border region was 34.6 percent in 2010 (Pelozzi et al., 2014). However, due to lower health care costs in Mexico’s border municipalities, there is a large flow of U.S. patients crossing into Mexico to be treated. By 2018, an estimated 2.4 million foreign patients were being treated in Baja California alone.

BINATIONAL ECOLOGY

The U.S.–Mexico border traverses a region of immense ecological diversity and abundant natural resources. McCallum, Rowcliffe, and Cuthill (2014) identified the area as one of America’s most biologically wealthy regions. The Commission for Environmental Cooperation, created to execute the North American Agreement on Environmental Cooperation, established by Mexico, the United States, and Canada, identified seven Level III ecoregions along the U.S–Mexico border (Wiken et al., 2011). From west to east, these ecoregions are: (1) the California coastal sage, chaparral (thicket), and oak woodlands; (2) the Sonoran desert; (3) the Madrean archipelago; (4) the Chihuahua desert; (5) the Edwards Plateau; (6) the southern Texas plains/interior plains and hills (with xerophytic shrub and oak forest); and (7) the western Gulf coastal plain. These ecoregions present various types of vegetation, from desert to grasslands to freshwater wetlands and marshes (Peters et al., 2018; Wiken et al., 2011).

In addition to being a habitat for a large number of species, south Texas’ ecosystems depend on the monarch butterfly and some species of neotropical birds, which pass through on their migratory journeys (Peters and Clark, 2018). Efforts to conserve migratory avian nesting habitats here, including the binational Migratory and Shore Bird Habitat Initiative, have been planned since 2013 (Good Neighbor Environmental Board [GNEB], 2014). Other binational conservation experiences in the border region include the Big Bend Binational Initiative and the National Park Service Sister Parks Initiative (GNEB, 2014). South of the border lies the extraordinarily rich environment of Cuatro Ciénegas, a hotspot of biodiversity that represents some of the conditions that prevailed in ancient ecosystems, and has thus attracted the interest of scientists at the National Aeronautics and Space Administration and other agencies and organizations interested in astrobiology (see Pérez Ortega, 2020). In general, conservation of the region’s ecology is the focus of numerous binational partnerships.

Threats to Biodiversity

In 2018, a group of more than 2,500 scientists noted that the border region contains a cumulative area of approximately 17,000 square miles (4.5 million hectares) protected through various biodiversity conservation programs, with approximately 10,000 square miles (2.6 million hectares) of sustainable-use programs (Peters et al., 2018). Four areas of protected land span the border: the Sonoran desert, Sky Islands, Big Bend, and the lower Rio Grande (Peters et al., 2018). These protected areas comprise 18 percent of the border region (Peters et al., 2018).

Various analyses of the region show that the path of the border line crosses a geographical range of 1,506 native species of terrestrial and aquatic plants and animals, including 62 that are reported as critically endangered, endangered, or vulnerable by the International Union for Conservation of Nature (Peters et al., 2018). Along the border, some organizations, such as Defenders of Wildlife, have identified five hotspots for the conservation of borderlands, which represent areas of high biological diversity that are now at risk due to the construction of the border wall (Córdova and de la Parra, 2007; Peters et al., 2018). In this regard, the Center for Biological Diversity identified 93 endangered, threatened, and candidate species that could be impacted during border wall construction, of which 88 have populations on both sides of the border and could experience a limited flow in their gene pool (Greenwald et al., 2017). This is the case for the peninsular bighorn sheep (Ovis canadensis nelsoni), an endangered species, which would see its regular roaming between Mexico and California significantly limited by a wall, endangering its access to birth sites and water sources. Other species that could face the same danger are the Mexican grey wolf (Canis lupus baileyi), the Sonoran pronghorn (Antilocapra americana sonoriensis), the jaguar (Panthera onca), and the ocelot (Leopardus pardalis) (Peters et al., 2018).

CROSS-BORDER WATER FLOW

Water is one of the most consequential resources shaping social and ecological dynamics in the region. The Colorado River and the Rio Grande (known as Rio Bravo in Mexico) are the two central river systems shared by Mexico and the United States, although the Tijuana River, New River, and multiple shared aquifers also cross the border (GNEB, 2014) and provide water to residents of both countries. Precipitation rates fluctuate along the border, and this variability influences the volume of usable water in the region. For example, in Imperial Valley, California, to the west, the yearly precipitation on average is 3 inches. In the east, the precipitation varies from place to place; in 2014, average rainfall was 19 inches in Nogales, 8 inches in El Paso, and 28 inches in Brownsville, which is located at the far east end of the border, where the mouth of the Rio Grande/Bravo meets the Gulf of Mexico (GNEB, 2014).

Rivers

In the case of the Rio Grande/Bravo, its basin encompasses an area of more than 180,000 square miles and frequently runs along the international border. This river supplies water for municipal use, and its waters irrigate a combined U.S.–Mexico extension of 2 million acres (U.S. Department of the Interior, Bureau of Reclamation, 2016a). After a century of use, a change

in the flow pattern is evident, and in recent decades, the amount of water has decreased (GNEB, 2014). An example of this is the Conchos River, a tributary of the Rio Grande/Bravo that joins it near the city of Ojinaga, Chihuahua. Historically, the Concho constitutes 70 percent of the flow of the Rio Grande/Bravo (Carter et al., 2017), allowing the latter to regain its water level, which in many sections before the junction drops to virtually zero. Since the 1990s, the Conchos River’s contribution to the Rio Grande/Bravo has decreased, and currently, it represents only 40 percent of the total flow (Carter et al., 2017). Consequently, only a small proportion of the river’s natural discharge reaches the Gulf of Mexico.

The Colorado River basin encompasses 246,000 square miles (629,000 square kilometers) across seven U.S. states and Mexico (U.S. Department of the Interior Bureau of Reclamation, 2016b). According to data from the U.S. Department of the Interior, Bureau of Reclamation (2013), “The Colorado River and its tributaries provide water to nearly 40 million people for municipal use, supply water to irrigate nearly 5.5 million acres of land, and is the lifeblood for at least 22 federally recognized tribes, 7 National Wildlife Refuges, 4 National Recreation Areas, and 11 National Parks.”

The Tijuana River watershed drains 1,750 square miles (4,532 square kilometers). This basin is one of the fastest-growing regions along the border, with roughly 4.5 million people—3 million of whom live in the San Diego County area and 1.5 million in the city of Tijuana (GNEB, 2014).

Aquifers

No consensus exists on the number of cross-border aquifers between Mexico and the United States. The International Shared Aquifer Resources Management, an initiative of UNESCO, recognizes 11 such aquifers; CONAGUA in Mexico lists 36; and the 16th report of the GNEB (2014) speaks of 20 (see also Sanchez et al., 2016). However, several studies in the United States recognize the existence of at least 38 aquifers, 12 of them along the Mexico–California border, 9 along the border with Arizona, 8 along the border with New Mexico, and 9 along the border with Texas (Sanchez et al., 2016). The differences among these estimates stem from the absence of a common definition between the two countries as to the characteristics of a cross-border aquifer, as well as the lack of agreement for delimiting cross-border aquifers. Sanchez, Lopez, and Eckstein (2016, p. 8) suggest the presence of up to 36 cross-border aquifers, “albeit with different levels of confidence of their transboundary nature.”

These aquifers constitute one of the largest sources of water supply in the border region and are often not addressed in binational water-sharing agreements. The most obvious and well-documented case is the binational urban complex in El Paso, Texas, and Ciudad Juárez, Chihuahua, that

pumps water from the Hueco Bolsón aquifer for the 1.5 million residents of Ciudad Juárez and to 40 percent of El Paso’s 730,000 residents (CRS, 2017). However, this is not the only case. Eckstein (2011) points out that approximately 20 binational aquifers are the only relevant domestic water supply sources for many twin border towns: Puerto Palomas, Chihuahua, and Columbus, New Mexico, Naco, Sonora, and Naco/Bisbee, Arizona; Nogales, Sonora, and Nogales, Arizona; Sonoyta, Sonora, and Lukeville, Arizona; and Tecate, Baja California, and Tecate, California.

In general, the overexploitation of aquifers in the border region creates problems such as land subsidence, which has damaged housing and urban infrastructure. This is a problem in the El Paso, Texas/Ciudad Juárez, Chihuahua area (CRS, 2017). Groundwater reservoirs in other areas have been damaged or decreased in volume, generating a significant water deficit; this phenomenon has been repeated in other border areas, such as Tijuana, Baja California/San Diego, California and Nogales, Arizona/Nogales, Sonora, as well as in the Monterrey, Nuevo Leon metropolitan area (El Colef, 2019).

Actions in the United States have also yielded negative consequences for groundwater recharge in Mexico, as in the case of the All-American Canal, which brings water from the Colorado River. The United States lined sections of the canal, in an attempt to minimize water losses as the water traveled through it. However, this decision came at the expense of reduced groundwater recharge from the canal into shared aquifers beneath the canal, harming critical wetlands habitat and reducing water available for irrigation (Maganda, 2005; Scott et al., 2014). As a result, Mexico filed a case in an international court over lost water resources.

Changes in Climate and Water Availability

Climate projections by the Intergovernmental Panel on Climate Change anticipate that temperatures across the border region (more specifically, in the western monsoon climate region) will increase by as much as 2 to 4 degrees C by 2050 and 3 to 5 degrees C by 2100, coupled with decreases in precipitation of 5 to 8 percent (Wilder et al., 2010). Projected increased temperatures and drier conditions will exacerbate existing water stress and water quality issues on either side of the border (Wilder et al., 2013). Climate change is also exacerbating the declining quality and overall depletion of aquifers because the decrease in surface water caused by warming is both increasing the demand for groundwater resources and reducing the recharge rate (Wilder et al., 2010). Other ongoing stressors, including population growth, urbanization and industrialization, polluted water resources, and existing competition among water users, will compound these climate change impacts, making management across the border region more complicated (NASEM, 2018).

URBANIZATION AND INFRASTRUCTURE

The border region has experienced a growing economy based on various commercial activities—agricultural, mining, industrial, and services—many of which rely on using arid areas for tasks such as the production of fodder, mining, timber production, animal husbandry, and camping, among others (NASEM, 2018). The implementation in 1994 of NAFTA drove a great deal of population growth, sprawling urbanization, and industrialization, mostly in Mexico, as agriculture and industry shifted south from the United States. Exacerbated by huge consumer demand from the United States and a comparatively weak Mexican economy, this development has put tremendous strain on the region, riddled by poverty and natural resource constraints (Varady and Ward, 2009). It also pushed prices for agricultural commodities down, which disproportionately harmed poor farmers working unirrigated, communal land (Shah et al., 2004).

Urban development in Northern Mexico has been accelerated by the growth of the maquiladora⁶ industry; for decades, the border region has seen population and growth rates above the national average (Peña Muñoz, 2018). One consequence of the presence of maquiladoras is that the traditional links between local production and consumption have been weakened or broken in several border towns (Díaz, 2009). The growth of the maquiladora industry in Mexico was established and maintained through the supply of low-wage labor and gender-based wages (Huesca et al., 2019). The development of Ciudad Juárez represents one of the most visible examples of this model (Peña Muñoz, 2018; Solís and Ávalos, 2017).

These economic drivers have resulted in the formation of informal, uninsured housing along border regions that is vulnerable to health and safety problems (Wilder et al., 2013). Worsening economic conditions for farmers have also spawned a rural-to-urban migration that has caused sprawling urbanization and the development of slum-like communities, resulting in poor environmental and public health outcomes (Spring, 2016). These health and environmental vulnerabilities are exacerbated by the fact that urban regions are expanding into areas that are prone to drought, wildfires, and flooding. This pattern of sprawl, as well as deficits in urban infrastructure, make the areas more prone to becoming urban heat islands—metropolitan areas that are warmer than the areas surrounding them (Wilder et al., 2013).

On the U.S. side of the border, communities referred to as “colonias” were granted official designation from the U.S. government in the 1990s. On both sides of the border, these often unincorporated and underfunded communities in both countries deal with complex and coupled challenges,

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⁶ The industry comprises factories in Mexico run by a foreign company whose products to that company are largely duty and tariff free.

such as the booms and busts of the agriculture and livestock industries (Hruska, 2019), violence and the drug war, the militarization of the border, inadequate living conditions, and low employment rates. Collectively, these challenges have depressed economic opportunities and social mobility and have exacerbated issues such as environmental pollution and access to safe and clean water supplies (Talmage et al., 2019). Despite the shared safety and economic concerns, U.S. colonias typically have more political autonomy, planned land use protocols, and basic infrastructure and services available to their residents than do the Mexican colonias (U.S. Department of Housing and Urban Development [HUD], 2020).

Poverty is widespread on both sides of the border, in poor U.S. counties, and unplanned Mexican colonias (Wilder et al., 2010). Per capita income among people living in the U.S. border counties is 85 percent of the average U.S. per capita income. If these counties were aggregated into a single state, it would be ranked 2nd highest in the nation in tuberculosis cases, 5th highest in unemployment, 39th in per capita income, 50th in health insurance coverage, and 50th in high school graduation rates (Soden, 2006).

Urban Water Infrastructure

Water and Wastewater Systems

Access to safe drinking water and sanitation services is inadequate for communities on both sides of the border, particularly in poorer communities with limited governmental and financial resources (Jepson, 2014). Population growth in both countries has outpaced the development of infrastructure in many urbanizing communities, adding pressure to the challenge of protecting public health.

In Mexico as a whole, 57 percent of the population lacked access to safely managed drinking water services⁷ and 50 percent lacked access to safely managed sanitation services overall in 2017.⁸ The colonias are particularly susceptible to water insecurity, as their populations are generally poor, marginalized, and often lack the critical infrastructure to deliver reliable water and sanitation services (Schur, 2017). While access to safe, potable water sources has improved over time, progress has been slow, and inadequate access to both safe water and sanitation remains critical (Wilder et al., 2013). Populations lacking piped water infrastructure are likely to be dependent on shared and often overexploited groundwater resources,

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⁷ More information is available at: https://data.worldbank.org/indicator/SH.H2O.SMDW.ZS?locations=MX.

⁸ More information is available at: https://data.worldbank.org/indicator/SH.STA.SMSS.ZS?locations=MX.

which are generally not well-governed or protected by international treaties (Sanchez and Eckstein, 2020). Households that have hookups to water service might still encounter service disruptions, and water is not generally of drinking quality (Wilder et al., 2010). Water rationing has occurred in major cities in Mexico, including Hermosillo and Nogales in Sonora, and informal communities often rely on water from trucks (Wilder et al., 2013).

Poor water quality is a major challenge to the provision of safe drinking water along the border. Arsenic and fluoride water contamination, two inorganic contaminants associated with serious health problems (e.g., cancer, heart disease), are naturally present in the border area’s groundwater aquifers, and concentrations of these contaminants have risen as a result of the over-pumping of aquifers, climate change, and rapid urbanization (Armienta and Segovia, 2008; Shaji et al., 2020). Drought and flooding can place even more pressure on a community’s access to drinking water when traditional sources become contaminated or unavailable during such events and access to nontraditional sources, such as water trucks, might be unavailable, difficult to access, or cost-prohibitive (Wilder et al., 2010).

A recent study investigated water insecurity by looking at the very large 13,313 square kilometer-wide Mimbres Basin Aquifer, an arsenic- and fluoride-contaminated groundwater resource spanning southwestern New Mexico and northern Chihuahua (Schur, 2017). This region is home to underserved populations on both sides of the border. There are challenges and trade-offs associated with addressing drinking water insecurity in both nations. For example, centralized and decentralized reverse osmosis systems were implemented in the adjacent communities of Columbus, New Mexico, and Palomas, Chihuahua, respectively, to relieve drinking water contamination that has plagued both regions for decades (Schur, 2017). While implementing these systems addressed the poor water quality, it created new problems for water affordability because of the large energy and economic costs of the treatment systems. Household water costs in Columbus rose nearly 60 percent between 2008 and 2016 since all the water delivered to utility customers there is a blend of reverse-osmosis filtered and unfiltered groundwater. Thus, although a reliable source of piped water has been created, 70 percent of the population surveyed in 2016 considered the price charged for the water unfair (Schur, 2017). However, reducing these costs is difficult since the population of customers is small and the utility faces financial difficulties in generating adequate revenues to cover its costs. In Palomas, water piped to residents is still contaminated, but three stations distributed around the city dispense reverse-osmosis treated water for purchase. Nearly half of the residents (43%) surveyed reported that accessing these decentralized stations is difficult, and 18 percent of the population in 2016 still depended on contaminated tap water for drinking (Schur, 2017). These examples underscore the complexity of providing safe water services

to poverty-stricken populations on either side of the border, particularly given the disparities in institutional support and funding mechanisms between the two countries (Giner et al., 2019; Schur, 2017).

High-salinity water, sewage flows, and flows of other polluted urban runoff present water quality challenges to be managed (Barker et al., 2000). Some of these water quality issues associated with the delivery of surface water from one side of the border to the other are managed through minutes to the 1944 U.S.–Mexico Water Treaty (Sanchez and Eckstein, 2020). The 1983 Mexico–U.S. Agreement on Cooperation for the Protection and Improvement of the Environment in the Border Area (i.e., the La Paz Agreement) was an important binational initiative to reduce and prevent pollution in the border region and provided a foundation for international collaborations that followed, which include NAFTA, BECC, and the Commission for Environmental Cooperation (Giner et al., 2019). Since the initiation of BECC (which has now been merged with NADB), the flows of untreated wastewater into shared water bodies have been an issue of great concern in the binational collaborations facilitated by NAFTA. Between 1994 and 2017, funding has been directed toward 59 wastewater treatment plants with a collective treatment ability of 450 million gallons a day serving more than 8 million residents in the United States and Mexico (Giner et al., 2019). These improvements to infrastructure and a marked reduction in sewage releases benefited an estimated population of 8.5 million residents during that period (Giner et al., 2019).

Despite these binational initiatives, wastewater treatment infrastructure is still woefully inadequate, particularly where burgeoning urbanization, industrialization, and population growth have boomed since the initiation of NAFTA. In Sonora, wastewater infrastructure statewide serves less than 40 percent of its population, and large populations of people live in colonias that are off the grid and might lack municipal services altogether. Tensions between the United States and Mexico have arisen over the costs of releasing treated wastewater flows originating from Nogales, Arizona, and Nogales, Sonora. Although the Nogales International Wastewater Treatment Plant treats the majority of wastewater, storm events still result in increased polluted flows from Mexico into the United States (Albrecht et al., 2018). Over time wastewater treatment capacity benefiting both sides of the border has increased due to binational cooperation of the United States and Mexico through BECC and the NADB (Giner et al., 2019).

Stormwater Management

Accelerating urbanization has added pressure to flood, stormwater, and wastewater management due to the expansion of impervious surfaces that impede the percolation of water back into soil and groundwater aquifers.

Average stormwater runoff can increase as much as 45 percent due to these decreases in infiltration, resulting in severe damage to private and public property through flooding and pollution flows, which can contain fecal matter, solid waste, oil, and sediment (Giner et al., 2019). Flood management is hindered by inadequate infrastructure in many parts of the border region, such as in Nogales, Arizona, and Nogales, Sonora. For example, in 2008, the U.S. Department of Homeland Security extended a portion of the border wall without coordinating with Mexican authorities, which resulted in catastrophic flooding of the Mexican side of the water near Nogales, Sonora, following a storm, when runoff that would have otherwise flowed northward (Wilder et al., 2010).

Despite some similarities in marginalized communities on either side of the border, the potential for outside resources is very mismatched. In the United States, unincorporated colonias can seek funding for infrastructure projects from a diversity of state and federal resources, in addition to international funding through the Border Environment Cooperation Commission. On the Mexican side, resources are much more limited and are typically only available from the federal government and binational agreements.

The costs accrued by emergency management departments and agencies in the United States, as well as by Mexico’s natural disaster management agency, Fondo de Desastres Naturales, have grown markedly over the past few decades. Nevertheless, there is still no strong, coordinated, binational strategy to deal with stormwater flows (Giner et al., 2019).

Desalination

Desalination has been proposed as a solution to manage some water quality impairment of some border-region rivers, notably at the Yuma Desalting Plant in Arizona just upstream of where the Colorado River forms the border. While the Yuma Desalting Plant was built to reduce the salinity of water delivered from the United States into Mexico, this facility has rarely operated due to high operational costs and surplus flows of the Colorado River since its completion in 1992.⁹ In 2012, the International Boundary and Water Commission entered an agreement to explore the feasibility of binational desalination for two prospective seawater desalination sites in Rosarito, Baja California, and Puerto Peñasco, Sonora, on the Sea of Cortes, which would export water to San Diego and Arizona, respectively (Wilder et al., 2016). There have been several proposals on how the United States and Mexico might share costs under a binational desalination regime. One proposed option would be for the United States to invest in a desalination facility in exchange for some portion of Mexico’s water rights on

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⁹ More information is available at: https://fas.org/sgp/crs/row/R43312.pdf.

the Colorado River (Albrecht et al., 2018). However, to date, CONAGUA has not agreed to such terms, and many criticize existing proposals as one-sided, asserting that Mexico would incur the majority of the costs and environmental damages associated with the proposed binational desalination schemes, while the United States would reap a disproportionate share of the benefits (Albrecht et al., 2018).

Desalination has been touted as a “drought-proof” approach to supplying water, increasing the volumes of high-quality water and thereby improving water security and protecting water quality (Wilder et al., 2016). However, desalination comes with large environmental, economic, and social tradeoffs that have thwarted efforts to execute plans for building desalination facilities. From an environmental perspective, desalination by reverse osmosis, currently the most economical desalination technology, is energy-intensive, and therefore emissions-intensive when the electricity is generated from fossil fuel sources (King et al., 2013). The intake screens in these plants can harm marine ecosystems (which in turn could negatively affect tourism activities, in addition to the environment), and the necessary transportation infrastructure, such as pipes, would need to cross delicate ecosystems (Albrecht et al., 2018). In addition to generating a potable water stream, desalination also generates a brine stream that is difficult to dispose of in an environmentally benign way. In part because of its high energy costs, desalination is also costly, driving up the cost of water compared to standard surface water supplies, which could negatively affect impoverished communities on either side of the border (Wilder et al., 2016).

AGRICULTURE AND LIVESTOCK

Since the beginning of the 20th century, Mexico’s proximity to the U.S. market has driven the deployment of irrigation infrastructure in the deltas and valleys of the Colorado, Sonora, and Rio Grande/Bravo rivers, and this has sustained commercial agriculture in the region. Therefore, it is not surprising that this region has also been the historical scene of agricultural disputes over the control of these means of production.

Despite the historical existence of cross-border agricultural systems, particularly in the western border region,¹⁰ agricultural activity in border towns still exhibits dramatic contrasts on both sides of the border.

According to statistical data from Mexico and the United States (Sistema de Información Agroalimentaria y Pesquera [SIAP], 2018a; U.S. Department of Agriculture [USDA], 2017), industrial agriculture prevailing on both sides

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¹⁰ There are documented links between the agricultural capital of Sonora and Arizona (Pavlakovich-Kochi, 2006), and the transfer of U.S. companies in shaping the agricultural scenario of the Mexican side of the border.

of the border is aimed directly at the United States. Most of the products are for food chains, but in the case of cotton, it is for industrial purposes.

The relevance of agricultural activity in the region to the economy of each country is quite different. While in Mexico agriculture represents one of the main areas of commerce, by way of export products, in the United States agriculture is secondary to livestock production, except for some irrigated valleys in California, Arizona, and Texas. According to the 2017 U.S. Census of Agriculture, concentrated livestock activity in Texas, California, and Arizona continues to focus on sheep and lamb production, although there is also significant cattle production along the border. A higher concentration of cattle is found in the far south between California, Arizona, and Texas, with milk production in areas near Phoenix, Arizona, and meat production found primarily in Texas (USDA, 2017).

On the Mexican side, agriculture, more than livestock, drives the configuration of the region. Agricultural production in the six border states accounts for 22.6 percent of Mexico’s domestic agricultural production, a proportion of 32.5 percent relative to the value of domestic production in irrigation mode, compared to just 5 percent of seasonal domestic production. In addition, Chihuahua and Sonora concentrate two-thirds of the border states’ production value and, in both cases, it is irrigation production that supports this dynamism. Focusing only on export agriculture, the border states make an even greater contribution, making up 75 percent of domestic production and comprising 65 percent of the total area in the country devoted to export culture. This concentration is centralized in Baja California and Sonora; these two Mexican states comprise 64.6 percent of exports, and 74.3 percent of its value (SIAP, 2018b).

Livestock

Livestock production in the Mexican border states accounted for 15.7 percent of the country’s livestock production and is focused on meat production, followed by the marketing of live cattle, goats, and pigs (Hernández Pérez, 2019; SIAP, 2019). The state of Sonora concentrates the livestock production of the region, with meat products, live cattle, and eggs. And while not all this production occurs on the border margin, there is a significant concentration of farms and ranches in the Sonora municipalities of Hermosillo, Navojoa, and Cajeme.

Agricultural Water Use and Environmental Effects

Water use for agriculture and ranching accounts for approximately 80 percent of total water usage across the shared border region (NASEM, 2018), dominating consumptive water use on either side of the border—although

rapid urbanization and industrialization are increasing demand for non-agriculture water uses (Wilder et al., 2010). In Arizona, agriculture represents 70 percent of consumptive water use, while in Sonora, Mexico, it represents 86 percent (Wilder et al., 2010).

Agro-industrial production in the United States is centered in four areas of intensive irrigation. Two of the irrigation centers are located near the banks of the Colorado and Gila rivers at the California-Arizona border; their main outputs are fruits and vegetables. A third region, just south of New Mexico in the valley formed by the Rio Grande at Las Cruces, produces alfalfa and pecans. The fourth irrigation center in Hidalgo, Texas, running to the mouth of the Rio Grande/Bravo, primarily produces cotton. As a consequence of heavy land use, the depletion of water has been recognized as a problem along the entire U.S. southern border, one characterized by low soil productivity, particularly in Southern California, Arizona, New Mexico, and the western tip of Texas (Miller et al., 2012). It is therefore not surprising that this region has also been the historical scene of agricultural disputes over the control of these means of production.

Recent changes in agricultural land use on either side of the U.S.–Mexico border has affected water usage. In the United States, more water is withdrawn for irrigated cropland than for urban land, on average. In Mexico, this trend is reversed, because urban regions generally have higher population density, despite lower per capita usage. Thus, a parcel of irrigated cropland converted to urban use in the United States would yield net decreases in water use, while in Mexico such a conversion would yield a net increase in use (Bohn et al., 2018).

NAFTA drove an expansion in irrigated agriculture in Mexico in the 1990s, particularly for the cultivation of fruits and vegetables for export, the overwhelming majority of which are exported to the United States. Despite the environmental provisions in the trade agreement, this expansion in agricultural production has resulted in the overdraft and salinification of the region’s groundwater aquifers, because it has put more pressure on limited surface water resources. Furthermore, agricultural production in the United States decreased during the same period, as markets shifted to the Mexican side, which brought agricultural water usage reductions to the former at the expense of increasing the water usage for land south of the border (Bohn et al., 2018). As a consequence of heavy land use, the depletion of water has been recognized as a problem along the entire U.S. side of the southern border, one characterized by low soil productivity, particularly in Southern California, Arizona, New Mexico, and the western tip of Texas (Miller et al., 2012).

The dynamic growth of agro-industrial production, the intensification of resource exploitation, and the regulatory heterogeneity under which the

region’s agro-industrial systems operate have triggered a variety of environmental and social problems beyond just water exploitation concerns. A review of the main cross-border management documents of the past few decades has shown the following primary problems:

• the practice of agricultural burning as a contributing factor to air pollution (EPA-SEMARNAT, 2012, p. 18);
• the intensive use of pesticides and the lack of regulation and education regarding their application, storage, application, and ultimate disposal (U.S. Environmental Protection Agency and Secretaría de Desarrollo Urbano y Ecología [EPA-SEDUE], 1991, pp. III–38–III-39; EPA-SEMARNAT, 2012, p. 29);
• contamination of groundwater and bodies of water because of pollution derived from the intensive use of pesticides and fertilizers (EPA-SEMARNAT, 2012, pp. 11, 15);
• water depletion and/or distribution exacerbated by high-water demand activities, such as industry and agriculture, occurring in an arid climate (EPA-SEMARNAT, 2012, p. 5, 19–20); and
• the marginalized working and living conditions of temporary agricultural workers, particularly their negative effect on workers’ health and education (EPA-SEMARNAT, 2012, p. 6; Osuchukwu et al., 2017; Villarejo, 2002).

Compounding the other causes of environmental degradation in the border strip is poor management of agricultural runoff (and wastewater), a problem that has been documented by the GNEB since its creation in 1992 (GNEB, 2014). Water quality issues spurred by these polluted streams of agricultural runoff have been so severe that they have generated “dead zones” at the mouths of border rivers, affecting populations of aquatic species and the people who depend on them.

One case that illustrates the coupled environmental impacts that can be exacerbated by intensive agricultural operations is the New River (Río Nuevo), which drains in the Salton Sea in California. It receives agricultural and urban runoff with a high concentration of pesticides, untreated wastewater, and industrial waste. This river is considered one of the most polluted in North America, and although binational cooperation has reduced its pollution levels, it remains a major problem for the population of the Imperial Valley (California Environmental Protection Agency [CalEPA], 2020). In particular, the border area presents serious problems not only of water pollution but also of air pollution, which was aggravated by the commissioning of fossil fuel-based power plants at the beginning of the 21st century (Ramos and Reyes, 2006). Data collected in 2016 by the World Health Organization found that the city of Mexicali, had some of

the highest average PM10 levels¹¹ in North America and the sixth-largest in the entire continent, with 85 micrograms per cubic meter (James, 2019). Between 2010 and 2016, at least 78 people died of asthma and 903 more people from chronic obstructive pulmonary disease in that city. Overall, this contamination is estimated to cause around 300 premature deaths annually in Mexicali (James, 2019). Mexicali’s is not the only case of air pollution on the border: in 2017, the EPA noted that the number of days in which air pollution reached a level classified as a risk to vulnerable people were 22 for El Paso, Texas; 27 for Las Cruces, New Mexico; 33 for El Centro, California; and 55 for San Diego, California (Eades, 2018).

In the 1990s, mirror cities shared similar air pollution levels, but they became increasingly dissimilar over the years due to differences in regulatory standards between the two countries. According to the Commission for Environmental Cooperation (CEC, 2004), this was the result of less stringent air quality standards implemented in Mexico, where those standards are perceived as objectives rather than as requirements to be implemented (see also Cresswell et al., 2009).

Agricultural burning, pesticides, and water scarcity have been addressed repeatedly in the binational programs agendas coordinated by the EPA and SEMARNAT, Mexico’s environmental agency. Work environment issues for agricultural day laborers were added to this agenda as part of a broader perspective that includes the deterioration of workers’ health resulting from pesticide use. While the contamination of groundwater by agricultural pollutants is regarded as a transcendent binational concern, there is no clear or specific work agenda around this in either country.

Financial Tensions

Natural resource challenges have been coupled with recent agricultural reforms in Mexico that have disproportionally affected poor farmers. Much of the agricultural development and intensification that occurred in the 20th century in the arid north was driven by large-scale irrigation projects executed by the government in “underutilized land.” The government granted direct agricultural subsidy payments enabling the development of ejidos, which are non-sellable communal land-use rights, mostly established for livestock and crop production (Hruska, 2019; Shah et al., 2004). The Mexico border region has approximately

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¹¹ PM is particulate matter, also called particle pollution. PM10 are inhalable particles that typically have diameters less than 10 micometers. See: https://www.epa.gov/pm-pollution/particulate-matter-pm-basics for additional discussion.

2,336 núcleos agrarios¹² (agricultural units) (Registro Agrario Nacional, 2019), many of which are large state-supported ejidos with large irrigation areas, created mostly in the 1930s and 1940s.¹³ In the north, ejidos have helped to generate incomes in rural areas, but in general, they have failed to produce sustainable profits for their members (ejidatarios) due to small parcel sizes, poor land quality, and initial poverty, which have precluded the efficient development of lands.

Since the 1990s, the development of NAFTA, and the consequent amendment of Article 27 of the Mexican Constitution, there has been a push for the privatization of ejidos and water and electricity systems (Shah et al., 2004). In 1992, Article 27 was modified to allow the ejidatarios, to mortgage or sell their land, as long as they had at least two-thirds support from their members (Shah et al., 2004). This reform resulted in the transfer of public land to private, wealthier entities, making it even more difficult for other poor ejidatarios to compete (Hruska, 2020). As a result of these reforms, governmental agricultural buying programs and subsidies were markedly reduced or eliminated, increasing the cost of production for rural farmers, and many ejidatarios were no longer able to afford necessary farming inputs. Exacerbating these financial tensions was a decade-long drought that made it nearly impossible for farmers dependent on rain-fed agriculture and rain-fed forage for their livestock. Drilling new groundwater wells is cost-prohibitive for a vast majority of ejidatarios. At the same time, crop prices were generally pushed down, prompting the emigration of many farmers to the United States (Vásquez-León et al., 2002).

Thus, areas where the majority of poor farmers and cattle owners share these communal lands are particularly vulnerable to water scarcity (Hruska, 2020). Although NAFTA expanded some markets for high-value crops like chiles and onions as crop production shifted from the United States to Mexico, declining governmental support and prolonged drought over the past few decades have made it difficult for many farmers to survive (Vásquez-León et al., 2002). In short, agriculture has continued to expand in northern Mexico since the implementation of reforms, but the massive reductions in government resources that propped up poor farmers who would not otherwise be self-sustainable created more economic stratification between farmers, that is, between those with the resources to survive with their financial resources and those who could no longer make a livable income (Hruska, 2020).

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¹² This number was generated by applying a 100-kilometer buffer south of the border to the most recent available database from Registro Agrario Nacional, using the online GIS. A freely downloadable dataset from 2017 is available at: http://132.248.14.102/layers/CapaBase:ran_nacional_2017_wgs84, but using this older dataset yields a different number (2,088) of núcleos agrarios.

¹³ More information is available at: https://mexico.leyderecho.org/nucleo-agrario/.

MINERAL RESOURCES AND MINING

Mining is an activity that has played a very important role in the region, historically, in economic development (representing about 10% of the country’s Gross Domestic Product [GDP]) (Aguilar-Pesantes et al., 2021), as well as the location of human settlements and urban growth. However, it is also an activity that has impacted the environment, as it is a consumer of water and energy. In addition, copper, more so than silver, plays an important role in the economy on both sides of the border. Mexico is the world’s largest silver producer, representing greater than 23 percent of global production in 2019.¹⁴ Chihuahua and Sonora are large silver-producing regions, representing 20.8 percent and 10.8 percent of the country’s production, respectively. Mexico also is the ninth-largest producer of the world’s gold,¹⁵ with Sonora and Chihuahua representing 33.2 percent and 17.2 percent of national gold production, respectively.

Sonora is Mexico’s largest mining region with gold, silver, copper, and molybdenum mining in its more mountainous regions. The state’s mining sector, representing about 17 percent of the state’s GDP, provides clear examples of the tensions between economic productivity and environmental sustainability in the region, given ongoing concerns of water scarcity and climate change (Zuniga-Teran et al., 2020). The state is home to the Buenavista del Cobre (Cananea) mine, the fourth largest copper mine in the world,¹⁶ located 35 kilometers south of the U.S.–Mexico border (Mendoza-Lagunas et al., 2019).

The mining industry has placed increasing priority on environmental sustainability and social responsibility. Many companies are developing and implementing active and ongoing programs with a focus on community relations, creating social value where they operate alongside an emphasis on environmental performance. A small number of high-profile mining accidents, such as the one in 2014 at the Buenavista del Cobre mine in Cananea, Sonora, 22 miles south of the U.S.–Mexico border (Mendoza-Lagunas et al., 2019), continue to serve as a reminder of the importance of advancing technology and governance for human and environmental safety. Partnerships are emerging among leading U.S. universities and mining companies that are making efforts to involve Mexican counterparts to share the benefits of research and further cooperation. For instance, the University

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¹⁴ More information is available at: https://www.statista.com/statistics/253339/leading-silver-producing-countries/.

¹⁵ More information is available at: https://www.gold.org/goldhub/data/historical-mine-production.

¹⁶ More information is available at: https://www.mining-technology.com/features/feature-the-10-biggest-copper-mines-in-the-world/.

of Arizona’s Lowell Institute for Mineral Resources¹⁷ works to advance responsible mining through binational and global networks to educate stakeholders on innovations in modern mining technology and practices.

Similar to the observation above for renewable energy, mining holds major potential for binational economic development and trade, and, therefore, for opportunities for binational sustainability partnerships.

Mining companies that are active on both sides of the border include Grupo México (in Arizona and Sonora) and Capstone (in Arizona and Zacatecas). Companies operating in one country alone are becoming increasingly aware of the benefits of binational partnerships that provide access to knowledge, resources, training, and technology for sustainability in arid regions through collaboration with universities whose research often transcends borders. Companies exploring these opportunities to date include ASARCO and Fresnillo plc.

CONVENTIONAL AND RENEWABLE ENERGY

The United States and Mexico are both large energy-producing and energy-consuming countries. The border region itself is a source of both renewable and nonrenewable energy resources, and it is the focal point of an important articulated network for the flow of energy between the two countries. This network has densified over the past two decades as both countries and Canada move toward a North American energy integration (U.S. Government Accountability Office [GAO], 2018). In terms of partnerships, the abundant renewable energy resources in the binational region present large opportunities for collaboration between the two countries.

Binational Energy Characteristics and Asymmetries

In 2018, the United States and Mexico represented the 1st and 11th largest petroleum-producing countries, respectively, and the 1st and 27th biggest natural-gas-producing countries in the world, respectively (U.S. Energy Information Agency [EIA], 2020a). In terms of total renewable energy generation (nuclear, renewable, and other production), they represented the 1st (United States) and 20th (Mexico) largest generators in the world. However, the two countries differ markedly in consumption. In 2018, the primary energy consumed in the United States amounted to 310 million British thermal unit (BTU) per person (ranking 10th in the world), whereas in Mexico it was 63 million BTU per person (88th in the world), reflecting wide disparities in the social and economic fabrics of the two countries (EIA, 2020a).

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¹⁷ More information is available at: https://minerals.arizona.edu/.

The U.S. total supply of primary energy in 2019, that is, its domestic energy production plus energy imports from other countries, minus exports and international bunkers amounted to 2,200,788 ktoe (kilotonne of oil equivalent) with petroleum, natural gas, and coal representing 36 percent, 33 percent, and 13 percent, respectively, while nuclear (9.9%), hydropower (1.1%), biofuels and waste (4.9%), and wind and solar (2.1%) made up the balance of the nonfossil fuel supply (International Energy Agency [IEA], 2020a). That same year, fossil fuels represented 80 percent of total U.S. primary energy consumption (petroleum: 37%, natural gas: 32%, and coal: 11%). Nuclear and renewable energy represented 8 percent and 11 percent of primary energy consumption, respectively (EIA, 2020b).

Over the past two decades, the energy landscape on the U.S. side of the border region has shifted dramatically chiefly due to three factors: the growth of renewable energy across the border states, the rapid growth of the fracking industry, and the decline of the coal industry (Peer and Sanders, 2018). Texas generated over a quarter of the country’s wind power and produced approximately a quarter of its natural gas in 2019 (EIA, 2020c). California and Arizona represent the first and second-largest producing U.S. states in terms of solar photovoltaic generation. Even New Mexico has grown in energy output from being the seventh-largest producer of crude oil in 2013 to the third-largest by 2018, due to growth in the shale oil industry, while also generating about a fifth of its electricity from wind that year (EIA, 2020c). The fossil fuel and renewable energy resources in these states have enjoyed extraordinary growth due to technological advancements, which have driven down the price of energy production. Mexico shares many of the same types of geologic and renewable resource potentials as these U.S. states.

In 2019, Mexico’s total primary energy supply, including imports, amounted to 184,021 ktoe of energy, comprised of 45 percent petroleum, 38 percent natural gas, 5 percent biofuels and waste, 1.6 percent nuclear, 1.4 percent hydropower, and 2.8 percent of wind and solar renewables (IEA, 2020b). The country’s total primary energy supply grew by approximately 46 percent between 1990 and 2018. In 2019, petroleum, natural gas, and coal represented 43 percent, 42 percent, and 7 percent of domestic total primary energy consumption, respectively, while nuclear, hydroelectricity and non-hydropower renewables represented 1 percent, 3 percent, and 4 percent, respectively (EIA, 2020d). In 2019, Mexico was the second-largest import source for the United States, importing 1.2 million barrels per day of petroleum (EIA, 2020e).

Mexico’s energy sector has been in decline over the past few decades, which spurred a series of institutional reforms in 2013 that have influenced the path of its energy industry (Vietor and Sheldahl-Thomason, 2017). The reforms were adopted in part because of very low oil prices, which put huge

financial pressure on Mexico’s state-owned petroleum company, Pemex, which has historically controlled the vast majority of oil and gas development in the country (Weijermars et al., 2017). Under the control of Pemex, oil production peaked in 2004 and has declined to nearly half of that peak in the 15 years since (Gross, 2019). The reforms ended Pemex’s 75-year monopoly in the oil and gas industry (Vietor and Sheldahl-Thomason, 2017). Similarly, the electricity sector, also controlled by a state-owned monopoly (Comisión Federal de Electricidad [CFE]) was challenged by an aging infrastructure and high prices before the reforms. Mexico’s former president, Enrique Peña Nieto, implemented reforms to address these declining industries with two goals: to create competition by attracting new technologies and market participants and to bring in capital to ensure the resources to meet growing energy demand (Gross, 2019; Vietor and Sheldahl-Thomason, 2017).

Renewable energy development accelerated after the energy reforms as international companies were incentivized to invest and operate in the country (Gross, 2019; Vietor and Sheldahl-Thomason, 2017). The total resource potential, based on very strong solar, wind, and geothermal resources, is large enough for Mexico to be a global leader in renewable energy development (Sanders et al., 2013).

Energy Transitions and Environmental Impact

Energy transitions, particularly those associated with the burgeoning U.S. shale industry, have spurred environmental concerns. The Eagle Ford shale region of southwest Texas has seen large surges in oil and natural gas development. Production in these shales and other tight formations has become economical only in the past two decades due to advancements in the coupling of hydraulic fracturing and horizontal drilling techniques that make it possible to extract fuels from impermeable rock (Jackson et al., 2013; Vidic et al., 2013). This development has come with a lot of environmental and social tradeoffs. Developing a well typically requires 10,000 to 30,000 cubic meters of water, depending on geology and the production methods (Rahm and Riha, 2014). It is estimated that 80 percent of the water used for hydraulic fracturing is freshwater and that 90 percent of this freshwater is sourced from groundwater (Mohtar et al., 2019).

The growth of the hydraulic fracturing industry has also triggered water quality concerns, such as gas migration into groundwater aquifers, accidental spills of toxic fracturing fluids, and the safe handling of wastewater produced during production (Vidic et al., 2013). There are other, non-water impacts as well, such as land degradation, air pollution, and increased greenhouse gases (Mohtar et al., 2019). There has also been a growing financial burden placed on communities that have had to pay for much of the damage caused to their

communities by increases in hydraulic fracturing that resulted in increases in truck traffic for water management (and the associated increases in road degradation and road accidents), as well as public health consequences (Jackson et al., 2013; Mohtar et al., 2019). Although energy, and particularly renewables, represent a major potential source of economic development, cross-border trade, and binational sustainability initiatives, efforts by the study committee to invite energy-sector representatives to the stakeholder workshop were unsuccessful; thus, this topic is absent from the report. Instead, the committee opted to list this as a theme for future partnership efforts.

RESOURCE GOVERNANCE, INNOVATION, AND PARTNERSHIPS

Water Governance

In comparison with other water-scarce countries sharing borders and waterways, the relationship between Mexico and the United States is unique (Bonner and Rozental, 2009). The 1983 Mexico–U.S. Agreement on Cooperation for the Protection and Improvement of the Environment in the Border Area (i.e., the La Paz Agreement) was an important binational initiative to reduce and prevent pollution in the border region and provided a foundation for international collaborations that followed, which include NAFTA, the Border Environment Commission, and CEC (Giner et al., 2019).

Water shortages on the Rio Grande and Colorado rivers have spurred many international water management disputes, but they have also motivated many successful instances of international collaborations (Sandoval-Solis et al., 2013; Wilder et al., 2010). Despite successes, managing shared water resources is incredibly difficult in arid regions, and stressors—such as climate change, the differences in the way that water is managed in each country, population growth, shifts in urbanization and industrialization patterns, and limited financial resources—will continue to add pressure to the management of shared surface water and groundwater resources.

In general, water management in the United States is more decentralized and fragmented than water management in Mexico (Carter et al., 2017; Gerlak, 2006). In the United States, water rights and water-related laws and governance are administered by a patchwork of agencies at the federal, state, and local levels, which represent a variety of priorities and environmental protections (e.g., water development, water quality, ecological flows, irrigation withdrawals, interstate, and international water sharing). Because the United States generally has more financial resources and more actors with a stake in local governance of water, it is generally easier for projects to be financed there than in Mexico, where there are far fewer options (Medgal and Scott, 2011).

In Mexico, water management is generally more centralized. It is controlled by the country’s national water commission, CONAGUA, which operates based on the country’s Law on National Waters. This centralization can make it hard to prioritize local projects, since the tax base supporting CONAGUA is national and, by design, focused on projects throughout the country (Goetz and Berga, 2006). While Mexico’s centralized control of the water system can enable more streamlined decision making in comparison with the United States (Wilder et al., 2013), reform efforts in recent decades have sought to decentralize aspects of Mexico’s water management regime to engage more local stakeholders and spur more participatory governance (Wilder and Romero, 2006). These reforms have produced positive outcomes, particularly in the creation of local watershed districts and irrigation districts in northern states. However, some argue that mechanisms to shift water management to local authorities have left many communities without adequate resources to run water utilities and fund infrastructure, exacerbating existing poverty, corruption, and issues related to transparency (Scott and Banister, 2008).

In addition to the challenge of managing surface water flows, there are a range of groundwater resource governance needs in the U.S.–Mexico border region. As discussed in the 2018 workshop, the overdraft and salinification of aquifers are major issues on both sides of the border (NASEM, 2018). Within each country, there are also asymmetries in groundwater ownership (Megdal and Scott, 2011). Groundwater in Texas, for example, is considered private property, while in Mexico it is national property (Sanchez and Eckstein, 2020). These asymmetries in institutional governance are considered by many to be a primary barrier to a binational treaty that would better manage the common pool resource (Albrecht et al., 2018; Mumme, 2005; Sanchez and Eckstein, 2020).

The 1944 U.S.–Mexico Water Treaty addresses shared surface waters and is largely silent on groundwater. However, several minutes to amend the treaty have been passed that address groundwater, among other issues, including Minutes 319 and 323 (Buono and Eckstein, 2014; Mumme, 2020). The United States tends to have more enforceable protections for groundwater overdraft than Mexico (although protections vary from state to state, as discussed below), and the latter has seen much more expansion of irrigation due to weak overdraft protections (NASEM, 2018).

In the United States, approaches to groundwater governance are uneven and span many levels of local, regional, and state governments. For example, Arizona’s 1980 Groundwater Management Act, managed by the state’s Department of Water Resources, was implemented to protect groundwater aquifers from overdraft through such provisions as prohibiting irrigated agriculture on new land, while Arizona’s Department of Environmental

Quality enforces water quality standards.¹⁸ Additionally, there are often more regional approaches to groundwater management, carried out by local governments (e.g., the Santa Cruz Active Management Area in the Santa Cruz basin of Arizona) (Scott et al., 2012). While there are no formal binational protections for groundwater, the U.S.–Mexico Transboundary Aquifer Assessment Act was designed to conduct and improve data sharing and scientific research on water quantity and quality issues across shared aquifers (Callegary et al., 2016). Subsequent binational negotiations between members of the International Boundary and Water Commission from the United States and Mexico led to the 2009 signing of the “Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program,” which provided a framework for the use and joint study of shared aquifers.¹⁹

Over time, variable and declining precipitation patterns, along with rising competition for water, have decreased the amount of surface water available for agriculture. As a result, the exploitation of groundwater aquifers has worsened over time. In 2003, a night-time tariff was introduced to promote more agricultural productivity; however, these tariffs have incentivized over-pumping, exacerbating depletion (Scott, 2013). Although these tariff programs have successfully transformed otherwise desert-like northern regions in Mexico into productive agricultural regions that produce large quantities of fruits and vegetables for export, the resulting levels of groundwater depletion have reduced the adaptive capacity of the region to respond to future water scarcity (Sietz et al., 2011).

Effects of Trade Policies on Natural Resources

The strong trade integration that NAFTA opened led to changes in the cross-border agricultural landscape, particularly in Mexico. The constitutional reforms carried out under the signing of NAFTA have had a strong impact on Mexico’s entire primary sector, mainly due to the entry of tariff-free agricultural goods and the parallel elimination of the marketing and production support system implemented decades ago by the Mexican government. These processes led to the disintegration of much of the agricultural production supplied by the domestic market, which encouraged productive specialization in export goods such as beef, vegetables, and fruit. As a result, the western border region has specialized in the production of fresh “winter” fruits and vegetables that respond to the demand of the U.S. market and are also exported to European and Asian markets.

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¹⁸ More information is available at: https://new.azwater.gov/sites/default/files/media/Arizona%20Groundwater_Code_1.pdf.

¹⁹ More information is available at: https://www.usgs.gov/centers/ot-water/science/transboundary-aquifer-assessment-program-taap?qt-science_center_objects=0#qt-science_center_objects.

This conversion has also promoted the industrialization of the sector, which has intensified the dispute over inputs such as water and land, as well as raising demand for a labor force mainly for vegetable and fruit growing. Although legislation introduced in 1992 opened the possibility that community-held ejido agricultural land could be sold, but only a small proportion (7%) has been privatized in the border region, mostly in industrial and suburban areas (Vidaurrázaga Obezo, 2003).

Asymmetries in communities on either side of the border affect farmers’ resilience in managing their livelihoods in times of drought. Agriculture in the United States has been less vulnerable to shocks, such as drought, due to technological interventions, including more efficient irrigation. However, pumped groundwater for irrigation is typically more expensive than surface water deliveries and still tends to be a limiting factor as to whether or not farmers can continue to operate (Vásquez-León et al., 2002).

As a result of rising water costs, as well as threats of disruptions in productivity because of prolonged drought, many communities have adopted technology-centric methods of ensuring a stable water supply to irrigate crops through methods such as drip irrigation and center-pivot irrigation (Vásquez-León et al., 2002). However, even with water-efficient irrigation, groundwater pumping is expensive, which has led to interesting tradeoffs between water use and the economics of crop production (Vásquez-León et al., 2002). While the increases in the cost of irrigation in groundwater-dependent regions have led to decreases in the agricultural land cultivated, there has also been a shift to crops that produce more economic value to offset irrigation costs, and some of these crops have high water needs (Vásquez-León et al., 2002). As a result, efforts to reduce water usage have been undermined by the movement toward more water-thirsty crops in groundwater-dependent regions.

Changes in Energy and Climate Governance

Even though it is a major fossil fuel-producing country, Mexico has established itself as a leader in international climate negotiations with its decarbonization goals, particularly in comparison to other emerging economies (von Lüpke and Well, 2019). Mexico passed its General Law on Climate Change in 2012 under President Felipe Calderon, which established a goal of reducing greenhouse gas emissions by 50 percent below 2000 emissions levels by 2050. A few years later, Mexico introduced a target to reduce greenhouse gas emissions by 2030 by 22 percent, relative to a business-as-usual scenario.²⁰

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²⁰ More information is available at: https://www4.unfccc.int/sites/ndcstaging/Published-Documents/Mexico%20First/MEXICO%20INDC%2003.30.2015.pdf.

Since the election of President López Obrador in 2018, Mexico’s leadership has deprioritized clean energy and climate change mitigation actions.

In March 2021, the Obrador administration approved a fast-tracked bill that modifies Mexico’s Electric Industry Law and rolls back much of his predecessor’s energy reform initiatives.²¹ Ending Mexico’s energy reforms has the potential to limit the domestic production of oil and gas resources in shale basins and difficult-to-access offshore locations that might require the expertise of international producers outside of Pemex (e.g., producers with expertise in developing U.S. shales) (Weijermars et al., 2017). Fracking has been a growing industry on the U.S. side, but despite its rich shale basins just south of some of Texas’s very productive shales, fracking is still a very new industry to Mexico. Two major trends have created a favorable environment for the domestic shale gas industry in recent years, namely a growing dependency on natural gas imports and regulatory reforms in the oil and gas sector, opening the country to foreign producers.

In 2002, Mexico became a net importer of natural gas, much of which is imported in the form of expensive liquified natural gas, incentivizing methods to grow domestic production. Pemex commenced exploration of the Eagle Ford shale play (shared with Texas), just south of the U.S.–Mexico border, in 2010, but no gas was identified until 2013 (Weijermars et al., 2017). The real game-changer for the fracking industry came a year later through the 2014 energy sector reforms. These have made it easier for foreign operators to produce in the country, thereby bringing in the expertise needed to produce in more difficult shale regions. The reforms spurred significant energy investments, much of which have been directed toward the still-nascent fracking industry in the northern regions of the country (Gross, 2019). Thus, the pivot by President López Obrador to direct control back to Pemex might stall the continued development of these harder-to-access resources (Weijermars et al., 2017). Yet, Mexico contains the world’s sixth-largest reserves of shale gas, concentrated in the north, where water-scarcity issues, particularly in terms of overexploited groundwater aquifers, are already pronounced (Weijermars et al., 2017). Thus, anticipated growth in the industry, which has been primarily concentrated in the United States at this point, will need to be undertaken with environmental protections in mind.

Energy development in the United States is much more market-based than in Mexico. The federal government does not have nearly as much power to influence the dynamics of the energy industry as it has in Mexico, as there are also state and local policies that can affect the development of energy policy. Thus, the pullback of energy reforms in Mexico in recent years is likely to have a much bigger potential to affect the energy landscape than any leadership change in the United States.

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²¹ More information is available at: https://www.elfinanciero.com.mx/nacional/senado-aprueba-en-lo-general-la-reforma-electrica-de-amlo.

SUMMARY

As described in Chapter 1, the May 2018 National Academies workshop “Advancing Sustainability of U.S.–Mexico Transboundary Drylands,” applied a thematic lens to the region’s challenges to explain sustainability dynamics more effectively than the conventional approach that looks at each resource and phenomenon individually. In considering partnerships that most effectively address binational sustainability, it is critical that these four themes in sustainability dynamics—interactions and flows; scarcity and abundance; shocks and stressors; and governance, innovation, and partnerships—be placed at the forefront.

Interactions and flows: The transborder region is constantly in flux with dynamic interactions and flows of people, resources, and ever-changing political arrangements. As a result of rapid industrialization and a decrease in agricultural production, many farmers have been forced to move to more urban regions, exacerbating the trend toward urban sprawl in unincorporated, slum-like communities. Changes in trade regimes have also shifted the region’s demographics and social activities over time. The large flow of commodities and industrial products across the border is more than matched by the movement of people going to Mexico as recreational or medical tourists and to the United States seeking jobs or escaping hardship and violence in Mexico or other places. The flow of economic migrants and refugees into the United States occurs both legally and illegally, a reality that often dominates the political agenda in both countries. Illegal trafficking of drugs and firearms between the two countries is a continued threat to population health and safety.

Scarcity and abundance: The U.S.–Mexico border region embodies both scarcity and abundance—rich in ecological, natural resource, and mineral wealth, while also characterized by aridity and desertification. Water security remains one of the chief concerns for the region, particularly as industrialization, shifts in economic opportunities, migration, and the proliferation of large agricultural developments on both sides of the border have increased water strain in recent years. The U.S.–Mexico border region struggles with severe water stress, exacerbated by irrigation and overgrazing activities, deforestation, and severe soil degradation associated with agricultural production. These challenges are particularly prominent in Mexico’s arid and semi-arid regions, which, despite receiving a small fraction of the country’s total precipitation, have most of its irrigated land (Díaz-Caravantes and Wilder, 2014).

Shocks and stressors: Rapid population growth in and around “mirror cities” (i.e., urban regions situated adjacent to one another on either side of the border), whose expansions have been characterized by sprawling urbanization and the development of formal and informal communities, have created anthropogenic shocks and stressors in the region. The lack of adequate infrastructure for essential needs such as basic drinking water and sanitation

services jeopardizes the public health and security of residents while straining natural resources, particularly in the context of climate change. Furthermore, differences between the United States and Mexico in terms of critical infrastructure, economic security, regulatory environment, culture, and language, often hinder efficient binational management of shared resources such as surface and groundwater. They also create challenges for mitigating shocks and stressors, such as excess flows of wastewater during flooding events.

Governance, innovation, and partnerships: The region is also a crucible for developing sustainability in governance, innovation, and partnerships. Many of the shifts in recent decades toward industrialization, urbanization, and migration were driven by the implementation of NAFTA in 1994, which resulted in vast increases in the international trade of agricultural commodities grown along the border and large decreases in the consumption of agricultural goods in the domestic market. Drivers of border challenges are often heavily determined by national policy initiatives. Differential financial resources and opportunities for public participation, as well as Mexico’s comparatively recent shift to a plural party democratic process, result in asymmetries in the countries’ capacities to respond to exogenous policy stressors affecting the border region.

The shift in Mexico from the local consumption of domestically produced goods to production for the transnational market led to the proliferation of maquiladoras/assembly plants and adversely affected farmers in the region by pushing down the price of agricultural commodities.

Additionally, while trade has been at the forefront of the U.S.–Mexico relationship, there have been successful partnerships in other areas. Both Mexican and U.S. communities along the border face common threats, such as water scarcity, inadequate infrastructure, and land and soil degradation, which have led to both country-specific and binational efforts to ensure adequate resource security. For example, the passage of the binational 1944 Mexican Water Treaty and the establishment of the International Boundary and Water Commission, the entity charged with determining the most effective way to execute the treaty by allocating surface water across shared river systems, have been viewed as successes in efforts to mitigate potential water disputes. However, although the 1944 Water Treaty marked progress in binational surface water management, it largely ignored the protection of groundwater resources and water quality, which continue to be large challenges for both countries.

Some existing binational initiatives have improved the planning, development, and implementation of cross-border environmental programs and infrastructure, and have resulted in increased access to drinking water, more effective management of wastewater flows, improved air quality, and better solid waste management. Despite examples of progress, there are still many areas of binational partnership that could facilitate better water resource management and offer a large potential for coordination.

Building desalination facilities to treat flows of wastewater and generate more potable water supplies is another area for expanding binational collaboration. Attempts to improve progress in these areas have faced well-known hurdles. Differences in regulation between countries, as well as increased population, urbanization, and industrialization, have complicated some efforts to manage shared water resources, particularly under the increasing challenges posed by climate change.

Other areas of the economy hold potential for binational collaboration. The coordination between such industries as energy and mining is still nascent, but both industries have placed increasing priority on environmental sustainability and social responsibility, presenting large opportunities for progress. The border region is particularly rich in energy resources, both in terms of renewable and nonrenewable sources. The vast renewable energy potential, in particular, could provide opportunities for binational grid expansion, which could facilitate larger penetrations of intermittent wind and solar generation resources to be integrated into a binational grid so that electricity could be traded more easily across borders. By diversifying and expanding the regional extent of the power grid, the challenges posed by the intermittencies of these variable renewable energy generators could be mitigated, since a large regional grid would be less vulnerable to local lapses in wind or solar resource availability. Similarly, while the United States has greatly expanded the use of hydraulic fracturing techniques for oil and gas development, particularly in Texas, the production of shale reservoirs in Mexico is nascent. Energy reforms in Mexico over time have vastly increased the potential for binational cooperation in the energy space to spur synergistic benefits for both countries.

FINDINGS AND CONCLUSIONS

The binational region is experiencing increasing interactions of people and commerce, the growing interdependence of the two countries on water stocks and flows, and expanding ecological linkages. The region’s sustainability challenges are exacerbated by stressors, such as global climate change, increasing urbanization and industrialization, and population and economic growth.

The movement of maquiladoras/assembly plants toward renewable energy resources is altering the industrial landscape of the region. While a relatively recent phenomenon, the maquiladora/assembly plants-dominated industrial environment at the border is being altered by the moves toward renewable energies and the ever-changing political imperatives in both countries. The increased focus on environmental sustainability and social responsibility, as well as the shift in mining technology and innovation, allow for partnerships with multiple actors and across sectors to address binational challenges.

Strategic partnerships, engaging a diversity of stakeholders on either side of the border, are needed to devise strategies that both support the region’s sustainable development and protect the well-being of humans and ecosystems within it.

REFERENCES

Buono, R.M., and Eckstein, G. (2014). Minute 319: A cooperative approach to Mexico–US hydro-relations on the Colorado River. Water International, 39(3), 263–276.

CalEPA (California Environmental Protection Agency). (2020). New River Strategic Plan Updates. Available: https://calepa.ca.gov/border-affairs-program/new-river-strategic-plan-updates/.

Callegary, J.B., Minjárez Sosa, I., Tapia Villaseñor, E.M., dos Santos, P., Monreal Saavedra, R., Grijalva Noriega, F.J., Huth, A.K., Gray, F., Scott, C.A., Megdal, S.B., Oroz Ramos, L.A., Rangel Medina, M., and Leenhouts, J.M. (2016). Binational Study of the Transboundary San Pedro Aquifer. United States and Mexico: International Boundary and Water Commission.

Campbell, H. (2007). El narco-folklore: Narrativas e historias de la droga en la frontera. Nóesis. Revista de Ciencias Sociales y Humanidades, 16(32), 46–70. Available: https://www.redalyc.org/pdf/859/85903203.pdf.

Carrillo, G., Uribe, F., Lucio, R., Ramirez Lopez, A., and Korc, M. (2017). The United States–Mexico border environmental public health: The challenges of working with two systems. Revista Panamericana Salud Publica, 41, 1–7.

Carter, N.T., Mulligan, S.P., and Seelke, C.R. (2017). U.S.-Mexico Water Sharing: Background and Recent Developments. Washington, DC: Congressional Research Service.

CEC (Commission for Environmental Cooperation). (2004). North American Air Quality and Climate Change Standards, Regulations, Planning and Enforcement at the National, State/Provincial and Local Levels. Available: http://www3.cec.org/islandora/fr/item/2145-north-american-air-quality-and-climate-change-standards-regulations-planning-and-en.pdf.

______. (2011). North American Terrestrial Ecoregions–Level III. Available: http://www3.cec.org/islandora/en/item/10415-north-american-terrestrial-ecoregionslevel-iii.

Córdova, A., and de la Parra, C.A. (2007). Una barrera a nuestro ambiente compartido: El muro fronterizo entre México y Estados Unidos. El Colegio de la Frontera Norte: Secretaría de Medio Ambiente y Recursos Naturales. Instituto Nacional de Ecología: Consorcio de Investigación y Política Ambiental del Suroeste.

Cresswell, A., Burke, G.B., and Navarrete, C. (2009). Mitigating Cross-Border Air Pollution: The Power of a Network. Albany, NY: Center for Technology in Government, University of Albany, SUNY. Available: www.ctg.albany.edu/publications/reports/jac_mitigating.

CRS (Congressional Research Service). (2017). U.S.-Mexico water sharing: Background and recent developments.

______. (2020). The North American Development Bank. In Focus, June 18. Available: https://crsreports.congress.gov/product/pdf/IF/IF10480.

Díaz, E. (2009). Mercado de trabajo e industria maquiladora en Sonora y la frontera norte. Región y Sociedad, 21(44), 43–70.

Díaz-Caravantes, R.E., and Wilder, M. (2014). Water, cities and peri-urban communities: Geographies of power in the context of drought in Northwest Mexico. Water Alternatives, 7(3), 499–517.

Eades, L. (2018). Air Pollution at the U.S.–Mexico Border: Strengthening the Framework for Bilateral Cooperation. Princeton, NJ: Association of Professional Schools and International Affairs and The Woodrow Wilson School of Public and International Affairs, Princeton University.

Eckstein, G.E. (2011). Buried treasure or buried hope? The status of Mexico-U.S. transboundary aquifers under international law. International Community Law Review, 13, 273–290. doi: 10.1163/187197311X582395.

EIA (U.S. Energy Information Administration). (2020a). International Energy Statistics. Available: https://www.eia.gov/international/overview/world.

______. (2020b). Monthly Energy Review, Tables 1.3 and 10.1. April 2020, preliminary data. Available: https://www.eia.gov/energyexplained/us-energy-facts/.

______. (2020c). U.S. States State Profiles and Energy Estimates. Available: https://www.eia.gov/state/.

______. (2020d). Country Analysis. Executive Summary: Mexico. Available: https://www.eia.gov/international/analysis/country/MEX.

______. (2020e). In 2019, the U.S. Imported $13 Billion of Energy Goods from Mexico, Exported $34 Billion. Available: https://www.eia.gov/todayinenergy/detail.php?id=45756.

El Colef. (2019). La era de Trump y sus impactos en la frontera norte de México. Economía, Población y Desarrollo. Cuadernos de Trabajo, 49(2), 1–35. Universidad Autónoma de Ciudad Juárez.

EPA (U.S. Environmental Protection Agency). (1996). US/Mexico Border XXI Program: Framework Document. Available: https://catalog.hathitrust.org/Record/101234357.

EPA-SEDUE (U.S. Environmental Protection Agency and Secretaría de Desarrollo Urbano y Ecología). (1991). Integrated Environmental Plan for the Mexico-U.S. Border Area (First Stage, 1992–1994): Working Draft. Available: https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=91017YO0.txt.

EPA-SEMARNAT (U.S. Environmenal Protection Agency and Secretaría de Medio Ambiente y Recursos Naturales). (2012). Border 2020 U.S-Mexico Environmental Program (Summary). Available: https://www.epa.gov/sites/production/files/documents/border2020summary.pdf.

GAO (U.S. Government Accountability Office). (2018). North American Energy Integration: Information about Cooperation with Canada and Mexico and Among U.S. Agencies. Report to the Subcommittee on the Western Hemisphere, Committee on Foreign Affairs, House of Representatives. GAO-18-575. Washington, DC.

Gerlak, A.K. (2006). Federalism and the U.S. water policy: Lessons for the twenty-first century. Publis, 26(2), 231–257.

Giner, M.E., Córdova, A., Vázquez-Gálvez, F.A., and Marruffo, J. (2019). Promoting green infrastructure in Mexico’s northern border: The Border Environment Cooperation Commission’s experience and lessons learned. Journal of Environmental Management, 248(10), 109–104. doi: 10.1016/j.jenvman.2019.06.005.

GNEB (Good Neighbor Environmental Board). (2014). Ecological Restoration in the U.S.-Mexico Border Region. 16th Report of the Good Neighbor Environmental Board to the President and Congress of the United States. Publication number EPA 130-R-14-001. Available: https://www.epa.gov/sites/production/files/2016-12/documents/16th_gneb_report_english_final_web.pdf.

Goetz, R.U., and Berga, D. (Eds.). (2006). Frontiers in Water Resource Economics (Vol. 29). Springer Science & Business Media. New York, NY: Springer Science & Business Media.

Greenwald, N., Segee, B., Curry, T. and Bradley, C. (2017). A Wall in the Wild: The Disastrous Impacts of Trump’s Border Wall on Wildlife. Tucson, AZ: Center for Biological Diversity.

Gross, S. (2019). Order from Chaos: AMLO reverses positive trends in Mexico’s energy industry. Brookings blog, December 20. Available: https://www.brookings.edu/blog/order-from-chaos/2019/12/20/amlo-reverses-positive-trends-in-mexicos-energy-industry/.

Hernández Pérez, J.J. (2019). Sistema de innovación agrícola como estrategia de competitividad de los productores sonorenses en el contexto del TLCAN. Estudios Sociales, 29(54), 2–35. doi: 10.24836/es.v29i54.828.

HHS (U.S. Department of Health and Human Services). (2017). The U.S.-Mexico Border Region. Available: https://www.hhs.gov/about/agencies/oga/about-oga/what-we-do/international-relations-division/americas/border-health-commission/us-mexico-border-region.

HUD (U.S. Department of Housing and Urban Development). (2020). Colonias History. Available: https://www.hudexchange.info/programs/cdbg-colonias/colonias-history/.

Huesca Reynoso, L., and Llamas Rembao, L.I. (2019). Crisis y resiliencia en género y salarios: el sector manufacturero en México y la frontera norte. Frontera Norte, 31(16), 1–23. doi: 10.33679/rfn.v1i1.2051.

Hruska, T. (2020). Evolving patterns of agricultural frontier expansion in Mexico’s Chihuahuan Desert: A political ecology approach. Journal of Land Use Science, 15(2-3), 270–289. doi: 10.1080/1747423x.2019.1646332.

IEA (International Energy Agency). (2020a). Total Energy Supply (TPES) by Source, United States, 1990–2019. Available: https://www.iea.org/countries/united-states.

______. (2020b). Total Energy Supply (TPES) by Source, Mexico, 1990–2019. Available: https://www.iea.org/countries/mexico.

Israel, E., and Batalova, J. (2020). Mexican Immigrants in the United States. Available: https://www.migrationpolicy.org/article/mexican-immigrants-united-states-2019.

Jackson, R.B., Vengosh, A., Darrah, T.H., Warner, N.R., Down, A., Poreda, R.J., Osborn, S.G., Zhao, K., and Karr, J.D. (2013). Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction. Proceedings of the National Academy of Sciences, 110(28), 11250–11255. doi: 10.1073/pnas.1221635110.

James, I. (2019). Poisoned cities deadly border: This city’s air is killing people. Who will stop it? Desert Sun, January 15. Available: https://www.desertsun.com/in-depth/news/environment/border-pollution/poisoned-cities/2018/12/05/air-pollution-taking-deadly-toll-u-s-mexico-border/1381585002/.

Jepson, W. (2014). Measuring ‘no-win’ waterscapes: Experience-based scales and classification approaches to assess household water security in colonias on the U.S.-Mexico border. Geoforum, 51, 107–120. doi: 10.1016/j.geoforum.2013.10.002.

King, C.W., Stillwell, A.S., Twomey, K.M., and Webber, M.E. (2013). Coherence between water and energy policies. Natural Resources Journal, 53(1), 117–215.

Maganda, C. (2005). Collateral damage: How the San Diego-Imperial Valley water agreement affects the Mexican side of the border. The Journal of Environment and Development, 14, 486–506. doi: 10.1177/1070496505282668.

McCallum, J.W., Rowcliffe, J.M., and Cuthill, I.C. (2014). Conservation on international boundaries: The impact of security barriers on selected terrestrial mammals in four protected areas in Arizona, USA. PLoS ONE, 9(4), e93679. doi: 10.1371/journal.pone.0093679.

Megdal, S.B., and Scott, C.A. (2011). The importance of institutional asymmetries to the development of binational aquifer assessment programs: The Arizona-Sonora experience. Water, 3, 949–963. doi: 10.3390/w3030949.

Mendoza-Lagunas, J.L., Meza-Figueroa, D.M., Martínez-Cinco, M.A., O’Rourke, M.K., Centeno-García, E., Romero, F.M., García-Rico, L., and Meza-Montenegro, M.M. (2019). Health risk assessment in children by arsenic and mercury pollution of groundwater in a mining area in Sonora, Mexico. Journal of Geoscience and Environment Protection, 7(6), 90–105. doi: 10.4236/gep.2019.76008.

Miller, B., Schaetzl, R., and Frank, J. (2012). The Soil Productivity Index: Taxonomically Based, Ordinal Estimates of Soil Productivity. New York: Association of American Geographers Annual Meeting. doi: 10.13140/2.1.3036.5127.

Mohtar, R.H., Shafiezadeh, H., Blake, J., and Daher, B. (2019). Economic, social, and environmental evaluation of energy development in the Eagle Ford shale play. Science of the Total Environment, 646(1), 1601–1614. Available: https://doi.org/10.1016/j.scitotenv.2018.07.202.

Mumme, S.P. (2005). Advancing binational cooperation in transboundary aquifer management on the U.S.-Mexico Border. Colorado Journal of International Environmental Law and Policy, 16(1), 77–94.

______. (2020). The 1944 Water Treaty and the incorporation of environmental values in US-Mexico transboundary water governance. Environmental Science and Policy, 112, 126–133.

NASEM (National Academies of Sciences, Engineering, and Medicine). (2018). Advancing Sustainability of U.S.-Mexico Transboundary Drylands: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/25253.

Osuchukwu, O., Nuñez, M., Packard, S., Ehiri, J., Rosales, C., Hawkins, E., Avilés, J.G.G., and Oren, E. (2017). Latent tuberculosis infection screening acceptability among migrant farmworkers. International Migration, 55(5), 62–74.

Pavlakovich-Kochi, V. (2006). The Arizona-Sonora Region: A decade of transborder region building. Estudios Sociales, 14(27), 25–55. Available: http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0188-45572006000100002&lng=es&tlng=en.

Peer, R.A.M., and Sanders, K.T. (2018). The water consequences of a transitioning US power sector. Applied Energy, 210(15), 613–622. doi: 10.1016/j.apenergy.2017.08.021.

Pelozzi, K., Kozo, J., Ferran, K., Wooten, W., Rangel Gomez, G., and AL-DeLaimy, W.K. (2014). One Bioregion/One Health: An integrative narrative for transboundary planning along the US–Mexico border. Global Society, 28(4), 419–440. doi:10.1080/13600826. 2014.951316.

Peña Muñoz, J.J. (2018). Recomposición de la migración laboral en la frontera norte de México. Frontera Norte, 30(59), 81–102. doi: 10.17428/rfn.v30i59.645.

Pérez Ortega, R. (2020). Pools in the Mexican desert are a window into Earth’s early life. Science, June 30. Available: https://www.sciencemag.org/news/2020/06/pools-mexican-desert-are-window-earth-s-early-life.

Peters, R., Ripple, W.J., Wolf, C., Moskwik, M.,Carreón-Arroyo, G., Ceballos, G., Córdova, A., Dirzo, R., Ehrlich, P.R., Flesch, A.D., List, R., Lovejoy, T.E., Noss, R.F., Pacheco, J., Sarukhán, J.K.,Soulé, M.E., Wilson, E.O., and Miller, J.R.B. (2018). Nature divided, scientists united: US-Mexico border wall threatens biodiversity and binational conservation. BioScience, 68(10), 740–743. Available: https://doi.org/10.1093/biosci/biy063.

Peters, R.L., and Clark, M. (2018). In The Shadow of the Wall: Park II—Borderlands Conservation Hotspots on the Line. Washington, DC: Defenders of Wildlife.

Piña Osuna, F.M., and Poom Medina, J. (2019). Deterioro social y participación en el tráfico de drogas en el estado de Sonora. Frontera Norte 31(1), 1–20. doi: 10.33679/rfn.v1i1.1976.

Rahm, B.G., and Riha, S.J. (2014). Evolving shale gas management: Water resource risks, impacts, and lessons learned. Environmental Science: Processes and Impacts, 16, 1400–1412.

Ramos, J.M., and Reyes, M. (2006). Organizaciones no gubernamentales y la contaminación del aire en la frontera de Baja California, Mexico-California, Estados Unidos. Contexto y desafíos. Región y Sociedad, 18(37), 37–84.

Registro Agrario Nacional. (2019). Datos Geográficos Perimetrales de los Núcleos Agrarios Certificados, por Estado. Available: http://datos.gob.mx.

Rodríguez, J.L.S. (2016). Matrices indígenas del norte de México. Desacatos. Revista De Ciencias Sociales, 50, 172–183. doi: 10.29340/50.1548.

Sanchez, R., and Eckstein, G. (2020). Groundwater management in the borderlands of Mexico and Texas: The beauty of the unknown, the negligence of the present, and the way forward. Water Resources Research, 56(3), e2019WR026068. doi: 10.1029/2019WR026068.

Sanchez, R., Lopez, V., and Eckstein, G. (2016). Identifying and characterizing transboundary aquifers along the Mexico-US border: An initial assessment. Journal of Hydrology, 535, 101–119. doi: 10.1016/j.jhydrol.2016.01.070.

Sanders, K.T., King, C.W., Stillwell, A.S., and Webber, M.E. (2013). Clean energy and water: Assessment of Mexico for improved water services and renewable energy. Environment, Development and Sustainability, 15, 1303–1321. doi: 10.1007/s10668-013-9441-5.

Sandoval-Solis, S., Teasley, R.L., McKinney, D.C., Thomas, G.A., and Patiño-Gomez, C. (2013). Collaborative modeling to evaluate water management scenarios in the Rio Grande Basin. Journal of the American Water Resources Association, 49(3), 639–653.

Santamaría, A. (2012). Las Jefas del Narco. México: Grijalbo.

SCERP (Southwest Center for Environmental Research and Policy). (2004). Indigenous groups of Mexico’s Northern Border Region. In M. Wilken-Robertson (Ed.), The U.S.-Mexican Border Environment: Tribal Environmental Issues of the Border Region. SERP Monograph series No 9. San Diego, CA: San Diego State University Press.

Schur, E.L. (2017). Potable or affordable? A comparative study of household water security within a transboundary aquifer along the U.S.-Mexico border. Journal of Latin American Geography, 16(3), 29–58. doi: 10.1353/lag.2017.0051.

Scott, C.A. 2013. Electricity for groundwater use: Constraints and opportunities for adaptive response to climate change. Environmental Research Letters, 8. doi: 10.1088/1748-9326/8/3/035005.

Scott, C.A., Vicuña, S., Blanco-Gutiérrez, I., Meza, F., and Varela-Ortega, C. (2014). Irrigation efficiency and water-policy implications for river-basin resilience. Hydrology and Earth System Sciences, 18, 1339–1348, doi: 10.5194/hess-18-1339-2014.

Scott, C.A., Megdal, S., Oroz, L.A., Callegary, J., and Vandervoet, P. (2012). Effects of climate change and population growth on the transboundary Santa Cruz aquifer. Climate Research, 51, 159–170. doi: 10.3354/cr01061.

Scott, C.A., and Banister, J.M. (2008). The dilemma of water management ‘regionalization’ in Mexico under centralized resource allocation. Water Resources Development, 24(1), 61–74.

Secretaría de Medio Ambiente y Recursos Naturales and U.S. Enviromental Protection Agency (2012). Border 2020: U.S.-Mexico Environmental Program. Available: www.epa.gov/Border2020.

Secretaría de Turismo. (2019). Compendio Estadístico del Turismo en México 2019. Subsecretaría de Planeación–Dirección General de Información y Análisis. Available: https://www.datatur.sectur.gob.mx/SitePages/CompendioEstadistico.aspx.

Shah, T., Scott, C., and Buechler, S. (2004). Water sector reforms in Mexico: Lessons for India’s new water policy. Economic and Political Weekly, 39(4), 361–370. Available: http://www.jstor.org/stable/4414554.

Shaji, E., Santosh, M., Sarath, K.V., Prakash, P., Deepchand, V., and Divya, B.V. (2020). Arsenic contamination of groundwater: A global synopsis with focus on the Indian Peninsula. Geoscience Frontiers. doi: 10.1016/j.gsf.2020.08.015.

SIAP (Sistema de Información Agroalimentaria y Pesquera). (2019). Cierre de la Producción Pecuaria (1980–2019). Available: http://nube.siap.gob.mx/cierre_pecuario/.

______. (2018a). Anuario Estadístico de la Producción Agrícola. Available: https://nube.siap.gob.mx/cierreagricola/.

______. (2018b). Estadística de la Producción Agrícola de 2018. Available: http://infosiap.siap.gob.mx/gobmx/datosAbiertos.php.

Sietz, D., Lüdeke, M.K.B., and Walther, C. (2011). Categorisation of typical vulnerability patterns in global drylands. Global Environmental Change, 21(2), 431–440. doi: 10.1016/j.gloenvcha.2010.11.005.

Soden, D.L. (2006). At the Cross Roads: US / Mexico Border Counties in Transition. IPED Technical Reports, Paper 27. El Paso: University of Texas at El Paso, Institute for Policy and Economic Development (IPED). Available: http://digitalcommons.utep.edu/iped_techrep/27.

Solís, M., and Ávalos, M. (2017). Construyendo ciudadanía laboral en la frontera norte de México. Trabajo y Sociedad, 29, 287–305. Available: https://www.redalyc.org/articulo.oa?id=387352369015.

Spring, Ú.O. (2016). The water, energy, food and biodiversity nexus: New security issues in the case of Mexico. In H. Brauch, Ú.O. Spring, J. Bennett, and O.S. Serrano (Eds.), Addressing Global Environmental Challenges from a Peace Ecology Perspective (4th ed., pp. 113–144). Switzerland: Springer International Publishing. doi: 10.1007/978-3-319-30990-3_6.

Talmage, C.A., Pjawka, D., and Hagen, B. (2019). Re-examination of quality of life indicators in US-Mexico border cities: A critical review. International Journal of Community Well-Being, 2, 135–154.

USDA (U.S. Department of Agriculture). (2017). Census Agriculture Atlas Maps. Available: https://www.nass.usda.gov/Publications/AgCensus/2017/Online_Resources/Ag_Atlas_Maps/index.php.

U.S. Department of the Interior, Bureau of Reclamation. (2013). The Colorado River Basin Water Supply and Demand Study Fact Sheet. Available: https://www.usbr.gov/lc/region/programs/crbstudy/FactSheet_June2013.pdf.

______. (2016a). Rio Grande Basin: Reclamation managing water in the west. Chapter 7 in SECURE Water Act Section 9503(c) — Reclamation Climate Change and Water 2016. Available: https://www.usbr.gov/climate/secure/docs/2016secure/2016SECUREReport.pdf.

______.(2016b). Colorado River Basin. Reclamation managing water in the west. Chapter 3 in SECURE Water Act Section 9503(c) — Reclamation Climate Change and Water 2016. Available: https://www.usbr.gov/climate/secure/docs/2016secure/2016SECUREReport.pdf.

Varady, R.G., and Ward, E. (2009). Transboundary conservation in the borderlands: What drives environmental change? In L. Lopez-Hoffman, E. McGovern, R.G. Varady, and K.W. Flessa (Eds.), Conservation of Shared Environments: Learning from the United States and Mexico (pp. 17–25). Tucson, AZ: University of Arizona Press.

Vásquez-León, M., West, C.T., Wolf, B., Moody, J., and Finan, T.J. (2002). Vulnerability to climate variability in the farming sector: A case study of groundwater-dependent agriculture in southeastern Arizona. CLIMAS Report Series CL1-02. Tuscon, AZ: Climate Assessment for the Southwest, The University of Arizona.

Vidaurrázaga Obezo, F.R. (2003). Los cambios en la política agropecuaria y la propiedad social rural en la frontera norte. Estudios Fronterizos, 4(8), 163–188.

Vidic, R.D., Brantley, S.L., Vandenbossche, J.M., Yoxtheimer, D., and Abad, J.D. (2013). Impact of shale gas development on regional water quality. Science, 340(6134). doi: 10.1126/science.1235009.

Vietor, R.H.K., and Sheldahl-Thomason, H. (2017). Mexico’s energy reform. Harvard Business School Case 717-1,207. Boston, MA: Harvard Business School Publishing.

Villarejo, D. (2002). The health of U.S. hired farmworkers. Annual Review of Public Health, 24, 175–93. doi: 10.1146/annurev.publhealth.24.100901.140901.

von Lüpke, H., and Well, W. (2019). Analyzing climate and energy policy integration: The case of the Mexican energy transition. Climate Policy. doi: 10.1080/14693062.2019.1648236.

Weijermars, R., Sorek, N., Sen, D., and Ayers, W.B. (2017). Eagle Ford Shale play economics: U.S. versus Mexico. Journal of Natural Gas Science and Engineering, 38, 345–372. doi: 10.1016/j.jngse.2016.12.009.

Wiken, E., Jiménez Nava, F., and Griffith, G. (2011). North American Terrestrial Ecoregions. Level III. Montreal, Canada: Commission for Environmental Cooperation.

Wilder, M.O., Aguilar-Barajas, I., Pineda-Pablos, N., Varady, R.G., Megdal, S.B., McEvoy, J., Merideth, R., Zúñiga-Terán, A.A., and Scott, C.A. (2016). Desalination and water security in the US–Mexico border region: Assessing the social, environmental and political impacts. Water International, 41(5), 756–775. doi: 10.1080/02508060.2016.1166416.

Wilder, M., Garfin, G., Ganster, P., Eakin, H., Romero-Lankao, P., Lara-Valencia, F., Cortez-Lara, A.A., Mumme, S., Neri, C., and Muñoz-Arriola, F. (2013). Climate change and U.S.-Mexico border communities. In G. Garfin, A. Jardine, R. Merideth, M. Black, and S. LeRoy (Eds.), Assessment of Climate Change in the Southwest United States: A Report Prepared for the National Climate Assessment, (pp. 340–384). Washington, DC: Island Press. doi: 10.5822/978-1-61091-484-0.

Wilder, M., and Romero, P. (2006). Paradoxes of decentralization: Water reform and social implications in Mexico. World Development, 34(11), 1977–1995.

Wilder, M., Scott, C.A., Pablos, N.P., Varady, R.G., Garfin, G.M., and McEvoy, J. (2010). Adapting across boundaries: Climate change, social learning, and resilience in the U.S.-Mexico border region. Annals of the Association of American Geographers, 100(4), 917–928. doi: 10.1080/00045608.2010.500235.

Zuniga-Teran, A.A., Mussetta, P.C., Lutz Ley, A.N., Díaz-Caravantes, R.E., and Gerlak, A.K. (2020). Analyzing water policy impacts on vulnerability: Cases across the rural-urban continuum in the arid Americas. Environmental Development. doi: 10.1016/j. envdev.2020.100552.