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Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
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2

The Human-Earth System

The opening session of the workshop was chaired by William Rouse (Stevens Institute of Technology and the chair of the workshop steering committee). B.L. Turner II (Arizona State University and steering committee member) and Rouse gave presentations during this session, followed by discussion with the participants.

UNDERSTANDING POPULATION IN HUMAN-ENVIRONMENT RELATIONSHIPS: SCIENCE SHAPED BY WORLD VIEWS OR EVIDENCE?

B.L. Turner II
Gilbert F. White Professor of Environment and Society,
School of Geographical Sciences and Urban Planning,
Arizona State University

B.L. Turner II began his presentation by explaining that he would address the history of how population and carrying capacity have been applied to impacts on the Earth system and human well-being. He pointed out that there is little debate over the data and empirical evidence, especially in regard to population and environmental change; the debate revolves around the interpretation of those data. Interpretations, he said, say as much, if not more, about the world views of the interpreter as they do about the data and analytics.

Turner described three foundational models of the human-envi-

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

ronment relationship during the course of his presentation—Malthus, Boserup, and Geertz—as well as two contemporary viewpoints—Cassandra and Cornucopia—linked to them. (See Box 2-1 for a description of each model and viewpoint.) He began with the model of Malthus. Thomas Malthus (1798) attempted to explicate the repercussions of the population growth of cities resulting from a huge influx of rural peasants in the late 18th century in the United Kingdom and focused on how this rapid urban growth could lead to negative outcomes (crises) for society at large. He said that there would be discrepancies between the growth rates of the population and of food supply sufficiently large to lead to a crisis, thereby inferring that technology is outside the demand-production system. While a Malthusian crisis is hypothetically possible, Turner stated that it is difficult to find in the historical evidence a “true” Malthusian

BOX 2-1
Models and Viewpoints of Human-Environment Interactions

Malthus Model. Thomas Malthus postulated that population growth, when unchecked, will surpass the food ceiling and generate a negative impact on the human-environment relationship, i.e., demand leads to crisis (Malthus, 1798).

Boserup Model. Ester Boserup stated that population increase, and the pressures that result from it, will increase the food ceiling; i.e., demand stimulates growth (Boserup, 1965).

Geertz Model. Clifford Geertz postulated the theory of agricultural involution in which a unit of labor (input) yielded a unit of production, a case of stagnation in which the population is fed but surpluses are absent (Geertz, 1963).

Cassandra (also referred to as neo-Malthusian). The Cassandra viewpoint is concerned about stresses from human demands placed on environment and resources over the long run. The Cassandra model accounts for all factors generating demand, not just population; it includes such drivers as affluence and entitlements (Dasgupta and Ehrlich, 2013; Ehrlich and Holdren, 1988). Most global indicators signal major declines in the states and function of the Earth system.

Cornucopia (also referred to as Technology Fix or Pollyanna). The Cornucopian viewpoint states that increases in population (demand) lead to technological innovation and substitution. This in turn leads to an increase in access to and decline in relative price of materials (Simon, 1988). Almost all indicators of human well-being have increased, but there is some recognition of the negative consequences on the environment.

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

BOX 2-2
What Is Carrying Capacity?

In ecology, carrying capacity is the maximum number of individuals of a species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available. In population biology, carrying capacity is defined as the environment’s maximal load.

Carrying capacity in regard to human beings refers to the maximum population size that the use of environment can sustain indefinitely while providing an appropriate supply of food, water, habitat, and other natural resources; it also encompasses many additional factors, such as governance, technology, and knowledge systems.

SOURCE: Adapted from presentation by B.L. Turner II.

crisis. Constraints on food production may be one potential factor that could escalate a crisis (i.e., famine), but access to food (i.e., entitlements) proves to be more robust in explaining famine and other crises. Turner noted that W.A. Dando (1980) put forward the idea that humans induced food shortages in the food supply system because of variables unrelated to production level. Dando’s work was, however, eclipsed by the development of entitlement theory (famine linked to entitlements) by Sen (1982), who received the Nobel Prize in economics for this work.

Turner then discussed carrying capacity (defined in Box 2-2), noting that its antecedents are found in the works of Malthus but modern development and use of the term emerges largely from the ecology of nonhuman biota. He pointed out that the more the environment is manipulated or constructed by people, the more difficult it becomes to apply the concept of carrying capacity because technology and management are important determinants of sustainable production. It is possible that carrying capacity might be applicable at the global level; hypothetically, the Earth system could be treated as a “closed” human-environment system with the single exogenous input of incoming solar radiation. In this view, human appropriation of the world’s net primary productivity (HANPP),1 which has been estimated to have been between 23-45 percent around the year 2000, serves as a limiting factor (Haberl et al., 2007). Turner stated that beyond such hypotheticals, carrying capacity is useful only as a heu-

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1Human Appropriation of Net Primary Productivity (HANPP) is an indicator of the amount and intensity of land use by humans. It is measured as a percentage of total potential vegetation, which in turn is a measure of the incoming solar radiation.

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

ristic device, and he cautioned against calculating specific measures for it with regard to human-environment systems. He told the workshop that carrying capacity has been largely abandoned as a concept in social and policy sciences.

Turner then turned to the Boserup model, which was initially developed to explain subsistence farmers’ responses to land pressures occasioned by population increases, but it was ultimately expanded to agricultural systems in general. Ester Boserup (1965) explained that the level of agricultural intensification (food production) was not set by some technological maximum but by the level of land pressure confronting farmers. As these land pressures increase, so does intensification, which raises the food ceiling. This process can take place because changes to techno-managerial inputs are considered as coming from within the system, rather than from outside (as in the Malthusian view). This model has been empirically demonstrated in many studies (e.g., Pingali et al., 1987), including production systems that are transitioning from subsistence to commercial farming.

Turner then briefly explained that the Geertz model (Geertz, 1963) is essentially a state of equilibrium; the change in output is equal to the change in input. This is also known as agricultural involution.

Are Malthus and Boserup, and by comparison, the Cassandra and Cornucopian viewpoints that draw on them, irreconcilable? Turner explained that the Boserup model, often considered to be an “anti-Malthusian” thesis, was intended to expand upon themes raised by Malthus while searching for an understanding in which economic growth rather than crises might follow from increases in population. He noted that demographer and economist Ronald D. Lee has demonstrated that Malthus and Boserup could, to a certain extent, be reconciled (Lee, 1986). Using phase-space models, Lee concluded that in Boserup’s model, space is the limiting condition, while Malthusian forces tend to view the system as the limiting condition. Turner and Ali (1996), in turn, have traced how increasing population and other demand factors push population-environment relationships into Boserup-, Geertz-, and Malthus-like conditions, in which the Boserup conditions tend to prevail in most systematic examinations. Understanding agricultural change sufficiently to predict outcomes, however, has proven difficult because human-environment systems operate as complex adaptive systems.

Turner then turned to a comparison of the Cassandra and Cornucopian viewpoints of population and environment as world views linked to Malthus and Boserup. He pointed out that the history of the human species is marked by both increasing the material well-being of humankind and increasing changes and degradation of the environment. The Cassandra view focuses on the consequences for the environment, whereas the

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

Cornucopian view focuses on human well-being. These foci, and drawing on either Malthus-or Boserup-like arguments, lead to different interpretations of the base relationship in question.

The Cassandra viewpoint (Ehrlich and Holdren, 1988) begins with the notion that the environment is ultimately unable to sustain services provision to humans under conditions of long-term degradation. It is guided by the IPAT equation (identity):

I = P · A· T

in which I = human impact on the environment, P = population, A = affluence, and T = technology. Turner argued that over the long term and at the global scale, resource use and environmental change correlate with the PAT variables more than any others; he said that few people question the use of IPAT as an identity. It is often used to infer causation, however, and this use is hotly debated and criticized as being too superficial, diverting attention from deeper causes of the observed correlations. And, at meso- to micro-spatiotemporal scales, Turner observed, PAT variables commonly do not track well with environmental change.

Turner then explained the Cornucopian view, which holds that increasing population leads to innovation and techno-managerial change, reflected in resource substitution (for example, fiber optics for copper wiring). As a result, over time the access to and production of raw materials increases in efficiency, lowering prices to the benefit of society. Because it is focused on resources and substitutes for them, the Cornucopian view de-emphasizes damages to the environment and emphasizes innovative ways to deal with damages.

Turner went on to discuss “the bet” made in 1980 between Paul Ehrlich and Julian L. Simon (the champions, in the public view, of the Cassandra and Cornucopian viewpoints, respectively) and the subject of the book The Bet (Sabin, 2013), to illustrate divergences in the two views of population and environment. Simon publicly bet that Ehrlich could pick any five minerals and that 10 years later, after considerable population growth worldwide, they would all be cheaper in constant dollars (Cornucopian view) as opposed to more expensive (Cassandra view). Simon won the bet, although subsequent economic analysis showed that had the period of assessment been other than the particular decade 1980 to 1990, Ehrlich would have won the majority of the time. In fact, Turner argued that the bet was a stunt, because market force complexities involve much more than simple demand emanating from population numbers. Simon wagered that over the following 10 years, all indicators of human well-being would increase. Ehrlich, together with eminent climatologist Steve Schneider, countered that all indicators of the state of the environ-

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

ment would decrease (Sabin, 2013). Turner reasoned that this dichotomy in the new proposed wagers not only illuminated distinctions in the two world views, but also it marked the reshaping of the Cassandra viewpoint to focus less on resource economics and more on the condition of the environment and Earth systems’ capacity to function as the sustainable biosphere that life (including human life) requires.

Turner pointed out that the two world views still persist in population-environment and resource assessments discussions. Cassandra followers treat population as one important factor among others that generate demand on nature; this viewpoint is increasingly observable in such global issues as climate change, loss in biodiversity, and possible planetary boundaries. On the other hand, Cornucopian-like assertions often underpin the positions of, for example, climate change naysayers or advocates of technological capacity to confront climate change through geoengineering. These positions in public debate have become politicized, as documented in The Bet (Sabin, 2013).

Turner ended by saying that emphasis in analysis and discussion on the role given to human population size, food supply, or any other environmental resource or service depends on the world view of the interpreter as much as it does on the actual evidence. Population is embedded within a complex system of factors that includes environmental change, food production, and sustainability. He stated that the world revisits these questions on decade-plus time scales; the questions are never resolved, but each time, new information is added.

EARTH AS A SYSTEM

William Rouse
Alexander Crombie Humphreys Chair in Economics of Engineering,
School of Systems and Enterprises, Stevens Institute of Technology

William Rouse began by explaining that he approaches the sustainability question from an engineering perspective, and he seeks to understand the effect of population on the Earth using systems engineering principles. He said his workshop presentation goals were to better understand the impact of the human population on the Earth and how population interacts with other attributes of the Earth, and he posed four questions to participants:

  1. How does the Earth respond to population changes? What do we, as researchers, know and still need to learn about its response?
  2. What can we, as a general population, do to influence the future of the Earth?
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
  1. What information can be leveraged from the physical, social, and behavioral sciences communities?
  2. What should be the research agenda for activities that would have an impact and enhance our ability to understand and act?

Rouse stated that the Earth is a single self-regulating system that exhibits multiscale temporal and spatial variation.2 He pointed out that human activities are influencing the Earth’s environment in a manner equivalent to the greatest forces of nature. He stated that there are cascading effects throughout the system, and system dynamics are characterized by critical thresholds and abrupt changes. Human activity on Earth may be shifting the Earth system to alternative modes of operation; this shift may be irreversible and may result in a planet less hospitable to humans. The Earth has moved well outside the realm of natural variability when considering environmental factors. Rouse stated that the Earth can even now support more than 10 billion people, but the quality of the lives of those people is a concern. He cited Glaeser (2011), who described how 10 billion people would fit within the state of Texas if the entire state were covered in townhomes. However, Rouse asked what the quality of life would be, and what impact those people would have on Earth.

Rouse explained that the Earth can be considered as a collection of different systems on different scales. (See Figure 2-1 for a schematic.) Loosely speaking, four systems are interconnected: environment, population, industry, and government. In this notional model, population consumes resources from the environment and creates by-products. Industry does the same, but it also produces employment. The government collects taxes and produces rules; the use of the environment is influenced by those rules. Each system component has a different associated time constant. In the case of the environment, the time constant is decades to centuries. The population’s time constant can be as short as a few days. Government’s time constant may be a bit longer, thinking in terms of years. Industry is longer still, on the order of decades. These systems can be represented at different levels of abstraction and/or aggregation, he said, although a hierarchical representation does not capture the fact that this is a highly distributed system, all interconnected. It is difficult to solve any one part of the problem, because it affects other pieces. Rouse pointed out that by-products are related to population size, so one way to reduce by-products is to moderate population growth. Technology may help to ameliorate some of the by-products and their effects, but it is also possible

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2See http://www.colorado.edu/AmStudies/lewis/ecology/gaiadeclar.pdf for more information [April 2014].

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

img

FIGURE 2-1 A schematic diagram of the Earth as a system, looking at four primary system components (population, environment, industry, and government).
SOURCE: Rouse presentation, slide 12.

that technology could exacerbate the effects. Clean technologies lower byproduct rates but tend to increase overall use, for instance.

Rouse then defined a “system of systems” as a collection of purposeful systems, each one of which is designed to do something different from the overall intent of the collection. The end result of a system of systems is a new, more complex system whose performance can be greater than the sum of the individual constituents. Each constituent system in the collection has its own agenda. In the Earth system, population and government are the sentient parts of the system. The environment, Rouse pointed out, is nonsentient—one cannot influence the environment through persuasion. How, therefore, can the alignment of goals among constituent systems be motivated? Rouse stated that it is important to identify information and incentives so that short-term benefits from lower-level system activities improve the long term and support long-term system goals.

He then pointed out that support for decisions will depend upon the credibility of the predictions of behavior, at all levels in the system. He stressed the importance of shared “space value” and “time value” discount rates: Consequences that are closest in space and time matter the

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

most, and attributes more distributed in time and space are discounted accordingly. He also pointed out that people will also try to “game” the system. The way to deal with that tendency is to make the system transparent enough to understand the game being played. Sometimes, he said, gaming the system is actually innovation.

Rouse identified three elements that he said are necessary to move forward:

  1. Information sharing: Broadly sharing credible information helps all stakeholders understand the situation.
  2. Incentive creation: Development of long-term incentives will enable long-term environmental benefits while maintaining short-term improvements.
  3. An experiential approach: An interactive visualization of models will enable people to see the results. (Rouse referred to this as a “policy flight simulator.”)

He noted people have difficulty buying into a model until they can take the controls, try options, and see the results (Rouse, 2014).

DISCUSSION

A participant asked about Rouse’s proposed “policy flight simulator,” asking whether an inventory of models could be shared. Rouse responded that there is an effort to compile such an inventory. Problems arise when the models cannot be audited to see how they work. Those models that are explicitly defined and published in the formal literature are well suited to be part of an inventory, but others cannot be inspected properly and they may not be suitable for inclusion. It is also difficult to develop compatible data representations.

The discussion then turned to tensions between the Cassandra and Cornucopian models. Rouse pointed out that the argument is less about the merits of the two approaches and more about the consequences of agreeing or finding middle ground. Turner agreed that the literature shows far less about the reconciliation of the two positions than their differences. He said that older researchers often developed an initial position in the discussion and now feel compelled to defend their decisions. Younger researchers, on the other hand, have more incentive to explore reconciliation. Turner postulated that Cassandra and Cornucopian supporters would not disagree on the factual basis of operation, as they have the same (reliable) population and growth numbers. The difference is that one group classifies them as a problem, the other as an opportunity.

In a discussion of the IPAT model, a participant pointed to increasing

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×

analytical work that shows statistically significant relationships between environmental and societal factors. However, in the participant’s view, this work may not resonate with social scientists who are more interested in the causes of increases in population, affluence, and technology development. Further, the IPAT model assumes that the population is homogeneous, when in fact consumption and vulnerability vary widely within a population. The participant commented that the picture becomes much richer when considering heterogeneity. For example, populations with greater levels of education are less vulnerable to environmental changes.

Several participants discussed social justice. The conversation began with a discussion of technology adoption. Rouse explained that the adoption of an innovative technology is a highly selective process, and those who embrace a technology or innovation first will experience it very differently from subsequent adopters. He posited that early adopters tend to receive the greatest benefit. While this leads to an aggregate increase in human well-being, ultimately it will also lead to increases in inequality. He suggested that the nature of innovation and its adoption be reconciled, using electricity as an example: Its technology adoption took many decades in the United States and required a huge change in infrastructure to have an impact on the population as a whole. He suggested electricity as an example in which near-term technology benefits those who least need the improvement. Turner then linked this to social justice. He proposed developing a charter vision about social justice and whether it is needed to move forward. Rouse pointed out the possibility that improvements to social justice could have negative environmental consequences.

The discussion also focused on the topic of metrics. A participant said that the world community tends to use gross domestic product (GDP) and life expectancy as indicators of success. A different set of metrics may be able to capture the intent, rather than just measuring the throughput. One person recommended a “gross national happiness” product. Turner pointed out that metrics are critical to the discussion to assess different options, but said he was not certain if a “right” metric exists. Another participant said that it would be important to measure not just current well-being, but also the impact on future well-being to understand how the present may be compromising or improving the future. Turner postulated that it may be important to understand the structure and function of tipping points and planetary boundaries and to have a measure of a tipping point time scale. Robert Hauser (National Research Council) informed the group that a National Research Council committee released a report on measuring well-being, with potentially useful information on metrics (National Research Council, 2013).

Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 15
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 16
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 17
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 18
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 19
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 20
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 21
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 22
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 23
Suggested Citation:"2 The Human-Earth System." National Research Council. 2014. Can Earth's and Society's Systems Meet the Needs of 10 Billion People?: Summary of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/18817.
×
Page 24
Next: 3 Challenges to the Earth System: Character and Magnitude of the Challenges in 2050 »
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The Earth's population, currently 7.2 billion, is expected to rise at a rapid rate over the next 40 years. Current projections state that the Earth will need to support 9.6 billion people by the year 2050, a figure that climbs to nearly 11 billion by the year 2100. At the same time, most people envision a future Earth with a greater average standard of living than we currently have - and, as a result, greater consumption of our planetary resources. How do we prepare our planet for a future population of 10 billion? How can this population growth be achieved in a manner that is sustainable from an economic, social, and environmental perspective?

Can Earth's and Society's Systems Meet the Needs of 10 Billion People? is the summary of a multi-disciplinary workshop convened by the National Academies in October 2013 to explore how to increase the world's population to 10 billion in a sustainable way while simultaneously increasing the well-being and standard of living for that population. This report examines key issues in the science of sustainability that are related to overall human population size, population growth, aging populations, migration toward cities, differential consumption, and land use change, by different subpopulations, as viewed through the lenses of both social and natural science.

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