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Hydrologic Effects of a Changing Forest Landscape 2 Forests and Water Management in the United States Forests and water are inextricably connected. Forests process the water that sustains agriculture, human settlements, and ecosystem functions. Forests vary due to differences in geography; ecology; and social, economic, and land use histories. Throughout the United States, forests are managed for a range of objectives and goals, using a wide variety of forest management practices, which are regulated by diverse laws at the federal and state levels. Like forests, water resources are managed to achieve multiple objectives and are constrained by various laws. These laws and institutions fragment the management of forests and water, despite their close physical and biological connections. The variations in forest types, regions, objectives, and management, combined with the fragmented management of forests and water, creates a new body of emerging issues for forest and water managers. This chapter describes current practices, past legacies, and future issues related to how forests are used and managed in the United States. It describes the regional differences in the relationships between forests and water; outlines forest management and water resource management objectives and practices; and examines how ownership patterns, laws, regulations, and institutions govern the use and management of forests and water. Finally, this chapter introduces the emerging issues for water and forests relevant to forest hydrology science and management in the twenty-first century. FORESTS AND WATER IN THE UNITED STATES The forests of the United States are diverse. They differ in regional characteristics and values, species composition, and forest types (Figure 2-2) and in ownership and management objectives. Forests account for 33 percent of all U.S. land area (Figure 2-3), covering about 750 million acres (300 million hectares) (Powell et al., 1993; Smith et al., 2004). Of this, 57 percent are privately owned, and the remainder is public forest. Ten percent of U.S. forests cannot be harvested for commercial timber because they are in areas designated as wilderness, parks, and other legally reserved classifications. Although the federal government owns or manages land in all 50 states, the vast majority of federal forest land is concentrated in 13 western states (Figure 2-3). The geography, ecology, economics, and land use histories of forests differ markedly by region (Smith et al., 2004). More than half of forest area in the United States lies east of the Mississippi River (Figure 2-1a). In eastern forests, precipitation exceeds evaporation and transpiration on an annual basis, provid-
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Hydrologic Effects of a Changing Forest Landscape FIGURE 2-1 Forest cover in the United States. SOURCE: Map created by Catchment Research Facility, University of Western Ontario.
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Hydrologic Effects of a Changing Forest Landscape FIGURE 2-2 Map of forest vegetation types for the United States. SOURCE: USDA Forest Service.
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Hydrologic Effects of a Changing Forest Landscape FIGURE 2-3 Federal lands in the United States. SOURCE: Reprinted, with permission, from Regional Economics Assessment Database (2002). Copyright 2002 by the Regional Economics Assessment Database.
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Hydrologic Effects of a Changing Forest Landscape ing abundant water supplies (Figure 3-2a). Northern and northeastern forests contain a mixture of broad-leaved (deciduous, hardwood) and conifer (evergreen, softwood) tree species, and slightly more than one-half of southern forests are conifer species (Figure 2-1b). The vast majority of eastern forests are second-growth that regenerated after land conversion to agriculture one to three centuries ago, followed by subsequent farm abandonment (Williams, 1989; Foster and Aber, 2004). More than 85 percent of the area of eastern forest is privately owned (Smith et al., 2004); compare Figures 2-1a and 2-1c. The remaining half of forest area in the United States is located in the Rocky Mountain, southwestern, Pacific Coast, and Alaska regions (Powell et al., 1992; Smith et al., 2004) (Figure 2-1a). Many western forests have been shaped less by human disturbances than by natural disturbance, especially wildfire. Almost three quarters of western forests are on public lands (Smith et al., 2004; compare Figures 2-1a and 2-1c). Western forests are dominated by conifer species, but aspen, oak, and riparian forests are important broad-leaved components (Figure 2-1b). Regional differences lead to contrasting relationships between forests and water in the West compared to the East. Precipitation in the West is strongly related to elevation, and at higher elevations most precipitation occurs as snow. In the West, most precipitation falls on forested mountains that are sparsely populated and on public lands, and these headwater areas provide the source water for public and private water supply systems that store, transfer, and deliver water to farms, people, and industry. In the East, headwater sources are often on private land, closer to end users, more densely populated, and containing a wider range of land uses than in the West; interbasin transfers are less common. As a result, issues involving forests and water in the West often focus on allocation of scarce water and involve federal agencies, whereas in the East, issues have focused on pollution and involve private as well as public land owners. MANAGING FORESTS AND WATER Forests and water are connected by physical and biological processes, so the management of forests affects the quantity, quality, and timing of water (Anderson et al., 1976; Waring and Schlesinger, 1985; Ice and Stednick, 2004). Federal laws and forest ownership influence the goals and objectives of forest and watershed management, which in turn determine management practices. Forest and water management is fragmented among many laws and institutions. Forest Management Objectives and Practices Forest management applies biological, physical, social, economic, and policy principles to meet specific goals and objectives. Forest management is a balancing act among the various uses and products. Forest management objec-
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Hydrologic Effects of a Changing Forest Landscape tives can encompass producing timber for wood products; protecting or enhancing flows of high-quality water; providing herbage (forage) for livestock or other herbivores; enhancing food, cover, and water for wildlife habitats; or creating landscapes for outdoor recreational values. Additional forest management objectives include sustaining forest ecosystems; preventing or mitigating wildfires or insect outbreaks; preserving habitat for native species and combating the spread of invasive species; and conserving biological diversity. Historically, many forest management practices have centered on timber management. Timber management encompasses silvicultural treatments to establish and sustain wood production; protection against or control of wildfire occurrences, insect infestations, and diseases; and of course, harvesting of merchantable trees in a forest. Silviculture, forest protection, and timber harvesting involve a number of actions that individually and cumulatively can modify water quantity, quality, and timing. Silvicultural practices include selection of species and genotypes, site preparation, planting, drainage, fertilization, watering, herbicide application, and thinning to maximize the growth of the most desirable species. Forest protection practices include fuel reduction treatments such as overstory thinning, understory removal, or prescribed fire; construction of fire breaks and fire lines; applications of soil, water, or fire-retardant chemicals; application of insecticides and fungicides; and introduction of biological control agents. Timber harvest practices include selection of the rotation age, which determines the ranges of forest ages; road and trail construction, including road drainage systems such as culverts; felling and skidding of logs to landings; and movement of logs, usually by trucks, to timber mills for processing. A number of laws and regulations govern the lands managed by the U.S. Forest Service. These laws stipulate how the effects of forest management on watersheds must be addressed in management plans and actions. The 1960 Multiple Use and Sustained Yield Act (16 USC 525-531) recognized that national forests are important watersheds. Water diversions and associated ditches, pipelines, and canals are authorized on national forests through the issuance of special use permits or the granting of rights of way. Since the 1970s, the Forest Service also has appropriated water resources and asserted water rights to protect instream flows for fish habitat and outdoor recreation (Wilkinson and Anderson, 1985). Public concern about adverse effects of clear-cutting for timber production led to passage of the National Forest Management Act in 1976 (16 USC 1604(g)(3)(E)). In management plans required by the Act, the Forest Service must ensure that timber is harvested only where soil, slope, or other watershed conditions will not be irreversibly damaged. The act also requires that timber harvest plans protect stream systems and stream banks, lakes and shorelines, wetland systems, and other bodies of water; prevent detrimental alterations in water temperatures; and limit sediment contributed to stream channels (see Box 2-1). States, municipalities, and counties own and manage forestlands for various goals and objectives, and they often give broad discretion to a specified organi-
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Hydrologic Effects of a Changing Forest Landscape BOX 2-1 Aquatic Conservation Strategy in the Northwest Forest Plan Many national forests have adopted specific policies to protect water and watersheds beyond the basic requirement of the National Forest Management Act of 1976. The Aquatic Conservation Strategy addresses water and watershed protection as part of the Northwest Forest Plan (USDA and USDI, 1994), which governs timber harvest on federal lands in the Pacific Northwest. This strategy is a part of the land and resource management plans for each national forest and Bureau of Land Management district in the area. Unlike conservation and management plans of the past, the Aquatic Conservation Strategy addresses the entire riparian ecosystem over a large landscape. It seeks to prevent further degradation of aquatic ecosystems and to restore and maintain habitat and ecological processes responsible for creating habitat over broad landscapes, as opposed to looking at the effects of individual timber sales (USDA and USDI, 1994). Implementation of the Aquatic Conservation Strategy (ACS) illustrates the challenge of managing forestlands at a watershed scale. Developers of the Aquatic Conservation Strategy recognized that periodic disturbances would occur over the many years needed to restore ecological processes and that short-term disturbances were critical for long-term aquatic ecosystem productivity. However, they did not expect all watersheds to have favorable conditions for fish habitats at any particular time. Implementation of the ACS brought major changes to the way the affected land management agencies viewed and managed aquatic resources and watersheds; the ACS changed the focus from small spatial scales (i.e., project areas) to larger landscapes. The implications of these changes have not been recognized fully or appreciated by the land management and regulatory agencies or the general public, and it has been difficult to implement this underlying scientific premise into forest plans (Reeves et al., 2006). Environmental plaintiffs used the objectives of the Aquatic Conservation Strategy to challenge individual timber sales. The forest plans were amended in 2004 to clarify that larger watersheds and long-term time frames are the appropriate level to evaluate progress toward these objectives, not specific projects (USDA et al., 2004). This decision was itself successfully challenged in Pacific Coast Federation of Fishermen’s Association v. National Marine Fisheries Service (U.S. Dist. LEXIS 23645 ), which underscores the difficulty of successfully moving to landscape-scale analysis. zation or agency to manage the lands (Rice and Souder, 1998). For example, laws direct state forests in California to be managed for maximum sustained production of high-quality forest products, while giving consideration to values for outdoor recreation, watershed, wildlife, range and forage, fisheries, and aesthetic enjoyment. Some states have independent certification to manage their forests sustainably, meeting watershed protection standards beyond those required by state law. Municipal or regional water authorities frequently own or manage forestlands to protect and control the watersheds from which they get their drinking water. The scale of management of these lands varies greatly from medium-sized towns that own and manage the watershed immediately surrounding their reservoirs to large urban areas that own reservoir lands and manage other lands in their larger watersheds through agreements designed to protect water quality (Boxes 2-2 and 2-3).
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Hydrologic Effects of a Changing Forest Landscape Private forestlands are managed to meet their owners’ goals and objectives. Private forest industry companies generally manage their lands to produce timber, pulp, or other wood products. Nonindustrial private forest landowners, including small family forests and Indian tribes, often manage their forests for a wider range of purposes than producing wood products, such as maintaining wildlife habitat conditions or providing opportunities for outdoor recreational experiences. A major shift in forestland ownership in the private sector and a concomitant change in management goals and objectives are occurring among large vertically integrated forest product companies. The passage of the Employee Retirement Income Security Act in 1974 encourages institutional investors to diversify their portfolios, which encouraged many industrial landowners to sell portions of their forestlands to timberland investment management organizations or real estate investment trusts. Instead of traditional forestry goals and objectives of supplying wood products, the primary management goal of these new kinds of investors is their own financial return. This shift in ownership accelerated in the 1990s with major restructuring in the forest products industry in response to increasing globalization as companies consolidated to become larger or even transnational. Forestry, therefore, has emerged as a new asset opportunity for investors rather than an asset owned by manufacturing companies and small woodlot owners (Sande, 2002). Watershed Management Objectives Watersheds are managed to provide sustained supplies of high-quality water for human uses (Heathcote, 1998). Cities and towns depend on watersheds, many of which are forested, for their water supplies. Many watersheds that provide drinking water supplies include forests that are actively managed (e.g., Dissmeyer, 2000; NRC, 2000). Many controversies arise when forest management in municipal watersheds is viewed as being in conflict with watershed management goals (Boxes 2-2 and 2-3). BOX 2-2 Forest and Watershed Management Conflicts for Oregon’s Largest Cities Like many communities in the Pacific Northwest, the cities of Portland, Eugene, and Salem, Oregon, depend on water supplies from surface water that originates in watersheds on which extensive forest management activities occur. These watersheds are predominantly forested, with federal lands in the upper basin above flood protection reservoirs and a mixture of private and state lands downstream of the reservoirs but above the municipal water intakes. Forest management activities on these watersheds include road building, timber harvesting, post-harvesting chemical treatments, fire suppression, and firefighting with flame retardants. The following examples illustrate the complex challenges faced by water managers in these forested watersheds.
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Hydrologic Effects of a Changing Forest Landscape In Portland, the challenge has been to reconcile timber management and water supply protection objectives. Since the early 1900s, the city of Portland has obtained a major source of unfiltered drinking water from the Bull Run watershed, which drains the Mount Hood National Forest. The USFS implemented austere restrictions on the uses of and access to the watershed in order to protect the city’s water source. Public entry to the watershed was prohibited, roads were paved to prevent sediment production, and even horses that were used for logging in the watershed were equipped with diapers. At the same time that public entry was restricted, the U.S. Forest Service continued its patch clear-cutting and salvage logging operations in the watershed from the 1950s to the 1980s, which caused tremendous public outrage. This outrage was exacerbated after extreme windstorms blew down forests along clear-cut edges in 1973; the USFS resumed salvage practices on the windthrown trees, creating new clear-cut edges; and further windstorms in 1983 blew down additional trees along the fresh clear-cut edges (Sinton et al., 2000). Public controversy over apparent risks to Portland’s water supply led to unilateral cessation of clear-cut logging in the watershed in the late 1980s. In Salem, the management challenge was a conflict between management objectives. The North Santiam is the sole source of drinking water for the city of Salem. In a major flood in February 1996, high turbidity in the river from private forestlands downstream of the federally managed reservoir caused the city of Salem to shut down its water supply system. Turbid water also was caught and held in the federally managed flood control reservoir in the upper basin, which drains federal forestland. Over a week following the flood, water releases from the flood control reservoir maintained high turbidity levels and kept Salem’s water supply shut down (Bates et al., 1996; GAO, 1996). In this case, federal management of a reservoir for one objective (flood control) conflicted with the achievement of another objective (water quality). In the city of Eugene, the challenge was incompatible management objectives. The McKenzie River is the sole source of unfiltered drinking water for Eugene. In the early 2000s, fisheries biologists judged that late summer releases of cold water from reservoirs in the McKenzie River drainage above Eugene were having deleterious effects on native fish populations. The U.S. Forest Service undertook a project to retrofit one of the flood control reservoirs in the basin with a temperature control tower in order to provide water releases whose temperatures would be suitable for downstream fish populations. During construction of the tower, the reservoir was drained, and sediment was mobilized within the lowered pool. This sediment contributed turbidity to the McKenzie River for a period of several months. In this case, federal management of a reservoir to meet one objective (water quality-temperature) compromised another objective (water quality-sediment). BOX 2-3 Forest and Watershed Management Conflict in Massachusetts In contrast to western U.S. cities, most cities in the northeastern United States derive their municipal water supplies from a combination of private and state-owned land. The Boston metropolitan area derives about 90 percent of its safe yield (300 million gallons per day) as an unfiltered water supply from the Quabbin Reservoir (http://www.mass.gov/dcr/waterSupply/watershed/water.htm). The Massachusetts Division of Water Supply Protection owns and manages 65 percent of the 486 km2 watershed; other public forests account for 7 percent and private forestland accounts for 24 percent of the total area. Conflicts arise over forest management in the Quabbin between groups that favor active forest management for timber production, wildlife habitat, and other values, versus conservation groups that favor forest preservation and natural disturbances. On the one hand, although many activities are strictly regulated in the watershed, the Massachusetts
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Hydrologic Effects of a Changing Forest Landscape Division of Water Supply Protection has practiced active forest management in 186 km2 of the Quabbin Forest since the early 1940s, harvesting about 4 to 8 km2 per year. Management practices include timber harvest aimed to protect forests from episodic disturbances (e.g., hurricanes, severe ice storms) and chronic disturbances (e.g., insect and disease outbreaks, browsing by white-tailed deer, atmospheric deposition). Forest management in the 1950s and 1960s focused on reforestation (with nonnative red pine) following the 1938 hurricane, which blew down trees in many parts of the watershed (Foster and Boose, 1992). In the mid-1960s some red pine stands were converted to grassland maintained by mowing and prescribed burning aimed to augment water yield. Since 1985, silviculture, forest protection, and timber harvest practices have aimed to diversify the vertical structure, age class distribution, and species composition of the forest. On the other hand, conservation groups and forest ecologists in Massachusetts, including scientists at the Harvard Forest, advocate forest preservation for wilderness values in the Quabbin watershed. The 235 km2 Quabbin Forest is the largest undeveloped forest area in Massachusetts. Conservation groups in the state have called for a cessation of logging to create a large “wildland” forest area (Foster et al., 2004). The Division of Water Supply Protection acknowledges that erosion from roads constructed for access to timber harvest and skid roads is a potential problem associated with timber harvest (Quabbin, 2007). Nevertheless, concerns about forest management effects on water quantity or quality appear to be secondary to arguments about forest conservation versus timber production in the debate over forest management in the Quabbin reservoir. SOURCE: Quabbin (2007). Fragmented Management for Forests and Water Forest management occurs in the context of complex and highly fragmented laws, regulations, and social institutions that deal with land and water use. Water management also can be fragmented along its path from the precipitation falling on the land, to water flowing through stream systems, to human or other uses of the water and ultimately to the ocean. Since John Wesley Powell’s Report on the Lands of the Arid Region of the United States (Powell, 1889), water researchers and policy makers have recommended an integrated approach to watershed management that organizes land and water management around hydrologic systems. Integrated management of forests and water at the watershed level involves many different public agencies, landowners, and a diversity of public and private stakeholder interests. Responsibilities and interests include management for drinking water supplies, flood control, reservoir operations for hydropower production, water for irrigation, fish and wildlife, and outdoor recreation. However, forest and water management remain fragmented (WWWPRAC, 1998; NRC, 1999). Fragmentation of ownerships and interests combined with fragmented responsibility for managing and regulating forest management has made integrated management of forests and water at the watershed scale virtually impossible (Arnold, 2005). Institutional fragmentation exists at multiple levels, ranging from the goals of the laws, regulations, and institutions; to land ownership responsibilities and interests; to specified missions of the agencies responsible
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Hydrologic Effects of a Changing Forest Landscape for management. Institutional regimes governing water use, water quality, and forestland use often evolved separately and frequently have different goals and objectives. Water use laws, regulations, and institutions usually focus on the use of water out that has been removed from water bodies, rather than the roles of water in streams, lakes, and other bodies of water. Water quality laws, regulations, and institutions are structured to help stakeholders control the impacts of land uses, including the effects of forest use and management practices on the quality of available water resources. Together, institutions and regulations specify how forests will be used and managed, setting some forests aside for timber production, some for watershed protection, and still others for preservation. Fragmentation of administrative responsibility for the effects of forest management on the hydrologic processes in watersheds and landscapes occurs both vertically and horizontally. Responsibilities are split vertically among various levels of government—federal, state, regional and local, and they are split horizontally within each level among agencies focusing on specific resources. One agency manages forestlands, another manages water resources, and a third regulates the impacts of forest management on water resources. Rarely does only one agency or manager control forest management and use across entire watersheds or landscapes. A further discussion of the institutional governance of water is presented in Appendix A. EMERGING ISSUES FOR FORESTS AND WATER A number of issues pose challenges for science to explain and predict the effects of forest management on hydrology. These issues can be grouped into the spatial, temporal, and social contexts of forests and hydrology; they are described in those contexts below and expressed with key questions, which are addressed in subsequent chapters of this report. Spatial Context Timber Management Practices Many forests continue to be managed for timber production. In those that are, large areas of some uneven-aged, native forest are converted to even-aged, managed forests. Selective cuttings continue in many uneven-aged forests. For decades, forest hydrology research has focused on how forests can be managed without adversely affecting stormflows, erosion, and adverse changes in water quality (Bosch and Hewlett, 1982; Brooks et al., 2003; Chang, 2003; Ice and Stednick, 2004). Nevertheless, issues remain about how much and which types of forest management can be practiced in a watershed while still maintaining water quantity and quality (see Boxes 2-2, 2-3, and 2-4).
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Hydrologic Effects of a Changing Forest Landscape Question: What are the magnitude and duration of hydrologic effects due to timber harvest? Riparian Ecosystems Removal of forests and other streamside vegetation within riparian corridors degrades stream ecosystems and reduces populations of aquatic organisms (Rinne and Minckley, 1991; Rinne, 1996; DeBano and Wooster, 2004). In the 1970s and 1980s, these findings and resulting public concern led to increased protection of streamside vegetation and riparian zone restoration as part of many forest management plans (Macdonald and Weinmann, 1997; Verry et al., 2000; Baker et al., 2004). Very wide riparian buffers, such as those required by the Northwest Forest Plan (USDA and USDI, 1994), occupy large portions of forest area. Riparian zones also contribute wood to streams that may be mobilized during floods, potentially exacerbating downstream flooding (Box 5-3). Question: What are the hydrologic effects of removing or retaining riparian forests over the long term and in large watersheds? Cumulative Watershed Effects Changes in forest cover and extent within a watershed can result from forest fragmentation (the subdivision of large, continuous forest patches into smaller, discontinuous patches); conversion from forest to developed uses; timber harvesting; and forest loss due to fire, disease, grazing, and insects. Cumulatively, the hydrologic effects could be considerable when assessed at the large-watershed or landscape scale. “Cumulative watershed effects” (CWEs) are the response to multiple land use activities that are caused by, or result in, altered watershed function (Reid, 1993; MacDonald, 2000). Question: What are the CWEs of forest cover loss in large watersheds? Temporal Context Past Timber Management Clear-cutting was historically a widespread timber harvest practice on public forestlands. Today, little clear-cutting occurs on public forestlands, and harvest of old growth rarely occurs. However, two aspects of past timber management have created legacies in present-day forests that may affect water. One of
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Hydrologic Effects of a Changing Forest Landscape these is the legacy of even-aged forest stands created mostly by patch clearcutting done in the twentieth century. As they grow, these young stands use water, but there is uncertainty about how much water is used compared to the older, native forest stands they replaced. A second legacy is the edges created by past clear-cutting, which may be susceptible to windthrow disturbance. Major windthrow events can augment flammable material in forests (Moser et al., 2008) and contribute to insect outbreaks (Powers et al., 1999), with potential direct and indirect effects on water. Question: How do past forest cutting patterns affect water quantity and quality? Past Grazing and Predator Removal Forestlands, especially western forests, were managed as public grazing lands in much of the twentieth century. Grazing of domestic cattle and sheep led to reductions in forest cover, soil compaction and erosion, increased overland flow, and sediment contributions to streams on many public forestlands. At the same time, eradication of native predators (wolves, cougars, etc.) led to increased populations of native grazers, such as elk and deer. Largely resulting from changes in USFS and Bureau of Land Management regulations, the grazing of domestic animals on national forests declined in the late twentieth century, while efforts to reintroduce predators have had some effect on native grazer populations and behavior, especially in national parks. Forest vegetation responses to reduced grazing pressure and the resulting effects on water use are largely unknown. Question: How have changes in grazing of both domestic and native grazers affected forests, and what are the indirect effects of those changes on water quantity and quality? Inherited Road Networks One legacy of past timber management is a 386,000-mile (620,000 km) road network on USFS land. These road networks were designed and constructed to meet forest management goals such as timber extraction, fire control, or recreational activities. However, many forest roads have been maintained infrequently and do not meet current road standards (Bell, 2000). Some portions of the road network have been decommissioned, but most of the original road network remains. Forest roads are major sources of landslides (Swanson and Dyrness, 1975; Megahan et al., 1978; Sidle et al., 1985; Sidle, 2000) and sediment loads in the streams originating in national forests (e.g. Reid, 1993; Wemple et al., 2001). The road network has been implicated in flooding (Box 2-4)
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Hydrologic Effects of a Changing Forest Landscape BOX 2-4 West Virginia Flooding In July 2001, several large, long-lasting thunderstorms passed over southern West Virginia. More than 6.5 inches (165 mm) of rain fell in a 100- or 500-year event. The resulting floods caused extensive property damage, personal injury, and death. A total of 489 private residential property owners filed lawsuits against 78 different defendants, including logging companies, alleging that timber harvesting, mining, and other resource extraction caused or contributed to the flood damage by eroding the soil and making storm runoff more intense. The damage claims are based on several theories of liability including strict liability; unreasonable use of land; negligence; interference with riparian rights; and nuisance. The state Supreme Court has rejected the strict liability theory, but the suits are proceeding on the other grounds. The plaintiffs claimed that timber companies were not following best management practices and that they carried out their harvesting, road building, and other activities in ways that unreasonably harmed downstream landowners by increasing the intensity of the runoff, eroding soil, and carrying logs downstream into buildings and other structures (Mortimer and Visser, 2004). A Flood Protection Task Force was formed by the governor and it prepared a new comprehensive Statewide Flood Plan (http://www.wvca.us/flood/). The task force concluded that while forest harvesting operations may affect flood flows due to soil compaction, the major flooding risk associated with logging relates to road and culvert design and maintenance. The task force recommended increased inspections of forest operations, prompt reforestation, and improved management of logging slash. and represents a potentially very large future source of sediment, which could adversely affect water quality in forested watersheds. Question: How do the legacies of road networks on forestland affect peak flows and sediment movement? Wildfire and Fire Suppression Fires are a natural disturbance in many forest ecosystems. Natural fires (or wildfires) range in recurrence-frequencies of less than 10 years in ponderosa pine forests in the Southwest to more than 1,000 years in balsam fir forests in the eastern United States (Swetnam and Baisan, 1996; Swetnam, 2005). Depending on their severity, wildfires may affect energy and nutrient flows, the soil environment, above- and below-ground plant growth, wildlife populations and their habitats, and hydrologic processes. For most of the twentieth century, wildfires were effectively suppressed to protect timber. As a result of fire suppression, flammable fuels have accumulated in many western forest ecosystems. These fuel accumulations are believed to contribute to increased wildfire size and severity (see Box 2-5). Forest managers have begun to reintroduce fire to some national forests using prescribed fire and “let-it-burn” policies (Schullery, 1986; Arno and Brown, 1991; Czech and Ffolliott, 1996). However, firefighting
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Hydrologic Effects of a Changing Forest Landscape BOX 2-5 Historical 2002 Wildfire Season and Lessons Learned More than 88,000 wildfires burned throughout forest and rangeland ecosystems of the United States in the 2002 wildfire season that burned a record near-7 million acres of forestland—almost twice the 10-year average. Aided by a widespread drought in the western regions that was comparable in severity to the Dust Bowl of the 1930s and the excessive buildup of flammable fuels, these wildfires initiated a heightened public awareness of the dire consequences of large and complex wildfires (White, 2004). Three historically large wildfires caused by human ignitions—the Rodeo-Chediski in Arizona, the Hayman in Colorado, and the Biscuit in southern Oregon and northern California—burned more than 1 million acres combined and placed the impacted ecosystems, communities, and people at risk. Given the inevitability of wildfires in the future; the escalating impacts of wildfires on natural, human, and economic resources; and the need for improved preparation to combat future wildfires, the experience from the 2002 fire season provided important lessons for foresters and fire managers: The need to improve knowledge of and ability to predict the risk of wildfires occurring in a particular locale; The need to develop plans for the recovery of ecosystems to fire;and The need to estimate and plan for the direct costs involved in mitigating wildfires and rehabilitating burned landscapes. remains a major forest management practice of the Forest Service on most national forests in the western United States (see Box 2-6). The Forest Service’s use of fire retardant chemicals is a source of controversy and concern (see Box 2-6). Questions: What are the hydrologic effects of forest fires and firefighting (such as fire breaks, soil disturbance, and application of fire retardants)? What are the hydrologic effects of high versus low-severity fires, including considerations of long-term effects and larger spatial scales? Impacts of Insect Outbreaks Under normal conditions, bark beetles, leaf defoliators, and other insects are present at low (endemic) levels in forest ecosystems. However, when conditions are favorable, endemic populations erupt into epidemics, altering forest species’ composition and structure and killing all of the trees in severely infested forest stands. In the early 2000s, much of the western United States has been experiencing bark beetle outbreaks at unprecedented levels, apparently as the result of warming climate (Bytnerowicz et al., 1998; Logan et al., 2003). Vast areas of western forest have been killed by these large-scale outbreaks, especially in the Rocky Mountains.
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Hydrologic Effects of a Changing Forest Landscape BOX 2-6 Judge Threatens to Block Forest Service Fire-Retardant Drops and Put Government Official in Jail A federal judge in Montana is threatening to block the Forest Service's use of fire retardant drops and throw the Agriculture Undersecretary in jail. In January 2008, the U.S. District Judge ordered the Forest Service to court to explain why the agency has failed to conduct proper studies of fire retardant drops in Missoula. If the agency's arguments are unpersuasive, the judge said he would consider enjoining the use of all aerial fire retardants nationwide, except for water, until the Forest Service complies with his orders and federal environmental laws. At issue is firefighters' use of fire retardants containing ammonia compounds. Federal and state agencies drop an average of 15 million gallons of retardant annually, up to 40 million gallons in some years. Fire retardant is approximately 85 percent water, but it contains ammonia compounds, thickeners such as guar gum and attapulgite clay, dyes, and corrosion inhibiters. Retardant rapidly reduces wildfire intensity and rate of spread by robbing the fire of oxygen and slowing the rate of fuel combustion with inorganic salts. The Forest Service Employees for Environmental Ethics (FSEEE) initiated the lawsuit in 2002, alleging that fire retardants are used without analysis of their environmental impacts and blaming fire retardants for fish kills, including the death of 20,000 fish in central Oregon in 2002. The lawsuit alleges that the USFS is violating the National Environmental Policy Act (NEPA) and failing to comply with Section 7 of the Endangered Species Act, which requires the agency to consult with the National Marine Fisheries Service and the Fish and Wildlife Service. A biological opinion from the National Marine Fisheries Service found potential harm to 24 threatened and endangered fish species in the Northwest, including nine species of chinook salmon, two species of chum salmon, two species of coho salmon, Snake River sockeye salmon, ten species of steelhead, the shortnose sturgeon, and the green sturgeon. In October 2007, the Forest Service made an initial finding of no significant impact. FSEEE sees the lawsuit as a way of making the Forest Service rethink traditional firefighting strategies that now consume half of the its budget, even as many national forests can no longer afford to maintain their campgrounds and trails. "Fire retardant is the wedge we're using to force a hard look at the way we fight fires—how we fight them, where we fight them, when we fight them, and why we fight them," said Andy Stahl, executive director of the group. The Forest Service's fire suppression budget has roughly doubled since 2000 as fires have grown more intense. The environmental group wants the Forest Service to treat fire retardants in the same manner as pesticides, which the agency uses infrequently and in limited areas, generally after much study. SOURCES: From the Oregonian, February 26, 2008, http://www.fseee.org/fsnews/ee080111.pdf. Available online at http://blog.oregonlive.com/pdxgreen/2008/02/top_bush_official_faces_jail_f/print.html. Questions: How do insect outbreaks affect water quantity and quality? How can future hydrologic effects of insect outbreaks be understood or predicted as indirect effects of climate change? Spread of Invasive Species The effects of invasive plant species on forest ecosystems are a major concern of foresters and ecologists (Young and Clements, 2005; Webster et al.,
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Hydrologic Effects of a Changing Forest Landscape 2006). At least one invasive species was found in 62 percent of the 200 forested plots studied in Oregon and Washington (Gray, 2007). Invasive species in forests include grass, herb, shrub, tree, insect, and bird species that are exotic (nonnative), as well as native species that spread beyond their historic range with undesirable impacts (see Box 2-7). Invasive plant species can displace native plants; modify habitat for native insects, birds, and animals; and alter ecosystem processes including nutrient cycling, fire, and water use (Flather et al., 1994; Wilcove et al., 1998; Callaway and Aschehoug, 2000). Eucalyptus, Russian olive, and tamarisk are common invasive tree species in western forests, and ailanthus and kudzu (a vine) affect eastern forests. Various forest management practices exist for control of invasive species (Wagner et al., 2000; Falk and Swetnam, 2003; Hull Sieg et al., 2003). The Forest Service, along with nongovernmental organizations such as The Nature Conservancy, has adopted practices to inventory and limit the introduction and spread of invasive species on many national forests and other forested lands. Question: What are the hydrologic effects of nonnative species’ presence and nonnative species’ removal treatments in forests? Changing Climate Changing climate is directly influencing forest ecosystems, with consequent effects on water quantity, quality, and timing of peak and low flows. Effects of climate change on forests involve interactions among increasing CO2, warming, changes in precipitation regimes (Melillo et al., 1993; Houghton, 1995), and the abilities of plant and animal species to migrate and keep pace with climate change or adapt to the changing conditions (Thomas et al., 2004). Ecological models incorporating alternative climate scenarios indicate that the location and extent of potential habitats for many tree species and forest ecosystems are likely to shift (U.S. Global Climate Research Program, 2000). Habitats for tree species favoring cool environments might move north or higher in elevation. Habitats of alpine and subalpine spruce-fir forests on isolated mountain tops in BOX 2-7 Invasive Plant Species: Some Characteristics and Features Timber harvest, road construction, fire, and grazing produce soil disturbance than can promote the establishment of invasive plant species in forests (Flather et al., 1994; Hull Sieg et al., 2003). Once introduced, invasive plants can be spread throughout a forest by traffic along road and trail networks (Parendes and Jones, 2000), potentially reaching sites that have experienced little or no human disturbance. Once they are present in a forest, invasive species also can be spread by natural disturbance, such as floods and wildfire (Watterson and Jones, 2006). Invasive species typically have life history traits that favor rapid establishment and spread, including high rates of seed production, edible seeds, vegetative reproduction, and persistence in the soil seed bank.
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Hydrologic Effects of a Changing Forest Landscape the southwestern region of the country could be eliminated if future elevational shifts are large enough. Aspen and eastern birch forests might contract in area in the United States and shift into Canada. Other ecosystems might expand in area, such as oak-hickory and oak-pine habitats in the eastern states and ponderosa pine forests and pinyon-juniper woodlands in the western states. Climate change will likely affect the yield, timing, and quality of water flowing from forest landscapes. Attempts to model forest responses to climate change and consequent water yield changes suggest a trend of declining water yields (Running and Nemani, 1991; Aber et al., 1995). A warming climate will reduce snowpack amounts and duration, and snowmelt will occur earlier. In some regions, spring peak runoff has already been documented as coming up to three weeks earlier than historical averages (Hodgkins et al., 2003; Dettinger et al., 2004; Payne et al., 2004). Even with conservative estimates of climate change, water resources to meet current demands are not guaranteed under future climate scenarios (Barnett et al., 2004). Climate change also may alter the frequency and magnitude of forest fires, increasing the size and severity of wildfires (see Box 2-5). The effects of climate change on fire susceptibility involve complex interactions among factors such as warming temperatures, soil moisture, forest growth, fuel loads, and fire ignitions (Prentice et al., 1993; Stocks et al., 1998). Western forests are already experiencing larger and more severe fires and longer fire seasons (Kasischke et al., 2006; Westerling et al., 2006). Questions: What are the hydrologic responses to climate change? Social Context Forestland Ownership Changes Most regions of the United States have experienced a major transformation in private forest ownership during the past 20 years. In contrast to the twentieth century, there are very few remaining large, publicly traded, vertically integrated wood products manufacturing businesses that own significant amounts of forestland. Forested land and mills are increasingly owned by two new forms of large, privately held companies that are referred to as timber investment management organizations and real estate investment trusts. These companies now own what used to be industrial timberlands. They are investing in forestland ownership for the long term, but they have different time horizons and goals for management compared to the former owners of these lands. At the same time, many family-held forestlands have undergone parcelization, which occurs at the time of intergenerational transfer when a forest changes ownership or is broken up and sold when the new owners cannot agree on goals
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Hydrologic Effects of a Changing Forest Landscape and purposes. About one-half of the private forest land in the United States has changed ownerships in the past decade (Alig and Plantinga, 2004). Question: How do changes in ownership affect forest management, and how do these changes affect water resources? Continuing Urbanization Urbanization has been a major cause of forest loss since 1950 and is anticipated to account for additional forest loss in the twenty-first century across the United States (Alig et al., 2003). Although forest area in the United States increased from the late 1800s through the middle 1900s, net forest area in the United States declined from the early 1950s to 1997 (Powell et al., 1993; Scott et al., 2004) (Figure 2-4). Forest area is expected to decrease by an additional 3 percent by 2050 relative to 1997 because of the conversion of forests to urban and developed uses. The U.S. Department of Agriculture’s 1997 National Resource Inventory showed that 1 million acres of forest, agricultural cropland, and open space were converted to urban and other developed uses from 1992 to 1997, and the national rate of urbanization increased notably compared to the period from 1982 to 1992 (Figure 2-5). In the 1990s, forestland was the largest source of land conversion to developed uses. Aligned with a projected population increase of more than 120 million people through 2050, urban and other developments are expected to continue to grow substantially, with the fastest rates of growth in the western and southern regions (Alig et al., 2003). From 1990 to 2000, 18 states in the West registered growth above the U.S. average. Continuing urbanization and increasing construction of second homes in forest settings has resulted in the expansion of “urban-forest interfaces” or “wildland-urban interfaces (Radeloff et al., 2005) throughout the country. Wildfires igniting in forests may spread into these communities and potentially be intensified if fuel buildup around homes is not managed (Cortner et al., 1990; Beebe and Omi, 1993; Vince et al., 2005). Question: What are the effects of the expansion of human settlements into forested areas, and the consequent changes in forest management, such as thinning for fuel reduction, on water quantity and quality? SUMMARY This chapter describes current and emerging issues of managing forests and water in the United States. It describes forest management decisions that have been made in U.S. forests and enumerates, in the form of a set of questions, emerging issues that face forest and water managers in the twenty-first century.
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Hydrologic Effects of a Changing Forest Landscape The next two chapters address these questions. Chapter 3 evaluates how forest management and forest disturbance influence the flowpaths of water from precipitation to the point of human or ecosystem use. Chapter 4 identifies research needed to address these questions. FIGURE 2-4 Change over time in forest cover by region of the United States. Forest cover declined greatly in the Northeast, South, and Midwest in past centuries, but in the twentieth century, forest cover declined in parts of the Pacific Northwest, and increased in the South, Northeast, and Midwest. In the twenty-first century, forest cover is projected to decrease in the South and Northeast to exurban development. SOURCE: Available online at http://www.usgcrp.gov/usgcrp/Library/nationalassessment/LargerImages/SectorGraphics/Forests/Percentages.jpg. Accessed June 24, 2008.
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Hydrologic Effects of a Changing Forest Landscape FIGURE 2-5 Proportion of rural area by county in 1980, 2000, and 2040. SOURCE: Reprinted, with permission, from Ecology and Society (2005). Copyright 2005 by David M. Theobald.
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Hydrologic Effects of a Changing Forest Landscape