Climate Change in Wildlands

Pioneering Approaches to Science and Management

Andrew J Hansen, William B Monahan, David M. Theobald, S. Thomas Olliff

• Editorial: Island Press
• Año: 2016
• ISBN:
  9781610917131
• Categoría: Sciences biologiques
• Categoría: Science générale

Scientists have been warning for years that human activity is heating up the planet and climate change is under way. In the past century, global temperatures have risen an average of 1.3 degrees Fahrenheit, a trend that is expected to only accelerate. But public sentiment has taken a long time to catch up, and we are only just beginning to acknowledge the serious effects this will have on all life on Earth. The federal government is crafting broad-scale strategies to protect wildland ecosystems from the worst effects of climate change. The challenge now is to get the latest science into the hands of resource managers entrusted with protecting water, plants, fish and wildlife, tribal lands, and cultural heritage sites in wildlands.Teaming with NASA and the Department of the Interior, ecologist Andrew Hansen, along with his team of scientists and managers, set out to understand how climate and land use changes affect montane landscapes of the Rockies and the Appalachians, and how these findings can be applied to wildlands elsewhere. They examine changes over the past century as well as expected future change, assess the vulnerability of species and ecosystems to these changes, and provide new, collaborative management approaches to mitigate expected impacts. A series of case studies showcases how managers might tackle such wide-ranging problems as the effects of warming streams on cold-water fish in Great Smoky Mountain National Park and dying white-bark pine stands in the Greater Yellowstone area. A surprising finding is that species and ecosystems vary dramatically in vulnerability to climate change. While many will suffer severe effects, others may actually benefit from projected changes. Climate Change in Wildlands is a collaboration between scientists and managers, providing a science-derived framework and common-sense approaches for keeping parks and protected areas healthy on a rapidly changing planet.

Chapter 1

Why Study Climate Change in Wildlands?

Andrew J. Hansen

Most nations around the world set aside some lands from where people live and work for the benefit of nature. Wildland ecosystems are those lands occupied chiefly by native plants and animals, not intensively used as urban or residential areas, and not intensively managed for the production of domesticated plants or animals (Kalisz and Wood 1995). Public parks, forests, grasslands, seashores, and other wildland ecosystems are central to the global strategy for the conservation of nature. These areas are also vital to the well-being of people. They provide essential ecosystem services, such as provisioning of food and water, supporting pollination and nutrient cycling, regulating floods and other disturbances, and providing aesthetic and recreational services (Wilkie et al. 2006; Friedman 2014).

While humans have benefited substantially from these services, impacts associated with our activities, particularly habitat loss from land conversion, climate change, and exotic species introductions, are driving major losses in biodiversity and subsequent disruption of ecosystem services (Millennium Ecosystem Assessment 2005). A major challenge facing humankind is how to sustain ecosystem services in the face of population growth and climate change. This challenge is particularly large in wildlands because they have become magnets for human development on their peripheries (Theobald and Romme 2007; Wittemyer et al. 2008; Radeloff et al. 2010). The challenge is also great because many wildlands are set in mountains or deserts that are undergoing particularly high rates of climate change (Hansen et al. 2014).

This book aims to link science and management to better understand human-caused change in wildland ecosystems and to better inform management to sustain wildland ecosystems and ecosystem services. Within the United States, the federal agencies that manage most of our wildlands have been charged with consideration of climate change since only 2009. Consequently, we focus on the challenge of understanding and managing wildland ecosystems under climate change but do so in the context of land use that is changing simultaneously.

Climate Change in Mountain Wildlands

The US Rocky Mountains in Montana, Wyoming, and Colorado are known for soaring summits, expansive public lands, iconic wildlife, blue-ribbon trout streams, and long, cold, snowy winters. In many ways, the wildland ecosystems of the region are framed by the harshness of the climate (fig. 1-1). The higher elevations are too cold and snowy for many plant species to tolerate; consequently, rates of ecological productivity are low, and the highest diversity of plant and wildlife species are at lower elevations with more equitable climate (Hansen et al. 2000). At first blush, one might think that climate warming would benefit ecosystems that are so limited by winter conditions. The interactions among climate, ecosystems, and plant and animal species are complex, however, especially in the context of human land use. There are many direct and indirect interactions that can lead to threshold changes and surprises. Understanding these interactions is essential to managing these wildlands to sustain native species and ecosystem services for people.

Forests at the highest elevations are dominated by pines, particularly whitebark pine (Pinus albicaulis) and lodgepole pine (P. contorta). Not only are these species uniquely adapted to tolerate cold climate and nutrient-poor soils, but they may require them. The mountain pine beetle (Dendroctonus ponderosae) is a native species that feeds on the cambium of these pines. A form of natural disturbance in this region, these beetles irrupt every few decades and kill large tracts of subalpine forests. In recent decades, however, the forest die-off has been larger in area and more continuous than in the past, and many old-growth whitebark pine stands have suffered 70 to 90 percent mortality (Logan, Macfarlane, and Willcox 2010). The cause? Winter low temperatures have not been cold enough in recent years to slow the population growth rate of the beetles, as had been the case historically. Thus, a natural disturbance to which the pine trees were adequately adapted has been intensified by climate warming, putting high-elevation forests at risk.

FIGURE 1-1 Image of the Teton Range near Jackson, Wyoming. The ecosystems of the Rocky Mountains are framed by the harshness of the climate, raising questions on the effects of global warming. (Photo by Andrew J. Hansen.)

Beyond leading to the recommendation of whitebark pine as a candidate threatened species, the forest die-off has effects that ripple across the ecosystem (chap. 15). The reduction in pine nuts, a major food source for grizzly bear (Ursus arctos horribilis) and other species, has led to the bears spending more time in lower-elevation habitats where they more frequently encounter humans, typically at the bears’ expense. Loss of subalpine forest also increases the melt rate of mountain snow and reduces summer streamflows, which are critical to native trout populations, recreationalists, irrigation-fed agriculturalists, and the fast-growing local communities downstream from the mountains. Most of the whitebark pine stands are located in federally designated wilderness areas, where management options are limited by law.

Unfortunately, there are many other examples of unexpected responses to changing climate. Within rivers and streams in the region, loss of native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) is occurring through hybridization with exotic rainbow trout (O. mykiss), with rates of hybridization positively linked to warming stream temperatures (chap. 12). The conifer forests that dominate much of the east slope of the Rockies are projected by the end of the century to have climate suitable for desert scrub vegetation now found in the Wyoming basin (chap. 9). The North American elk (Cervus elaphus) in Yellowstone National Park may benefit from less snow in winter habitats, but reproduction may be impeded because summer warming of mountain grasslands has reduced the availability of green forage during the time that cow elk are recovering from nursing their offspring (Middleton et al. 2013).

In addition to these more subtle and indirect effects of climate change, there are direct and obvious effects. The iconic glaciers in Glacier National Park are melting, and the larger glaciers are forecast to disappear entirely by 2030 (US Geological Survey 2015). The frequency of severe fire has increased, and the extreme 1988 Yellowstone fires are projected to become the norm in future decades (chap. 10). Summer flows of rivers and streams have been declining and are projected to decline even more in the future (chaps. 7 and 12).

These examples from the Rocky Mountains illustrate how mountain ecosystems may be especially sensitive to climate change. Temperature, precipitation, and solar radiation levels vary with elevation and aspect in mountains. Many species are adapted to narrow ranges of climate in these systems. Under climate warming, species may be able to track suitable habitats by shifting to higher elevations. However, land area decreases at higher elevations and suitable climate conditions may eventually “move off the tops of the mountains,” leaving species that depend on alpine conditions stranded (chaps. 6, 9, 10, and 15). Moreover, management options are constrained by law in the national parks, wilderness areas, and roadless areas that dominate land allocation at these higher elevations. For example, most of the whitebark pine stands are located in federally designated wilderness areas, where management options are limited by law (chaps. 10 and 15).

In contrast to the Rocky Mountains, signs of response to climate change are much less obvious in the Appalachian Mountains in the eastern United States (chaps. 5, 7, 8, and 11). The Appalachians are a veritable garden of Eden compared to the Rockies. The warm, humid climate, summer rains, and fertile soils result in the Appalachians being cloaked in forest. These forests are some of the fastest growing and most diverse in plant species in North America (Whittaker 1956). The effects of past climate change are less obvious here than in the Rockies. There has been some forest die-off of subalpine forests in the Great Smoky Mountains, but this is primarily due to air pollution and the introduction of exotic forest pests (chap. 8). The differences between the Rockies and the Appalachians in rates and reactions to climate change illustrate that local study is needed to understand and manage wildlands under global change.

Although the potential effects of climate change are both interesting and worrisome in some locations, our knowledge of the rates of climate change, the tolerances of species to these changes, and the potential changes in ecosystem services to humans is embryonic. For any given unit of land, such as a national park or national forest, certain fundamental questions have not yet been addressed:

• How much has climate changed over the past century, and how is it projected to change in the future?

• Has there been a trend in climate change above the natural variability?

• Which of the directional climate changes are significant ecologically?

• What ecosystem processes and species are most vulnerable to projected climate change and in which places are they most vulnerable?

• For vulnerable species, which adaptation and management options are feasible and likely to be effective?

Also poorly understood are means of managing wildland ecosystems to make them more resilient to climate change. Both the science and the management are challenged by the very nature of human-induced climate change (chap. 3). It is manifest over time periods (decades) that are long relative to resource management and scientific study horizons and even relative to the career spans of scientists and managers. It is occurring across regional to continental-sized areas that greatly exceed the spatial domains of individual national forests and national parks, necessitating interagency collaboration. Disentangling the signal of human-induced climate change from the pronounced natural variation is difficult and creates doubt in some sectors of society as to whether humans are altering global climate. Land use intensification around wildlands constrains management options. In combination, these factors result in climate change being a major challenge to resource managers. Agency policies are not yet well defined. Methods of linking climate science with management are underdeveloped. And few case studies exist of implementing management actions to mitigate the effects of climate change.

Fortunately, scientific and natural resource agencies and organizations in the United States have launched a plethora of initiatives, programs, and studies in recent years to bolster the capacity to respond and to increase knowledge on the science and management of climate change (chaps. 2, 3, and 13) (Halofsky, Peterson, and Marcinkowski 2015). For example, both the US Department of the Interior (DOI) and the US Department of Agriculture have initiated various programs to meet these management challenges. The National Park Service Inventory and Monitoring Program (NPS I&M) was created in 2000 to provide a framework for scientifically sound information on the status and trends of conditions in the national parks (Fancy, Gross, and Carter 2009).

Based partially on the success of the NPS I&M, in 2009 the DOI launched the creation of landscape conservation cooperatives (LCCs) across networks of the federal lands (US DOI 2009). The goal of the LCCs is to craft practical, landscape-level strategies for managing climate change impacts, with emphasis on (1) ecological systems and function, (2) strengthened observational systems, (3) model-based projections, (4) species-habitat linkages, (5) risk assessment, and (6) adaptive management. Related funding agencies, such as the National Science Foundation and the National Aeronautics and Space Administration (NASA) Earth Science Program, have created initiatives to support research and application of climate change science.

The DOI recently adapted an existing framework for linking science and manageme...