Ecosystems Impacts & Adaptation

Climate Impacts on Ecosystems

Climate is an important environmental influence on ecosystems. Climate changes and the impacts of climate change affect ecosystems in a variety of ways. For instance, warming could force species to migrate to higher latitudes or higher elevations where temperatures are more conducive to their survival. Similarly, as sea level rises, saltwater intrusion into a freshwater system may force some key species to relocate or die, thus removing predators or prey that were critical in the existing food chain.

Climate change not only affects ecosystems and species directly, it also interacts with other human stressors such as development. Although some stressors cause only minor impacts when acting alone, their cumulative impact may lead to dramatic ecological changes. ^[1] For instance, climate change may exacerbate the stress that land development places on fragile coastal areas. Additionally, recently logged forested areas may become vulnerable to erosion if climate change leads to increases in heavy rain storms.

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Changes in the Timing of Seasonal Life-Cycle Events

For many species, the climate where they live or spend part of the year influences key stages of their annual life cycle, such as migration, blooming, and mating. As the climate has warmed in recent decades, the timing of these events has changed in some parts of the country. Some examples are:

• Warmer springs have led to earlier nesting for 28 migratory bird species on the East Coast of the United States. ^[1]
• Northeastern birds that winter in the southern United States are returning north in the spring 13 days earlier than they did in the early 20th century. ^[4]
• In a California study, 16 out of 23 butterfly species shifted their migration timing and arrived earlier. ^[4]

Changes like these can lead to mismatches in the timing of migration, breeding, and food availability. Growth and survival are reduced when migrants arrive at a location before or after food sources are present. ^[4]

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Range Shifts

As temperatures increase, the habitat ranges of many North American species are moving northward in latitude and upward in elevation. While this means a range expansion for some species, for others it means a range reduction or a movement into less hospitable habitat or increased competition. Some species have nowhere to go because they are already at the northern or upper limit of their habitat.

For example, boreal forests are invading tundra, reducing habitat for the many unique species that depend on the tundra ecosystem, such as caribou, arctic fox, and snowy owl. Other observed changes in the United States include expanding oak-hickory forests, contracting maple-beech forests, and disappearing spruce-fir forests. As rivers and streams warm, warmwater fish are expanding into areas previously inhabited by coldwater species. ^[5] Coldwater fish, including many highly valued trout species, are losing their habitats. As waters warm, the area of feasible, cooler habitats to which species can migrate is reduced. ^[5] Range shifts disturb the current state of the ecosystem and can limit opportunities for fishing and hunting.

See the Agriculture and Food Supply Impacts & Adaptation page for information about how habitats of marine species have shifted northward as waters have warmed.

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Food Web Disruptions

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The Arctic food web is complex. The loss of sea ice can ultimately affect the entire food web, from algae and plankton to fish to mammals. Source: NOAA (2011)

The impact of climate change on a particular species can ripple through a food web and affect a wide range of other organisms. For example, the figure shows the complex nature of the food web for polar bears. Declines in the duration and extent of sea ice in the Arctic leads to declines in the abundance of ice algae, which thrive in nutrient-rich pockets in the ice. These algae are eaten by zooplankton, which are in turn eaten by Arctic cod, an important food source for many marine mammals, including seals. Seals are eaten by polar bears. Hence, declines in ice algae can contribute to declines in polar bear populations. ^{[4] [5] [6]}

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Threshold Effects

In some cases, ecosystem change occurs rapidly and irreversibly because a threshold, or "tipping point," is passed.

One area of concern for thresholds is the Prairie Pothole Region in the north-central part of the United States. This ecosystem is a vast area of small, shallow lakes, known as "prairie potholes" or "playa lakes." These wetlands provide essential breeding habitat for most North American waterfowl species. The pothole region has experienced temporary droughts in the past. However, a permanently warmer, drier future may lead to a threshold change—a dramatic drop in the prairie potholes that host waterfowl populations and provide highly valued hunting and wildlife viewing opportunities. ^[3]

Similarly, when coral reefs become stressed, they expel microorganisms that live within their tissues and are essential to their health. This is known as coral bleaching. As ocean temperatures warm and the acidity of the ocean increases, bleaching and coral die-offs are likely to become more frequent. Chronically stressed coral reefs are less likely to recover.

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Pathogens, Parasites, and Disease

Climate change and shifts in ecological conditions could support the spread of pathogens, parasites, and diseases, with potentially serious effects on human health, agriculture, and fisheries. For example, the oyster parasite, Perkinsus marinus, is capable of causing large oyster die-offs. This parasite has extended its range northward from Chesapeake Bay to Maine, a 310-mile expansion tied to above-average winter temperatures. ^[8] For more information about climate change impacts on agriculture, visit the Agriculture and Food Supply Impacts & Adaptation page. To learn more about climate change impacts on human health, visit the Health Impacts & Adaptation page.

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Extinction Risks

Climate change, along with habitat destruction and pollution, is one of the important stressors that can contribute to species extinction. The IPCC estimates that 20-30% of the plant and animal species evaluated so far in climate change studies are at risk of extinction if temperatures reach levels projected to occur by the end of this century. ^[1] Projected rates of species extinctions are 10 times greater than recently observed global average rates and 10,000 times greater than rates observed in the distant past (as recorded in fossils). ^[2] Examples of species that are particularly climate sensitive and could be at risk of significant losses include animals that are adapted to mountain environments, such as the pika, animals that are dependent on sea ice habitats, such as ringed seals, and cold-water fish, such as salmon in the Pacific Northwest. ^[5]

For information about how communities are adapting to the impacts of climate change on ecosystems, visit the Ecosystems Adaptation section.

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References

1. Fischlin, A., G.F. Midgley, J.T. Price, R. Leemans, B. Gopal, C. Turley, M.D.A. Rounsevell, O.P. Dube, J. Tarazona, A.A. Velichko (2007). Ecosystems, their Properties, Goods, and Services. In: Climate Change 2007: Impacts, Adaptation and Vulnerability . Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson (eds.). Cambridge University Press, Cambridge, United Kingdom.

2. Millennium Ecosystem Assessment (2005). Ecosystems and Human Well-Being: Biodiversity Synthesis (PDF). World Resources Institute, Washington, DC, USA.

3. CCSP (2009). Thresholds of Climate Change in Ecosystems . A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Fagre, D.B., Charles, C.W., Allen, C.D., Birkeland, C., Chapin, F.S. III, Groffman, P.M., Guntenspergen, G.R., Knapp, A.K., McGuire, A.D., Mulholland, P.J., Peters, D.P.C., Roby, D.D., and Sugihara, G. U.S. Geological Survey, Department of the Interior, Washington DC, USA.

4. CCSP (2008). The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States . A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Backlund, P., A. Janetos, D. Schimel, J. Hatfield, K. Boote, P. Fay, L. Hahn, C. Izaurralde, B.A. Kimball, T. Mader, J. Morgan, D. Ort, W. Polley, A. Thomson, D. Wolfe, M. Ryan, S. Archer, R. Birdsey, C. Dahm, L. Heath, J. Hicke, D. Hollinger, T. Huxman, G. Okin, R. Oren, J. Randerson, W. Schlesinger, D. Lettenmaier, D. Major, L. Poff, S. Running, L. Hansen, D. Inouye, B.P. Kelly, L Meyerson, B. Peterson, and R. Shaw. U.S. Environmental Protection Agency, Washington, DC, USA.

5. USGCRP (2009). Global Climate Change Impacts in the United States . Karl, T.R., J.M. Melillo, and T.C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.

6. ACIA (2004). Impacts of a Warming Arctic: Arctic Climate Impact Assessment . Arctic Climate Impact Assessment. Cambridge University Press, Cambridge, United Kingdom.

7. NRC (2008). Understanding and Responding to Climate Change: Highlights of National Academies Reports . National Research Council. The National Academies Press, Washington, DC, USA.

8. NRC (2008). Ecological Impacts of Climate Change . National Research Council. The National Academy Press, Washington, DC, USA.

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Adaptation Examples in Ecosystems

Climate change is likely to alter ecosystems and the ability of ecosystems to react to stress. While plants, animals, and microorganisms have been adapting to environmental changes for millions of years, the pace of climate changes happening now will require species to adapt more quickly. Climate change impacts on ecosystems may include salt water intrusion, habitat shifts, increased invasive species survival, enhanced competition for limited resources, and amplification of existing stressors, such as habitat fragmentation and pollution. To learn more about how climate change will likely impact ecosystems, visit the Ecosystems Impacts section.

Natural resource managers across the country are working to increase ecosystem resilience by reducing other stressors and promoting healthy habitats. Ecosystem adaptation measures include a wide variety of activities that can be tailored to address the climate change impacts on specific ecosystems. Specific approaches include:

• Removing or controlling invasive species
• Promoting biodiversity and landscape diversity
• Protecting intact healthy watersheds and natural corridors
• Collaborating across borders to create habitat linkages
• Managing wildfire risk with controlled burns and thinning

The following case studies, examples, and related links are illustrative and not intended to be comprehensive.

Resource managers maintain biodiversity in the face of changing environments

Map of the National Marine Protected Areas System. Source: NOAA National Marine Protected Areas Center (2011)

Climate change is accelerating the rate at which species must adapt to new conditions. Changes in climate may threaten species' ability to survive in their current habitats. Some species will be able to migrate to new locations, while other species will see their numbers decline. Ecosystems that have a high degree of species diversity are often more able to adapt to stresses, including climate change. Protecting species can therefore help ecosystems cope with climate change. ^{[1] [2] [3]} Natural resource managers can take a variety of approaches to protect species. For example, managers can:

• Identify species that may be sensitive to changes in temperature, precipitation, water availability, sea level, and ocean chemistry. Refuges can protect species from a variety of stressors, such as development and pollution. For example, the National Oceanic and Atmospheric Administration's (NOAA) National Marine Protected Areas Center manages a network of over 250 Marine Protected Areas (MPAs). The center plans to consider climate change threats to marine resources as it establishes more MPAs (PDF).
• Limit hunting or capture of animals that are threatened by climate change. For example, NOAA’s North Pacific Climate Regimes and Ecosystem Productivity program advises fishery resource managers on establishing sustainable harvest limits. ^[4]
• Improve monitoring of ecosystems to respond more quickly to outbreaks of diseases and pests that threaten native species. Increased temperatures and changes in competition may increase the potential for these outbreaks. ^[2]
• Take a proactive and strategic systems approach to conserve healthy components of watersheds to avoid future water quality impairments and to increase resilience to climate change.

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Communities, private organizations, and federal agencies protect critical habitats

Protecting the water, soil, and air is important to help ecosystems adapt to changing climate conditions. These physical components of ecosystems are essential to healthy habitats. Several ways to protect these components and make ecosystems more resilient to climate change are described below. ^{[1] [2] [3]}

• Communities can improve how they manage stormwater. Flooding and heavy rainfall can lead to erosion along rivers and coasts. Cities like Portland, Oregon are building "green streets" that use plants to reduce stormwater runoff.
• The EPA is restoring coastal wetlands, which serve as both habitats and natural storm barriers. EPA's Climate Ready Estuaries program is working with coastal managers to assess key vulnerabilities in estuarine habitats and identify adaptation strategies to improve resiliency.
• Non-profit groups, such as Ducks Unlimited, are working to protect the Prairie Pothole region of the Great Plains, which is an important habitat for waterfowl.
• The Bureau of Land Management (BLM) is assessing potential impacts to inform adaptation. BLM is conducting Rapid Ecoregional Assessments (REA) to synthesize the existing information about the ecological values, conditions, and trends in ecoregions (large areas with similar ecological conditions, like the Sonoran Desert). The REAs identify important habitats and the potential for climate change, wildfires, invasive species, and development to impact those habitats.

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U.S. develops a National Fish, Wildlife and Plants Climate Adaptation Strategy

In response to observed and anticipated climate change impacts on America's natural resources, Congress called for the development of a national, government-wide strategy in 2010. The Steering Committee, which consists of representatives from federal, state, and tribal governments, is developing the National Fish, Wildlife, and Plants Climate Adaptation Strategy, a draft of which is now available. The Strategy will outline a unified approach to maintaining the key terrestrial, freshwater, and marine ecosystems needed to sustain fish, wildlife, and plant resources and the services they provide in the face of accelerating climate change.

References

1. FWS (2010). Rising to the Urgent Challenge: Strategic Plan for Responding toAccelerating Climate Change . U.S. Fish and Wildlife Service, Washington, DC, USA.

2. NRC (2010). Adapting to the Impacts of Climate Change. National Research Council. The National Academies Press, Washington, DC, USA.

3. CCSP (2008). Preliminary Review of Adaptation Options for Climate-Sensitive Ecosystems and Resources . A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [Julius, S.H., J.M. West (eds.), J.S. Baron, B. Griffith, L.A. Joyce, P. Kareiva, B.D. Keller, M.A. Palmer, C.H. Peterson, and J.M. Scott (authors)]. U.S. Environmental Protection Agency, Washington, DC, USA.

4. NOAA Research (2004). North Pacific Climate Regimes and Ecosystem Productivity Science Plan . National Oceanic and Atmospheric Administration.

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