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Climate Change Impacts

International Climate Impacts

Farmers need access to weather and market information to make decisions, especially as climate change alters historical patterns. Source: USAID

On This Page:

Introduction to Global Issues

BasicÂ Needs: Food, Water, Health and Shelter

Vulnerable Populations

National Security

Regional Impacts

			Â

Key Points

Countries around the world will likely face climate change impacts that affect a wide variety of sectors, from water resources to human health to ecosystems.

Impacts will vary by region and by population.

Many people in developing countries are more vulnerable to climate change impacts than people in developed countries.

Impacts across the globe can have economic, health, and national security implications for the United States and other nations.

Introduction to Global Issues

Human basic needs, such as food, water, health, and shelter, are affected by climate. Changes in climate may threaten these needs with increased temperatures, sea level rise, changes in precipitation, and more frequent or intense extreme events.

Climate change will affect individuals and groups differently. Certain groups of people are particularly sensitive to climate change impacts, such as the elderly, the infirm, children and pregnant women, native and tribal groups, and low-income populations.

Climate change may also threaten key natural resources, affecting water and food security. Conflicts, mass migrations, health impacts, or environmental stresses inÂ

other parts of the world could raise economic, health, and national security issues for the United States. [1], [2], [3]

Although climate change is an inherently global issue, the impacts will not be felt equally across the planet. Impacts are likely to differ in both magnitude and rate of changeÂ in different continents, countries, and regions. Some nations will likely experience more adverse effects than others. Other nations may benefit from climate changes. The capacity to adapt to climate change can influence how climate change affects individuals, communities, countries, and the global population.

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Related Links

EPA:

Office of International and Tribal Affairs

Other:

Global Change Research Program

IPCC Fifth Assessment Report, Working Group IIÂ Exit

U.S. Department of Agriculture â€“ Climate Change and Food Security

NRC America's Climate Choices: Advancing the Science of Climate ChangeÂ Exit

United Nations Environment ProgrammeÂ Exit

World Meteorological OrganizationÂ Exit

United Kingdom Climate Impacts ProgramÂ Exit

U.S. Department of State

U.S. Agency for International Development

The World BankÂ Exit

Impacts on BasicÂ Needs

Impacts on Agriculture and Food

Changes in climate could have significant impacts on food production around the world. Heat stress, droughts, and flooding events may lead to reductions in crop yields and livestock productivity. Areas that are already affected by drought, such as Australia and the Sahel in Africa, will likely experience reductions in water available for irrigation. [2]

At middle to high latitudes, cereal crop yields are projected to increase slightly, depending on local rates of warming and crop type. At lower latitudes, cereal crop yields are projected to decrease. The greatest decreases in crop yields will likely occur in dry and tropical regions. In some African countries, for example, wheat yields could decline by as much as 35% by 2050. [4], [5]

Climate change is affecting many fisheries around the world. Increasing ocean temperatures have shifted some marine species to cooler waters outside of their normal range. Fisheries are important for the food supply and economy of many countries. For example, more than 40 million people rely on the fish caught in the Lower Mekong delta in Asia, which is the largest freshwater fishery in the world. Projected reductions in water flows and increases in sea level may negatively affect water quality and fish species in regions like these, affecting the food supply for communities that depend on these resources. [5], [6]

Climate change is very likely to affect global, regional, and local food security by disrupting food availability, decreasing access to food, and making utilization more difficult. [7]Â Climate risks to food security are greatest for poor populations and in tropical regions. The potential of climate change to affect global food security is important for food producers and consumers in the United States.

For more information about the impacts of climate change on agriculture and food production, please visit the Agriculture and Food Supply Impacts & Adaptation page.

Impacts on Water Supply and Quality

		Areas in Africa currently at risk for (a) hunger, (b) natural hazard-related disaster risks, (c) malaria (derived from historical rainfall and temperature data [1950-1996]), and (d) epidemics of meningococcal meningitis (based on epidemic experience, relative humidity [1961-1990] and land cover). Source: IPCC (2007) (PDF) Exit

Click on the image to see a larger version.

Semi-arid and arid areas (such as the Mediterranean, southern Africa, and northeastern Brazil) are particularly vulnerable to the impacts of climate change on water supply. Over the next century, these areas will likely experience decreases in water resources, especially in areas that are already water-stressed due to droughts, population pressures, and water resource extraction. [2], [6], [8]

As climate changes, water is very likely to become scarce at least part of the time in many areas, but more plentiful part of the time in some areas as well. The availability of water is strongly related to the amount and timing of runoff and precipitation.Â With a 2.7Â°F rise in global mean temperature, annual average streamflow is projected to increase by 10-50% at high latitudes and in some wet tropical areas, but decrease by 10-50% in some dry regions at mid-latitudes and in the subtropics. As temperatures rise, snowpack is declining in many regions and glaciers are melting at unprecedented rates, making water less available in areas that depend on it from melting snow and glaciers during spring and summer. Droughts are likely to become more widespread. When it does rain, more precipitation is expected to fall in extreme heavy precipitation events. Increases in heavy precipitation events would not increase water supply, but instead result in increased flooding, except in river basins with large dams able to hold excess water until it is needed. [8]

Indus River in Southern Pakistan (Left: August 2009; Right: August 2010). In August 2010, record monsoon rains flooded significant portions of Pakistan. Twenty percent of the country was underwater as a result of the floods, affecting about 20 million Pakistanis and rendering six million homeless. In the image from 2009, the Indus is about 0.6 miles wide. In the 2010 image, the river is 14 miles wide or more in parts. Source: NASA (2010)

Click on the image to see a larger version.Water quality is important for ecosystems, human health and sanitation, agriculture, and other purposes. Increases in temperature, changes in precipitation, sea level rise, and extreme events could diminish water quality in many regions. Large rainstorms may cause large amounts of pollutants to enter rivers and estuaries, as excess water may overwhelm wastewater systems and natural buffers.Â  Increased pollution as well as increasing water temperatures can cause algal blooms and potentially increase bacteria in water bodies. In coastal areas and small islands, saltwater from rising sea level and storm surges threaten water supplies. These impacts may require communities to begin treating their water in order to provide safe water resources for human uses. [1], [8]Â Â

For more information about the impacts of climate change on the water supply, please visit the Water Impacts & Adaptation page.

Impacts on Human Health

The risks of climate-sensitive diseases and health impacts can be high in countries that have little capacity to prevent and treat illness. There are many examples of health impacts related to climate change. [1]

Increases in temperatures are linked to more frequent and severe heat stress.

Worsened air quality that often accompanies heat waves or wildfires can lead to breathing problems and exacerbate respiratory and cardiovascular diseases. [9]

Impacts of climate change on agriculture and other food systems can increase rates of malnutrition and foodborne illnesses. [9]

Climate changes can influence infectious diseases. The spread of meningococcalÂ (epidemic) meningitis is often linked to climate changes, especially drought. Areas of sub-Saharan and West Africa are sensitive to the spread of meningitis, and will be particularly at-risk if droughts become more frequent and severe. [4]

The spread of mosquito-borne diseases such as malaria, dengue, and West Nile virus may increase in areas projected to receive more precipitation and flooding. Increases in rainfall and temperature can cause spreading of dengue fever. [9]

Changes in precipitation patters and extreme weather events can lead to cascading health impacts, particularly when power, water, or transportation systems are disrupted. Diarrheal diseases from contaminated water and food sources are a major concern, particularly for children.

The effects of globalÂ climate changeÂ on mentalÂ healthÂ and well-being are integral parts of the overall climate-related human health impacts. Mental health consequences of climate change range from minimal stress and distress symptoms to clinical disorders, such asÂ anxiety,Â depression, post-traumatic stress, and suicidal thoughts. [1]

Certain groups of people in low-income countries are especially at risk for adverse health effects from climate change. These at-risk groups include urban people living in poverty, older adults, young children, traditional societies, subsistence farmers, and coastal populations. Many regions, such as Europe, South Asia, Australia, and North America, have experienced heat-related health impacts. Rural populations, older adults, outdoor workers, and those without access to air conditioning are often the most vulnerable to heat-related illness and death. [9] For more information about the climate impacts on vulnerable populations, please visit the Society Impacts & Adaptation page.

Impacts on Shelter

Climate change affects the migration of people within and between countries around the world. A variety of reasons may force people to migrate into other areas. These reasons include conflicts, such as ethnic or resource conflicts, degraded ecosystem services, such as lack of viable agricultural land or fresh water, and extreme events, such as flooding, drought, and hurricanes. Extreme events displace many people, especially in areas that do not have the ability or resources to quickly respond or rebuild after disasters. Many types of extreme events are becoming more frequent or severe because of climate change, which exacerbates existing conflicts. This will likely increase the numbers of people migrating during and after these types of events. [10]

Coastal settlements and low-lying areas are particularly vulnerable to climate change impacts, such as sea level rise, erosion, and extreme storms. Rising ocean temperatures and acidity may also threaten coastal ecosystems. [11] As coastal habitats (such as barrier islands, wetlands, deltas, and estuaries) are destroyed, coastal settlements can become more vulnerable to flooding from storm surges and erosion. Both developing and developed countries are vulnerable to the impacts of sea level rise. For example, Bangladesh, the Netherlands, and Guyana are particularly at-risk.

For more information about the impacts of climate change on coastal areas, please visit the Coastal Impacts & Adaptation page.

For low-elevation coastal areas, this graphic projects current and future population exposure to inundation due to a 1-in-100 year extreme event with sea level rise of 0.15 m (.5 ft, low emissions scenario) to 0.50 m (1.6 ft, high emissions scenario, due to partial melting of Greenland and West Antartic Ice Sheets. IPCC (2014) [12]

Click on the map to see a larger version.

Megacities

For the first time in human history, more people are living in cities than in rural areas. The term "megacities" refers to cities with populations over 10 million. Fifteen of the world's 20 megacities are threatened by sea level rise and increased coastal storm surges. A 2010 study by the Asian Development Bank, the World Bank, and the Japan International Cooperation Agency looked at the effects of climate change on three of Asia's megacities. The study estimated that 26% of the population in Ho Chi Minh City is currently affected by extreme storm events. By 2050, this number could climb to more than 60%. In Manila, a major flood under a worst-case scenario could result in the loss of nearly a quarter of the gross domestic product (GDP) of the metropolitan area. Manila faces not only sea level rise and extreme rainfall events but also typhoons. The study concluded that such climate-related risks must be an integral part of city and regional planning for vulnerable megacities.

Sources:

ADB, JICA, and World Bank, 2010: Climate Risks and Adaptation in Asian Coastal Megacities, A Synthesis Report. The International Bank for Reconstruction and Development / The World Bank, Washington, DC. (PDF)Â Exit

World Bank, 2010: Cities and Climate Change: An Urgent Agenda. The International Bank for Reconstruction and Development / The World Bank, Washington, DC.Â Exit

Impacts on Vulnerable Populations

Three women reach their water source, a low water level lake in India. Photo Credit: 2006, Joydeep Mukherjee, Courtesy of Photoshare. Source: USAIDIndigenous groups in various regions--such as the United States, Latin and South America, Europe, and Africa--are already experiencing threats to their traditional livelihoods. Rising sea levels and extreme events threaten native groups that inhabit low-lying island nations. Higher temperatures and reduced snow, ice, and permafrost threaten groups that live in mountainous and polar areas. Climate effects in these areas can affect hunting, fishing, transport, and other activities. [1], [10]

Approximately 1.4 billion people, close to one fifth of the worldâ€™s population, live below the World Bank's measure of extreme poverty, earning less than US $1.25 a day [13] Many lower-income groups depend on publicly provided resources and services such as water, energy, and transportation. Extreme events can affect and disrupt these resources and services, sometimes beyond replacement or repair. Many people in lower-income countries cannot afford or gain access to adaptation mechanisms such as air conditioning, heating, or disaster insurance. This lack of adaptive capacity makes the worldâ€™s poor especially vulnerable to the impacts of climate extremes, exacerbating existing conditions of poverty and inequality, and ultimately leading to more poverty. [13]

Older and younger people are also especially sensitive to climate change impacts. Children's developing immune, respiratory, and neurological systems make them more sensitive to some climate change impacts, including more frequent or severe extreme events, increased heat, and worsened air quality. [1], [9] Elderly populations are also at risk due to frail health and limited mobility. Extreme heat and storm events can disproportionately affect older people. [1], [9]

Climate change impacts can differ according to gender. Worldwide, women have a higher rate of mortality than men from severe storms or other extreme events, although there is regional variation. In some regions, working-age men who work outdoors are more vulnerable to heat-related deaths.Â Women developing countries women may be particularly vulnerable to extreme events due to differences in poverty and physical vulnerability due to undernutrition or pregnancy.Â As climate change causes extreme events to become more frequent or severe, women may be disproportionately affected. [9]

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Impacts on National Security

Water scarcity led to tensions in southern Kazakhstan. USAID responded by increasing access to drinking water and irrigation. Source: USAIDClimate change impacts are expected to exacerbate national security issues and increase the number of international conflicts. [1]Â The Department of Defense reports that climate change is likely cause instability in other countries-- impairing access to food and water, damaging infrastructure, spreading disease, uprooting and displacing large numbers of peopleâ€”which also affects the United States. They report: â€œClimate change will affect the Department of Defense's ability to defend the Nation and poses immediate risks to U.S. National security.â€? [14]

Many concerns revolve around the use of natural resources, such as water. In many parts of the world, water issues cross local and national borders. Access to consistent and reliable sources of water in these regions is greatly valued. Changes in the timing and intensity of rainfall would threaten already limited water sources and potentially cause future conflicts. [2] Evidence suggests most conflict is likely to occur between local communities, socioeconomic groups, and states, while bilateral and multilateral interactions have shown evidence of formal cooperation over resources. [8]

Threatened food security in parts of Asia and sub-Saharan Africa could also lead to conflict. Rapid population growth and changes in precipitation and temperature, among other factors, are already affecting crop yields. Resulting food shortages could increase the risk of humanitarian crises and trigger population migration across national borders, ultimately sparking political instability. [2], [4], [10], [15]

The ongoing loss of the ice cover in the Arctic Ocean is very likely to have with national security implications. The Arctic Ocean has a long history of modest, though growing, shipping activity, including trans-Arctic shipping routes. Declining sea ice coverage will allow more access to these waters. However, a number of other international issues will influence the potential growth in shipping. In the case of the Arctic Ocean, increasing access to these waters means that issues of sovereignty (priority in control over an area), security (responsibility for policing the passageways), environmental protection (control of ship-based air and water pollution, noise, or ship strikes of whales), and safety (responsibility for rescue and response) will become more important. [16]

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Regional Impacts

Highlights of recent and projected regional impacts are shown below.

Impacts on Africa [4]

Africa may be the most vulnerable continent to climate variability and change because of multiple existing stresses and low adaptive capacity. Existing stresses include poverty, food insecurity, political conflicts, and ecosystem degradation.

By 2050, between 350 million and 600 million people are projected to experience increased water stress due to climate change. Urban population is also projected to triple, increasing by 800 million people, complicating urban poverty and access to basic services.

Climate variability and change is projected to severely compromise agricultural production, including access to food, in many African countries and regions.

Toward the end of the 21st century, projected sea level rise will likely affect low-lying coastal areas with large populations, including Senegal, Liberia, and Mozambique.

Climate variability and change can negatively impact human health. In many African countries, existing health threats â€“ such as malnutrition, malaria and other vector-borne diseases -- can be exacerbated by climate change.

Impacts on Asia [6]

Glaciers in Asia are retreating at faster rates than ever documented in historical records. Some glaciers currently cover 20% of the land that they covered a century ago.Â  Melting glaciers increase the risks of flooding and rock avalanches from destabilized slopes.

Climate change is projected to decrease freshwater availability, especially in central and southeast Asia, particularly in large river basins. With population growth and increasing demand from higher standards of living, this decrease could adversely affect more than a billion people by 2050.

Increased flooding from the sea and, in some cases, from rivers threatens coastal areas, especially heavily populated delta regions in south and southeast Asia.

The impacts of climate change on crop yields are likely to vary drastically depending on region, crop type, and regional changes in temperature and precipitation. For example, by the mid-21st century, climate change could increase crop yield up to 20% in east and southeast Asia, while decreasing yield up to 30% in central and south Asia.

Sickness and death due to diarrheal disease will likelyÂ increase in east, south, and southeast Asia due to projected changes in the hydrological cycle associated with climate change.

Impacts on Australia and New Zealand [17]

Water security problems are projected to intensify with a 1Â°C global average warming in southwestern and southeastern Australia, and in the northern and some eastern parts of New Zealand.

Biodiversity within some ecologically rich sites, including the Great Barrier Reef and Queensland Wet Tropics, will be at significant risk by 2050.

Sea level rise and more severe storms and coastal flooding will continue to affect coastal areas. Coastal development and population growth in areas such as Cairns and Southeast Queensland (Australia) and Northland to Bay of Plenty (New Zealand), would place more people and infrastructure at risk.

Increased drought and fire are projected to cause declines in agricultural and forestry production over much of southern Australia and the northern and eastern parts of New Zealand.

Cascading and interacting economic, social, and daily life circumstances have accompanied prolonged drought in rural regions. Drought-related worry and psychological distress increased in drought-declared Australian regions, particularly for those experiencing loss of livelihood and industry.Â Long-term drought has been linked to increased incidence of suicide among male farmers in Australia. [1]

Extreme storm events are likely to increase the failure of dikes, levees, drainage, and sewerage systems. They are also likely to increase the damage from storms and fires.

More heat waves are likely to cause more deaths and more electrical blackouts.

Indigenous populations are more exposed the risks of climate change than most other Australians and New Zealanders.

Impacts on Europe [18]

Wide-ranging impacts of climate change are already being documented in Europe, including retreating glaciers, sea level rise, longer growing seasons, species range shifts, and heat wave-related health impacts.

Future impacts of climate change will likely negatively affect nearly all European regions, with adverse social, health, and infrastructure effects. Many economic sectors, such as agriculture and energy, could face challenges.

In southern Europe, higher temperatures and drought may reduce water availability, hydropower potential, summer tourism, and crop productivity, hampering economic activity more than other European regions.

In central and eastern Europe, summer precipitation is projected to decrease, causing higher water stress. Forest productivity is projected to decline. The frequency of peatland fires is projected to increase.

In northern Europe, climate change is initially projected to bring mixed effects, including some benefits such as reduced demand for heating, increased crop yields, and increased forest growth. However, as climate change continues, negative impacts are likely to outweigh benefits. These include more frequent winter floods, endangered ecosystems, and increasing ground instability from thawing permafrost.

Impacts on Central and South America [19]

By mid-century, increases in temperature and decreases in soil moisture are projected to cause savanna to gradually replace tropical forest in eastern Amazonia.

In drier areas, climate change will likely worsen drought, leading to salinization (increased salt content) and desertification (land degradation) of agricultural land. The productivity of livestock and some important crops such as maize and coffee is projected to decrease in some areas, with adverse consequences for food security. In temperate zones, soybean yields are projected to increase.

Sea level rise is projected to increase risk of flooding, displacement of people, salinization of drinking water resources, and coastal erosion in low-lying areas. These risks threaten fish stocks, recreation, and tourism.

Changes in precipitation patterns and the melting of glaciers are projected to significantly affect water availability for human consumption, agriculture, and energy generation.

Climate change and land use changes are expected to increase the rates of species extinction.

Warmer weather, milder winters, and changes in precipitation may increase incidence of some vector-borne diseases, such as the chikungunya virus, which is transmitted by mosquitoes.

Impacts on North America [20]

Warming in western mountains will decrease snowpack, increase winter flooding, and reduce summer flows, exacerbating competition for over-allocated water resources.

Disturbances from pests, diseases, and fire are projected to increasingly affect forests, with extended periods of high fire risk and large increases in area burned.

Moderate climate change in the early decades of the century is projected to increase aggregate yields of rain-fed agriculture in northern areas, but temperature increases will reduce corn, soy, and cotton yields in the Midwest and South by 2020. Crops that are near the warm end of their suitable range or that depend on highly utilized water resources will likely face major challenges. High emissions scenarios project reductions in yields by as much as 80% by the end of the century.

Increases in the number, intensity, and duration of heat waves during the course of the century are projected to further challenge cities that currently experience heat waves, with potential for adverse health impacts and increased stress on energy systems. Older populations are most at risk.

Climate change will likely increasingly stress coastal communities and habitats, worsening the existing stresses of population, development, and pollution on infrastructure, human health, and the ecosystem.

Impacts on Polar Regions [21]

Climate changes will likely reduce the thickness and extent of glaciers and ice sheets.

Changes in natural ecosystems will likely have detrimental effects on many organisms including migratory birds, mammals, and higher predators as marine species shift their ranges.

In the Arctic, climate changes will likely reduce the extent of sea ice and permafrost, which can have mixed effects on human settlements. Negative impacts could include damage to infrastructure and changes to winter activities such as ice fishing and ice road transportation. Positive impacts could include more navigable northern sea routes.

The reduction and thawing of permafrost, sea level rise, and stronger storms may worsen coastal erosion and disrupt both natural and social systems.

Climate change effectsâ€”such as increases in coastal erosion, changes in the ranges of some fish, increased weather unpredictabilityâ€”are already disrupting traditional hunting and subsistence practices of indigenous Arctic communities, and may force relocation of villages. [21]

Terrestrial and marine ecosystems and habitats are projected to be at risk to invasive species, as climatic barriers are lowered in both polar regions.

Impacts on Small Islands [22]

Small islands, whether located in the tropics or higher latitudes, are highly vulnerable to extreme weather events, changes in sea level, increases in air and surface temperatures, and changing rainfall patterns.

Deterioration in coastal conditions, such as beach erosion and coral bleaching, will likely affect local resources such as fisheries, as well as the value of tourism destinations.

Sea level rise is projected to worsen inundation, storm surge, erosion, and other coastal hazards. These impacts would threaten vital infrastructure, settlements, and facilities that support the livelihood of island communities.

By mid-century, on many small islands (such as the Caribbean and Pacific), climate change is projected to reduce already limited water resources to the point that they become insufficient to meet demand during low-rainfall periods.

Invasion by non-native species is projected to increase with higher temperatures, particularly in mid- and high-latitude islands.

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References

[1]Â USGCRP (2016).Â The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. Crimmins, A., J. Balbus, J.L. Gamble, C.B. Beard, J.E. Bell, D. Dodgen, R.J. Eisen, N. Fann, M.D. Hawkins, S.C. Herring, L. Jantarasami, D.M. Mills, S. Saha, M.C. Sarofim, J. Trtanj, and L. Ziska, Eds. U.S. Global Change Research Program, Washington, DC, 312 pp.

[2]Â NRC (2010). Advancing the Science of Climate Change. ExitÂ National Research Council. The National Academies Press, Washington, DC, USA.

[3] USGCRP (2014) Climate Change Impacts in the United States: The Third National Climate Assessment. Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe (eds.). United States Global Change Research Program. 841 pp.

[4] Â IPCC (2014). Niang, I., O.C. Ruppel, M.A. Abdrabo, A. Essel, C. Lennard, J. Padgham, and P. Urquhart (2014). Africa. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects, Chapter 22 (Africa). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1199-1265.

[5] IPCC (2014). Porter, J.R., L. Xie, A.J. Challinor, K. Cochrane, S.M. Howden, M.M. Iqbal, D.B. Lobell, and M.I. Travasso (2014). Food security and food production systems. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part A: Global and Sectoral Aspects, Chapter 7 (Food security and food production systems). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 485-533.

[6] IPCC (2014). Â Hijioka, Y., E. Lin, J.J. Pereira, R.T. Corlett, X. Cui, G.E. Insarov, R.D. Lasco, E. Lindgren, and A. Surjan (2014). Asia. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects. Chapter 24 (Asia). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1327-1370.

[7] USDA (2015). Brown, M.E., J.M. Antle, P. Backlund, E.R. Carr, W.E. Easterling, M.K. Walsh, C. Ammann, W. Attavanich, C.B. Barrett, M.F. Bellemare, V. Dancheck, C. Funk, K. Grace, J.S.I. Ingram, H. Jiang, H. Maletta, T. Mata, A. Murray, M. Ngugi, D. Ojima, B.Oâ€™Neill, and C. Tebaldi. 2015. Climate Change, Global Food Security, and the U.S. Food System. 146 pages.

[8] IPCC (2014).Â Â JimÃ©nez Cisneros, B.E., T. Oki, N.W. Arnell, G. Benito, J.G. Cogley, P. DÃ¶ll, T. Jiang, and S.S. Mwakalila (2014). Freshwater Resources. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 3 (Freshwater Resources). pp. 229-269

[9]Â Â Smith, K.R., A. Woodward, D. Campbell-Lendrum, D.D. Chadee, Y. Honda, Q. Liu, J.M. Olwoch, B. Revich, and R. Sauerborn (2014). Human health: impacts, adaptation, and co-benefits. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part A: Global and Sectoral Aspects, Chapter 11 (Human Health). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 709-754.

[10]Â Â Adger, W.N., J.M. Pulhin, J. Barnett, G.D. Dabelko, G.K. Hovelsrud, M. Levy, Ãš. Oswald Spring, and C.H. Vogel (2014). Human security. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part A: Global and Sectoral Aspects, Chapter 12 (Human security). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 755-791.

[11] Â IPCC (2014). Wong, P.P., I.J. Losada, J.-P. Gattuso, J. Hinkel, A. Khattabi, K.L. McInnes, Y. Saito, and A. Sallenger (2014). Coastal Systems and Low-Lying Areas. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. ExitÂ Part A: Global and Sectoral Aspects, Chapter 5 (Coastal systems and low-lying areas). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 361-409.

[12] Â IPCC (2014). Handmer, J., Y. Honda, Z.W. Kundzewicz, N. Arnell, G. Benito, J. Hatfield, I.F. Mohamed, P. Peduzzi, S. Wu, B. Sherstyukov, K. Takahashi, and Z. Yan, 2012: Changes in impacts of climate extremes: human systems and ecosystems.Â Chapter 4 in: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC). pp. 231-290.

[13] IPCC (2014). Olsson, L., M. Opondo, P. Tschakert, A. Agrawal, S.H. Eriksen, S. Ma, L.N. Perch, and S.A. Zakieldeen (2014). Livelihoods and poverty. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. ExitÂ Part A: Global and Sectoral Aspects, Chapter 13 (Livelihoods and poverty). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 109-111

[14] U.S. Department of Defense (2014).Â  Climate Change Adaptation Roadmap.Â (20 pp, 1.6 MB,Â About PDF)

[15] CCSP (2008). Analyses of The Effects of Global Change On Human Health and Welfare and Human Systems. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors). U.S. Environmental Protection Agency, Washington, DC, USA.

[16] Arctic Council (2009). Â Arctic Marine Shipping Assessment 2009 Report .Â ExitÂ (103Â pp, 7 MB,Â About PDF)Â Â

[17] Â IPCC (2014). Reisinger, A., R.L. Kitching, F. Chiew, L. Hughes, P.C.D. Newton, S.S. Schuster, A. Tait, and P. Whetton (2014). Australia. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects, Chapter 25 (Australasia). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 35-94.

[18] Â IPCC (2014). Kovats, R.S., R. Valentini, L.M. Bouwer, E. Georgopoulou, D. Jacob, E. Martin, M. Rounsevell, and J.-F. Soussana (2014). Europe. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects, Chapter 23 (Europe). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1267-1326.

[19] Â IPCC (2014). Magrin, G.O., J.A. Marengo, J.-P. Boulanger, M.S. Buckeridge, E. Castellanos, G. Poveda, F.R. Scarano, and S. VicuÃ±a (2014). Central and South America. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects,Chapter 27 (Central and South America). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1499-1566.

[20] IPCC (2014). Â Romero-Lankao, P., J.B. Smith, D.J. Davidson, N.S. Diffenbaugh, P.L. Kinney, P. Kirshen, P. Kovacs, and L. Villers-Ruiz (2014). North America. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects, Chapter 26 (North America). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1439-1498.

[21] Â IPCC (2014). Larsen, J.N., O.A. Anisimov, A. Constable, A.B. Hollowed, N. Maynard, P. Prestrud, T.D. Prowse, and J.M.R. Stone (2014). Polar regions. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects, Chapter 28 (Polar Regions). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1567-1612.

[22] Â IPCC (2014).Â Nurse, L.A., R.F. McLean, J. Agard, L.P. Briguglio, V. Duvat-Magnan, N. Pelesikoti, E. Tompkins, and A. Webb (2014). Small islands. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. ExitÂ Part B: Regional Aspects, Chapter 29 (Small Islands). Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 1613-1654.

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Climate Impacts in Alaska

On This Page:

Overview

Permafrost

Ecosystems

Oceans and Coasts

Alaska Natives

Overview

Key Points

Warming in Alaska is already thawing permafrost, decreasing Arctic sea ice, changing ecosystems, and threatening the traditional livelihoods of native Alaskans.

Extensive permafrost thaw is expected by the end of this century, increasing the risk of infrastructure damage.

Arctic sea ice is projected to continue to decline, with nearly ice-free periods possible by mid-century.

Changes are expected in the extent, location, and productivity of critical marine and terrestrial habitat for fish and wildlife.

Native Alaskans are expected to experience declining availability of traditional foods and reduced access to sea ice hunting grounds.

Alaska is the largest state in the United States, accounting for about 20% of the total area of the United States and more than twice the land area of Texas. Alaska includes lands on both sides of the Arctic Circle, which makes the United States an Arctic nation. The state spans a wide range of climatic and ecological conditions that include rainforests, glaciers, boreal forest, tundra, peatlands, and meadows. Alaska contains 16 national wildlife refuges spanning 76 million acres and hosts 60% of the total area managed by the National Park Service, including the largest U.S. National Park (Wrangell-St. Elias with 13.2 million acres).[1][2]

Over the past 60 years, the average temperature across Alaska has increased by approximately 3°F.[3] This increase is more than twice the warming seen in the rest of the United States. Warming in the winter has increased by an average of 6°F [3] and has led to changes in ecosystems, such as earlier breakup of river ice in the spring. As the climate continues to warm, average annual temperatures in Alaska are projected to increase an additional 2 to 4°F by the middle of this century.[3] Precipitation in Alaska is projected to increase during all seasons by the end of this century. Despite increased precipitation, the state is likely to become drier due to greater evaporation caused by warming temperatures and longer growing seasons.[3]

Rising temperatures may provide some benefits in Alaska, such as a longer growing season for agricultural crops, increased tourism, and access to natural resources that are currently inaccessible due to ice cover, like offshore oil. However, climate change is also having adverse effects on many ecosystems and species, and is creating new hardships for Native Alaskans.

Permafrost

Related Links

EPA:

National Climate Assessment: Alaska

EPA Region 10 (including AK, ID, OR, and WA)

Environmental Protection in Indian Country

EPA Climate Change Indicators: Arctic Sea Ice

EPA Climate Change Indicators: River Ice Breakup in Alaskan Rivers

Other:

Alaska Department of Commerce: Climate Change Office Exit

State of Alaska: Climate Change in Alaska

The Alaska Climate Research Center Exit

U.S. Arctic Research Commission

ITEP, Tribes & Climate Change Exit

Permafrost is frozen ground that is typically located a few feet below the soil surface in extremely cold regions. Eighty percent of Alaska's surface lies above permafrost.[3] Permafrost typically remains frozen year-round, but as air temperatures rise, permafrost is thawing in many areas. As permafrost thaws, ice in the permafrost melts and can cause the soil above to sink, resulting in ground subsidence and damage to roads, homes, and other structures. The impacts of melting permafrost on transportation, forests, other ecosystems, and the economy could have widespread implications for Alaskans.

Transportation and Infrastructure Impacts

Climate change leads to more permafrost thaw and disruptions to freeze-thaw cycles that can increase frost heaves and subsidence. This can potentially cause damage to transportation infrastructure in Alaska, including highways, railroads, and airstrips.[4] Uneven sinking of the ground in response to permafrost thaw is likely to add significant costs to the maintenance and repair of transportation infrastructure and buildings.[3] Many of Alaska's highways are built in permafrost areas and are subject to damage if the permafrost thaws. Additionally, warming leads to a shorter period when ice roads are usable and a shorter season during which oil and gas exploration on the tundra can occur.[3]

For more information on climate change impacts on transportation, please visit the Transportation Impacts page.

Ecosystems

Alaska highways susceptible to permafrost. Source: U.S. Arctic Research Commission (2003)[4]

Click the image to view a larger version.Two pairs of aerial photographs of pond areas in Alaska. The two images on the left show the pond areas in 1951 and images on the right show the same pond areas in 2000. The pond areas shown on top shrunk from 180 to 10 acres, and the pond areas shown in the bottom went from 90 to 4 acres in size. Source: USGCRP (2009)[9]Climate change is causing changes in lakes, ponds, wetlands, plant composition, and wildfires that impact human health, wildlife, and ecosystems.[3] Lakes are changing size, with most lakes shrinking in area in the southern portion of the state.[3] Surface waters and wetlands provide breeding habitat for millions of waterfowl and shorebirds that winter in the lower 48 states. These wetland ecosystems and wildlife resources are also important to Alaska Natives who hunt and fish for food.

Lakes get smaller through a combination of increased evaporation caused by warmer temperatures, permafrost thaw which allows lakes to drain more readily, and greater accumulation of decomposing plant material on lake bottoms caused by greater plant growth.[3] In areas where permafrost is discontinuous or fragmented across the landscape, lakes are expected to continue shrinking in area. Some lakes are growing in area because of lateral permafrost thaw, which causes the edges of the lake to collapse inward, thereby increasing the area of the lake. Lake growth is expected to continue in areas underlain with continuous permafrost.[3]

As the climate warms, shrubs are expanding into the tundra. In some areas, shrubs are replacing lichens and other tundra vegetation. Lichens are an important winter food source for caribou, and the loss of lichens can lead to declines in the growth and abundance of these animals. Caribou, in turn, are a critical food source for predators such as bears and wolves, as well as for some Alaska Natives.[5]

In recent years, an increase in large wildfires has been seen in Alaska. Credit: USGCRP (2014)Higher temperatures and drier conditions increase the risks of drought, wildfire, and insect infestation. Large wildfires have consumed more boreal forest in Alaska in the last ten years than in any other decade recorded, and the area burned annually is projected to double by 2050.[3] Fires change forest habitat, improving conditions for moose and some plant species, but reducing the lichen that caribou rely on in winter. Warmer temperatures are also expected to worsen insect damage to forests across much of the state, which may increase the area of standing dead, highly flammable trees that are especially vulnerable to wildfire.[6]

Oceans and Coasts

Sea ice is frozen seawater that floats on the surface of the ocean. Some sea ice persists from year to year (known as perennial sea ice), often getting thicker as it piles up against Arctic shorelines. Other sea ice is seasonal, melting during the summer and refreezing in winter.

Sea ice extent has, on average, been declining in recent decades. This figure shows the extent from 1979 to 2015. Source: US EPA (2015)[10]

Click the image to view a larger version.Over the past several decades, perennial sea ice has declined. This decline is, in part, a result of extended periods of above-freezing air or water temperatures. Ocean currents and wind patterns have also played an important role.[7] September 2012 had the lowest sea ice extent (or area of ocean covered by ice) on record, 49 percent below the 1979-2000 average for that month. The September 2014 sea ice extent was nearly 700,000 square miles less than the historical 1979-2000 average for that month - a difference more than twice the size of Texas.[10] The thickness and age of sea ice is also declining throughout the Arctic, with recent measurements indicating a loss of 50% of sea ice since 1979.[3] Climate models project that sea ice will continue to decrease and indicate that the Arctic could be nearly ice free during the late summer by the 2030s.[3]

Diminishing sea ice is opening new opportunities for shipping, oil and gas exploration, tourism, and other economic activities. However, it also creates a pathway for invasive species and habitat loss for a variety of ice-dependent species, including walruses and polar bears.[3] Changes in sea ice can also affect the timing and location of plankton blooms, which can in turn affect the areas where commercial fisheries can thrive. Sea ice along the shoreline and permafrost in coastal areas help to protect human settlements from flooding and erosion. As coast erosion increases due to declining sea ice, residents are becoming more vulnerable.[3]

For more information on climate change impacts on coasts, please visit the Coastal Impacts page.

Alaska Natives

The ground under a home in Shishmaref, Alaska collapses from erosion.

Image credit: The Alaska Conservation Foundation (2010) ExitAlaska is home to 229 federally recognized tribes that are already experiencing the impacts of climate change in their everyday lives.[3] Alaska Native peoples depend economically, nutritionally, and culturally on fishing and hunting animals, including polar bears, walruses, seals, caribou, and fish. As the supply of fish and game decline, they are likely to travel onto thinning ice in search of food and are being forced to seek alternative food sources. Arctic plants and animals, including those harvested as subsistence food, are also at higher risk for diseases in a warming climate, further affecting food availability and human health.[3]

Locations of 12 Native Villages considering relocation. Source: GAO (2009)[11]The health of native communities is also threatened by loss of clean water, saltwater intrusion, and sewage contamination from thawing permafrost, as well as by the northward expansion of diseases. Warming also increases exposure to pollutants, such mercury and organic pesticides, that have been transported to Arctic regions and are released from thawing soils.[3]

Thawing permafrost, loss of coastal sea ice, sea level rise, and more intense extreme weather events are also increasing erosion and flooding along Alaska's northwestern coast. More than 30 Native villages are either in the process of or in need of relocating their entire village. In Shishmaref, Kivalina, and Newtok, for example, erosion is causing extensive damage, creating new dangers to residents, and deepening pressure to relocate.[8] However, due to high costs and land constraints, tribal communities in Alaska have been experiencing difficulty relocating to safer areas.

For more information on climate change impacts on society, please visit the Society Impacts page.

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References

[1] U.S. Fish & Wildlife Service, National Wildlife Refuge, Alaska Region.

[2] National Park Service (2014) United States. Alaska Regional Office. U.S. Department of the Interior.

[3] USGCRP (2014). Chapin, F.S., S.F.Trainor, P. Cochran, H. Huntington, C. Markon, M. McCammon, A.D. McGuire, and M. Serreze, 2014: Ch. 22: Alaska. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds, U.S. Global Change Research Program, 514-536.

[4] U.S. Arctic Research Commission Permafrost Task Force (2003). Climate Change, Permafrost, and Impacts on Civil Infrastructure. Special Report 01-03(72 pp, 4.8 MB, About PDF), U.S. Arctic Research Commission, Arlington, Virginia.

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

[6] USGS (2012). Markon, C.J., Trainor, S.F., and Chapin, F.S., III, eds., 2012, The United States National Climate Assessment - Alaska Technical Regional Report: U.S. Geological Survey Circular 1379, (166 pp, 11.3 MB, About PDF).

[7] National Snow and Ice Data Center: Exit

	National Snow and Ice Data Center (3 Oct. 2014). Arctic Sea Ice News & Analysis: A better year for the cryosphere. Exit

	National Snow and Ice Data Center (7 Oct. 2014). Arctic Sea Ice News & Analysis: 2014 melt season in review. Exit

[8] USGCRP (2014). Bennett, T. M. B., N. G. Maynard, P. Cochran, R. Gough, K. Lynn, J. Maldonado, G. Voggesser, S. Wotkyns, and K. Cozzetto, 2014: Ch. 12: Indigenous Peoples, Lands, and Resources. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 297-317.

[9] USGCRP (2009). Global Climate Change Impacts in the United States.

[10] US EPA (2015). Climate Change Indicators in the United States.

[11] GAO (2009). Alaska Native Villages: Limited Progress Has Been Made on Relocating Villages Threatened by Flooding and Erosion(53 pp, 2.2 MB, About PDF).

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Climate Change Impacts

Climate Impacts on Ecosystems

On This Page:

Overview

Timing of Seasonal Life-Cycle Events

Range Shifts

Food Web Disruptions

Threshold Effects

Pathogens, Parasites, and Disease

Extinction Risks

Key Points

Climate change can alter where species live, how they interact, and the timing of biological events, which could fundamentally transform current ecosystems and food webs.

Climate change can overwhelm the capacity of ecosystems to mitigate extreme events and disturbance, such as wildfires, floods, and drought.

Mountain and arctic ecosystems and species are particularly sensitive to climate change.

Projected warming could greatly increase the rate of species extinctions, especially in sensitive regions.

Overview

Climate is an important environmental influence on ecosystems. Changing climate affects ecosystems in a variety of ways. For instance, warming may 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 are 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 SeasonalÂ 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 reproduction. As winters have become shorter and milder, the timing of these events has changed in some parts of the country:

Related Links

EPA:

Ecosystems Services Research

Climate Ready Estuaries

Other:

National Climate Assessment: Ecosystems, Biodiversity, and Ecosystem Services

IPCC: Fifth Assessment ReportÂ Exit

NAS: America's Climate ChoicesÂ Exit

USGCRP: Climate Change and Agriculture, Land Resources, Water Resources, and Biodiversity

UNEP: Links between Biodiversity and Climate ChangeÂ Exit

U.S. FWS: Landscape Conservation Cooperatives

Terminology

An ecosystem refers to the animals, plants, and microorganisms that live in one place, as well as the environmental conditions that support them.

Ecosystem services include the products and services provided by ecosystems, such as food, fuel, timber, water, clean air, and medicines. It also includes less material benefits, such as regulation of local climate conditions and aesthetic value or cultural identity.[11]

An ecological threshold is the point at which there is an abrupt change in an ecosystem quality, property, or phenomenon, or where small changes in one or more external conditions produce large and persistent responses in an ecosystem.[8]

A biome is a large, naturally occurring community of plants and animals occurring in a regional or global land area.

A food web is a group of predators and prey that interact in a habitat or ecosystem.

A stressor is a factor that reduces the health or productivity of an ecosystem (i.e., causes stress).

Earlier 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 a century ago.[2]

In a California study, 16 out of 23 butterfly species shifted their migration timing and arrived earlier.[2]

Because species differ in their ability to adjust, asynchronies can develop, increasing species and ecosystem vulnerability. These asynchronies can include mismatches in the timing of migration, breeding, pest avoidance, and food availability. Growth and survival are reduced when migrants arrive at a location before or after food sources are present.[2][3]

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Range Shifts

As temperatures increase, the habitat ranges of many North American species are moving north and to higher elevations. In recent decades, in both land and aquatic environments, plants and animals have moved to higher elevations at a median rate of 36 feet (0.011 kilometers) per decade, and to higher latitudes at a median rate of 10.5 miles (16.9 kilometers) per decade. While this means a range expansion for some species, for others it means movement into less hospitable habitat, increased competition, or range reduction, with some species having nowhere to go because they are already at the top of a mountain or at the northern limit of land suitable for their habitat.[4][5] These factors lead to local extinctions of both plants and animals in some areas. Â As a result, the ranges of vegetative biomes are projected to change across 5-20% of the land in the United States by 2100.[4]

For example, boreal forests are invading tundra, reducing habitat for the many unique species that depend on the tundra ecosystem, such as caribou, arctic foxes, and snowy owls. Other observed changes in the United States include a shift in the temperate broadleaf/conifer forest boundary in the Green Mountains of Vermont; a shift in the shrubland/conifer forest boundary in New Mexico; and an upward elevation shift of the temperate mixed/conifer forest boundary in Southern California.

As rivers and streams warm, warmwater fish are expanding into areas previously inhabited by coldwater species.[5] As waters warm, coldwater fish, including many highly-valued trout and salmon species, are losing their habitat, with projections of 47% habitat loss by 2080.[4] Â In certain regions in the western United States, losses of western trout populations may exceed 60 percent, while in other regions, losses of bull trout may reach about 90 percent.[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 page for information about how habitats of marine species have shifted northward as waters have warmed.

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Food Web Disruptions

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 below shows the complex nature of the food web for polar bears. Not only is the decline of sea ice impairing polar bear populations by reducing the extent of their primary habitat, it is also negatively impacting them via food web effects. 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.[2][6][7]

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)

Click the image to see a larger version.

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The Pika

The American pika is a hamster-sized relative of the rabbit that is found in the cold, mountainous of the western United States. Because of their sensitivity to hot temperatures, the warming climate is causing pika populations to die off at elevations below 7,000 feet. Of 25 pika populations studied in the Great Basin between the Rocky Mountains and the Sierra Nevada, more than one third have disappeared in the past few decades. However, because of their retreat to colder climates, they are well-distributed in higher elevations and are not endangered species.[5][12]

			Climate change is likely the leading factor decreasing the populations and shifting habitat range of the American pika (Ochotona princeps). Source: National Climate Assessment (2009).

Penguins and Climate Change: A Case of "Winners" and "Losers"

Even within a single ecosystem, there can be winners and losers from climate change. The AdÃ©lie and Chinstrap penguins in Antarctica provide a good example. The two species depend on different habitats for survival: AdÃ©lies inhabit the winter ice pack, whereas Chinstraps remain close to open water. During the past 50 years, a 7â€“9Â°F increase in midwinter temperatures on the western Antarctic Peninsula has led to a loss of sea ice. Over the past 25 years, the population of AdÃ©lie penguins decreased by 22%, while the population of Chinstrap penguin increased by an estimated 400%.[13]

Buffer and Threshold Effects

Ecosystems can serve as natural buffers from extreme events such as wildfires, flooding, and drought.Â  Climate change and human modification may restrict ecosystemsâ€™ ability to temper the impacts of extreme conditions, and thus may increase vulnerability to damage. Examples include reefs and barrier islands that protect coastal ecosystems from storm surges, wetland ecosystems that absorb floodwaters, and cyclical wildfires that clear excess forest debris and reduce the risk of dangerously large fires.[4]

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 changeâ€”a dramatic drop in the prairie potholes that host waterfowl populations, which subsequently provide highly valued hunting and wildlife viewing opportunities.[8]

Similarly, when coral reefs become stressed from increased ocean temperatures, 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.[5][9]

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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.[10] For more information about climate change impacts on agriculture, visit the Agriculture and Food Supply Impacts page. To learn more about climate change impacts on human health, visit the Health ImpactsÂ 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 the levels projected to occur by the end of this century.[1] Global rates of species extinctions are likely to approach or exceed the upper limit of observed natural rates of extinction in the fossil record.[1] Examples of speciesÂ 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 polar bears; and coldwater fish, such as salmon in the Pacific Northwest.[4][5]

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References

[1] IPCC (2014).Â Settele, J., R. Scholes, R. Betts, S. Bunn, P. Leadley, D. Nepstad, J.T. Overpeck, and M.A. Taboada. Terrestrial and Inland Water Systems. In: Climate Change 2014: Impacts, Adaptation and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.) Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

[2] CCSP (2008).Â 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.

[3] USGCRP (2014). Horton, R., G. Yohe, W. Easterling, R. Kates, M. Ruth, E. Sussman, A. Whelchel, D. Wolfe, and F. Lipschultz, 2014: Ch. 16: Northeast. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 16-1-nn.

[4] USGCRP (2014). Groffman, P. M., P. Kareiva, S. Carter, N. B. Grimm, J. Lawler, M. Mack, V. Matzek, and H. Tallis, 2014: Ch. 8: Ecosystems, Biodiversity, and Ecosystem Services. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 200-201.Â

[5] USGCRP (2009). Global Climate Change Impacts in the United States. â€œClimate Change Impacts by Sectors: Ecosystems.â€? 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] USGCRP (2014).Â Chapin, F. S., III, S. F. Trainor, P. Cochran, H. Huntington, C. Markon, M. McCammon, A. D. McGuire, and M. Serreze, 2014: Ch. 22: Alaska. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 514-536.

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

[8] 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.

[9] USGCRP (2014). Leong, J.-A., J. J. Marra, M. L. Finucane, T. Giambelluca, M. Merrifield, S. E. Miller, J. Polovina, E. Shea, M. Burkett, J. Campbell, P. Lefale, F. Lipschultz, L. Loope, D. Spooner, and B. Wang, 2014: Ch. 23: Hawaiâ€˜i and U.S. Affiliated Pacific Islands. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 537-556.

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

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

[12] USFWS (2010). Endangered and Threatened Wildlife and Plants; 12-month Finding on a Petition to List the American Pika as Threatened or Endangered. U.S. Fish and Wildlife Service.

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

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Climate Change Impacts

Climate Impacts in the U.S. Islands

On This Page

Overview

Water Resources

Communities and Agriculture

Infrastructure and Economy

Ecosystems

Key Points

Warmer and more acidic oceans are adding to existing stresses on coral reefs and fish communities.

Sea level rise is expected to threaten the water supplies, ecosystems, and infrastructure of U.S. tropical islands.

Climate change is likely to affect livelihoods, as well as tourism and other important economic sectors on tropical islands.

Overview

The U.S. tropical islands include Puerto Rico and the U.S. Virgin Islands in the Caribbean, and Hawai’i, Guam, the Northern Mariana Islands, and American Samoa in the Pacific. Many islands are especially vulnerable to the risks of climate change because of their small size, low elevation, remote geographical location, and concentration of infrastructure along coastlines.[1][2] Islands are also home to unique ecosystems, including coral reefs, mangrove forests, and diverse populations of native species found nowhere else in the world. Island ecosystems are already stressed from human development and pollution, making them particularly sensitive to additional stresses from climate change.[1][2]

Islands are experiencing rising air temperatures and sea levels, and warmer, more acidic coastal waters.[1] Temperatures are expected to increase into the future, but will vary in the extent of warming that occurs based on location, elevation, and changes in ocean conditions. In Hawai’i and the Central North Pacific, temperatures are projected to rise by 1.5°F to 3.5°F by mid-century, while in Guam and Northern Mariana Islands, increases of 1.9°F to 2.6°F are projected.[1] In the Caribbean, Puerto Rico is projected to warm by 2°F to 5°F by the end of this century.[3]

Related Links

EPA:

EPA Region 2 (including Puerto Rico and the U.S. Virgin Islands)

EPA Region 9 (including Hawaii and the Pacific Islands)

EPA Indicators, Ocean Acidification

Other:

USGCRP, Climate Change Wildlife and Wildlands: Caribbean

USGCRP, Climate Change Wildlife and Wildlands: Pacific Islands

Global Coral Reef Monitoring Network: Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 2005 (150 pp, 3.9 MB, About PDF)

USGCRP, Hawai’i and Pacific Islands

USGCRP, Southeast and Caribbean

IPCC Fifth Assessment Report 2014, Working Group II, Small Islands Exit(42 pp, 3.5 MB, About PDF)

NRC: America's Climate Choices Series: Adapting to the Impacts of Climate Change Exit

NOAA, Ocean Acidification Program

Changes in precipitation are also being observed. The Pacific Islands are highly influenced by El Niño and La Niña events, which create annual variability in storms and precipitation. Despite this variability, a trend for decreasing precipitation has been observed in Hawai’i, while a small increase has been measured in the Northern Mariana Islands and in Guam.[1] Future precipitation patterns are less certain, but for Hawai’i, projections suggest a small decrease in precipitation during the wet season and a small increase during the dry season.[1] Some parts of the Caribbean are experiencing reduced precipitation while other areas are have seen increases.[3] Continued variation in trends is expected in the future, but on average, precipitation is expected to decrease across the Caribbean. In Puerto Rico, an increasing amount of rain has been falling in the form of heavy downpours in recent history.[4] Limited information for American Samoa shows no significant change in precipitation.

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Water Resources

Climate change is expected to affect the availability of water on some islands, particularly on small islands and atolls. On islands where precipitation decreases, ground and surface water supplies may not be recharged, resulting in less freshwater availability.[2] This can impact both drinking water supplies and irrigation water for crops.[1][3] Sea level rise and coastal erosion may also reduce water availability by inundating land with saltwater, contaminating freshwater, and preventing recharge of the freshwater supply.[2] Increased temperatures coinciding with reduced precipitation are also expected to increase the likelihood of drought.[1][3]

Freshwater Lens: Many island communities rely on freshwater lenses, especially for irrigation.[2] Freshwater lenses form when freshwater enters aquifers and floats on top of saltwater, which is much more dense.[5] The amount of water contained in a freshwater lens is determined by the size of the island, the amount of rainfall, water withdrawal, the permeability of the rock beneath the island, and mixing with saltwater. These lenses can be as shallow as a few inches or as deep as 65 feet. Credit: USGCRP (2009) (196 pp, 13 MB, About PDF)

Click the image to view a larger version.In contrast, some islands are expected to receive heavier downpours, which can cause flooding, overload water infrastructure systems, and result in sewage contamination and public health concerns.[1] On islands where populations are growing or where infrastructure is old or poorly maintained, the impacts on water supplies may be especially severe.[1][2]

For more information about climate change impacts on water, please visit the Water Resources page.

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Communities and Agriculture

Climate change will have far-reaching effects on local island culture, health, and livelihoods, altering traditional lifestyles on the islands.[1] Cultural structures may be lost to rising seas while availability of traditional foods may decline because of coral reef losses, drought, or saltwater inundation of agricultural lands. Residents in coastal areas may need to relocate if climate-related damages become too extreme. For more information about climate change impacts on culture, please visit the Society page.

Saltwater inundation caused by storm surges or very high tides can kill important agricultural crops. This taro crop requires 2-3 years of growth before harvest. After inundation, it can take 2 years for the salt to be flushed from the soils to allow replanting. Credit: USGCRP (2014)Climate change is also expected to negatively impact human health. The incidence of some diseases, such as dengue fever, are likely to increase in the Pacific Islands.[1] In the Caribbean, diseases already present, including malaria and dengue and yellow fevers, could increase with warming temperatures.[3]

Coastal agriculture is also affected by climate change. Sea level rise can lead to saltwater inundation, causing soils to become saltier and less fertile on some islands. Water supplies can suffer as a result of reductions in rainfall or from saltwater intrusion, reducing both drinking water and irrigation water availability.[1][2]

For more information about climate change impacts on agriculture and food, please visit the Agriculture and Food Impacts page.

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Infrastructure and Economy

Island infrastructure and economic development are at greater risk due to climate change. Island settlements, social and leisure events, and economic activity tend to be concentrated close to the coasts, especially on smaller islands. This makes them especially vulnerable to climate change impacts from sea level rise, coastal inundation, storm surge, flooding, and shoreline erosion.[1][6]

Coastal houses and an airport in the U.S.-affiliated Federated States of Micronesia rely on mangroves' protection from erosion and damage due to rising sea level, waves, storm surges, and wind. Credit: USGCRP (2009) (196 pp, 13 MB, About PDF)Higher sea levels, inundation, flooding, and shoreline and beach erosion are expected to affect critical transportation, energy, and water infrastructure, including airports, roads, ports, and wastewater systems.[1] Because of their geographic remoteness, islands largely rely on imported food, fuel, and materials, making damage to airports or ports especially critical to the well-being of island residents.[1] The impacts of sea level rise are already being felt. In Rincón, Puerto Rico, sea level rise is currently eroding the coastline at a rate of about three feet per year.[3]

Climate change will affect tourism, an important source of revenue for islands. Sea level rise, warming water temperatures, increasing storm intensity, beach erosion, and ocean acidification could pose risks to beaches and threaten coastal activities, such as coral reef exploration, boating, and fishing. Closures to island beaches due to damage or harmful algal blooms could have large economic impacts, particularly on the tourism sector. In Puerto Rico, 3.5 million tourists spent $3.5 billion in 2009.[3] Tourism accounts for 26% of the state income in Hawai’i.[1] The loss of the Waikiki Beach in Hawai’i alone could reduce the state annual income by $2 billion.

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Ecosystems

Islands are home to unique ecosystems and species that provide economic opportunities, safety, and cultural value to island communities.[1][6] Rising sea levels, temperatures, and ocean acidification of coastal waters are threatening the stability and functioning of these ecosystems.

Climate change is increasing the temperature and acidity of the world’s oceans. These changes threaten the health and survival of coral reef ecosystems. Credit: USGCRP (2014)Coral reefs serve as an important habitat for many fish and marine organisms. They also provide shoreline protection, valuable fisheries, and revenue through tourism. In Hawai’i, the goods and services provided by coral reefs are estimated to bring in approximately $385 million each year.[1] In the Caribbean, income losses associated with degraded reefs are conservatively estimated to be several hundred million dollars each year.[2]

Reef ecosystems are stressed by coastal development, pollution, and invasive species. Warmer, more acidic coastal waters further stress reefs, and coral disease outbreaks and bleaching events tend to coincide with warming waters. As the oceans warm, coral cover is expected to decline greatly.[1]

Oceans are also becoming more acidic.[8] This occurs as the higher levels of carbon dioxide in the atmosphere react with sea water to produce carbonic acid. Since the Industrial Revolution, ocean acidity has increased by 30%, a rate that is approximately 50 times faster than the known historical change prior to this period.[4] Acidity is projected to increase by an additional 37% to 50% above present levels by the end of the century.[1]

Increases in ocean acidity (measured by lower pH values) changes the balance of minerals in the water. This change makes it more difficult for corals, some types of plankton, and other organisms to produce calcium carbonate, which makes up and strengthens the marine organisms’ hard skeletons and shells.[8]

As carbon dioxide levels increase in the atmosphere, more carbon dioxide dissolves into the oceans and forms carbonic acid. As this occurs, the pH decreases (increasing acidity). This pattern has been observed near numerous islands, including Hawai’i. Source: US EPA (2015)[8]

Click the image to view a larger version.As climate change alters coral reefs, reduction in fish populations that inhabit these ecosystems is expected.[1] Many island communities depend on local fisheries for survival and economic development. Changes in ocean temperatures can also damage fish habitats and cause shifts in the reproduction or migration behaviors of certain fish species, including tuna.[1][7] These impacts may exacerbate existing stresses on fisheries, such as those from pollution and overfishing, and may ultimately lead to a decline in the abundance and health of fishery populations.[7]

Sea level rise will result in flooding or loss of tidal marshes, swamps, and other coastal habitats.[1][2][3] These ecosystems provide important habitat for birds and aquatic organisms, and losses will exacerbate existing stresses on vulnerable species.[1][4] In the Caribbean, forests are retreating from the coastlines. Mangrove forests, which help to protect shorelines, are expanding in some parts of the Caribbean,[2] but are shrinking in parts of the Pacific.[1]

Plants and animals are increasingly stressed by high temperatures and, on some islands, reduced rainfall.[1] High-elevation ecosystems are especially vulnerable because they have limited ability to find suitable habitat. Climate change is also providing conditions that increase the spread of invasive species, pathogens, and diseases, which will affect populations of native plants, birds, and freshwater organisms.[1][3]

For more information about climate change impacts on ecosystems, please visit the Ecosystems Impacts page.

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References

[1] USGCRP (2014). Leong, J.-A., J. J. Marra, M. L. Finucane, T. Giambelluca, M. Merrifield, S. E. Miller, J. Polovina, E. Shea, M. Burkett, J. Campbell, P. Lefale, F. Lipschultz, L. Loope, D. Spooner, and B. Wang, 2014: Ch. 23: Hawai‘i and U.S. Affiliated Pacific Islands. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 537-556.

[2] 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.

[3] USGCRP (2014). Carter, L. M., J. W. Jones, L. Berry, V. Burkett, J. F. Murley, J. Obeysekera, P. J. Schramm, and D. Wear, 2014: Ch. 17: Southeast and the Caribbean. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 396-417.

[4] USGCRP (2014). Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens, P. Thorne, R. Vose, M. Wehner, J. Willis, D. Anderson, S. Doney, R. Feely, P. Hennon, V. Kharin, T. Knutson, F. Landerer, T. Lenton, J. Kennedy, and R. Somerville, 2014: Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 19-67.

[5] U.S. Geological Survey Pacific Islands Water Science Center (2015). Hydrology of Ocean Islands. Accessed May 5, 2015.

[6] IPCC (2014). Nurse, L.A., R.F. McLean, J. Agard, L.P. Briguglio, V. Duvat-Magnan, N. Pelesikoti, E. Tompkins, and A. Webb, 2014: Small islands. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change Exit [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White(eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1613-1654.

[7] IPCC (2007). Mimura, N., L. Nurse, R.F. McLean, J. Agard, L. Briguglio, P. Lefale, R. Payet and G. Sem (2007). Small Islands. In:Climate Change 2007: Impacts, Adaptation and Vulnerability. Exit 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.

[8] US EPA (2015). Climate Change Indicators in the United States: Ocean Acidity.

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