CLIMATE CHANGE EFFECTS
Consequences for Wildlife
Polar bear. Credit: USFWS
A growing body of evidence has linked accelerating climate change with observed changes in fish and wildlife, their populations, and their habitats in the United States. Polar bear population declines have already been noted in Canada, and extirpations of Bay checkerspot butterfly populations in the San Francisco Bay area are also documented. Across the continental United States, climate change is affecting the migration cycles and body condition of migratory songbirds, causing decoupling of the arrival dates of birds on their breeding grounds and the availability of the food they need for successful reproduction.
Climate change has very likely increased the size and number of wildfires, insect outbreaks, pathogens, disease outbreaks, and tree mortality in the interior West, the Southwest, and Alaska. In the aquatic environment, evidence is growing that higher water temperatures resulting from climate change are negatively impacting cold- and cool-water fish populations across the country. Along our coasts, rising sea levels have begun to affect fish and wildlife habitats, including those used by shorebirds and sea turtles that nest on our coastal National Wildlife Refuges. In the oceans, subtropical and tropical corals in shallow waters have already suffered major bleaching events driven by increases in sea surface temperatures.
The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report estimates that approximately 20-30 percent of the world’s plant and animal species assessed as of 2006 are likely to be at increasingly high risk of extinction as global mean temperatures exceed a warming of 2 – 3°C above preindustrial levels. Global average temperature increases of 0.74°C are already documented, and temperature increases in some areas are projected to exceed 3.0°C over the next decade. The IPCC further concludes that substantial changes in structure and functioning of terrestrial ecosystems are very likely to occur with a global warming of more than 2-3°C above preindustrial levels. These changes will have predominantly negative consequences for biodiversity and ecosystem goods and services (e.g., water and food). The IPCC also reports that the resilience of many ecosystems around the world is likely to be exceeded this century by an unprecedented combination of climate change; disturbances associated with climate change, such as flooding, drought, wildfire, and insects; and other global change-drivers, including land-use changes, pollution, habitat fragmentation, urbanization, and growing human populations and economies. These projected changes have enormous implications for management of fish and wildlife and their habitats around the world.
Climate change has the potential to cause abrupt ecosystem changes and increased species extinctions.