Global Warming
Global warming is quickly becoming the biggest threat to the long-term survival of America’s wildlife. Changes are happening much faster than were predicted just a few years ago.
Average temperatures in the U.S. over the last century have already increased by more than one degree, with much greater increases in some regions like Alaska. Temperatures are expected to rise another 2-10 degrees by 2100. These changes are having noticeable effects on wildlife.
Observed Changes in Wildlife and Ecosystems
- Changes in range: Wildlife and plants that are able to adjust are shifting their ranges northward or to higher altitudes to adjust to warming temperatures. Wildlife that already live at high altitudes or latitudes, such as the American pika or polar bears in the Arctic, may find themselves with nowhere to go.
- Changes in timing of natural events: Many species take their cues about when to migrate, flower, nest or mate from seasonal changes in temperature, precipitation and daylight (phenology). Global warming is confusing those signals. The changes in the climate force wildlife to alter life cycle and seasonal events. Sometimes they might get out of synch with other species in their ecosystem or with other natural events. For example, some animals are laying eggs, migrating, or emerging from hibernation much earlier than they used to, only to find that the plants or the insects they need for food have not yet emerged.
- Widespread forest loss: In the western U.S., warming and drought stress are causing trees to die and making them more vulnerable to pine beetle and other insect infestations. Higher temperatures and increased fuel from dead trees have led to more wildfires.
- Coral bleaching: Coral bleaching occurs when colorful algae that live in corals die or are expelled from corals under stress. The algae live symbiotically with coral polyps, providing them with nutrients and oxygen. If the algae die and are not replaced, the corals will also die. Scientists believe that the biggest cause of coral bleaching is warm sea surface temperatures caused by global warming. If coral reef bleaching continues, many other marine organisms that depend on coral reefs will also be in jeopardy.
- Melting of Arctic sea ice: Arctic ice is melting at a faster pace than was predicted even a few years ago. Some scientists are now saying that the Arctic could be ice free in the late summer as early as 2012. Many Arctic mammals, such as polar bears, walrus, and seals depend on sea ice for their survival.
Additional Threats to Wildlife from Global Warming
- Loss of wetlands: Higher temperatures will lead to drier conditions in the Midwest’s Prairie Pothole region, one of the most important breeding areas for North American waterfowl.
- Sea-level rise: Sea-level rise will inundate beaches and marshes and cause erosion on both coasts, diminishing habitat for birds, invertebrates, fish, and other coastal wildlife.
- Invasive species and disease: Higher average temperatures and changes in rain and snow patterns will enable some invasive plant species to move into new areas. Insect pest infestations will be more severe as pests such as mountain pine beetle are able to take advantage of drought-weakened plants. Pathogens and their hosts that thrive in higher temperatures will spread to new areas.
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