Climate change impacts are occurring more often and causing more damage than at any time in recorded human history. A growing body of evidence links accelerating climate change climate change Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change with observed changes in fish and wildlife, their populations, and their habitats across the United States.
Polar bear population declines in Alaska and Canada, and extirpations of Bay checkerspot butterfly populations in the San Francisco Bay area are just two examples of how climate change is harming wildlife. Across the United States, climate change is affecting the migration cycles and biology of migratory songbirds, causing a mismatch between when birds arrive on their breeding grounds and when their food is available.
Climate change has very likely increased the size, intensity, and number of wildfires, insect outbreaks, disease outbreaks, and tree mortality in the interior West, the Southwest, and Alaska. In aquatic environments, evidence is growing that higher water temperatures from climate change are negatively impacting cold- and cool-water fish populations, like salmon, across the country. Along our coasts, rising sea levels have begun to affect fish and wildlife habitats, including shorebird and sea turtle nesting habitat. In the oceans, subtropical and tropical corals in shallow waters have already suffered major bleaching events driven by increases in sea surface temperatures.
Below are examples that highlight the impacts to wildlife and their habitats from around the country.
Alaska
Across Alaska, the wildfire season now stretches from April to September—about a month longer than in the past, in part due to climate change climate change Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change . The longer season, combined with drier conditions, is leading to more frequent and more severe wildfires.
Firefighters work to contain the Swan Lake Fire in Alaska in 2019.
Farther south in Alaska’s Kenai Peninsula, increased wildfire activity has consumed subalpine and alpine habitats that usually do not burn. Warmer and drier conditions have also brought more beetle infestation and fire disturbance to spruce forests. Forest regeneration is no longer supported in these stands. Instead, a savannah grassland is emerging, totally altering the region’s historic ecosystem.
Southern United States
In Florida, National Key Deer Refuge is slowly sinking, succumbing to sea-level rise. As the island shrinks, so does habitat for imperiled Key deer, which live only in the Florida Keys.
Tropical plant species like mangroves are creeping further north as cold snaps become less frequent. These cold snaps have historically kept warm-climate species from spreading into areas where they would become invasive. Along the Texas coast near Aransas National Wildlife Refuge, invasive mangroves are encroaching into salt marshes that provide winter habitat for endangered whooping cranes. Land managers worry that if the expansion continues, it will shrink winter habitat for these rare birds.
Warming temperatures, changes in precipitation, rising sea levels, and loss of coastlines will continue to affect water supply and quality, which impacts human health, infrastructure, and local ecosystems. In Louisiana, stands of dead Cypress have become a common sight due to saltwater intrusion, which is expected to become a more serious issue as the effects of climate change climate change Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change continue to intensify. As freshwater species, Cypress trees cannot survive in saltwater environments, and the risk to these trees, and other freshwater-dependent species, will increase with sea level rise, coastal erosion, and incursion from extreme weather events. Similarly, Oak trees in southern coastal areas are dying off due to saltwater intrusion, flooding, and depletion of nutrients.
Along the South Carolina coast, the islands of Cape Romain National Wildlife Refuge provide important nesting habitat for the endangered loggerhead sea turtle. But rising seas are eroding nesting areas so badly that staff and volunteers must often rescue and relocate turtle nests before they are washed out to sea.
The American crocodile, native to southern Florida, faces pressure from rising seas. Staff at Crocodile Lake National Wildlife Refuge must add sand to historic nesting mounds to elevate them and “buy time” for these ancient reptiles.
East Coast & Midwestern United States
At Agassiz National Wildlife Refuge and elsewhere in northern Minnesota, warmer temperatures and accompanying habitat changes are pushing cold-loving moose farther north. Growing numbers of white-tailed deer are taking over habitat previously occupied by moose. With the deer come deer ticks, which further stress the moose that remain and present threats to human health and well-being.
In the Northeast, warmer spring and winter temperatures, along with increased pressure from invasive weeds and pests, may lead to large portions of the region becoming unsuitable for growing fruits, like apples and blueberries, and other crops, like grain and soybeans. This then has a cascading effect on the local wildlife and insects, including pollinators, which then affects the local plant life.
In the Great Plains, some bird species are shifting their range up to 360 miles northward, according to recent studies. Some species that used to winter in the South may no longer need to migrate as far to find food or shelter. This is especially true for waterfowl, which seek open water and food in winter. This has a number of impacts to local food chains and ecosystems that can cause cascading effects across wildlife, insects, and plant life.
The American West
Over the past six decades, there has been a steady increase in the number and size of fires in the western United States. The number of megafires—fires that burn more than 100,000 acres (156 square miles)—has increased in the past two decades. In fact, no documented megafires occurred before 1970. These fires threaten communities and wipe out habitat for wildlife, causing loss of life and property, as well as disconnecting critical landscapes.
The 2014 Tomahawk wildfire burns at the entrance to Naval Weapons Station Seal Beach Detachment Fallbrook. The Tomahawk Fire was the second largest wildfire in San Diego County that year. It burned more than 6,500 acres across Camp Pendleton and Fallbrook area, and more than 250 people in the area had to be evacuated.
Droughts and heat waves are occurring more often and becoming more intense across the United States, particularly in the West and Southwest, causing dangerous conditions as well as affecting the supply of water and snowpack. Drought conditions in the West continue to worsen, and water allocations are at historic lows, particularly in areas like the Klamath River Basin and the Colorado River Basin.
In some areas around the Rocky Mountains, small mammals are climbing higher to beat the heat. Some, like the pika, a tiny rabbit-like mammal, are running out of places to move because they already live high in the mountains.
More severe and prolonged drought forecast for the Southwest, made more extreme by climate change climate change Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change , is expected to change the makeup of pinion-juniper forests and the animals that live in them. Pinion trees depend on birds like the pinion jay to broadly distribute their seeds. When there are fewer pinions and fewer birds as a result of drought, both suffer losses.
Pacific Islands
When ocean water becomes too warm, sea corals expel the algae living in their tissues and turn white. Without the algae that they need to grow, corals become stressed and vulnerable to further damage. Such “coral bleaching” events tied to climate change climate change Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change are becoming more common in areas around Rose Atoll National Wildlife Refuge and elsewhere in the Pacific Ocean.
Check out our stories about how climate change climate change Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
