Defenders Magazine

The Hot Ten

Ten aspects of global warming are highlighted, using different species to illustrate how each impacts the natural world. No canaries here, but that doesn't mean the coal mine is safe.

We can talk about climate change in terms of rising temperatures and receding glaciers, but how do those gauges relate to wildlife? In many respects--some of them surprising. Melting ice and hotter temperatures are changing habitats, life cycles and behaviors in ways large and small. Birds are migrating sooner, deserts are expanding, pests are spreading to new areas, coral reefs are bleaching. According to a recent report from the U.N. Intergovernmental Panel on Climate Change, of the 500 species researchers studied--including birds, amphibians, mammals, reptiles, plants, mollusks and insects--more than 80 percent are altering their behavior in response to global warming. Some plants and animals will successfully make the adjustments needed for their survival. Others will find themselves without enough room or time, and slip into extinction. On the following pages, we've highlighted 10 aspects of global warming, using different species to illustrate how each impacts the natural world. No canaries here, but that doesn't mean the coal mine is safe.

Sea ice meltdown

As if polar bears didn't already have enough to contend with: icy winds, fierce blizzards, oil drilling and the pesticides PCB and DDT in their systems. Now there's melting ice, which has put them so at risk of extinction that the U.S. Fish and Wildlife Service is considering whether they should be protected under the Endangered Species Act. Polar bears depend on sea ice to mate, give birth and launch hunting expeditions for ringed seals, their primary prey. Some populations need the floes all year round, while others move to land with the spring melts--which is coming two weeks sooner and before they've built up enough fat reserves. The result is drowning bears, starving bears and lower cub-survival rates. One study even suggests the bears are turning to cannibalism to survive.

Too much carbon dioxide

Staghorn and elkhorn coral

The rainforests of the ocean, coral reefs support a dazzling array of species. But die-offs of as much as 98 percent in some locations in the last 25 years landed two coral species on the endangered species list earlier this year. Staghorn coral and elkhorn coral form massive thickets and provide cover for an array of reef fish. But warming ocean temperatures are stripping corals of the algae they need to survive, while carbon dioxide emissions are also turning the naturally alkaline oceans acidic and the reefs to rubble by lowering the concentration of carbonate ion, a building block of the calcium carbonate found in coral.

Changes in average precipitation

Desert tortoise

Elephantine limbs and long claws help the desert tortoise dig burrows to dodge the desert heat in the four U.S. states where it occurs: Arizona, California, Nevada and Utah. But the threatened reptile may not escape the results of a warming planet. Every region will experience the effects of climate change differently, and in the desert average precipitation is likely to decrease. Although the species is well-suited to store water for long periods, during severe droughts it's not uncommon to see clusters of empty shells. Couple this with habitat loss as more and more land on the desert margin gets gobbled up by urbanization and for use as military-training grounds, and it could spell the end of a species.

Changing migration patterns

Tree swallow

Some species can change patterns in their drive to survive. Problem is, a new rhythm takes over and throws everything out of synch with nature. Take the ubiquitous tree swallow, harbinger of spring--and of global warming. Warmer temperatures in the last three decades have prompted the small, graceful birds with the iridescent blue feathers to nest earlier. On its face, this could look like a good thing: Early nesting typically means more eggs. What's unknown is how the insects they rely on will change as the climate shifts--will prey adapt and also be available earlier each year? As biologists wait and watch, they also worry about what the climate changes could mean for "specialist" birds, such as flycatchers and warblers, whose diet is more limited and whose future is more precarious.

More intense storms

Manatee

As robust as these rotund ‘sea cows' may appear, they are actually quite fragile. Manatees are prone to pneumonia if waters get too cold, and many die each year after being struck by motor boats. Global warming raises the odds against these already endangered creatures by increasing the likelihood of larger and more frequent hurricanes. Researchers with the U.S. Geological Survey in Florida say that, in years with intense hurricanes and other major storms in the northern Gulf of Mexico, fewer manatees seem to survive. The scientists are currently analyzing data from the catastrophic years of 2004 and 2005 (think Charley, Frances, Dennis and Katrina), and they note that "future impacts to the population by a single catastrophic hurricane, or series of smaller hurricanes, could increase the probability of extinction."

Habitat movement

Edith's checkerspot butterfly

When the planet warms, shift happens. Habitat shift, that is. As formerly cozy places turn hot and dry, creatures must move or die. Witness this colorful butterfly, which once lived happily on the West coast from northern Mexico to southern Canada. In the past 40 years, southern and low-lying checkerspot populations have been dying off faster than those elsewhere. It seems that plants on which checkerspot caterpillars live and feed in these areas are withering away, thus starving the insects before they can take wing. As a result, the butterfly's range has shifted north by 63 miles, perhaps dooming the southernmost subspecies, the endangered Quino, to eventual extinction.

Flooding

Streamside salamander

Too little water is clearly a problem for wildlife--but so is too much. In some places, global warming is causing flooding to become more common and more extreme. This is a major threat to both plants and animals that inhabit the margins of waterways, such as the unassuming streamside salamander. This four- to five-inch-long amphibian lives in forested ravines in Indiana, Kentucky, Ohio, Tennessee and West Virginia. The streamside salamander is already challenged by logging, development, pollution and other meddling in its habitat. Increased flooding could leave it down the stream without a paddle.

Invasive species

Lobster

Climate change has American lobsters seeing red--but not for the reasons you might expect. Yes, these tasty crustaceans prefer cold water, thus their prevalence in the waters and restaurants of New England. And as water temperatures warm, lobsters get ruddy and unhappy. But the rising temperatures also may be turning northeastern waters into a haven for pesky foreign creatures like sea squirts. Some varieties of sea squirts unseen in these parts just a few decades ago have lately established bloblike colonies covering huge swaths of ocean floor. In the process, they've smothered shellfish and plants, making life for lobsters and other native sea creatures that much harder.

Rising sea levels

Hawaiian monk seal

The good news for rare Hawaiian monk seals: President Bush recently designated their home--a remote archipelago northwest of Hawaii--as a marine national monument, the largest in the world. The bad news: some of the islands in that sanctuary could be underwater before the century is out. The culprit is--you guessed it--global warming. Less than 50 years ago, one of the seals' chief breeding and resting places--a group of low-lying islets called French Frigate Shoals--covered about 110 acres. Today, only about 38 acres are left. As beaches disappear under rising seas, there are fewer safe places for the endangered seals to escape from sharks. As a result of this and other causes, more pups and juveniles are dying. Further loss of habitat, researchers warn, "can only be expected to exacerbate an already lamentable situation."

Longer droughts

Desert bighorn sheep

Even in the best of times, things are precarious for desert bighorn sheep. They inhabit steep, rocky terrain in the driest areas of the Southwest. They live in small groups, often separated by miles of blazingly hot terrain. So it's little wonder that global warming is beginning to push them over the edge. As temperatures have risen over the past century, drought has become more common in parts of the bighorns' range. In southeastern California, for example, rainfall has declined by as much as 20 percent. Longer dry spells mean that plants and springs--both already scarce--are drying up. As food and drinking water go, so, too, do the sheep: More than a third of the groups that once lived in California's mountains have disappeared in the past century. If droughts in the Southwest continue, look for more groups of bighorns to bite the dust.