Climate Change Will Put Heat On Mountain Habitats

Two new scientific reports on global climate change paint a disturbing picture of the future for aquatic and terrestrial ecosystems in the Southern Appalachians.

The reports — “Aquatic Ecosystems and Global Climate Change” from the Pew Center on Global Climate Change, and “Habitats At Risk: Global Warming and Species Loss in Terrestrial Ecosystems” from the World Wildlife Fund — identify higher-elevation forests and streams in the Southern Appalachians as extremely vulnerable to climate change.

Most climatologists, including those with the National Oceanographic and Atmospheric Administration, agree that average global surface temperatures are projected to rise by 1.5 to 5.8 degrees Celsius by 2100. However, temperature spikes may be higher in the United States.

The Pew report, authored by three university scientists, looked at 113 land-based regions of the world, finding that huge parts of the globe are at risk of ecological collapse as global temperatures rise. In the U.S., the hardest hit areas will be areas in California, the Pacific Northwest, and the Northern Prairie.

The report found that Appalachian and Mixed Mesophytic Forests, which dominate lower elevations here, were among the most stable habitats and least likely to be affected by climate change. However, researchers also noted that “island ecoregions…may be of special risk because of small populations, limited opportunities for migration, and sea level rise.”

About 20 rare and threatened plants and animals live in the highest elevations of the Southern Appalachians, including the northern saw-whet owl, spruce-fir moss spider, Carolina northern flying squirrel, and pigmy salamander.

The spruce-fir forests where they live are habitat islands, created when glaciers retreated at the end of the last Ice Age, stranding these species at the highest elevations of the southern mountains. Known as the Canadian zone, this high elevation area shares many characteristics of ecosystems far to the north.

According to the Pew study, as human induced emissions of carbon dioxide and other greenhouse gases raise the average global temperature, species living in the highest elevation habitats of the Southern Appalachians may have nowhere to go. “Migration is likely to be especially problematic for isolated island ecoregions,” the report said.

Some high-elevation species, such as the spruce-fir moss spider and Gray’s lily, will be unlikely to disperse quickly, and are likely to go extinct if rising temperatures make their current habitat unsuitable. “In nonglaciated regions, where previous selection for high mobility has not occurred, species may suffer disproportionately,” the report said.

Global warming is likely to have a “winnowing effect” on these islanded ecosystems, the report said, “filtering out species that are not highly mobile and favoring a less diverse, more ‘weedy’ vegetation and ecosystems that are dominated by pioneer species, invasive species and others with high dispersal capabilities.”

The Pew report recommends that the United States immediately ratify the Kyoto Protocol, an international treaty lowering greenhouse gases. The U.S. is the largest producer of greenhouse gases in the world. The Bush administration has refused to sign the agreement, claiming it unfairly allows developing Third World countries off the hook.

The WWF report outlining global warming’s effects on aquatic systems is even more harrowing. It predicts over the next century, increases in water temperature as a result of climatic change will alter fundamental ecological processes, shift the distribution of native species, and change seasonal rainfall patterns and stream flows.

“Coldwater fish like trout and salmon are projected to disappear from large portions of their current geographic range in the continental United States, when warming causes water temperatures to exceed their thermal tolerance limits,” the report said. “Species that are isolated in habitats near thermal tolerance limits or that occupy rare or vulnerable habitats may become extinct in the U.S.”

The Southern Appalachian strain of brook trout is found as far south as north Georgia, mostly above high waterfalls that prevent brown and rainbow trout from invading and outcompeting them. The WWF study confirms what U.S. Forest Service ecologist Patricia Flebbe reported in 1997:

“Effects of global climate change could be significant, both for brook trout and the trout guild in the southern Appalachians, where present-day distributions are already fragmented and restricted to higher elevations. Whether rainbow and brown trout might retreat to higher elevations, displacing brook trout as air and stream temperatures increase, or would be lost from the region before brook trout cannot be determined.”