Climate Change Could Devastate U.S. Wetlands

By Cat Lazaroff

WASHINGTON, DC, January 29, 2002 (ENS) - Global climate change threatens the health of lakes, streams, rivers and wetlands throughout the United States, finds a new report from the Pew Center on Global Climate Change. The temperature increases and variations in weather patterns projected for the next 100 years will change the distribution of freshwater fish and affect many other aquatic species, the report argues.


Coastal wetlands like the Florida Everglades host thousands of species, all of which could be threatened by rising sea levels (Photo courtesy Florida International University College of Engineering)
"The United States' freshwater and wetland ecosystems face multiple threats to their health and stability, including changes in land use, environmental pollution, and the diversion of water for drinking, irrigation, and other uses," said Eileen Claussen, president of the Pew Center on Global Climate Change. "To these threats we must now add the very real and very serious effects of global climate change and its potential to transform the essential character of our lakes, rivers, streams and wetlands."

The Pew Center report, "Aquatic Ecosystems and Global Climate Change: Potential Impacts on Inland Freshwater and Coastal Wetland Ecosystems in the United States," draws on a variety of sources to summarize researchers' current understanding of the potential impacts of climate change on U.S. aquatic ecosystems.

Dr. Mark Brinson, a professor of biology at East Carolina University and one of the report's authors, notes that climate change will worsen the already major problems facing wetlands from human activities like logging, development and polluted runoff.

"Freshwater wetlands are absolutely essential for maintaining biodiversity in the U.S.," Brinson said during a press conference releasing the report. "There are species that occur there that occur nowhere else."


Mountain streams like this one in New Mexico could become too warm for the cold water species which depend upon them (Photo courtesy U.S. Forest Service)
More than half the nation's historic wetlands have been destroyed since colonial times, Brinson noted. Those that remain have been degraded by pollution and changes such as logging or dredging, he said.

Dr. N. Leroy Poff, an assistant professor of Biology at Colorado State University, warned that climate change could fundamentally alter the ecological processes of aquatic ecosystems. For example, increased water temperatures will make some streams, rivers and lakes too warm for the fish and other creatures that now live there, said Poff, a coauthor of the report.

Some animals may be able to move farther north to reach cooler waters. But climate scientists project that to reach waters of optimal temperature, some species might need to move more than 400 miles (644 kilometers) farther north - a prohibitive distance, Poff noted, considering the natural and manmade barriers that lie along many waterways.

Dams and waterfalls may prevent fish and other creatures from moving upstream in rivers that flow north and south. Other rivers flow largely from east to west, making northward movement impossible. Chemical barriers like pollution can also trap migrating aquatic species.


Fish like these rainbow trout could be hurt by rising water temperatures and changes in the amount and timing of spring runoff (Photo courtesy Pacific Northwest National Laboratory)
Some species like trout, which live only at the pure, cold headwaters of streams, may go extinct, Poff warned. In lakes, large species may be lost as the level of dissolved oxygen in the water falls due to rising temperatures.

Coauthor Dr. John Day, a professor of environmental sciences at Louisiana State University, detailed the problems which rising sea levels could pose for coastal wetlands and estuarine systems, which he called "among the most highly productive and diverse ecosystems on Earth."

A half meter (1.6 foot) rise in sea level brought on by melting glaciers and ice caps - which many climate scientists consider a likely result of a warming climate - would inundate some 46,000 square miles (119,000 square kilometers) of coastal wetlands, Day said. The repercussions could include increased coastal flooding due to the loss of buffering wetlands, and reductions in the populations of game fish that depend on shallow wetlands as nursery habitat.


As permafrost melts, shallow summer groundwater tables will drop, drying out wetlands and increase the risks of peat fires (Photo courtesy University of Cincinnati)
Rising global temperatures will cause the wetland areas of Alaska and Canada to release additional carbon dioxide and other greenhouse gases into the atmosphere, increasing and accelerating the impacts of global warming, the authors noted.

Among the other key conclusions of the report:


Isolated wetlands like this bog may dry up and disappear completely as temperatures warm and rainfall patterns shift (Two photos courtesy EPA)
"Our rivers, lakes, streams, and wetlands support economically important fisheries and provide Americans with clean drinking water, water for irrigation, recreational opportunities, and more," said Claussen. "This report shows that climate change puts all of these services at risk, but it also shows there are things we can do to reduce that risk."

"Aquatic Ecosystems and Global Climate Change" is the seventh in a series of Pew Center reports examining the potential impacts of climate change on the U.S. environment. Earlier reports have focused on domestic and international policy issues, climate change solutions, and the economics of climate change.

The report is available at: