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 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)

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)

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)

Among the other key conclusions of the report:

• Increases in water temperatures as a result of climate change will alter the geographic distribution of aquatic plant and animal species.

  The severity of these impacts may be limited if species can migrate to new areas as climate changes. However, the ability of species to migrate may be compromised by human activities that block migration corridors, potentially causing reductions in biodiversity.

• Changes in precipitation will alter river and streamflows affecting ecosystem productivity and reducing water quality.

  Populations of aquatic organisms are sensitive to the effects of floods, droughts and other extreme weather events, which are likely to increase as a result of climate change.

• Aquatic ecosystems have a limited ability to adapt to climate change.

  Governments, communities, businesses and individual citizens can take a number of steps to reduce the likelihood of significant impacts to these systems while improving their ability to adapt to climate change.

  These actions, which the authors call climate insurance, include: maintaining riparian forests; reducing pollution from a variety of sources; restoring damaged ecosystems; minimizing groundwater withdrawal; and strategically placing new reservoirs to minimize their ecological impacts.

Isolated wetlands like this bog may dry up and disappear completely as temperatures warm and rainfall patterns shift (Two photos courtesy EPA)

"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: http://www.pewclimate.org