Acid Rain Continues to Damage Northeastern Forests

By Cat Lazaroff

WASHINGTON, DC, March 26, 2001 (ENS) - A new study by 10 leading acid rain researchers finds that despite emissions cuts required by 1990 changes to the Clean Air Act, northeast lakes, forests and streams are not recovering from the effects of acid rain. In fact, years of exposure to acid rain have made these ecosystems even more sensitive to additional pollution.

The researchers conducted the study in the same New Hampshire forest where acid rain was first detected almost 30 years ago, the Hubbard Brook Experimental Forest.

Many lakes and streams in New York's Adirondack mountains are seriously acidic (Photo courtesy New York State)

An additional 80 percent reduction in sulfur emissions from electric utilities would be required to bring sensitive streams back to non-acidic levels within 20-25 years, shows a scientific model developed by the researchers.

The study, published in the March issue of the journal "BioScience," is the first to look at acid rain's effect in the Northeast since the 1990 Clean Air Act amendments that cut sulfur emissions from power plants. While progress has been made in cutting some emissions that cause acid rain, it will not be adequate for recovery in the Northeast and other acid sensitive regions, the researchers conclude.

Marble surfaces exposed to acid rain develop a rough sugary texture because the calcite grains are loosened as the edges dissolve in the rain water. This effect is visible on this column capital volute on the Jefferson Memorial, Washington, DC (Photo by Elaine McGee, courtesy U.S. Geological Survey)

The report documents the harm caused by acid rain and concludes that acid rain has caused greater environmental impacts than many had projected 10 years earlier, when the 1990 Amendments of the Clean Air Act were implemented.

The report presents findings in three areas:

• Soil: Acid rain has caused the depletion of large quantities of available calcium, an important plant nutrient, in soils across the Northeast. Further, it has mobilized a form of aluminum that can harm forest ecosystems and aquatic organisms.

• Water: A recent survey concluded that 41 percent of lakes in the Adirondack region of New York and 15 percent of lakes in New England are either chronically or periodically acidic. Most lakes and streams in this region have shown little improvement in water quality despite decreases in sulfur dioxide emissions and still show reduced aquatic life and species diversity.

• Trees: The loss of nutrients such as calcium and magnesium from soil and foliage stresses and weakens trees, making them more susceptible to climatic and insect stress. Red spruce at high elevations and sugar maple on poor sites appear to be particularly at risk.

Power plants emit about 60 percent of all sulfur dioxide, with the largest amount coming from the midwestern United States. Prevailing winds blowing from west to east carry pollutants to New England and Canada where they are deposited in rain, snow, fog, gases and particles.

Pollution controls initiated through the 1970 Clean Air Act and 1990 amendments have already reduced sulfur dioxide emissions 38 percent nationwide. Still, sulfur emissions remain very high compared to historic levels and nitrogen emissions continue to increase.

Coal burning power plants like this one in Michigan emit about 60 percent of U.S. sulfur dioxide pollution (Photo by Carole Swinehart, courtesy Michigan Sea Extension)

Scientific models used in the study project that the condition of soil and surface waters will improve thanks to the 1990 emission reductions, but will likely be inadequate to achieve full ecosystem recovery even in the next 25 to 50 years. An additional 40 percent reduction would improve conditions and an 80 percent reduction in sulfur dioxide emissions from electric utilities would be required to bring streams at the Hubbard Brook Experimental Forest back to non-acidic levels in about 20 to 25 years, according to the scientific model.

An 80 percent reduction in utility emissions of sulfur dioxide is equivalent to a 44 percent reduction in total U.S. emission of the pollutant.

The researchers report that recovery from acid rain is likely to occur in two stages. Chemical recovery will bring about lower acidity in soils, lakes and streams. As chemical conditions improve, biological recovery of the plants and animals can occur.

Research suggests that insects and other invertebrates in streams may rebound relatively rapidly, within about three years, while zooplankton in lakes may need a decade or more to fully reestablish. Fish populations should recover within five to 10 years following the return of the zooplankton on which they depend.

Red spruce forests on western facing slopes of Adirondack Park's High Peaks region are stunted and dying from acid rain (Photo courtesy Colgate University)

The report was authored by a team of 10 independent scientists convened by the Hubbard Brook Research Foundation, a nonprofit group that promotes ecosystem stewardship through scientific research, monitoring and public education.

More information is available at: http://www.hbrook.sr.unh.edu/hbfound/hbfound.htm

The full article is available on the American Institute of Biological Sciences Web site at: http://www.aibs.org/biosciencelibrary/vol51/mar01special.ldml