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New Report Shows High Levels of Mercury in Terrestrial Ecosystems


Mercury is a pollutant that is cause for concern at local, regional, and global scales. While areas of high contamination (known as biological mercury hotspots) may occur near mercury-emitting sources, often they do not depending on the mercury species being present. Because mercury released into the atmosphere can circle the world before being deposited, wildlife living in habitats located far from point sources of mercury can still be at risk.

In the United States, mercury becomes an air pollutant largely through emissions from coal-fired power plants; in some areas, cement plants and mining related industries also add to mercury pollution. Airborne mercury eventually returns to the earth in rain, snow, and fog droplets, as well as in dry form. Under the right conditions, mercury is transformed into methylmercury, an organic toxin that becomes magnified as it is ingested up the food chain.

The human health effects of mercury contamination are well documented; adverse effects include impacts on cardiovascular health, IQ, workplace productivity, and motor control. Similarly, mercury negatively affects wildlife populations by hindering behavior and reproduction. Past investigations have emphasized adverse impacts to fish-eating wildlife, such as common loons, bald eagles, and river otters. Although great strides have been made to reduce mercury released into the air and water from human activities, the new BRI report illustrates that high levels of mercury persist in many wildlife species distributed across many habitat types.

The new BRI report:
Hidden Risk: Mercury in Terrestrial Systems of the Northeast highlights BRI’s scientific findings on high levels of mercury contamination in songbirds and bats throughout 11 northeastern states from Maine to Virginia. More than 50 researchers contributed to the information in this report, which illustrates the continued interest in advancing our understanding of the impacts of air pollution—in particular mercury—on nature and people.

“While the risk of mercury to people is well known—there are more than 3,700 fish consumption advisories issued in the U.S.—we are still learning about mercury’s effects on wildlife,” says David C. Evers, Ph.D., BRI’s executive director and chief scientist. “Mercury accumulation has many implications for the health and survival of wildlife species across habitats, not just those that live and feed in aquatic habitats. Our research has found that mercury concentrations in animals that live in terrestrial environments are significant enough to cause physiological and reproductive harm. This knowledge is creating a major paradigm shift in ecotoxicological research, assessment, monitoring, management, and policy.”

The Hidden Risk Report documents, for the first time, elevated levels of mercury in a new group of animals—terrestrial invertivores—that until now has largely been ignored in mercury investigations. Among the findings:

  • Current environmental mercury loads have the ability to significantly reduce reproductive success in several songbird species of conservation concern in the northeastern U.S., including the saltmarsh sparrow and rusty blackbird;
  • Bats also build up significant body burdens of mercury; individuals from multiple species from all 10 areas sampled in the northeastern U.S. exceeded the subclinical threshold for changes to neurochemistry;
  • Mercury loading in songbirds is not only restricted during the breeding season; for some species, such as the northern waterthrush, high levels of mercury accumulate during migration and in tropical wintering grounds.

Hidden Risk presents findings from at-risk habitats, and associated indicator species are identified based on the species’ level of conservation concern, relative abundance, and ability to build up mercury in the body. The report demonstrates the significant costs of mercury to wildlife that were not factored into previous cost/benefit analyses.

“While air pollution impacts people and nature on public and private lands, the good news is that when action has been taken to reduce mercury emissions, the results are very promising,” says Dr. Timothy Tear, New York director of science for the Conservancy. “Research has shown that reduction in mercury levels do make a difference to dramatically and quickly reverse mercury contamination trends in fish and wildlife. Reducing this neurotoxin from the environment will benefit wildlife and people.”

Hidden Risk outlines a number of management actions that can be taken to reduce the mercury risk in various terrestrial ecosystems, ranging from cleaning up legacy dump sites to reducing atmospheric deposition. The U.S. Environmental Protection Agency (EPA) has recently finalized the Mercury and Air Toxics Standards (MATS) Rule that requires coal-fired power plants to update their mercury pollution control technologies, and this report highlights the importance of tracking the biological implications of this rule through better national and international monitoring programs. The report also calls for the establishment of critical loads for air-borne contaminants that are based upon preserving healthy ecosystems. Critical loads identify the maximum level of pollutant deposition that ecosystems can handle before harmful effects occur.

Air pollution continues to be an important area of environmental concern. The recent U.S. EPA MATS ruling and release of the National Acid Precipitation Assessment Program Report to Congress: An Integrated Assessment underscore the fact that although efforts to reduce air pollution in the United States are working, there is still much more work to be done.

Source: Adapted from The Nature Conservancy

The cited and other related reports

D.C. Evers, A.K. Jackson, T.H. Tear and C.E. Osborne. Hidden Risk: Mercury in Terrestrial Ecosystems of the Northeast. Biodiversity Research Institute. Gorham, Maine (2012) 33 pages.

C. Osborne, D. Evers, M. Duron, N. Schoch, D. Yates, O. Lane, D. Buck, I. Johnson, and J. Franklin. Mercury Contamination Within Terrestrial Ecosystems in New England and Mid-Atlantic States: Profiles of Soil, Invertebrates, Songbirds, and Bats. BRI Report 2011-09. Available from Researchgate

G.M. Lovett, T.H. Tear. 2008. Threats from Above: Air Pollution Impacts on Ecosystems and Biological Diversity in the Eastern United States. The Nature Conservancy and the Cary Institute of Ecosystem Studies.

Related EVISA Resources

 EVISA Link database: Environmental cycling of mercury
 EVISA Link database: Environmental mercury pollution

Related EVISA News

December 23, 2011: EPA Issues First-Ever Limits on Mercury & Toxic Air Pollution
December 19, 2011: Anthropogenic Mercury Releases Into the Atmosphere from Ancient to Modern Time
October 15, 2011, Mercury pollution in the Great Lakes region -- nearly forgotten, but not gone
June 17, 2009: 'Surprisingly High Levels' of Methylmercury Contamination found in Groundwater
May 3, 2009: Ocean mercury on the rise
March 11, 2007: Methylmercury contamination of fish warrants worldwide public warning
February 18, 2007: New research results suggest that mercury hotspots in the northeastern US are home made
October 9, 2006: Linking atmospheric mercury to methylmercury in fish
September 13, 2005: Regulating Mercury Emissions from Power Plants: Will It Protect Our Health?
April 3, 2005: Dissension on the best way to fight mercury pollution

last time modified: March 3, 2024


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