Studies find mercury widespread in U.S. wildlife
Mercury pollution is making its way into nearly every habitat in the U.S., exposing countless species of wildlife to potentially harmful levels of mercury, a new report from the National Wildlife Federation shows. The report features the work of Dr. David Evers, wildlife toxicologist and leading researcher in this field, whose work with common loons was supported by Earthwatch volunteers.
"Scientific understanding of the extent of mercury contamination in wildlife has expanded significantly in recent years," says Dr. David Evers, executive director of the Biodiversity Research Institute. "We are finding mercury accumulation in far more species, and at much higher levels, than we previously thought was occurring. This poses a very real threat to the health of many wildlife populations, some of which are highly endangered."
The National Wildlife Federation report, Poisoning Wildlife: The Reality of Mercury Pollution, is a compilation of over 65 published studies finding elevated levels of mercury in a wide range of wildlife species. The report highlights mercury levels in fish, mammals, birds, reptiles and amphibians living in freshwater, marine, and forest habitats from across the country.
"Mercury is more widespread and is a deeper problem in the environment than once considered," said Evers, former principal investigator of Earthwatch's Loons of Maine project. "The more people research mercury effects, the more wildlife effects are found."
Earthwatch teams worked for several years in the 1990s with Evers and colleague James Paruk (Feather River College, US), exploring the impact of mercury on population dynamics and behavior of loons in Michigan, Wisconsin, and Maine. Their data suggest that at least 22 percent of the breeding loon population is at risk in Maine, where teams conducted more than 1,500 hours of behavioral observations.
"Loons were indeed the focal wildlife indicator model for years," said Evers. "They were the 'tip of the iceberg' for wildlife."
The accumulation of mercury in fish has been well-known for years, leading 46 states in the U.S. to issue consumption advisories warning people to limit or avoid eating certain species of fish. However, scientists have recently discovered that mercury accumulates in forest soils, indicating that wildlife that live and feed outside aquatic habitats are also at risk of exposure to mercury.
Mercury accumulation has many implications for the health and survival of wildlife species across habitats. Fish with high mercury levels have difficulty schooling and spawning, birds lay fewer eggs and have trouble caring for their chicks, and mammals have impaired motor skills that affect their ability to hunt and find food. For instance, Earthwatch teams found that Maine loons with blood mercury levels higher than 3 parts per million (ppm) fledged 40 percent fewer young than loons with blood levels below 1 ppm.
Mercury is a toxic byproduct of waste incineration, coal-fired power plants, and chlorine production as well as some natural processes. Human activities have doubled or tripled the amount of mercury released into the atmosphere every year, adding 2,000 to 6,000 tons globally. When rain, snow, or wind deposit mercury on water bodies, anaerobic bacteria convert it into organic methyl mercury, a powerful neurotoxin that disintegrates nerve and brain cells in humans and other vertebrates.
Several states have already taken action to reduce mercury pollution from major sources like waste incinerators, chlorine manufacturers, power plants, and consumer products, and the results are very promising. In places where mercury emissions have been cut, such as Florida, Wisconsin, New Hampshire, and Massachusetts, mercury levels in fish and wildlife have been reduced in a matter of years, not decades, as scientists have previously thought.
"The key step toward reducing the impact of mercury on wildlife is to reduce mercury emissions and effluents," said Evers. "Nature can clean itself up quite quickly." For instance, Evers found that loon mercury levels were reduced by 50 percent in four years after mercury emissions were severely reduced locally.
Poisoning Wildlife: The Reality of Mercury Pollution is available at http://www.nwf.org/news
Editors Notes