AMC Outdoors, March 2008
Loons affected by mercury poisoning. A high-pitched loon call, often referred to as “crazy laughter,” means a bird may be annoyed or alarmed. Given current environmental conditions, it has good reason to be.
In the western watershed of Maine’s upper Kennebec River, for example, 43 percent of adult loons have blood mercury levels considered poisonous (more than the established adverse effects threshold of 3 parts per million), according to a study by the Hubbard Brook Research Foundation. Loon pairs with this much mercury produce up to 40 percent fewer young than healthier loons, and that spells trouble for population stability. Loon numbers in an area may begin to drop, researchers concluded, if at least one in four loons have blood mercury levels exceeding the threshold.
The region in Maine is one of five biological mercury hotspots researchers have identified in the northeastern U.S. and southeastern Canada. The others are located in the Adirondacks, the upper Connecticut and Androscoggin river valleys, the Merrimack River valley in southern New Hampshire and northeastern Massachusetts, and Nova Scotia. Mercury is a neurotoxin that causes brain and spinal cord damage, particularly in children and fetuses. (In 2001, one in 10 women of childbearing age had mercury in their bodies that exceeded what the EPA deems safe for unborn children, according to the Centers for Disease Control and Prevention.) There is a finite amount of mercury on earth that does not break
down or degrade. Prior to industrialization, the chemical element was released mostly by natural forces at levels wildlife could handle. But human activity, particularly the use of coal-fired power plants, is now the single biggest source of airborne mercury, accounting for two-thirds of all global emissions. Live downwind of a plant, and mercury deposition within an ecosystem could be 10 to 20 times higher than pre-industrial levels.
Mercury concentrates (or “bioaccumulates”) as it moves up the food chain. After being released into the air, depending what form it is (elemental, reactive gaseous, or particulate), mercury can travel anywhere from less than one mile to several thousand before falling back to earth in rain or snow.
If that mercury enters a waterway, specialized bacteria convert it to its organic, more toxic form—methyl mercury. This compound may then be absorbed by microscopic organisms consumed by insects and small fish, which are eaten by bigger fish, which are eventually eaten by loons, bald eagles, and humans. (Forty-four states had one or more fish consumption advisories in 2004 due to high concentrations of mercury.) Methyl mercury increases in concentration with each species jump so that, under certain conditions, levels in a loon can be 10 million times higher than when the mercury first entered the watershed. As a result, some loons have difficulty flying or swimming. There has also been “a significant impact where the loons would not sit on their eggs as much as they should if they have high mercury levels,” says Dave Evers, co-author of the Hubbard Brook study and director of the Biodiversity Research Institute in Maine.
But there is good news. “We can end mercury as being a problem if we put our will and minds to it,” Evers says. In southern New Hampshire, efforts to curb regional pollutants resulted in a 45 percent decline in mercury emissions between 1997 and 2002. In loon blood samples collected in that area, mercury concentrations fell by 64 percent between 1999 and 2002. If we halted all mercury emissions today, we would eventually return to historic, more tolerable levels, Evers says.
The EPA established a Clear Air Mercury Rule in 2005 that demands a 70 percent reduction in emissions from coal-fired power plants by 2025, but that rule is being challenged by environmental organizations and several Northeastern states, which argue that the cap-and-trade system permitting power plants to offset their emissions by purchasing “allowances” may not be effective in reducing deposition from local sources.
Two bills before Congress would increase the emissions reduction goal to 90 percent and fund a National Mercury Monitoring Program to track how the mercury travels and which ecosystems are most in jeopardy. “The more you look the more you find,” Evers says, “so we better keep looking.”
Track industry environmental practices by region at www.mapecos.org
—By Karen Finogle
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