Wildlife Waste Is Major Water Polluter, Studies Say
Friday, September 29, 2006
Does a bear leave its waste in the woods?
Of course. So do geese, deer, muskrats, raccoons and other wild animals. And now, such states as Virginia and Maryland have determined that this plays a significant role in water pollution.
Scientists have run high-tech tests on harmful bacteria in local rivers and streams and found that many of the germs -- and in the Potomac and Anacostia rivers, a majority of them-- come from wildlife dung. The strange proposition that nature is apparently polluting itself has created a serious conundrum for government officials charged with cleaning up the rivers.
Part of the problem lies with the unnaturally high populations of deer, geese and raccoons living in modern suburbs and depositing their waste there. But officials say it would be nearly impossible, and wildly unpopular, to kill or relocate enough animals to make a dent in even that segment of the pollution.
That leaves scientists and environmentalists struggling with a more fundamental question: How clean should we expect nature to be? In certain cases, they say, the water standards themselves might be flawed, if they appear to forbid something as natural as wild animals leaving their dung in the woods.
"You need to go back and say, 'Maybe the standards aren't exactly right' if wildlife are causing the problem," said Thomas Henry, an Environmental Protection Agency official who works on water pollution in the mid-Atlantic.
The story of how wild animals -- which usually are considered the victims in environmental dramas -- came to be cast as villains begins with the EPA's limits on bacteria levels in streams. Bacteria such as E. coli and other fecal coliform, which are found in both human and animal waste, can cause sickness on their own, and they can serve as a warning that other, even nastier pathogens might also be present.
In the Washington area, violations of the bacteria standards have put more than two dozen streams, including the Potomac and Anacostia rivers, on the federal "impaired waters" list. That means they do not meet the ideal conditions for swimming and need cleaning up.
So who -- or what -- is responsible for the contamination? The answer has become much clearer in the past five or so years, because of high-tech tests sponsored by states that pinpoint from which animal a particular sample of bacteria came.
In this area, some of what these surveys have found is not surprising. One recent study by a Virginia Tech team found that humans are responsible for 24 percent of the bacteria in the Anacostia and 16 percent of the Potomac's, whether the source is a broken septic tank or the District's large sewage overflows during heavy rains. Livestock were also a major problem around the area -- responsible for 10 percent of the Potomac's bacteria, for instance -- because their manure washes out of pastures and the farm fields where it is spread as fertilizer.
Then there are nature's own polluters.
In the Potomac and the Anacostia, for instance, more than half of the bacteria in the streams came from wild creatures. EPA documents show that similar problems were found in Maryland, where wildlife were more of a problem than humans and livestock combined in the Magothy River, and in Northern Virginia tributaries such as Accotink Creek, where geese were responsible for 24 percent of bacteria, as opposed to 20 percent attributable to people.