News of the Wild
Tree cutting, the downy woodpecker, air pollution, and Walt Disney make headlines.
Tree Loss Burns Up Cities
When the Olympic athletes arrived in Atlanta this summer, they knew that one of their biggest opponents would be heat. What they may not have known was that the cutting of trees in the Atlanta region during the past 24 years has intensified the city's summer sweat.
Using data from a Landsat satellite, American Forests, a conservation group in Washington, D.C., has found that development in Atlanta claimed about 65 percent of the city's trees between 1972 and 1993. Loss of forest canopy has helped bring on the heat. In 1972, the hottest part of the city was 6 to 9 degrees warmer than surrounding countryside. Today, the difference amounts to as much as 12 degrees, and the affected area has tripled in size.
Many cities across the nation have become similar heat islands, affecting air quality and straining local utility companies that power air conditioning. In Atlanta, according to the American Forests report, elevated temperatures may be creating a low-pressure area that traps hot, polluted air in the city center.
About 30 percent of any given city's air-pollution problems stems from increased temperatures, according tosome studies at California's Lawrence Berkeley Laboratory. Every 1 degree increase above 72 degrees raises by 6 percent the possibility that smog will occur, researchers at the lab report.
Cities can reduce heat generation by preserving tree cover and using light, rather than dark, surfaces on buildings and other structures. Every 10 percent increase in forest canopy produces a 1- to 2-degree reduction in temperature, according to American Forests.
A Mystery In Blue
The downy woodpecker is a familiar black-and-white bird that ranges in many of the nation's woodlands. But when Stephen Lang, a high-school math teacher in Madison, Wisconsin, photographed one near his home last winter, he had captured quite an unfamiliar image on film--a blue downy woodpecker.
Was the bird a fake, dyed by some prankster? University of Wisconsin ornithologist Stan Temple, one of the nation's leading bird experts, is convinced that it is not.
The real mystery, says Temple, is how this downy got the blues. No known bird has blue feather pigment. Instead, avian blue results from structural properties that cause certain feathers to reflect blue light. Temple speculates that this woodpecker inherited a mutation that altered its feather structure. This is the only blue downy ever recorded.
Harmless Chemicals Yield Dangerous Combination
Since the early 1990s, scientists have been scurrying to see if an increased risk of breast cancer in women and a decline in human semen quality have resulted from synthetic chemicals that human society has released into the environment. Biologists suspect the same cause in reproductive abnormalities plaguing a variety of species ranging from Florida alligators to otters in the Pacific Northwest. Now, data from biochemists at Tulane University in New Orleans and the University of Florida have tightened the link to environmental chemicals and suggest that the danger may lie in relatively harmless compounds that form hazardous combinations after release.
The biochemists tested four pesticides--endosulfan, toxaphene, dieldrin and chlordane. Endosulfan is one of the most widely used pesticides in the United States. The other three were banned in the 1980s but linger in the environment in many areas. All four mimic female estrogen hormones in the body, but show weak effects when tested alone. "However, these compounds occur as mixtures in the environment, and their combined action has not been well studied," the researchers reported in the journal Science.
The scientists found that combining the chemicals dramatically boosts their potential as health hazards. For example, a mixture of endosulfan and dieldrin had 160 to 1,600 times the estrogenic potency of the individual chemicals.
"These results are truly astounding," observed Lynn Goldman, the Environmental Protection Agency's assistant administrator for pesticides and toxics. The research, she said, "is the best case for synergy between chemicals at low doses that I have ever seen." She called for further research to corroborate the new data, which suggest that the EPA, by testing chemicals singly, may be underestimating the potential health hazards.
Thirty-three Years Ago
Walt Disney served as honorary chairman of the National Wildlife Federation's annual Wildlife Week in 1963, helping NWF's efforts to educate Americans about the hazards posed by misuse of toxic chemicals. In the years since, NWF has produced several studies on such potential hazards.
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