- Historic Sites
A Heritage In Peril
In a mere three hundred years we have despoiled a rich continent and seriously disturbed its balance of life. Nature may not let us escape the consequences much longer
August 1966 | Volume 17, Issue 5
And positive steps are being taken to broaden our understanding of the whole field of game and livestock protection. In research centers at Patuxent, Maryland, and Denver, Colorado, the United States Fish and Wildlife Service is experimenting with new solutions to predator—and rodent-control problems. Their trouble-shooting inventions range from sonic warning systems to ward off blackbirds to birth-control drugs for coyotes. In the Southwest, golden eagles, implanted with tiny transistor radios, are being tracked to determine how much—if any—damage they do to herds of sheep and goats. A federal law was enacted in 1962 to protect the eagles, after some 20,000 had been shot in twenty years of intensive campaigns. As might be expected, it is being appealed by ranchers.
In wilderness, of course, is sanctuary. Two years ago President Johnson signed an act that would preserve, in perpetuity, nine million acres of Wilderness Areas, accessible only on foot or on horseback. But powerful commercial interests block every new acquisition, and some private companies are already at work undermining the Wilderness Act. San Gorgonio Wilderness Area, near Los Angeles, is now being contested before a House subcommittee by would-be developers of a ski area. Southern California’s last forty condors, huge scavengers from the ice age with wings spanning nine and a half feet, are being made more secure at their Sisquoc Falls roost by its reclassification as the San Raphael Wilderness Area; but they face destruction in another part of the Los Padres National Forest. Builders of a proposed dam on Sespe Creek, just north of their nesting grounds, are planning to drive an access road from the town of Fillmore directly through the heart of the refuge. In March of this year the taxpayers of Ventura County rejected the $50 million project by a margin of only forty votes. Most of them were more concerned about the project’s effect upon their tax bill than upon the condors, however. And the promoters will be back.
The use of poisons to control pests has not been limited to the western ranges. A whole new group of chemicals has been developed for use against insects that prey on shade trees, on field cops, even on lawns and ornamental shrubs: because these are readily available and seemingly effective, we have used them in large quantities over large areas, without much regard for their ultimate effects.
Recently, however, we have begun to learn some alarming facts. In the first place, it has become apparent that most of these compounds can be only a treatment for insect irruptions, not a cure. They do not completely eradicate pests; on the contrary, the pests often build up a resistance to them. This phenomenon has been known for half a century, but it was not borne in upon the public consciousness until just after World War II, when it was generally noticed that houseflies and mosquitoes, after being sprayed with the initially effective DDT, came back in numbers greater than before, and this time DTT could not control them. To the present day 120 species of insects have managed to outlive the development of stronger and stronger pesticides.
Not only do pesticides damage nature’s own system of controls by killing less prolific insect enemies of the target pests along with the pests themselves; they kill other wildlife as well, either by direct application, through aerial drift of the chemical sprays, or through the runoff of residual poisons into watercourses.
Another insidious fact has been discovered: relatively small, “safe” amounts of poison are stored in animal bodies and passed along the natural food chains in larger and larger concentrations. Food-chain poisoning was first brought to public attention in 1958, when Dr. R. J. Marker published the results of his research into the deaths of robins and other birds on the campus of the University of Illinois. There elm trees had been repeatedly sprayed with DDT to combat Dutch elm disease, a fungus that had spread throughout some twenty states. Trees sprayed in the summer dropped contaminated leaves, causing a concentration of DDT in the soil and in the bodies of earthworms. By the time the robins returned in the spring, their favorite food was poisonous. A single worm harbored ten limes more DDT than the soil, and a diet of a hundred worms was enough to kill a robin. In sixty eastern and midwestern communities, robin populations dropped drastically, anywhere from thirty to ninety-eight percent. Nor were robins the only victims: approximately eighty species of birds were affected—orioles, warblers, and vireos of the treetops (which picked up the DDT from spray-drenched insects), flickers (which eat bark beetles), and falcons (which feed on flickers). It is suspected that a similar DDT concentration process may be responsible for the nesting failures of bald eagles on Lake Michigan, in Maine, and in the mid-Atlantic states; of the osprey north of Chesapeake Bay; and of the beautiful peregrine falcon, which has today virtually disappeared from the entire Northeast. Pilot investigations by the California Fish and Game Department in 1961 have shown that in rice fields treated with DDT, ring-necked pheasants laden with this and other pesticides are able to hatch eggs, but the survival rate of the young is very poor.