icut nests-roughly 36 percent, somewhat less than the percentage that had been hatching all along in Maryland but significantly better than the Connecticut record. However, only one of the Connecticut eggs hatched in Maryland. The difficulty therefore seemed to be something intrinsic in the egg, and not in any aberrant behavior of the Connecticut parents. It appears significant that two-thirds of the Connecticut eggs sent to Maryland broke under the sitting birds. About two weeks after the eggs hatched, Bill and Paul tested another point, the capacity of the Connecticut food supply to sustain a normal brood. A batch of young ospreys was brought by plane from Maryland so that every nest on Great Island held a full complement of three. The foster parents readily accepted them, and in the weeks that followed all the babies save one grew fat, eventually fledged, and flew. DEATH CREEPS FROM BUG TO FISH TO BIRD Thus it would seem that environmental pollution affecting the eggs through the food chain may be the basic problem, and not the behavior of the adults, inadequate food supply, or such other local factors as disturbance of the nests. But which pollutants are critical and what are the mechanisms? We know that DDT and other chlorinated hydrocarbon pesticides sprayed widely over farms and orchards persist in the environment a long time. Insects poisoned by these chemicals are consumed by fingerlings; these are eaten by larger fish, which in turn are caught by the osprey. The concentrated poisons are then, presumably, transferred to the osprey's own tissues. Recent studies at the University of Wisconsin by Professor Joseph J. Hickey and Daniel W. Anderson show a definite relationship between the presence of DDE, a derivative of DDT, in the eggs of certain fish-eating birds and the thickness of the eggshells. Osprey eggshells examined in New Jersey weighed 25 percent less than those collected before the use of chlorinated hydrocarbons. (Significantly, shells from the more stable Maryland population have changed much less.) The presence of DDT and related compounds could explain the high percentage of egg breakage and egg disappearance in our Connecticut nests. Actually, DDT is only one of many pollutants coursing through our rivers. Research will pinpoint the problems and cures. With rare insight, young Paul Spitzer remarked to me, "Ospreys are more than just birds to be enjoyed. They are an alarm system of things gone haywire in the river, the estuary, and the sound. They are sensitive indicators of the environment." That is precisely why all birds are important. But one who loves birds as exemplars of nature's wild beauty finds much sadness in the peril of a species. Almost as dependable as the tides, our Connecticut ospreys return to our estuary during the last 10 days in March. But one year soon, I fear, I shall go down to Great Island at the usual time of their spring arrival, and there will be no ospreys-not one. Part of the lovely Connecticut River will have died. [From Time magazine, July 11, 1969] ECOLOGY PESTICIDE INTO PEST Few chemicals concocted by man have been so widely used and so thoroughly applauded as dichlorodiphenyltrichloroethane, more commonly known as DDT. It has proved its unmatched power in the worldwide battle against those pestborne killers, typhus, encephalitis and, particularly, malaria. Its mastery over the mosquitoes that carry malaria has undoubtedly spared millions of people from death and debilitating infection. Equally potent in saving crops, it has almost doubled the yield from U.S. cotton fields in the past two decades by controlling the boll weevil. Even the Swedes, who have decided to ban the chemical, readily acknowledge its effectiveness. In 1948 they awarded the Nobel Prize for chemistry to Swiss Chemist Paul Müller for his discovery of its "miraculous" capacity for destroying insects. Now, growing numbers of scientists and politicans are convinced that Müller's miracle is more curse than cure. Long after exterminating the bugs at which it is aimed, DDT goes on performing its lethal work, washing from fields into rivers, lingering on the leaves of trees, floating about in the atmosphere for years-and contaminating everything it touches. There are some scientists who estimate that as much as two-thirds of the 1.5 million tons of DDT produced by man may still be adrift. POISONOUS BROTH More widespread than radioactive fallout, DDT is found in every kind of aquatic life and in almost every animal. Even mother's milk exhibits traces of DDT two or three times as high as the maximum standard for cow's milk set by the Food and Drug Administration. In any other container, a current quip has it, mother's milk would be prohibited from crossing state lines. It is also in trouble within the states, Arizona has already banned DDT spraying. Michigan recently imposed a similar ban after the FDA condemned some 700,000 coho salmon from Lake Michigan because they had unacceptably high concentrations of DDT. Stringent controls are now being considered in the states of Massachusetts, New York and Wisconsin. Europeans have taken even more decisive action. Following discovery of the chemicals in their herring catch, the Swedes ordered a two-year ban on DDT, as well as the related pesticides lindane, aldrin and dieldrin. The Netherlands, decided to stop using DDT. So did Denmark. West Germany limits spraying so severely that only 192 tons of the substance were used throughout the country last year. France and Britain are keeping a watch on pesticide levels within their borders. The Russians, too, are concerned, as Premier Aleksei Kosygin indicated when he offered to join with the Swedes in cleaning up what Europeans call the "poisonous broth" conditions in the Baltic Sea. THE DEADLY SEVEN That will be no easy task, considering DDT's extraordinary durability and mobility. The chemical belongs to a family of organochlorine pesticides-the "deadly seven" as ecologists call them.1 Like the other organochlorines, DDT does not dissolve in water. Thus it accumulates in rivers, lakes and seas for years after the original contamination. Moreover, its unusually long half-life of ten to 15 years means that it retains 50% of its effectiveness for more than a decade after it is first used. Despite its resistance to water, DDT is easily soluble in fats and highly suscetible to "biological magnification" as it makes its way up the food chain. A typical case of this kind of metabolic mayhem occurred in Long Island Sound. After some mosquito-infested marshes were sprayed, the DDT was found in the nearby water in a "safe" concentration of 0.000003 parts per million. Nonetheless, the DDT quickly accumulated in more concentrated form in the Sound's tiny Zoplankton (.04 ppm), then built up further in the fatty tissue of planktoneating fish (.5 ppm). These small fish, in turn, were devoured by larger fish with yet another increase in DDT concentration (2.0 ppm). By the time the chemical had passed into the bodies of such fish-eating birds as cormorants, mergansers and ospreys its concentration (25 ppm) had increased an astounding 10 million times over the original amount. DDT also interferes with the reproductive cycle. Adult fish, for example, are able to tolerate relatively high levels of DDT. The fish embryo, on the other hand, dies almost immediately when it begins to absorb the pesticide through the fatty yolk sac. In birds, DDT kills off the young by interfering with the female's egglaying process. Though the exact chemistry is still obscure, the pesticide apparently sends the mother bird's liver into a frenzy of enzyme production. The excess enzymes break down such steroids as estrogen that are essential to the manufacture of calcium. Lacking adequate calcium, the bird's eggs emerge thinshelled and flaky, offering scant protection for the embryo. In at least one instance, reports the National Audubon Society, which has just joined the public crusade against DDT, a bald-eagle egg was found on the shores of Lake Superior with no shell at all-just a fragile membrane. According to University of Wisconsin Ecologist Joseph Hickey, DDT has caused a disastrous decline in the population of the bald eagle, which is the U.S. national symbol-and the emblem of next week's Apollo 11 flight. Other predators, such as the osprey and peregrine falcon, are gradually vanishing, as are the brown pelican and the extremely rare Bermuda petrel. 1 The others: dieldrin, aldrin, endrin, heptachlor, chlordane and lindane. They are also sometimes called chlorinated hydrocarbons. AIRBORNE CATS Beyond the danger to fish and birds lies DDT's threat to the whole ecological system. Concentrations of DDT no larger than a few parts per billion in plankton, says Biologist Charles F. Wurster Jr., chief scientific adviser to a New York conservationist group called the Environmental Defense Fund, can substantially hinder the photosynthesis process. On a larger scale, such interference could have an effect on the chemical's use; its efficiency has been impaired by the resistance developed by many strains of insects. One scientist estimates that 150 pests formerly controlled by DDT are now immune to it. Nor do scientists expect to produce a new all-purpose bug killer. Instead they are emphasizing more subtle and selective methods of pest control-among them, the breeding of new insectresistant crops, trapping pests with light and sound, and eliminating insects through sterilization. None of these methods pose anything like the dangers of DDT. The problem is that neither do they promise anything like its effectiveness. |