In desperation, a housewife wrote to Robert Cushman Murphy, honorary curator of birds at the American Museum of Natural History in Hesdale, Illinois (a world-renowned ornithologist):
"Our village has been spraying elms for several years (this letter was written in 1958). When we moved here six years ago, there were many birds here, so I started to raise them. Throughout the winter, cardinals, tits, woolly birds and fifty birds flew over here continuously; In summer, cardinals and tits fly back with their birds.
After spraying DDT for several years, there are almost no robins and starlings in this city; I haven't seen tits on my bird rack for two years, and this year the cardinals have disappeared; There seems to be only a pair of pigeons left in the community, and there may be a nest of cats and birds nesting.
The children learned the federal law to protect birds from being killed at school, so I told them that it was not good for birds to be killed. Will they come back? The children asked, and I was speechless. The elm tree is dying, and so are the birds. Are measures being taken? What measures can be taken? what can I do? "
A year after the federal government began to implement a huge spraying plan to kill fire ants, an Alabama woman wrote, "For more than half a century, our place has been a real refuge for birds. Last July, we all noticed that there were more birds here than before. However, suddenly, in the second week of August, all the birds disappeared. I am used to getting up early every day to feed my beloved mare who gave birth to a foal, but I can't hear any birds singing. This situation is frustrating and disturbing. What have people done to our beautiful world? Finally, it was not until five months later that a blue ostrich and wren appeared. "
In the autumn mentioned by this woman, we received some equally depressing reports from Mississippi, Louisiana and the remote south of Alabama. The quarterly publication "Field Chronicle" published by the National Atto Institute and the US Fish and Wildlife Service records that there are some terrible blank spots in this country without any birds, which is shocking. The field chronicles are compiled from reports written by some experienced observers, who have conducted field investigations in specific areas for many years and have unparalleled rich knowledge of normal bird life in these areas. An observer reported, "When he was driving in southern Mississippi that autumn, he couldn't see any birds in the distance." Another observer in Ruger, Belden reported that the feed she put there "has not been touched by birds for weeks"; By then, the shrubs in her yard should have been stripped, but the branches are still full of berries. Another report said that his window "used to be composed of forty or fifty cardinals and a large group of other birds, but now it is rare to see one or two birds." Morris Brooks, an authority on birds in Appalachia and a professor at the University of West Virginia, reported that "the decline in the number of birds in West Virginia is unbelievable".
Here is a story that can be used as a symbol of the tragic fate of birds-this fate has conquered some species and threatened all birds. This story is the well-known story of robin. For millions of Americans, the appearance of the first robin means that the rivers in winter have thawed. The arrival of the robin was reported as news in the newspaper, and everyone eagerly told each other at dinner. With the gradual arrival of migratory birds, the forest began to turn green, and thousands of people listened to the first song of robin dawn chorus in the morning. But now, everything has changed, and even the return of birds is no longer taken for granted.
Robins, and indeed many other birds, seem to be closely related to American elms. From the Atlantic coast to the Rocky Mountains, this elm tree is an indispensable part of the history of thousands of towns. It decorates streets, cottages and campuses with solemn green arches. Now this kind of elm is sick, and the disease has spread to all areas where elm grows. The disease is so serious that experts admit that it is futile to try our best to save elm in the end. It is sad to lose the elm, but if we throw most of our birds into the darkness of extinction in our futile efforts to save the elm, it will be a double tragedy. This is what threatens us.
The so-called dutch elm disease was introduced in about 1930 when the United States imported sleepers for panel industry from Europe. This disease is a fungal disease. Germs invade the water pipes of trees, and their spores spread through liquid flow. Elm branches wither and die because of its toxic secretions and blocking effect. The disease is spread from diseased trees to healthy trees by elm bark beetles. The tunnel dug by the insect under the dead bark was later polluted by the invading fungal spores, which attached to the beetle and were taken to all the places where it flew. Efforts to control this elm disease depend largely on the control of insect spreaders. Therefore, in the areas where elm trees are concentrated in the United States-the Midwest of the United States and the States of New England, it has become a daily work to spray drugs widely in the countryside.
What does this spraying mean to birds' life, especially to robins? George wallace, a professor at the University of Michigan, and John Miner, one of his graduate students, gave a clear answer to this question for the first time. When Mr Miner started his doctoral thesis at 1954, he chose a research topic about robin population. It was a complete coincidence, because no one doubted that the robin was in danger at that time. However, while he was doing this research, something happened, which changed the nature of the subject he wanted to study and deprived him of his research object.
The spraying of drugs in dutch elm disease started in a small area of the university campus of 1954. In the second year, campus spraying was expanded to include Donglan Star City (where the university is located). In the local plan, not only gypsy moth, but also mosquitoes were sprayed in this way. The rain of chemicals has increased to the point of pouring down.
From 1954 to spraying a small amount of medicine in the first year, everything seems to be going well. The following spring, the migrating robins began to return to campus as usual. Just like the wild hyacinthus orientalis in Tom Linsen's essay The Lost Woods, when they reappeared in familiar places, they didn't "expect any misfortune". However, it was soon discovered that something was wrong. Dead and dying robins began to appear on campus, and birds used to be seen almost everywhere where birds pecked at birds. Few birds build nests, and few young birds appear. The following spring, this situation recurred monotonously. The spraying area has become a fatal trap, and a group of migratory robins can be eliminated in just one week. Then, new birds fall into the trap again, increasing the number of birds doomed to failure; You can see these doomed birds on campus, and they all tremble in the struggle before death.
Professor Wallans said: "For most robins who want to find a place to live in spring, the campus has become a graveyard." But why? At first, he suspected that this was due to some diseases of the nervous system, but it soon became clear that "although people who used pesticides promised that their spraying was harmless to birds, those robins did die of pesticide poisoning, and robins showed well-known symptoms of losing balance, followed by trembling, convulsions and even death."
Some facts show that robin poisoning is not caused by direct contact with pesticides, but indirectly by eating earthworms. Earthworms on campus were accidentally used to feed crickets for a research project, so all the crickets died soon. A snake in a laboratory cage trembled violently after eating the earthworm. However, earthworms are the main food for robins in spring.
Dr Roy Barker of the Illinois Institute of Natural History in Ubana quickly solved the mystery of the death of this doomed robin. Barker's book was published in 1958, and he discovered the complicated circular relationship of this incident-the fate of robins was linked with elms due to the action of earthworms, and elms were sprayed in spring (usually at the rate of 2-5 pounds DDT per 50-foot tree, equivalent to 23 pounds DDT per acre of elm-intensive areas), and often sprayed again in July, with the previous concentration. A powerful sprayer sprays poisonous hoses at the top and bottom of the tallest tree, which not only directly kills bark beetles to be eliminated, but also kills other insects, including pollinators and spiders and beetles that prey on other insects. The poison formed a thick film on the leaves and bark, which could not be washed away by the rain. In autumn, leaves fall to the ground, accumulate into a wet layer and begin to become a part of the soil. In this process, they get the help of earthworms that eat leaf debris, because elm leaves are one of their favorite foods. Earthworms will swallow pesticides while eating leaves, and pesticides will accumulate and concentrate in the body. Dr Barker found DDT deposits in the digestive tract, blood vessels, nerves and body walls of earthworms. There is no doubt that some earthworms can't resist poison and die, while others who survive have become "biological amplifiers" of poison. In spring, when the robin came, another link in this cycle happened. As long as 1 1 earthworm can transfer the lethal dose of DDT to robin. And 1 1 earthworms are only a small part of a bird's daily food intake, and a bird can eat 10- 12 earthworms in a few minutes.
Not all robins have taken lethal doses, but another consequence will definitely lead to the extinction of this species and inevitable poisoning. The shadow of infertility hangs over all birds, and its potential threat has extended to all living things. Every spring, only twenty or thirty robins can be found on the entire 185 acre campus of Michigan State University. By contrast, there were about 370 birds here before spraying. 1954, every robin nest observed by Miner hatched young birds. By the end of June 1957, at least 370 young birds (the normal successors of adult birds) should be looking for food on campus, but Miner has only found one robin now. A year later, Professor Wollance reported, "In the spring and summer of (1958), I didn't see a robin with long hair anywhere on campus, and I haven't heard of anyone seeing any robin."
Of course, part of the reason why no young birds are born is that one or both of a pair of robins died before the nesting process was completed. But Florence has remarkable records, which point out something even more ominous-the reproductive ability of birds has actually been destroyed. For example, he recorded that "birds such as robins can't build nests and lay eggs, and other eggs can't hatch birds." We recorded a robin crouching confidently for 2 1 day, but failed to hatch a bird. The normal dormancy time is 13 days. Our analysis found that there is a high concentration of DDT in the testicles and ovaries of birds crouching in the nest. " In 1960, Volans told Congress about this situation: "10 has 30- 109/ million DDT in the testicles of male birds and151-21in the follicles of two female birds.
Then studies in other areas began to find that the situation was equally worrying. Professor Yusuf Heck of the University of Wisconsin and his students reported that the mortality rate of robin was at least 86%-88% after carefully comparing the spraying area with the non-spraying area. The Cranbrook Institute of Science near Baihua Mountain in Michigan tried to estimate the bird loss caused by spraying elm. In 1956, it requires that all birds thought to have died of DDT poisoning be sent to the research institute for laboratory analysis. This request received a completely unexpected response: within a few weeks, all the instruments that the institute had not used for a long time were operated to the maximum workload, so that other samples had to be rejected. 1959, only one village reported or handed in 1000 poisoned birds. Although robins were the main victims (a woman called the institute and reported that 12 robins had died on her lawn when she called), the institute also tested 63 other birds. Robins are only part of the destructive chain reaction related to elm spraying, and the elm spraying plan is just one of various spraying plans to cover the earth with poison. About 90 species of birds have suffered serious casualties, including those most familiar to suburban residents and nature lovers. In some sprayed towns, the number of nesting birds has generally decreased by as much as 90%. As we will see, all kinds of birds will be affected-birds foraging on the ground, birds foraging in the treetops, birds foraging in the bark and raptors.
It is reasonable to think that all birds and mammals whose main food is earthworms and other soil organisms are threatened like robins. About 45 species of birds feed on earthworms. The woodcock is one of them. This bird has been wintering in the south where heptachlor has been sprayed heavily recently. Now there are two important discoveries in woodchucks. In the incubator in New Brunswick, the number of young birds decreased obviously, and the analysis of adult birds showed that there were a lot of DDT and heptachlor residues.
There are disturbing records that more than 20 species of ground foraging ants have died in large numbers. The food of these birds-worms, ants, maggots or other soil organisms-has been poisoned. Among them, there are three kinds of thrush-olive-backed bird, thrush and hummingbird. Their songs are the most beautiful among birds. There are sparrows, singing sparrows and white birds grazing on the lush shrubs in the forest, rustling in the leaves. These birds have also become victims of elm spraying.
Similarly, mammals can easily participate in this chain reaction directly or indirectly. Earthworms are an important food for raccoons, and kangaroos often eat earthworms in spring and autumn. Underground cave animals such as gophers and moles also prey on earthworms, and then they may pass toxins on to raptors such as owls and barn owls. In Wisconsin, after the spring rainstorm, several dead owls were found. Maybe they died of earthworm poisoning. Some eagles and owls were found to be in a state of convulsion-among them, long-horned owls, owls, red-shouldered eagles, sparrows and moorhawks. They may die of secondary poisoning by eating birds and mice that have accumulated pesticides in their livers and other organs.
The victims are not only birds that prey on the ground, but also birds of prey that are endangered by spraying elm leaves. Elves in forest areas-red-crowned cranes and golden-crowned wrens, tiny mosquito traps and many songbirds fly through the forest in droves in spring, and all birds looking for insects from leaves disappear from areas where pesticides are sprayed heavily. 1956 In the late spring, the spraying time was delayed, which happened to meet the migration climax of a large group of songbirds. Almost all songbirds flying to this area have been killed in large numbers. In White Fish Bay, Wisconsin, at least 65,438+0,000 migratory hickory birds can be seen in normal years, while in 65,438+0,958 after spraying elm trees, observers only see two birds. With the continuous spread of bird deaths in other towns and villages, this list has gradually become longer. Some songbirds killed by spraying chemicals fascinate everyone who sees them: black-and-white birds, goldfinches, magnolia birds and May Peng birds, roast birds whose songs echo in the forest in May, black-roasted birds with burning wings, chestnut birds, Canadian birds and green birds with black throats. These birds foraging on the branches are either directly affected by eating poisonous insects or indirectly affected by lack of food.
The loss of food also dealt a heavy blow to the swallows wandering in the sky. They desperately searched for flying insects like herring and tried to catch plankton in the sea. A Wisconsin naturalist reported, "The swallow was badly hurt. Everyone is complaining that there are fewer swallows now than four or five years ago. Only four years ago, the sky above us was full of flying swallows. Now we rarely see them ... This may be because there are fewer bugs in spraying or the bugs are poisoned. "
Referring to other birds, the Observer wrote: "Another obvious loss is the stork. Although there are no birds of prey that prey on larvae everywhere, the common emu that has been strong since childhood can no longer be seen. I saw one this spring and only one last spring. Other birdwatchers in Wisconsin have the same complaint. I used to have five or six pairs of cardinals in North America, but now I don't. Wren, robins, cats and owls nest in our garden every year. There is nothing now. There are no birds singing in the summer morning. Only birds, pigeons, starlings and English swallows are left. This is extremely tragic and I can't stand it. "
Spraying elm regularly in autumn makes poison enter every small crack in the bark, which is probably the reason why the number of birds such as tits, fifty finches, flowers and birds, woodpeckers and brown woodpeckers is rapidly decreasing. In the winter between 1957 and 1958, Professor Wallace found for the first time in many years that there were no tits and fifty finches in his bird feeding place. He later summed up a sad fact, showing the causal relationship among the 350 finches he found: one of the 50 finches was pecking at elm trees, another died of DDT poisoning, and the third one was dead. It was later found that the tissues of 50 dead birds contained 26/ million DDT.
After spraying pesticides on insects, the eating habits of all these birds not only make them particularly vulnerable, but also cause extremely heavy losses in economic and other less obvious aspects. For example, the summer food of fifty white-breasted finches and brown woodpeckers includes a large number of eggs, larvae and adults of insects harmful to trees. Three quarters of tits' food is animal, including many kinds of insects at various growth stages. The way tits feed is described in the immortal Life History, which describes North American birds: "When a flock of tits fly to a tree, each bird carefully searches for some food (spider eggs, cocoons or other hibernating insects) on the bark, branches and trunk."
Many scientific studies have confirmed that birds play a decisive role in insect control in various situations. Woodpeckers are the main controllers of conifer beetles in Engeman, which reduced the number of these beetles from 55% to 2% and played an important role in controlling codfish moths in apple orchards. Tits and other birds left in winter can protect orchards from inchworms and the like.
But what happened in nature can't happen again today, when chemical drugs are saturated. In this world, spraying drugs not only kills insects, but also kills their main natural enemies-birds. As usual, when the insect population recovered later, there were no more birds to stop the increase. For example, O. J. Clomi, curator of birds in Milwaukee Museum, wrote in Milwaukee Daily: "The biggest enemies of insects are other carnivorous insects, birds and some small mammals, but DDT indiscriminately kills everything, including the guards and police of nature itself ... In the name of development, are we going to be victims of our vicious insect control? This kind of control can only get temporary comfort, and it will fail in the future. So what methods will we use to control new pests? The elm tree was destroyed and the guardian bird of nature died of poisoning. At that time, these pests will eat the remaining tree species. "
Mr Clomy reported that since Wisconsin began spraying drugs, telephone calls and letters reporting bird deaths have been increasing. These questions tell us that birds are dying in the spraying area.
Ornithologists and observers in most research centers in the Midwest of the United States agree with Clomi's experience, such as the Crane Creek Institute in Michigan, the Natural History Survey in Illinois and the University of Wisconsin. As long as you look at the letters from newspaper readers in almost all areas where drug spraying is being carried out, it will clearly show the fact that residents not only know this and feel indignant, but also realize the harm and irrationality of drug spraying more deeply than those officials who ordered it. A woman in Miwalker wrote: "I am really worried that many beautiful birds in our backyard will die!" " The day of leaving is coming now. ""This experience is very pitiful and sad ... Besides, it is disappointing and angry, because it obviously failed to achieve the goal of this massacre ... In the long run, can we just plant trees instead of raising birds? Aren't they interdependent in natural organisms? Can't we help nature regain its balance without destroying it? "
In other letters, I have expressed the view that although Yucun is a majestic and tall tree, it is not India's "god cow", which cannot be the reason for endless movements aimed at destroying all other forms of life. Another woman in Wisconsin wrote: "I have always liked our elm tree, which is like a lighthouse in the field, but we have many other kinds of trees ... we must also save our birds." Who can imagine how gloomy and lonely a spring without robin singing will be? "
Do we want birds? Or elm? In the eyes of ordinary people, either one or the other seems to be a very simple thing. But the problem is not that simple. The irony of chemistry in drug control is that if we continue on today's road, we may end up with neither birds nor elms. Chemical spraying is killing birds, but it can't save elms. The illusion that sprayers can save elms is a dangerous jack-o'-lantern, which leads people astray. It is causing one village after another to fall into the quagmire of huge expenses, but it has no lasting effect. Greenwich, Connecticut, has been spraying pesticides regularly for ten years. However, the dry year brought particularly favorable conditions for beetle reproduction, and the mortality rate of elm increased tenfold. Dutch elm disease first appeared in 195 1 in Albany, Illinois, where the University of Illinois is located. Chemicals were sprayed on 1953. By 1959, although it had been sprayed for six years, 86% of elms were still lost in the school campus, half of which were victims of dutch elm disease.
In Toledo, Ohio, the same situation prompted Joseph A. Sweeney, the manager of the Forestry Department, to take a realistic attitude towards spraying drugs. 1953 started spraying until 1959. Mr. sweeney noticed that the widespread spread of cotton maple tinea became more serious after spraying, which was always recommended by "books and authorities" before. He decided to personally check the results of spraying dutch elm disease. His discovery surprised him. He found that in Toledo, the only areas where the disease was controlled were those where we took decisive measures to remove diseased trees or plant trees, while in areas where we relied on chemical spraying, the elm disease was not controlled. In the United States, elm disease does not spread as fast in untreated places as it does in cities. This situation shows that the spraying of chemical drugs has eliminated all natural enemies of elm disease.
"We give up spraying dutch elm disease. This led me to argue with people who support the USDA, but I have facts in my hand and I will get them into trouble. "
It is hard to understand why these towns in the midwest (which have only recently developed elm disease) have participated in ambitious and expensive spraying plans without thinking, and have not done some investigations in areas that have long known about this problem. For example, new york must have a long experience in controlling dutch elm disease. About as early as 1930, the diseased elm entered the United States from new york Port, and the disease was introduced. New York State still has an unforgettable record of stopping and eradicating this disease. However, this control does not depend on drug spraying. In fact, the agricultural additional management project in this state does not suggest spraying as a prevention method in towns and villages.
So, how did New York State achieve such good results? From the early struggle to protect elm trees to today, the country has been relying on strict defensive measures, that is, quickly transferring and destroying all sick or infected trees. At the beginning, some results were disappointing, but this was because at the beginning, I didn't realize that I had to destroy not only the diseased trees, but also all the elms where beetles might lay eggs. The infected elm trees were cut down and stored as firewood. As long as it is not burned before spring, there will be many beetles with bacteria in it. Mature beetles that wake up from hibernation in late April and May in search of food can spread dutch elm disease. Entomologists in new york know from experience what kind of wood beetles lay eggs, which is really important for spreading diseases. By concentrating these dangerous timber, it is not only possible to obtain good results, but also to keep the cost of the defense plan at a low limit. By 1950, the incidence of dutch elm disease in new york was reduced to 0.2% of the 55,000 elms in the city. 1942, Westchester county launched a defense movement. In the following 14 years, the average loss of elm was only 0.2% per year. Buffalo with 18500 elm has lost only 0.3% in recent years due to defense work, and has achieved excellent results in controlling this disease. In other words, at this rate of loss, all the elms in Buffalo will take 300 years to disappear.
What happened in Syracuse was particularly unforgettable. No effective plan was put into practice before 1957. During the period of 195 1- 1956, nearly 3000 elms were lost in Syracuse. At that time, under the guidance of H C· Millie of New York State Forestry College, a campaign to eliminate all diseased elms and all possible sources of elm beetles was going on vigorously. The loss rate has now dropped to 1% per year.
When controlling dutch elm disease, experts from New York emphasized the economy of preventive measures. J·G· Messi of new york Agricultural College said: "In most cases, the actual cost is very limited." "As a preventive measure to prevent property damage and personal injury, if a big branch is dead or broken, it's best to cut it off, so that it won't hurt houses and people again. If it is a pile of firewood, it can be used up before the arrival of spring. You can peel off the bark or store the wood in a dry place. For the stolen dying or dead trees, in order to prevent the spread of dutch elm disease, it will not cost more to quickly remove the diseased elms, because most of the dead trees in big cities will eventually be removed. "
If rational and wise measures are taken, dutch elm disease's prevention and control is not completely hopeless. Once dutch elm disease has settled down in a community, it can't be put out in any way known now. Only protective measures can be taken to contain it within a certain range, not those tragic methods that have no effect and lead to the destruction of birds' lives. There are other possibilities in the field of forest origin. In this field, this experiment provides hope for cultivating a hybrid elm to resist dutch elm disease. European elms are very tough, and many of them have been planted in Washington, D.C. ... Even when elms in most cities are affected by diseases, dutch elm disease has not been found in these European elms.
In those villages and towns that are losing a lot of elms, it is urgent to transplant trees through an emergency afforestation plan. This is very important. Although these plans may have taken into account the strong resistance of European elm trees, these plans should pay more attention to establishing the diversity of tree species, so that future epidemics will not take away all the trees in a town. As the British ecologist Charlie Eldon said, the key to a healthy plant or animal community lies in "maintaining diversity". What is happening now is largely due to the simplification of biology in the past generations. Even a generation ago, no one knew that planting a single kind of trees on a large scale would bring disaster, so all towns have streets and parks, which are beautified with elms. The elm tree died today, and so did the birds.
Like robin, another American bird seems to be on the verge of extinction. It is the national symbol-the eagle. In the past ten years, the number of eagles has decreased sharply. Facts show that there are some factors at work in the living environment of the eagle, which have actually destroyed its reproductive ability. We don't know what the specific factors are, but there is some evidence that pesticides can't escape the blame.
The most thoroughly studied eagles in North America are those that nest along the coastline from Mudan to Ford on the west coast of Florida. Charlie Brober, a retired banker from Winnipeg, won a great reputation in ornithology during the period of 1939- 1949 because he marked more than 1000 vultures. (Before that, all birds were marked with only 16 eagles in history. ) Mr. Bob marked the young eagles a few months before they left the nest. Later, the rediscovery of marked birds showed that these Florida-born eagles flew north along the coastline to Canada as far as Prince Edward Island. However, people always think that these eagles will not migrate. In autumn, they returned to the south, and this migration took place on the peak of Hawke in eastern Pennsylvania.