It is incredible when you think about it. As smart as human beings are, Mankind has pulled off some serious blunders and when it comes to animals and other species, the blunders were enormous and the cost has run into billions of dollars and grief. The ‘law of unintended consequences’ describes the well-documented fact that stupid actions often have adverse and unpredictable consequences.
Since their introduction from Europe in 1859, the effect of rabbits on the ecology of Australia has been devastating. Rabbits are suspected of being the most significant known factor in species loss in Australia. Rabbits often kill young trees in orchards, forests and on properties by ringbarking them. Rabbits are also responsible for serious erosion problems as they eat native plants, leaving the topsoil exposed and vulnerable to sheet, gully and wind erosion. The removal of this topsoil is devastating to the land as it takes many hundreds of years to regenerate. The common rabbit is becoming so numerous throughout the colony, that they are running about on some large estates by thousands.
The current infestation appears to have originated with the release of 12 wild rabbits by Thomas Austin on his property, Barwon Park, near Winchelsea, Victoria, in October 1859 for hunting purposes. Upon arriving in Australia, which had no native rabbit population, Austin asked his nephew William Austin in England to send him 12 grey rabbits, five hares, 72 partridges and some sparrows so that he could continue his hobby in Australia by creating a local population of the species. However William could not source enough grey rabbits to meet his uncle's order. So he topped it up by buying domestic rabbits. One theory as to why the Barwon park rabbits adapted so well to Australia is that the hybrid rabbits that resulted from the interbreeding of the two distinct types were particularly hardy and virile. Many other farms released their rabbits into the wild after Austin. At the time he had stated, "The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting."
Obviously that mistaken theory backfired. Rabbits are extremely prolific creatures, and had spread rapidly across the southern parts of the country. Australia had ideal conditions for a rabbit population explosion. With mild winters, rabbits were able to breed the entire year. With widespread farming, areas that may have been desert, scrub, or woodlands were instead turned into vast areas with low vegetations, creating ideal habitat for rabbits. Like all explosions, the rabbit population expanded until it got out of control. In a classic example of unintended consequences, within ten years of the introduction in 1859, rabbits had become so prevalent that two million could be shot or trapped annually without having any noticeable effect on the population. It was the fastest spread ever recorded of any mammal anywhere in the world.
By the late 1960s, it had become clear that there was an environmental conservation problem on Macquarie Island, a small possession of Australia located halfway between New Zealand and Antarctica. The island’s population of rabbits that was introduced over a century before had become quite large, and authorities feared the rabbits were causing ecological problems by eating too much of the island’s vegetation.
Macquarie Island had hosted rabbits for about one hundred years, as well as feral cats and rats, both of which were introduced into the environment at about the same time. The ecosystem was not in a state of crisis in the 1960s, as the survival of the island’s major species was not threatened but the situation was undesirable from a conservationist point of view.
In response to the problem, the Australian government decided to drastically reduce the population of rabbits by exposing the population to the myxomatosis virus, an extremely efficient bunny killer. The plan achieved its narrow objective: in just over ten years, the rabbit population had dropped from 100,000 to just 10,000.
However, in terms of the broader objective of the policy—strengthening the ecosystem of Macquarie Island—the rabbit extermination was a disaster. It turned out that the rabbits had been the primary food source for the island’s population of feral cats, and with the rabbits all but eliminated, the cats began to aggressively hunt the island’s population of seabirds.
The cats quickly began to decimate the seabird population, hunting the native bird
species to the brink of extinction. Desperate to save the remaining seabirds, the Australian government authorized a $500,000 program to remove the island’s cat population. The scientists once again succeeded in their narrow objective; the last cat was removed from the island in the year 2000. But once again, the best laid plans of the conservation scientists wrought havoc on the broader ecosystem
they were trying to preserve.
With the cats eliminated, the island’s population of rats exploded.As the rats’ diet included the eggs and chicks of the native seabirds, the huge growth in the rat population quickly posed as big a threat to the native bird species as had the feral cats. What’s more, with the cats gone, the small fragment of the rabbit population
that had survived the initial extermination attempt were uncontrolled by predation.
The rabbits that survived the initial cull were the strongest and healthiest of
the initial population, and by the time the cats were removed these surviving
rabbits had developed immunity to the myxomatosis virus and were therefore much more difficult for humans to cull. Without a predator, the rabbit population once again thrived, growing back to and actually surpassing the numbers that had prompted the initial response. Within just six years, the rabbit population rebounded from a low of 10,000 to a new high of 130,000. The rabbits once again began to devour the local vegetation even more aggressively than before, stripping huge swaths of the island bare.
Today, the island’s ecosystem is in worse condition than ever and the Australian government has allocated $25 million to attempt to address the catastrophe by killing off the island’s rats and rabbits. But the efforts of the government brought
the island to the brink of an “ecosystem meltdown,”a cure much worse than the actual
disease they set out to address.
Crocodile-killing culprits are cane toads. Australia had no native toads, but in 1935 they imported these amphibians to battle beetles that were damaging the sugar cane crops. The invasive amphibians quickly spread out of control, however, multiplying like rabbits across the Australian continent. In the last few years, they have entered the habitats of Australia’s rare freshwater crocodiles, which saw the toads as something good to eat. Unfortunately, the toads’ poisonous skin spells death for any unlucky croc that consumes them.
Once the toads moved into their territory, freshwater crocs dropped in numbers from more than 600 in 2006 to less than 400 last year. The crocodiles’ plight should serve as a warning against importing one species to kill another. Invasive species can spread like wildfire, so bringing them in as mercenaries seems like a dubious plan loaded with possible unintended consequences. Cane toads don’t know that they’re wrecking the Australian ecosystem—they’re just trying to survive and multiply, and doing a great job of doing it.
In the early 1970s, the Audubon Society and the Natural Resources Defense Council, spurred on by Rachel Carson's book Silent Spring, successfully pressed the US government to stop foreign aid to any country using the insecticide DDT, arguing that the insecticide caused cancer and harmed wildlife. The government relented, and many third world countries stopped using DDT. But banning this insecticide almost certainly led to more, not fewer, deaths. Why?
The incidence of malaria increased dramatically in countries that had stopped using DDT, since the insecticide had been previously very effective in killing the mosquitoes that carry the disease. Tens of millions have died over the past few decades because of the DDT ban, which still remains in place.
Consider the Endangered Species Act (E.S.A.) of 1973, which protects flora and fauna as well as their physical habitats. The economists Dean Lueck and Jeffrey Michael wanted to gauge the E.S.A.'s effect on the red-cockaded woodpecker, a protected bird that nests in old-growth pine trees in eastern North Carolina. By examining the timber harvest activity of more than 1,000 privately owned forest plots, Lueck and Michael found a clear pattern: when a landowner felt that his property was turning into the sort of habitat that might attract a nesting pair of woodpeckers, he rushed in to cut down the trees," to keep the woodpeckers out so that he would not come under the auspices of the Endangered Species Act and in which case the woodpeckers might die or have to go somewhere else, where another landowner spots 'em and says, "Uh-oh, I gotta get rid of you guys before the feds show up." So he cuts down his trees even if they're not ready to be cut down or even if he's going to take a loss doing it. It's a short-term loss versus permanent loss of the use of his property. They know that if their land is declared as a haven for endangered species, they can’t use their land. Because of that possibility, the birds the authorities of the E.S.A are trying to save, are being killed off anyway by farmers who don’t want to lose the use of their land.
When the Soviet geneticist Dmitri Belyaev began to breed for tameness in the silver fox, he did get very tame silver foxes. He also wound up producing foxes that were spotted– some of them marked like border collies. These were, of course, useless as fur-bearers. But the results did show how selecting for a trait can also include selection for other traits. Belyaev selected for lower adrenaline levels in his foxes, but adrenaline is believed to share a biochemical pathway with melanin, which controls pigment. When he selected for lower adrenaline, he was also selecting for lower melanin. You breed for tame foxes, and you get tame ones with spots which of course won’t help the farmer sell the furs.
There have been similar results in broiler chickens. Temple Grandin theorized that the selection for larger breast in broiler chickens actually made the roosters very aggressive and also selected for roosters that did not give off the appropriate courtship behaviors. As a result, a large number of roosters used in producing broilers are so aggressive and libidinous that they rape then hens with whom they mate and then kill them. In her recent work, though, Grandin feels that this isn’t correct.
In breeding for heavier breasted chickens, the broiler breeders have produced chickens that have reduced fertility, which is why the roosters don’t demonstrate the courtship behaviors. To correct, this problem, the breeders have selected for what they observe to be higher sex drive in their roosters. However, what they were observing may not have been sex drive at all. It may have been aggression. So the broiler breeders have selected for chickens with big breasts and very low fertility and sex drive. But those roosters that do have fertility and sex drive are so aggressive towards the hens that they kill them after they mate with them. And all of those were the result of several unintended consequences in selective breeding. It has been a real selective breeding comedy of errors.
Most turkeys that are mass-produced for the table cannot breed naturally. Indeed, virtually all turkeys that can be purchased at the supermarket have been the result of artificially inseminated. Most strains of these turkeys have been selected for huge breast. But over the generations, this selective breeding has produced tom turkeys that cannot mount the hens. They are simply too massive to do so. Some defective toms are produced that are so massive in the breast that they cannot even stand up.
English springer spaniels in North America and English cocker spaniels in Europe can be great pets for children. But many are bred to have a lunging gait for dog shows. It turns out that breeding for that lunging gait also predisposes the dogs to a disorder called “avalanche of rage syndrome.” This syndrome is characterized with dogs that are normally quite docile suddenly attacking people, objects, or other animals for no reason. Now, neither of those breeds is required to show any aggression in their working behavior. Indeed, these dogs are often recommended as family pets. However, no one wants a dog that suddenly goes for the children, but it turns out that this syndrome was selected for when they began breeding for that particular gait. . In domestic dogs, the ability of the animal to develop unusual and novel body shapes, colors, coat-types, and sizes is reaching its breaking point. We now have dogs that are so distorted from what could be considered healthy conformation. Today we have pekes and bulldogs without muzzles, dachshunds that are built like weasels, German shepherds that stumble around with their sloped backs and weirdly angulated hindquarters, extremely small Chihuahuas and Yorkies, and many other distortions of the basic canine shape. And who knows what sort of genetic disorders have resulted from this sort of selective breeding?
Back in the Nineteen-fifties, there was an “innovation” in livestock fencing. It was multiflora rose, said to be “horse-high, bull strong, and hog-tight.” Plant this along fence-rows, and forget about setting replacement posts and repairing wire. Except it seeds through pips that pass through birds’ digestive tracts unchanged, and the thorny exuberant bushes will sprout anywhere: in the middle of pastures, in hayfields. It’s a bear to get rid of, too. Even goats won’t eat it. Fifty years after its introduction, it’s an outright problem, and has been for most of those fifty years.
Introduced to North America in the 1970s to stop the spread of algae, the silver and bighead species of Asian carp escaped from southern U.S. fish farms in the 1990s during flooding.They have infested parts of the Mississippi and Illinois rivers, wiping out other fish populations."They are ferocious feeders," said Robert Lambe, chairman of the Great Lakes Fishing Commission."They tend to wipe out the lower food chain, so other fish tend not to survive."
The silver variety of the Asian carp has a unique characteristic that makes it particularly dangerous to humans: the sound of a boat motor startles the fish, causing it to leap as high as ten feet out of the water. The large fish, some longer than a metre and weighing up to 50 kilograms, are a serious threat to boaters, who have reported injuries ranging from serious bruises to broken jaws.
Asian carp have the ability to spread rapidly, reproduce in large numbers, and become the predominant species in an ecosystem. Once established, fishery managers have little chance to control the fish. Like the sea lamprey, they could become a permanent element of the Great Lakes if they enter the system.
There are many more invasive animals that have attacked our ecosystems and at a later date, I will write another article about them.
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