Introduction It is very important for us to be aware of the effect that civilization has on our
natural
world but we need also to understand some of the ways in which natural forces - out of our control - affect that same world. Natural disasters are those caused as a result of extreme examples of natural phenomena. These include ferocious winds, extraordinary amounts of water, devastating fire, massive earth movements, or the excessive behavior of animals, plants, or micro-organisms. The disasters described on this page vary in intensity and effect but all are particularly damaging in their own way. We have addressed four types of biological disasters. These involve a)
rabbits, b) an insect, c) a bacterium, and d) a virus. Currently we have only introduced one cause of physical disaster and that is fire.
DISASTER CAUSED BY RABBITS 1. Is it possible for rabbits to cause a natural disaster? Yes, if they occur in extreme
numbers.
In Australia in the 1950s rabbits, with few natural enemies, had multiplied dramatically. They are herbivores (they eat plants) and in some areas had picked the land so bare that erosion set in and the land could no longer be farmed.
2. How did the Australians deal with the rabbit plague?
The government put up thousands of miles of wire fences but the rabbits burrowed beneath them to find their food. Farmers tried poisons but other animals found the poison too. Foxes were introduced but they preferred lambs and chickens which were easier to catch than the rabbits. Finally, in yet another attempt to reduce the numbers of rabbits they were intentionally infected with an experimental virus.
3. What was the most successful effort to deal with this plague?
The virus infection. In 1950 Australian scientists infected some rabbits with a virus that had, for many years, been known to cause disease in rabbits and had been tested in Brazil in the late 1940s. They released the infected rabbits into the areas where the worst rabbit infestions existed. The virus, myxoma, was transmitted from rabbit to rabbit by mosquitos and rabbit fleas. Over the next three years rabbits died of myxomatosis by the millions, grass grew back on the pastures, and sheep farming began to flourish again.
4. What else happened as a result of the introduction of Myxoma to the rabbit population?
There was a sudden upset in the balance of nature. The Myxoma virus had been successfully introduced into European rabbits too and, especially in England, with a scarcity of rabbits, foxes began eating poultry, rats and mice. The resulting reduction in the numbers of mice caused a decline in the numbers of owls whose normal diet (mice) became less abundant - and the upset continued on down the food chain. Scientists believe that, as populations of rabbits with resistance to Myxoma increase, there will be rabbit plague problems again.