The reproductive capacity of some species of rabbits is such that, under optimal conditions, about 30 million descendants can emerge from a single pair in the short span of three years. It is an exponential increase that would put the balance of any ecosystem at risk.
For Australia, a continent that had evolved independently over millions of years and developed some peculiar ecological characteristics, this would inevitably become a problem. In fact, it was more than that, it was a complete disaster.
It all started innocently enough when, in 1859, Thomas Austin imported European rabbits for his Victorian estate in South Australia. He wanted to let them run free and breed so that he could later do some hunting. Besides, it was not the first time that rabbits had been brought to Australia. The reality is that no one, at that point, could ever imagine the catastrophe that was coming.
Thomas Austin was a member of the Acclimatisation Society, a volunteer organisation that became especially popular during the nineteenth and early twentieth centuries, coinciding with the European colonial period. The idea was to introduce new species of animals and plants into the newly colonised territories. In turn, they introduced in Europe species that were considered exotic, had medicinal value or were useful for other practical purposes. The large population of European eucalyptus trees, for example, come from Australia. They were a species of tree that grew rapidly and were therefore useful in the reforestation of large, previously deforested territories.
The ultimate goal of the acclimatisation societies was to enrich the flora and fauna of all countries. It was a very noble objective. However, what the members of these societies failed to understand at the time was that species live in a permanent struggle for resources, and the introduction of a new species is often made at the expense of another. Today, eucalyptus trees are considered an invasive species in some areas since they compete and destroy other native species. In all fairness, it must be said that it was a time when the theories of Charles Darwin were not yet very well known, and ecology had not been developed as a scientific discipline. It is easier for us to see in hindsight the mistake it was in the long term.
Many of the British settlers tried to introduce new species of plants and animals to ‘correct’ the supposed natural deficiency of some of the colonies within the British empire. These settlers were clearly nostalgic for their homelands and they tried to recreate the landscape by introducing species from the British Isles.
Thomas Austin was just one of those settlers who also had a passion for hunting. When he arrived in Australia, he wanted to continue that practice. He wrote to his nephew asking him for 12 grey rabbits. Unable to get that number, his nephew decided to send specimens of another breed as well. In turn, these two breeds interbred to form a third one that was particularly well adapted to Australian conditions.
In less than 10 years, the situation was already out of control. In 50 years, rabbits had spread over an area greater than half of Europe. It is the largest increase in the number of mammals ever recorded in history (at least on one particular continent). The rabbits wiped out the vegetation of large areas and were responsible for a serious problem: deforestation. Vast areas that were previously grassy were reduced to desert.
In 1887, the government of New South Wales offered $25,000 to anyone who could find an effective method of eradicating the problem. However, out of nearly 1,500 suggestions, none could be found that was both effective and safe for humans and other species of animals.
Due to the extreme seriousness of the problem, the government could not stand idly by. It was imperative to do something to reverse the situation. As of that moment, farmers were free to eliminate as many rabbits as possible. Unfortunately, this measure was far from sufficient to reduce their number so they decided that they would erect barrier fences to prevent rabbits from advancing further. In addition to that, all access to water sources was covered so they would die of thirst during heat waves. But all seemed futile. In the 1950s, the situation was so worrying that the government decided to introduce a new strategy: biocontrol. Several rabbits infected with the myxomatosis virus (which only affects rabbits) were released. At first, the measure seemed to be effective and both farmers and the authorities were optimistic for the first time.
The population of 600 million was reduced to about 100 million, but the rabbits developed immunity against the virus, and the population began to recover. By the 1990s, given the persistence of the problem, another pathogen was introduced: the rabbit haemorrhagic disease virus (known as RHDV). In combination with the poison that was being used, there was a significant reduction in the number of rabbits. However, even today, the problem persists, and experts continue to search for solutions to reduce the number further. The fly that transmits the RHDV virus cannot survive in colder areas and rabbits retreat there, where the populations are still too large.
(Extract from the book: The of Everything (A society in transition)