The South Downs is an area of outstanding chalk downland that stretches from East Sussex, right the way across the south of England to Hampshire. There is a public footpath that takes you from Eastbourne at one end to Winchester at the other, called 'The South Downs Way'. This route was Britain's first long-distance bridleway, and it is 99 miles (160 kilometres) long.
The Downs have been designated as an area of outstanding natural beauty and along the route there are a number of national and local nature reserves as well as numerous historical sites of interest. Fortunately, much of the Downs have now been declared as 'environmentally sensitive' and farmers are encouraged to use traditional farming methods such as grazing, rather than using chemically-reproduced fertilisers and pesticides, which would have an adverse effect on this environment.
The South Downs has a rich biodiversity of living organisms. From the plants that grow there to the predators that hunt in this environment, it encompasses a very complex community. If we look at one of the living organisms in the middle of this environment, we can see the interrelationships of this species with other organisms. In this case it is the European rabbit, Oryctolagus cuniculus. A species that was introduced fairly recently in our history.
The Interrelationship of the Rabbit with Other Animals
One of the first things to be explained must be the interrelationships of the rabbits. They are herbivores, in other words, primary consumers. They keep the surrounding vegetation short, which benefits other species such as the stone curlew, a species that prefers to inhabit short grass. Other species benefiting from the natural behaviour of rabbits are wheatears; another type of bird that uses abandoned rabbit holes for nesting. These provide protection from the elements as well as a safe place to rear their young. The minotaur beetle also relies on the rabbit population. The dung produced by the rabbits is used by the larvae of this beetle for food.
There are other animals that the rabbits interact with. The brown hare competes with the rabbit for food and territory. In addition at the top of this food chain there are the predators also known as carnivores: badgers, foxes and buzzards, Then, of course, we cannot forget mankind.
The Interrelationship of the Rabbit with Vegetation
The interrelationship of rabbits with vegetation is yet another factor that we must take into consideration. As the rabbits are herbivores, plant eaters, they are an important influence on the environment. The plants favoured by the rabbits are juniper and hawthorn. Although these plants grow quite quickly they are kept under control by their feeding habits.
Other plants found on the Downs include ragwort and elder bushes. Ragwort usually has trouble establishing itself as other faster growing plants usually crowd it out. As the rabbits scratch around for food they reveal bare patches of soil allowing plants such as the ragwort to take hold. Elder bushes survive mainly because the rabbits find them unpalatable and competing plants are kept to a minimum. Trees that try and establish themselves soon find they have become part of the food chain. As trees grow from the top down, when rabbits consume the leaves the trees die and decay. The nutrients return to the soil and are used by other plants.
The Impact of Myxoma on the Environment
When the myxoma virus was introduced in the early 1950s, the impact on the whole ecology of the South Downs was devastating. However, it took time before the full impact of this virus was recognised. When the virus was introduced from France it rapidly spread across the rabbit population. As the rabbits died, because they had no immunity to this virus, the surrounding vegetation began to change. As the juniper and hawthorn were left ungrazed they grew, rapidly. Ragwort and the elder bushes began to be crowded out and more competitive plants flourished. Young trees began to grow as they were not being eaten and the Downs, instead of being a rich and vibrant community began to show marked changes. The numbers of plants of various types recorded began to decline, as did various forms of animal life. It began to evolve into a shrub land and if left unattended would establish itself as a woodland.
The effects of the myxoma virus had far reaching consequences on the South Downs. The balance and biodiversity that was present before the introduction of the virus has not been fully re-established. In some areas mankind has had to intervene by introducing sheep grazing and at times has physically had to chop down trees such as hawthorn. Although the rabbits have developed an immunity to the virus, mainly through the process of natural selection, the rabbit population has still not recovered to what it was previously.
We can see from this example that what at first appears to affect only one species, will in fact affect all other surrounding organisms as well. This provides evidence as to how easily our countryside can be damaged and changed forever unless we look after it and protect the natural heritage of the UK.