Since European settlement, approximately 80% of Australia's eucalypt forests have been cleared. Almost none of the 20% remaining is protected, and most occurs on privately-owned land. Settlers have favoured the rich fertile lands along the eastern seaboard to have their farms and urban developments. Unfortunately, this is where the majority of Koalas are already living because they favour trees in the same fertile soil.
How habitat destruction affects koalas
Clearing of the eucalypt forests means that all wildlife, including Koalas, will suffer from:
- increased disturbance by humans
- injury or death from traffic
- injury or death from dogs and cats
- effects of garden pesticides getting into waterways
- increased competition for food and territory because of overcrowding
- increased stress on animals, making them more susceptible to disease.
Koala populations only occur if suitable habitat is available. The two most important factors that make habitats suitable are:
(1) the presence of tree species preferred by Koalas (usually eucalypts, but also some non-eucalypts) growing in particular associations on suitable soils with adequate rainfall
(2) the presence of other Koalas.
Research shows that socially stable Koala populations occur only when there are primary (or favourite) tree species present. Even if a selection of tree species known to be used by Koalas occurs within an area, it will not support a Koala population, or at least the Koala population will not use it, unless one or two favourite species are present. Leaving out the key species from tree plantings to restore Koala habitat could be a waste of time and effort. (Learn more about the right trees for Koalas in your area here.)
Research shows that the Koalas' selection of tree species influences the social structure of populations and the maintenance of each individual Koala's home range within the population. A greater understanding of the Koala's behaviour is a very important factor when identifying suitable Koala habitat. Planning for future protection and management of Koala habitat needs to take such factors into consideration.
Koalas live in societies, just like humans, so they need to be able to come into contact with other Koalas. Therefore they need to have areas of suitable eucalypt forest large enough to support a healthy Koala population, with room for expansion by maturing young Koalas.
It is important to understand the relationship between the Koala and its environment. Koalas rely on tress to provide them with food, shelter and a place to interact with other Koalas. When their habitat is cleared to make way for a new road, housing estate or farm, it is an extremely disorienting and stressful experience for Koalas. If they do manage to survive, finding a new home has its problems too. If the area is already built up, Koalas will face dangers like disorientation, cars, dog attacks and swimming pools. Unless they have access to a safe haven of undisturbed habitat large enough to support a Koala colony, their days as suburban Koalas are numbered. Scientists have found that Koalas facing these sorts of problems are more prone to disease and also have a lower rate of reproduction.