Biological systems are difficult to predict but even species low down the food chain can get into difficulties when the system is unbalanced. Take Australia, for example; in the Fifties the numbers of rabbits exploded. In similar circumstances this boom can easily be followed by a bust – through an animal population effectively eating its own food supply. Also in Australia cattle introduction led to such a build-up of cowpats that they were destroying the habitat through the build-up of their own waste – until a suitable dung beetle was introduced.
Generally speaking, predator species help provide a balance, keeping animals lower down the food chain in check therefore allowing primary producers (plants) to provide the resources on which the rest of the system depends. Meanwhile, other contributors to the system, such as decomposers, also help the system stay in shape. Without these checks and balances individual species are prone to boom, bust or potentially to future extinction.
Answered by Dr Robert Bloomfield, director at the IYB-UK.