It may take Centuries to re-grow a forest that was cut down by humans or destroyed by fire, and many of the world's severely threatened animals and plants live in these forests. If the current rate of forest loss continues, huge quantities of plant and animal species will disappear. It seems like its time now to turn around and reverse the effects of what we have done. .
When you think of a native species ordinarily you think of a species that has been in that specific area for a long time. They are well adapted to their local environment and are accustomed to the presence of other native species within the same general habitat. Exotic species, however, are foreign invaders. These species are introduced into new environments by way of human activities either intentionally or accidentally. These invaders are viewed by the native species as foreign elements. They may cause no obvious problems and may eventual be considered as natural as any native species in the habitat. However, exotic species may also seriously disrupt delicate environmental balances and may produce a tidal wave of harmful consequences. .
The worst of these unintended yet harmful consequences arise when introduced exotic species put native species in jeopardy by preying on them. This can alter the natural habitat and can cause a greater competition for food. Species have been biologically introduced to environments all over the world, and the most destructive effects have occurred on islands. Introduced insects, rats, pigs, cats, and other foreign species have actually caused the endangerment and extinction of hundreds of species during the past five centuries. Exotic species are certainly a factor leading to endangerment.
A species that faces overexploitation is a species that becomes endangered because of the rate in which he was using them. Unrestricted whale catching during the 20th century is an example of overexploitation, and the whaling industry brought many species of whales to extremely low population sizes.