Overcropping
This is defined as killing more animals than can be replaced in the natural breeding cycle. Many of the world's whale population has declined through whaling, this is an example of overcropping.
Introduced Species
Foreign animals brought to Australia are known as introduced species. Some of these animals are predators that kill native animals, such as bilbies. Some compete with the native species for food, whilst others destroy habitats.
Chemical Pollution
Increased production of Carbon Dioxide gas by human activities, such as factories and cars, is thought to be contributing to global warming. If the atmosphere is warming, it could also change wind and rainfall patters and sea level.
Habitat Destruction
Habitat destruction is defined as the damage done to any of the factors in an environment which influence an organism's survival. Some examples are land clearing and logging.