Biodiversity and invasive species
Animals and plants moving around the world are also big threats to biodiversity. When a new, non-native species arrives in an area, it is often called an alien species. Mostly this movement doesn't cause a problem. However, if that species causes harm to wildlife or humans, it is called an invasive alien species.
Invasive species are often introduced through human activity, either deliberately or accidentally. One example is rabbits in Australia, which were brought to Australia by human colonisers in the eighteenth century to be bred for food. Their population soon exploded and quickly caused devastation because of the huge amount of plants they ate.
Even now, rabbits in Australia can kill young orchards and cause serious erosion problems by eating trees and native plants.
This story is echoed all over the world. It is an especially big problem on islands, where wildlife has evolved in isolation over millions of years, and the ecosystem can be more vulnerable to the introduction of new animals and plants.
Invasive species can reduce biodiversity and species richness, cause extinctions and dramatically change ecosystems.
