The problem of invasive aliens species
The introduction of invasive alien species is breaking down the barriers created by the physical distance between earth’s continents. The introduction of invasive alien species has been described to be one of the greatest threats against the maintenance of present day biological diversity, second only, to the effects of habitat destruction and fragmentation.
The damage done by invasive alien species may even become the major cause for biodiversity losses in the future, since there remains few undisturbed natural habitats to be destroyed. Humans now affect most parts of the globe ecologically and these are exposed to the invasion by introduced species. Furthermore, the successful invasion by an alien species is almost irreversible since the living organisms are self-reproducing as opposed to such ecological problems as pollution.
Natural range expansions of organism have always taken place, but the speed at which changes happen has dramatically increased. Many of the alien plant and animal species are beneficial to humans because they are crop or farm species used to sustain the world’s growing human population. However, some of the alien species become invasive and are harmful to humans or affect human economy negatively while others have negative effects on the world’s ecosystems.
Invasive alien species may affect biodiversity negatively by:
- Altering the local food web
- Competing with other organisms
- Being toxic
- Being a reservoir for parasites or a vector for pathogens,
- Hybridising with a related species or varieties,
- Causing extinction of native species
The effects of biological invasions can not be isolated from other global and local environmental changes such as climate change, habitat alteration and pollution, including eutrophication. An increase in global temperature may facilitate the establishment of non-native species with higher temperature requirements, while invasive alien species may in their turn increase eutrophication or habitat deterioration.
Prevention is indeed easier and much cheaper than the cure, since it is almost impossible and certainly very costly to eliminate most invasive species. Since introduction of new species has proven to have many negative effects in most parts of the world, it is important to adopt a precautionary approach to future intentional introductions.
|
