Tonight I saw a rather disturbing documentary, State of the planet made by Sir David Attenborough of the BBC.
It dealt with a (perhaps) imminent sixth wave of mass-extinction on our planet (in fact it's a 3 part series, so I'll probably even more worried when I see the other parts...).
According to scientists mankind causes this mass-extinction (mentioned in other writeups in this node) in 5 ways:
- killing species at a greater speed than these species can reproduce themselves.
eg. thanks to new technology (eg. sonar, better fishing gear...), man fishes too efficient, making it harder every year for mother nature to recover.
- destroying the unique habitat of species.
eg. by destroying the forest, some species depending on it will disappear.
Even worse: other species who rely on this animal (for food, symbiosis, ...) will go extinct too. It's a kind of Domino -effect.
- importing species to places where they didn't occur before.
Because lack of predators, they become too succesful and replace the original inhabitants, or they are too efficient in hunting, eliminating the totally unprepared original species. Animals are conditioned to deal with their own predators, and are not familiar with techniques used by the imported ones, or simply don't recognize the predator as a threat.
eg. cats, rabbits in Australia
- creation of islands.
Man tries to preserve pieces of nature in national parks. While this is of course a good thing, it doesn't stop the extinction of some species. Populations get separated from eachother if the distance is too big (this distance depending on species of course) or some other hazard has been created by man. They end up being on islands. When a population on an island dies for some reason (eg. disease or weather conditions), it will not be replaced by animals from another island. To illustrate the fragility of the balance: some species consider even a road as a border between islands.
The list wouldn't be complete without this one, it's also the best known I guess. eg. Global warming (use of fossil fuels) causes climatical changes (in spite of what mr. Bush says...). Species react on this by moving to other areas. Only this time, the climate changes at a faster rate...