09 novembre 2007
Recently Extinct Species
Petite présentation orale que l'on avait à faire pour le cours d'anglais... Je vous le met tel quel, flemme de le traduire en français ^^
I want to talk about recently extinct species, particularly, extinctions caused by human activity.
First, you have to know that the number of endangered species grows every year. In 2007, there are 16 306 endangered species in the world, up from 16 118 last year. Among them, we can cite gorillas, African and Asian elephant, whales, red wolf, snow leopard and others… And 99% of threatened species are at risk from human activities.
Extinction is a natural feature of evolution because for some species succeed, others must fail. Since life began, about 99 percent of the earth's species have disappeared and, on at least five occasions, huge numbers have died out in a relatively short time. The most recent of these mass extinctions, about 65 million years ago, swept away the dinosaurs and many other forms of life. However, despite such catastrophes, the total number of living species has, until recently, followed a generally upward trend.
Today, the extinction rate is increasing rapidly as a result of human interference in natural ecosystems. Primates, tropical birds, and many amphibians are particularly threatened. For the foreseeable future, this decline is set to continue because evolution generates new species far more slowly than the current rate of extinction.
The first animal I want to talk is the Chinese Lake Dolphin, also called Baiji. It’s a dolphin species which lived in China, in the Yangtze River. It has been declared “functionally extinct” in December 2006. A six-week expedition organized by The Baiji Foundation travelled for almost 3500 kilometres to the Yangtze Delta. They were equipped with sophisticated optical instruments and underwater microphones but they didn’t get any sign of the dolphin.
The Baiji declined due to many threats to the species: a period of hunting for their skin and their flesh during the Great Leap Forward (an economic and social plan to develop China), entanglement in fishing gear, the illegal practice of electric fishing, collisions with boats, habitat loss and pollution. The Three Gorges Dam, completed in 2000, has considerably reduced the habitat of the River Dolphin and facilitated an increase in ship traffic: the Baiji wasn’t able to survive…
In 2006, another species was declared extinct: the Western Black Rhinoceros. Intensive surveys were to locate any surviving of this subspecies of rhinoceros in their last refuges in northern Cameroon but as the Baiji, they found no sign of Western Black Rhinoceros.
Their extinction was caused by pouching for their horn. Little efforts had been made to limit poaching but it wasn’t enough. There was not real preventive measure to save this species.
But not everyone agrees with this extinction, so new surveys will be conducted and might result of the “rediscovery” of the Western Black Rhinoceros.
Humans can cause extinction by introduce an alien invasive species. An alien invasive species is a foreign species which is introduce in a new ecosystem and threatened native biological diversity. The impacts of these species are immense, insidious and usually irreversible. They may be as damaging to native species and ecosystems on a global scale as the loss and degradation of habitats. Although in the past many losses have gone unrecorded, we know that hundreds of extinctions have been caused by alien invasive species.
The Nile Perch is an example of alien species. It was introduced to Lake Victoria in the 1960s where it is fished commercially and has had a catastrophic effect on local fish, causing the extinction of several hundred native species. Among the Lake Victoria population, the Nile Perch’s diet consists on native fishes, at least half of whose species have been extirpated. But as Nile Perch stocks decrease due to commercial fishing, at least, some of them are making a comeback. The documentary Darwin’s Nightmare deals with the damage that has been caused by Nile Perch introduction.
Now, I’m going to speak about global warming. Global warming has the potential to cause extinctions in a majority of the world’s especially valuable ecosystems. Depending on a species response to the warming, especially their ability to migrate to new sites, habitat change in many eco-regions has the potential to result in catastrophic species loss.
The Golden Toad has been a victim of global warming. This species was known only from a few kilometres of ridge top in Montverde, Costa Rica at elevations of 1,500–1,620 m. None have been seen since 1989. It last bred in normal numbers in 1987, and its breeding sites were well known. In 1988, only eight males and two females could be located. In 1989, a single male was found; this was the last record of the species. Extensive searches since this time have failed to produce any more records.
These examples are just the beginning. If climate change continues to melt the North Pole’s ice, polar bears could disappear before 2030, because they need the ice to feed. More and more polar bears die every year because they have to walk and swim for long time to find food.
The last report of IUCN (the World Conservation Union) shows that there is a real decline of great apes. The Western Gorilla (Gorilla gorilla) has moved from Endangered to Critically Endangered after discovery that the main subspecies the Western Lowland Gorilla has been decimated by the commercial meat trade and the Ebola virus.
The other ape which is also listed in the Critically Endangered category is the Orang-utan. They are threatened by habitat loss due to illegal and legal logging and forest clearance for palm oil plantations.
If we don’t want that these species be declared “functionally extinct”, we have to make preventive measures and maybe change our way of life.
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