Correction texte en anglais

Sujet du devoir

En anglais, je dois rédiger un petit texte sur une actualité.
Et du coup j'aimerais être sur que mes tournures de phrases sont cohérentes et compréhensibles.
Donc voila, si vous vous débrouillez bien en anglais et que vous avez un peu de temps je serais pas contre un peu d'aide ;)

Où j'en suis dans mon devoir

Voila mon texte:

The first victims of the 6th mass extinction

According to a US study, the marine species disappear 100 to 1000 times as fast as its natural rhythm. And, the overfishing of the biggest animals is the prime cause. In other words, it's because of the Humans.

The last time, it was the dinosaurs. Since 66 million years, the animal species ever died out so fast and so widely. And a new report of Stanford's university shows that in the oceans, human is the main responsible for this massacre.
Published in the review Science, the study reveals that this sixth mass extinction is really different from the five previous ones.
They used the available information thought fossils to show that what happens in the oceans at the moment is completely different from what took place during the previous extinctions.
The scientists realize that the threat of extinction depend on the size of the species : the more an animal is big, the more he is in danger.
The hunting of whales, sharks or bluefin tuna are very reprsentative of this phenomenon.
24 to 40 % of the marine vertebrates should disappear during this sixth mass extinction which has already started.
The big animals, generally at the top of the food chain, disappears.
But the small ones proliferate, what is going to change durably the oceanic ecosystems.
However, the scientists are convinced that it is not too late, in seas as on earth, to turn the tide. The scientists think which we can't do much to resolve quickly serious problems like the ocean warming for exemple. But we can modify international hunt and fishing convetions.
Moreover, a few week ago, Barack Obama anouced the creation of natural reserve in Pacific, then an other in Antlantic.