Gustave <3
There is a lot of causes of the animal disappearence. Some are due to the human actions.
For Exemple Habitat loss, as a result of human demand, is widely considered to be the most important cause of animal extinction. For exemple the animals living in forests are very affected. Tropical rainforests are cleared for wood resources, development of petroleum resources, mineral resources, for cash-crop plantations and subsistence farming.

Some animals are also hunted for their fur.

Every year, the well-organized fur trade spends millions of dollars to glamorize fur coats and accessories and to mask the real price of fur: pain, mutilation, and death for millions of animals. To give you an idea, to make one fur coat you must kill at least : eighteen red foxes, twenty seven raccoons, one hundred chinchillas or one hundred squirrels. It’s huge!

We can think that the real price of fur must be measured in deaths and not in dollars. There are several methods used to trap animals in the wild. The most common is the steel-jaw leghold trap. Animals caught in a hidden steel jaw trap suffer a slow, excruciating death. The trap snaps down on the limb of an unsuspecting animal, sometimes breaking the limb. The trapped animals often freeze to death or are attacked by predators from whom they cannot flee.
An other cause of animal disappearance is the Overfishing. Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. For exemple we can talk about sharks. Sharks have been around for a long time, we're talking a few hundred million years. Sharks have survived everything Mother Nature has thrown at them over that span. So we can think that they will live for another couple hundred million years. But this may not be the case. Why? Because of the human action like overfishing of this species by commercial and recreational fishermen. The price of the shark’s fin is very high. For exemple it’s about $700 per kilogram in Asia.