Over the past 40 years, the Earth has already lost half of its wildlife, according to WWF. The planet is in the midst of a 6th mass extinction. But what makes this one worse than the previous 5 mass extinction is that the rate is becoming comparable if not rapid. The growing human population and their increasing demand for resources has cost the lives of tens of thousands of species. 865 species have already gone extinct, including 13% of birds and 25% of all mammals.