Scientists are warning that the Earth’s sixth mass extinction is already underway. In a new study published in the journal Proceedings of the National Academy of Sciences, the researchers said billions of populations of animals have disappeared from the Earth, amid what they called a “biological annihilation.” They said the findings were worse than previously thought. The scientists say the main causes of the mass extinction of wildlife is human overpopulation and overconsumption, especially by the rich; the destruction of animals’ habitats; toxic pollution; and climate change. The report also warns that humans will be impacted by this mass extinction, writing, “The resulting biological annihilation obviously will have serious ecological, economic and social consequences. Humanity will eventually pay a very high price for the decimation of the only assemblage of life that we know of in the universe.”