For many decades, scientists have warned that human activity is pushing life on our planet beyond the point of no return. In the Earth's history there have been five mass extinction events, most recently the Cretaceous–Tertiary mass extinction that occurred almost 65 million years ago and was thought to have been caused by the massive impact of an asteroid on Planet Earth. In the 21st century, we face a sixth mass extinction. According to an article published in July by Gerardo Ceballos and colleagues, the Earth is experiencing a huge decline in species' populations and a great reduction in their range that could have profound effects on the ecosystems on which human civilisation depends. They found that about 30% of land vertebrates including reptiles, birds, and amphibians are experiencing a decline and losses in local population. In some parts of the world they are losing 70% of their species because of habitat degradation. The authors describe their findings as a biological annihilation, claiming that the sixth mass extinction might be already underway.
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