Some 8.7 million unique species live on Earth. But thanks to hunting, environmental destruction and climate change, a growing number continue to make the endangered species list at an alarming rate.According to WWF, destructive human activities mean the current rate is at least 100–1,000 times higher than the expected natural rate of extinction.That might explain why nearly one in four mammals worldwide are at risk for extinction, says a 2008 assessment by the International Union for Conservation of Nature.Read More... More on Animals