The world's biodiversity is down 30 percent since the 1970s, according to a new report, with tropical species taking the biggest hit. And if humanity continues as it has been, the picture could get bleaker.

Humanity is outstripping the Earth's resources by 50 percent — essentially using the resources of one and a half Earths every year, according to the 2012 Living Planet Report, produced by conservation agency the World Wildlife Fund (WWF).