the last of which occccurred 65 million years ago. >> there was a mass extinction from an enormous media or,, asteroid that hihi thehe earth t cost tremendous debris to go up into the atmosphere and cooled the planet for a long time. >> half of all species went extinct, including the dinosaurs. the rate of species loss today is on par with that event, and is by far and away the highest rate of species loss since humans have been around. their rate of species loss today is probably at least 100 times that which occurred before humans were around. for many groups of species, the rate is near to 1000. mass extinction is caused by one species -- man. >> we are on pace t to lose 50%f species by 212100, largegely duo habitat loss and clclimate chan. >> the major danger is habitat destruction. each spepecies has very special habitat requirements. once you destroy those, you destroy the spececies. >> we are cutting down our rain forests at ann alarming rate. wewe are overfishihing in the ocean, we are consumiming naturl resources at an unsustainable rate. the earth's surface has already been alt