"Several times in the distant past, catastrophic extinctions have swept the Earth, causing more than half of all species - from single-celled organisms to awe-inspiring behemoths - to suddenly vanish and be replaced by new life forms. Today the rich diversity of life on the Earth is again in grave danger - and the cause is not a sudden cataclysmic event but rather humankind's devastation of the environment. Is life on our planet teetering on the brink...