By 2050, at bio-extinction's current rate, between 25 per cent and 50 per cent of all species will have disappeared or be too few in numbers to survive. There'll be a few over-visited parks, the coral reefs will be beaten up, grasslands overgrazed. Vast areas of the tropics that have lost their forests will have the same damn weeds, bushes and scrawny eucalyptus trees so that you don't know if you're in Africa or the Americas.