There is a big climate conference going on in Copenhagen at the moment. The Nature crew, including Oliver Morton, have been blogging it. This new post from Oli is going to give me nightmares:
The studies suggest that a) there is a threshold level of warming beyond which much of the Amazon forest is committed to die back (probably being replaced by savanna) and b) that for significant parts of the forest that threshold is alarmingly low. Indeed it is quite possibly either unavoidable in the near future or already dwindling in the rear-view mirror.