Global warming slashes growth rate of trees in rainforests
The study is contained in Nature magazine, which says these effects of global warming have been largely overlooked.
If other rainforests follow suit as world temperatures rise, important carbon stores such as the pristine old-growth forests of the Amazon could conceivably stop storing carbon, said Ken Feeley of Harvard University's Arnold Arboretum in Boston, who presented the research at the annual meeting of the Ecological Society of America in San Jose, California.
The amount of carbon a forest stores depends on the balance between the rate it draws carbon dioxide from the atmosphere through photosynthesis, and the rate it gives carbon dioxide back through respiration. In carbon sinks, mostly found at high latitudes, photosynthesis outstrips respiration and the amount of carbon storage increases.
If the bio-fuel market
If the bio-fuel market continues to expand, this will become moot, as the rainforests are cut down to make way for oil palm plantations and "save the planet". (The Law of Unintended Consequences.)
This is very bad news
It is going to take a while for these results to be properly tested and to filter through the extremely rigorous models that Goddard and Hadley (among others) are using, but this story appears to set the stage for news that is bad enough to be seriously worrying. I hate this kind of story. But, putting that aside, some mainstream GCMs now predict that significant areas of the Amazon will be converted to a kind of savanna in the coming century. If tree growth rates diminish with elevated atmospheric [CO2], then a simplistic reading of those models makes that outcome seem more likely, maybe also faster and more extensive. There's a research project in here for someone! That sort of outcome falls well within what I think of as sort of apocalyptic: I don't think we want to see that kind of world. But here's the good news: most of the contrarians are old enough that they won't have to! Just their kids...
On the other hand, I really hope this discovery proves wrong.
Jeremy Kerr
http://www.science.uottawa.ca/~jkerr