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Global warming is actually good for rainforests, say boffins
+3°C, 1000ppm CO2 did jungles a world of good last time
Opinion OK, so let's take it that global warming is coming: that temperatures are set to rise by easily 3°C by the end of the century. Disaster, right? The tropical rainforests - lungs of the planet - will die, CO2 levels will thus rise even faster, a runaway process will set in and planet Earth will be transformed into a baking lifeless hell.
Not so much, according to top boffin Carlos Jaramillo of the US Smithsonian Institution. Jaramillo, who works at the Smithsonian's Tropical Research centre, says that 60 million years ago temperatures were up to 5°C higher than now and atmospheric CO2 was running close to 1000 parts per million - way beyond the planet-busting thresholds set by the UN - and yet the rainforests flourished.
"It is remarkable that there is so much concern about the effects of greenhouse conditions on tropical forests," says Jaramillo's Smithsonian colleague Klaus Winter.
Scientists led by Jaramillo examined the fossil record of the Paleocene-Eocene jungles of Colombia and Venezuela. Their research is published today in leading boffinry mag Science. The boffins write:
We observed a rapid and distinct increase in plant diversity and origination rates, with a set of new taxa, mostly angiosperms, added to the existing stock of low-diversity Paleocene flora. There is no evidence for enhanced aridity in the northern Neotropics. The tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculations that tropical ecosystems were severely compromised by heat stress.
"Rainforests were doing very well" during the high-carbon, significantly-hotter "thermal maximum" period studied by the scientists. They found that rather than making species extinct the warmth drove diversity and brought many new species into the world - including both passionflowers and chocolate.
So it would seem that even if temperatures do climb as many forecasters predict, the consequences may not be disastrous after all.
Jaramillo and his colleagues' paper, Effects of Rapid Global Warming at the Paleocene-Eocene Boundary on Neotropical Vegetation, can be read by Science subscribers here. ®