Are trees good for us?
A group of climate modelers have found some counter-intuitive results from eliminating the world’s trees. Apparently, the impact of forests partly depends on which latitudes they are in. Report from The Economist:
“When Dr Bala ordered global clearcutting, the model calculated that the atmosphere’s carbon dioxide levels would roughly double by 2100. This is a much greater increase than happens in a business-as-usual simulation, but it would, paradoxically, make for a colder planet. That is because brighter high latitudes would reflect more sunlight in winter, cooling the local environment by as much as 6°C. The tropics would warm up, since they would be less cloudy, but not by enough to produce a net global heat gain. Overall, Dr Bala’s model suggests that complete deforestation would cause an additional 1.3°C temperature rise compared with business as usual, because of the higher carbon-dioxide levels that would result. However, the additional reflectivity of the planet would cause 1.6°C of cooling. A treeless world would thus, as he reports in the Proceedings of the National Academy of Sciences, be 0.3°C cooler than otherwise.
No one, of course, would consider chopping down the world’s forests to keep the planet cool. But having made their point, Dr Bala and his colleagues then went on to look at the nuances of forest growth and loss at different latitudes.
In Russia and Canada, cutting trees down led mostly to local cooling. The carbon dioxide this released into the atmosphere, though, warmed the world all over. Around the equator, by contrast, warming acted locally (as well as globally), so a tropical country would experience warming that it, itself, created by cutting down trees.”