Planting Forests to Offset Global Warming

Can we plant a forest somewhere to atone for our fossil-fuel burning sins and emit with a clear conscience? According to several recent news stories, planting forests to combat global warming may be a waste of time, especially if those trees are at high latitudes. This story is a bit of a simplification of a pair of papers presented by Ken Caldeira, Govindasamy Bala, and others at the 2006 fall meeting of the Americal Geophysical Union.

There have been several other papers with similar conclusions in recent years by these authors, but without the media attention. What these authors are looking at is not just the capacity for trees to absorb carbon in a reassuringly visible way, but their effect on evaporation and albedo, compared to other ground cover.

Trees are darker than snow. Snow reflect light back out into space. Trees absorb it. Plants also release water into the air. This forms fluffy white clouds that also reflect light back out into space. Trees absorb carbon, but they are also little radiators, absorbing and releasing light and heat. The models behind the studies conclude that Their ability to block the light from the snow or to be blocked by clouds has an effect on temprature that is comparable to and can be greater than the cooling effect of their absorption of carbon. All of these effects depend on latitude. For northern latitudes, grasses are better than, say, desert.

Which is not to say that forests are bad. Whatever the short-term effects of albedo on a daily or seasonal basis, CO₂ and methane are long-term effects, and photosynthesis is one of the only ways we have of keeping the levels in check. By we, I mean the Earth. People have a great ability to interfere with the process, but there is not much that we can do to help it along besides reducing our ecological footprint.

To paraphrase current research, forests in general are not really good carbon sinks. They can go either way. Peat bogs are good, definitely, as long as they are not flooded, for instance to produce clean hydroelectricity. And oceans are good, but they work slowly. Artificial carbon sequestration is, at best, entertaining hocus-pocus, and at worst an expensive way to ensure a quick end to life on earth some time in the future.

So the best thing is to reduce our energy use, preserve as much wilderness as possible, stop using peat for topsoil, and protect all peat bogs, encourage agricultural methods that are shown to accumulate carbon in soils, and work with tropical countries to help them do the same. Use your money to get more efficient, not to pay out to the forest protection racket.

References
http://news.bbc.co.uk/1/hi/sci/tech/6184577.stm
Will afforestestion strategies help mitigate global warming?
Carbon, Biophysics, and Climate: Where do Forests Warm? Where do Forests Cool?
http://www.llnl.gov/tid/lof/documents/pdf/324200.pdf
http://www.mcgill.ca/reporter/32/15/roulet/
http://www.nwo.nl/nwohome.nsf/pages/NWOP_5X5LD5

Tags: Greenhouse Gas Climate Change Kyoto Protocol Carbon Sequestration Environment

[] permanent link Comments: 0