More from RealClimate - commentary from Abby Swann of the U of Washington.
This past month, an op-ed by Nadine Unger appeared in the New York Times with the headline “To save the climate, don’t plant trees”. The author’s main argument is that UN programs to address climate change by planting trees or preserving existing forests are “high risk” and a “bad bet”. [Ed. There is more background on the op-ed here]
However, I don’t think that these conclusions are supported by the science. The author connects unrelated issues about trees, conflates what we know about trees from different latitudes, and fails to convey the main point: tropical trees keep climate cool locally, help keep rainfall rates high, and have innumerable non-climate benefits including maintaining habitat and supporting biodiversity.
Numerous scientists have already replied to the original op-ed, highlighting the points above and adding others. But some of those responses made confusing arguments too, muddying things further.
So what is going on? Why is it so complicated to say scientifically what trees do to climate? The answer lies in the fact that trees have multiple pathways for influencing climate, and the relative importance of these pathways varies depending on where we look on the globe.