This anti-tree thing has gone too far

There has been a lot of discussion on blogs about the various reports saying that planting trees outside of the tropics can actually cause a problem as far as global warming is concerned. The argument is that trees have a lower albedo than farms, pastures, or soil, so planting trees could make the earth darker overall, increasing light absorption, and warming the Earth. (There has also been some claim that more trees mean more water vapor but that seems to be less of a concern.)

I think a lot of this discussion is overblown. First of all, I don't know who is talking about replacing farms and pastures with trees, except in tropical countries where there's no controversy regarding forest benefits, and it's not something that I have heard any serious discussion about. And on the question of albedo, planting trees and cities and suburban areas could actually make albedo higher instead of lower. A 7% reflectivity in urban areas is less than 9% for pine forests, and 13% for deciduous trees (the ones usually planted in cities).

So while the anti-tree thing may intrigue people because it's counterintuitive, you still have to look at the particular tree planting program to determine whether or not it is problematic. Any we should definitely plant trees in the cities.

UPDATE: Thought I'd add that the most important global warming impact of urban trees is the amenity effect - by making cities nicer places to live, people will be more willing to stay rather than commute from the suburbs.