Is it better to plant trees or not?

A long time ago in Northern Europe, dense forest was converted to farmland and has remained so ever since. Now there’s a movement to reforest some of those lands in an effort to counteract climate change.

But the picture is complicated. Farmland may not absorb much carbon, but it accumulates snow in the winter which reflects light back into space creating a cooling effect in the atmosphere. Dark-colored forests, on the other hand, absorb a lot of heat, but the vegetation also locks down carbon. So is it better to plant trees or not?

Previous studies showed that farmland was a better mitigator of climate change in the Northern Europe than forests. But a new study out in the most recent edition of Geophysical Research Letters challenges that conclusion. Research led by Julia Pongratz at Stanford University found that you have to look more closely at the land to make a determination.

Using computer simulations, the researchers found that the most productive farmland would be better to convert back into forests, from a climate perspective. That’s because productive land can support a lot of vegetation. It would thereby capture more carbon than it would serve as a light reflector back into space when snow-covered.

It turns out, not surprisingly, that the most productive land in Northern Europe is farmland, and is also in areas with lower snowfall. The researchers conclude that, on the whole, reforesting farmland in Northern Europe would be a good thing for climate change mitigation.

They didn’t get into the economic or social aspects of taking the most productive farmland out of food production. No doubt that’s bound to raise some hackles.