Previous studies that have attempted to understand the balance between cooling and warming from regrowing a forest considered unrealistic and highly idealized scenarios. The study by Pongratz and colleagues for the first time evaluated the climate cooling potential of reforestation taking historical patterns of land-use conversion into consideration.
Pongratz and colleagues found that farmers generally chose to use land that was more productive than average, and therefore richer in carbon. Furthermore, farmers generally chose to use land that was less snowy than average. While this result is not in itself surprising, its implications for the cooling potential of reforestation previously had been ignored. Regrowing forest on these productive lands can take up a lot of the greenhouse gas carbon dioxide, and therefore have a strong cooling influence. Because these lands are not very snowy, regrowing forests would not absorb very much additional sunlight. The net effect of the historical preference for productive snow-free land was to increase the climate cooling potential for reforestation on this land.
"Taking historical factors into account, we believe that we have shown that reforestation has more climate cooling potential than previously recognized," Pongratz said. "We are still not yet at the point where we can say whether any particular proposed reforestation project would have an overall cooling or warming influence. Nevertheless, broad trends are becoming apparent. The cooling effect of reforestation is enhanced because farmers in the past chose to use productive lands that are largely snow free."
|Contact: Julia Pongratz |