Print PageTerrestrial systems are committed to change in response to changes in climate. The redistribution of forest biomes could dampen or amplify climate change through alterations in biogeochemical and biogeophysical cycles. An analysis of the palynological database suggests that warmer temperatures will promote rapid forest expansion in extratropical zones, but to keep pace with predicted warming, expansion rates in the next century would have to be several times higher than that observed historically. Multi-proxy investigations suggest that the displacement of glaciers in the northern hemisphere will promote wetter conditions in the tropics, maintaining continuous forest expansion that initiated in the mid-Holocene.
Results/Conclusions
Forest expansion across biomes is expected as a result of climate change. Globally, forest expansion attenuates warming through carbon sequestration. Tropical and temperate forests also mitigate warming through evaporative cooling. However, changes in albedo may outweigh the benefits of carbon sequestration and evaporative cooling in boreal regions, where expansion could represent a net positive climate forcing. Evidence suggests that tropical forest expansion could be orders of magnitude slower than that observed in temperate and boreal regions, but rates of tropical forest expansion remain unknown. Better estimates of forest dynamics and increased understanding of underlying mechanisms in response to global ecological change are required to determine the outcome of many feedback loops that govern the complex forest-atmosphere system.
