A recent growth spurt among forests in the Northern Hemisphere may be the result of climate change, suggests new research. Until now, regrowth as a part of natural ecosystem recovery after disturbances such as logging or clearing has obscured the influence of climate change on recent boosts in forest biomass.
Sean McMahon of the Smithsonian Environmental Research Center, Edgewater, Maryland, and colleagues analysed changes in biomass over the past 22 years in 55 temperate deciduous forest plots in the United States where the history of disturbances was known, together with 100 years of local climate data. They found that in 78 per cent of the forest plots, increases in forest biomass over the past two decades have outpaced increases predicted from natural recovery by an average of 4.15 tonnes per hectare per year. The increase in growth was independent of stand age and year of sampling, found the authors, who attribute the growth spurt to a combination of increasing temperatures, longer growing seasons and higher concentrations of atmospheric carbon dioxide.
Continuous monitoring of forests worldwide will be necessary to decipher exactly which of these factors is the most influential, say the authors.