Sunday, May 15, 2016
Another finding that increased CO2 is greening the earth
Increased greening over 25% to 50% of the global vegetated area
Greening of the Earth and its drivers by Zaichun Zhu et al.
Global environmental change is rapidly altering the dynamicsof terrestrial vegetation, with consequences for the functioningof the Earth system and provision of ecosystem services1,2. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982–2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition(9%), climate change (8%) and land cover change (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography,differences in regional management intensities for croplandand pastures, and other emerging productivity constraints such as phosphorus availability.
Posted by John J. Ray (M.A.; Ph.D.).