Vegetation on the Earth’s land surface provides many vital goods and services upon which the welfare of the humanity depends. One of these services is removing CO2 from the atmosphere and stores the carbon as biomass, mitigating global warming. Knowing the role of vegetation in global carbon cycle is essential for policy making regarding carbon emission reduction.
In this talk, I will report the most recent findings from my lab that the land surface of our planet Earth is greening based on a time series of remotely sensed data, not browning as previously believed. Integrating the global vegetation dynamics into a Coupled Carbon and Water model using climate factors as the drivers, we found that vegetation productivity is not increasing in proportion to the greening, but with a much weaker increasing trend, primarily caused by drought stress as a result of rising atmospheric temperature. Moreover, more than half of the greening areas occur in croplands, which do not provide much room for carbon storage. The most important biome for carbon storage, forests, are actually browning on the global scale, primarily driven by deforestation in Tropical America. These findings indicate that we may not count on more for carbon removal by vegetation despite a greening Earth, and thus a rigorous anthropogenic carbon emission reduction is needed to meet the Paris target for global warming mitigation.