Despite decades of deforestation, the Earth is getting greener
By Yi Liu; Albert Van Dijk, Australian National University, and Pep Canadell, CSIROMarch 31st, 2015
A new investigation of satellite records reveals that the Earth is getting greener, despite ongoing deforestation in Indonesia and South America.
While the news coming out of forests is often dominated by deforestation and habitat loss, research published today in Nature Climate Change shows that the world has actually got greener over the past decade.
Observations from space have shown the world overall is getting greener despite deforestation and drought. Image: Carl Davies/CSIRO, CC BY-SA
Despite ongoing deforestation in South America and Southeast Asia, we found that the decline in these regions has been offset by recovering forests outside the tropics, and new growth in the drier savannas and shrublands of Africa and Australia.
Plants absorb around a quarter of the carbon dioxide that people release into the atmosphere by burning fossil fuels. With a greening globe, more plants may mean more absorption of carbon dioxide. If so, this will slow but not stop climate change.
However, questions remain over how long plants can keep pace with our increasing emissions in a warmer climate.
Measuring carbon in plants
We studied how plants and vegetation are faring by determining the amount of carbon stored in living plant mass (or “biomass”) above the ground.
We developed a new technique to map changes in vegetation biomass using satellite measurements of changes in the radio-frequency radiation emitted from the Earth’s surface, a technique called passive microwave remote sensing. The radiation varies with temperature, soil moisture and the shielding of water in vegetation biomass above the ground.
We extracted this vegetation information from several satellites and merged them into one time series covering the last two decades. This allowed us to track global changes in biomass from month to month, something that was not possible before.
For the period 2003-12, we found that the total amount of vegetation above the ground has increased by about 4 billion tonnes of carbon.
Still losing rainforests, but gaining forests elsewhere
Our global analysis shows losses of vegetation in many regions, particularly at the frontiers of deforestation in the tropics of South America and Southeast Asia.
As expected, the greatest declines have been in the so-called “Arc of Deforestation” on the southeastern edge of the vast Amazon forests. In Southeast Asia we found the most widespread declines in the Indonesian provinces of Sumatra and Kalimantan – the Indonesian part of Borneo.
However, we found that these rainforest losses have been offset by increases in biomass in other parts of the world.
For example, forests have spontaneously regrown on farmland abandoned after the fall of communism in Russia and neighbouring countries, while large-scale tree planting projects in China have measurably added to the global biomass. This roughly offset half of the carbon loss by tropical deforestation.
We also found unexpectedly large vegetation increases in savannas and shrublands of Australia, Africa, and South America. Previous analyses have focused on closed forests and did not measure this increase.