According to a new study conducted on the world's largest tropical forest, Amazon is particularly sensitive to drought. The 30-year study, published in Science, provides the first practical evidence that drought causes a loss of large amounts of carbon in this tropical forest.
Professor Oliver Phillips of the University of Leeds and the lead author of the study said: 'For many years the Amazon forest has played a role in slowing the climate change process. But relying on this natural support is also very dangerous'.
'If the Earth's carbon sink slows or reverses, carbon dioxide concentrations will even increase faster. Cutting emissions will be necessary to stabilize our climate. '
The study, with a global collaboration between more than 40 institutions, is based on an unusual drought in 2005 at Amazon. Through this event, scientists have an overview of the region's climate in the future, in which the warm North Atlantic Ocean can lead to drier and hotter seasons.
The 2005 drought reversed many decades of Amazon's carbon sequestration. In normal years, the forest absorbs nearly 2 billion tons of carbon dioxide. The drought caused more than 3 billion tons of losses . In total, the impact of the drought - 5 billion tons of atmospheric carbon dioxide - exceeds the combined annual emissions of Europe and Japan.
Professor Phillips explains: 'Most forests seem to be affected very little, but our records show a high rate of dead trees. Because the area is so large, even small ecological impacts can be replicated into a major impact on the Earth's carbon cycle. '
Peruvian botanist and co-author Abel Monteagudo said: 'Some plants, including important, very delicate palm trees, are very vulnerable. This indicates that drought also threatens biodiversity '.
Amazon accounts for half of the world's rainforest, covering an area 25 times larger than the UK . No ecosystem on Earth has the ability to control the carbon cycle and is home to many such plants and animals. The study involved 68 scientists from 13 countries working for RAINFOR, a research network that monitors the Amazon forest.
In order to calculate carbon change, they analyzed more than 100 forest plots in the area of 600 million hectares of Amazon , identified and measured over 100,000 trees , and recorded dead trees as well as new trees. The weather cycle is also analyzed and charted.
When the 2005 drought occurred, the RAINFOR team took advantage of this natural experiment and focused on assessing the effects of drought on the forest.
The study found that in at least two years, the Amazon forest acts as a giant carbon sink. A similar process appears in Africa.
In fact, in recent decades, tropical forests have absorbed one-fifth of global fossil fuel emissions. But in 2005, the process was reversed. The rate of dead plants is highest in places where the most severe droughts, and mild dry locations are also affected. We now know exactly how sensitive Amazon is to drought.
If repeated, the Amazon drought will accelerate the warming of the climate, making the consequences of future droughts even more serious. The research was funded by the Natural Environment Research Council, along with Gordon and Betty Moore Foundation.