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Savannahs slow climate change

EurekAlert (21-May-2015)

Savannahs slow climate change

EurekAlert (21-May-2015)

Tropical rainforests have long been considered the Earth’s lungs, sequestering large amounts of carbon dioxide from the atmosphere and thereby slowing down the increasing greenhouse effect and associated human-made climate change. Scientists in a global research project now show that the vast extensions of semi-arid landscapes occupying the transition zone between rainforest and desert dominate the ongoing increase in carbon sequestration by ecosystems globally, as well as large fluctuations between wet and dry years. This is a major rearrangement of planetary functions.

An international study released this week, led by Anders Ahlström, researcher at Lund University and Stanford University, shows that semi-arid ecosystems—savannahs and shrublands—play an extremely important role in controlling carbon sinks and the climate-mitigating ecosystem service they represent.

Tropical rainforests are highly productive, and this means that they take up a lot of carbon dioxide, but rainforests are crowded places with little room to fit in more plants to do more photosynthesis and to store carbon. In addition, the typical moist, hot weather conditions are ideal for growth and do not change much from year to year.

In savannahs it is different. As productivity increases there is room to fit in more trees whose growing biomass provides a sink, or store, for carbon sequestered from the atmosphere. In addition, savannahs spring to life in wetter years, causing large fluctuations in carbon dioxide uptake between wet and dry years. Large enough, Ahlström and colleagues show, to control the amount of carbon dioxide in the atmosphere.

We have long known that we need to protect the rainforests but, with this study, the researchers show that a heightened effort is needed to manage and protect the semi-arid regions of the world as well.

Story Source  : Lund University

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Page publiée le 18 mars 2016