NASA study finds capacity of rainforests to absorb carbon dioxide decreases


Scientists have created maps of carbon sources and sinks resulting from land use changes such as deforestation, habitat degradation and forest planting, as well as forest growth. To do this, they analyzed data on global vegetation collected in space using instruments such as NASA’s geoscience laser altimeter system.GLASS) on board ICESat and the agency’s moderate resolution imaging spectroradiometer (MODIS) aboard the Terra and Aqua satellites, respectively. The analysis used a machine learning algorithm that the researchers first trained using vegetation data collected on the ground and in the air using laser scanning instruments.

Take stock

“A lot of previous research has not been spatially explicit – we haven’t had a map showing where the carbon fluxes are occurring,” said Nancy Harris, forestry program research director at the World Resources Institute in Washington and a authors of the study.

Other ways to estimate the amount of carbon exchanged between vegetation zones and the atmosphere is to look at the number of plants or forests in a particular region and study land use changes, combining this information with estimates of carbon emissions. But these methods have spatial or temporal limitations that the study authors tried to resolve with their machine learning method.

Knowing where plants take up carbon and where they emit it is important for monitoring how forests and other vegetated areas are responding to climate change. “The Amazon was considered a substantial carbon sink due to vast areas of virgin forest that absorbed carbon dioxide,” said Sassan Saatchi, senior scientist at JPL and lead researcher on the study. “However, our results show that overall, the Amazon Basin is becoming almost carbon neutral as deforestation, degradation and the impacts of warming, frequent droughts and fires over the past two decades release dioxide. of carbon in the atmosphere. “

Saatchi and his colleagues developed their analysis to make it easier to track changes in vegetation areas based on data collected in the field as well as remotely. “Our approach is designed to ensure that we can consistently balance the global carbon budget each year, and that countries can use the results and methodology for carbon management and their own reporting needs,” he said.

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