Amazon tipping point: Last chance for action

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Science Advances  20 Dec 2019:
Vol. 5, no. 12, eaba2949
DOI: 10.1126/sciadv.aba2949

Thomas E. Lovejoy

Carlos Nobre

Although 2019 was not the worst year for fire or deforestation in the Amazon, it was the year when the extent of fires and deforestation in the region garnered full global attention. This year, the winds brought smoke from the fires into São Paulo, so thick that—after encountering moist air blowing from the ocean—the afternoon skies were darkened and street lights had to be lit 3 hours early for the city to continue to function. The rampant winds awoke the Brazilian populace and indeed the world to the harsh reality that the precious Amazon is teetering on the edge of functional destruction and, with it, so are we.

For more than 50 years, scientists and policy makers have known unequivocally (1) that the hydrological cycle of the Amazon depends squarely on the transpiration of the forest’s multitude of leaves and on the evaporation from the complex surfaces of the rain forest. When it rains on the Amazonian forest landscape, at least 75% of the moisture is returned to the westward-moving air mass. The rainforest recycles the moisture five to six times before it turns southward, feeling the proximity of the high wall of the Andes. Over the whole basin, the air rises, cools, and precipitates out close to 20% of the world’s river water in the Amazon river system.

The moisture of the Amazon is not confined to the basin …

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