[This article was written with the support of the Pulitzer Center on Crisis Reporting.]
Some Brazilian scientists fear that the Amazon may become a grassy savanna — with profound effects on the climate worldwide.
By Alex Cuadros Jan. 4, 2023
One of the first times Luciana Vanni Gatti tried to collect Amazonian air she got so woozy that she couldn’t even operate the controls. An atmospheric chemist, she wanted to measure the concentration of carbon high above the rainforest. To obtain her samples she had to train bush pilots at obscure air-taxi businesses. The discomfort began as she waited on the tarmac, holding one door open against the wind to keep the tiny cockpit from turning into an oven in the equatorial sun. When at last they took off, they rose precipitously, and every time they plunged into a cloud, the plane seemed to be, in Gatti’s words, sambando — dancing the samba. Then the air temperature dipped below freezing, and her sweat turned cold.
Not that it was all bad. As the frenetic port of Manaus receded, the canopy spread out below like a shaggy carpet, immaculate green except for the pink and yellow blooms of ipê trees, and it was one of those moments — increasingly rare in Gatti’s experience — when you could pretend that nature had no final border, and the Amazon looked like what it somehow still was, the world’s largest rainforest.
The Amazon has been called “the lungs of the earth” because of the amount of carbon dioxide it absorbs — according to most estimates, around half a billion tons per year. The problem, scientifically speaking, is that these estimates have always depended on a series of extrapolations. Some researchers use satellites to detect changes that indicate the presence of greenhouse gases. But the method is indirect, and clouds can contaminate the results. Others start with individual tree measurements in plots scattered across the region, which allows them to calculate the so-called biomass in each trunk, which, in turn, allows them to work out how much carbon is being stored by the ecosystem as a whole. But it’s hard to know how representative small study areas are, because the Amazon is almost as large as the contiguous United States, with regional differences in rainfall, temperature, flora and the extent of logging and agriculture. (One study even warned of the risk of “majestic-forest selection bias.”)