But this arrangement has vulnerabilities. If enough of the forest’s eastern expanses are cut down, moisture may run off and out of the basin rather than sail into deeper sections of the forest that need it, Finer says. “That deforestation cuts off the whole system.”has been cleared, Finer and colleagues reported in a 2022 MAAP report. Deforestation averaged across the whole forest may not yet have crossed that 20 to 25 percent threshold, but “in that eastern third, it’s way worse,” Finer says.
Where degradation reduces vegetation, it shrivels transpiration. For each leaf lost, the forest’s moisture loses one little gate back into the sky. During a typical dry season, severely degraded forests may release 34 percent less water back to the sky. That loss directly sabotages the forest’s rain recycling, imperiling trees that depend upon it.
Projections from the Coupled Model Intercomparison Project, which coordinates and standardizes climate projections, also point to localized Amazon diebacks. For a 2022 study, researchers examined projections from, analyzing models that simulate the response of vegetation to climate change. Five of the seven analyzed CMIP6 models indicate that the risk of sudden, local diebacks will climb as the world reaches and surpasses 1.5 degrees C of global warming above preindustrial levels.
The várzea’s uliginous counterpart, the igapós, consists of swamp forests that also flood seasonally, though with nutrient-poor waters as dark as maté, steeped in tannins leached from decaying plants. Igapó trees grow slowly, but they grow dense and excel at sequestering carbon.