“The Cerrado, the central savannas, is far more threatened than the Amazon because that biome has been out of sight,” says André Guimarães, executive director of Brazil’s Amazon Environmental Research Institute. “These are the largest biomes in Brazil — the Amazon and the Cerrado, the central savanna. These two biomes, they represent more than 70 percent of the Brazilian territory.”

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The word “savanna” can be a little misleading in the case of the Cerrado — the majority of the native vegetation consists not of open grassland, but rather relatively dry but woody forests and scrubland. The Portuguese word “cerrado” actually translates as “closed,” “thick” or “dense.”

But the Cerrado has lost more than half of its native vegetation, by some estimates, and has much less legal protection than the Amazon. As a result, the region has seen major agricultural expansion, a trend that is expected to continue.

“The Amazon is around 18 percent deforested, the Cerrado is around 50 percent deforested,” Guimarães continues. “That’s where most of the grain production from Brazil comes from. The Brazilian government has put a lot of effort into Amazon conservation in recent years. So in terms of being threatened, the Cerrado is even more than the Amazon.”

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“It’s a totally different ballgame. It’s essentially Brazil’s Midwest,” says Stephanie Spera, a Brown University graduate student who was lead author of a new study in Global Change Biology showing just how dramatically the Cerrado is losing its native trees and vegetation and how that, in turn, is probably driving the decline in rainfall. This loss of rain not only hurts agriculture — which, ironically, is what the land is being cleared for — but may also actually starve the adjoining Amazon of much-needed rains. (The work was published with collaborators from Brown, the University of Vermont in Burlington and the Woods Hole Research Center.)

Spera’s study used satellite imagery to examine changes in Matopiba, a region of the Cerrado that crosses four Brazilian states, tracking agricultural expansion. It found that from 2003 to 2013, cropland in this part of the Cerrado boomed, adding 2.3 million hectares in area, roughly the size of New Jersey. Seventy-four percent of the new land converted to agriculture was, originally, native Cerrado ecosystem, the research suggested.

And the study found that as this has happened, evapotranspiration — in which plants and soils give up water to the air — declined, driving down rainfall. The study found that in 2013, 3 percent less water was recycled by the region — an amount adding up to 14 billion tons.

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That could have huge consequences, within the Cerrado and beyond it — it borders, for instance, on the Amazon to its northwest. “If you affect the amount of water that comes up, you’re going to affect the amount of water that comes down. So if less of that is transported over the Amazon, you have less rain,” Spera said.

One reason this occurs is that there is a strong rainy-season-and-dry-season cycle in this region, and native Cerrado vegetation, naturally adapted to such a regime, can draw deep underground water through its roots even when there is little or no rain. “If you have a fallow agricultural field, there’s no water to bring up,” Spera says.

The story is in some ways quite similar to what is happening in the Amazon, where scientists also fear that the loss of too many trees will weaken the hydrological cycle of the region — leading to less rain and, at times, major droughts. Those, in turn, can drive fires and further tree loss.

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One key debated issue is whether stronger attempts to protect the Amazon of late have pushed deforestation elsewhere. Brazil has been widely celebrated for reducing deforestation over the past decade or decade and a half, although levels have ticked up again more recently.

“Part of this reduction in the deforestation rate, there is a leakage of deforestation to the Cerrado,” says Paulo Moutinho, an expert with Brazil’s Amazon Environmental Research Institute, although he emphasized that it is very difficult to determine just how much Cerrado deforestation actually represents spillover or leakage from the Amazon.

Still, the new study similarly embraces the idea that “increased deforestation governance in Brazil’s Amazon tropical forest and land scarcity in older frontier regions have led both farmers, states, and the federal government to seek out new areas for development.” It also observes that the presence of 40 million additional hectares of land in the Cerrado that can be legally deforested makes “continued exploitation of this region, rather than the much more protected Amazon, likely in the coming decades.”

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The study does find one possible middle ground between rampant agricultural expansion and strict Cerrado preservation. It finds that the practice of double-cropping — planting, say, soy followed by corn — actually reduces the problem of Cerrado water loss. This suggests that agricultural management, in addition to stricter environmental protections, can help rescue at least some of the lost rain.

“This region is so dynamic, but no one is giving it the attention it deserves,” Spera says.