Millions of acres of Brazil's forest and grasslands have been cleared over the past 30 years to grow soybeans, making the country the world's biggest soybean producer. But the deforestation that facilitated Brazil's soybean boom is now undermining it, bringing hotter and drier weather that makes soybeans less productive, according to two recent studies.

One paper published this week in the journal World Development concluded that hotter temperatures which result from clearing natural vegetation already are costing Brazil's soybean farmers more than $3 billion each year in lost productivity. These local and regional temperature increases are on top of global climate change, which also is intensified as deforestation adds carbon dioxide to the atmosphere.

"This is something that the soybean sector should be taking into consideration in the future," says Rafaela Flach, a researcher at Tufts University and co-author of the study.

This economic harm to the soybean industry from these regional weather changes still is outweighed by the profits that soybean farmers collectively can gain by claiming more land, according to the new study. But Flach and her colleagues say that when this damage is added to other incentives to stop deforestation, such as a possible tax on carbon emissions, the economic argument against deforestation could become compelling.

Brazil grows more than a third of the entire global soybean supply. Its harvest feeds hogs and chickens, and is converted into oil for food products all over the world. Additional areas of the country's forest have been cleared to graze cattle, or for logging and mining.

The harm to soybean harvests from deforestation may not be immediately evident to Brazil's farmers, though, because their soybean yields have actually been rising. This is because of better technology and farming practices. According to the new analysis, those yields would have increased even more in the absence of deforestation.

In another study, published recently in Nature Communications, researchers in Brazil and Germany analyzed rainfall records in the southern Amazon, parts of which have been heavily deforested. They found that rainfall decreased significantly in areas that lost more than half of their tree cover. According to the researchers, continued deforestation would cut rainfall so much that soybean growers in that region would lose billions of dollars worth of soybean production each year.

Brazil is currently in the midst of a drought. Flach says that it is provoking more discussion about whether "this drought is something that we have caused in some way, and how can we stop this from happening in the future." Yet the past year also has seen large areas of land burned or cleared. "There is a disconnect there," Flach says, "but there is a lot of discussion as well."