Large parts of Brazil, a country that holds over a tenth of the world’s fresh water, are on fire. They include vast areas of the Amazon rainforest and the Pantanal, the world’s largest wetlands, as well as the Cerrado grasslands and the Atlantic forests along the country’s eastern coast.

The number of fires in the country has more than doubled compared with last year, burning an area the size of Costa Rica in August alone.

Smoke covered large parts of South America this month and blackened the skies of some of the region’s biggest cities, including Buenos Aires, Argentina; Sao Paulo; and La Paz, Bolivia. As if that weren’t dystopian enough, black rain from the soot produced by the fires has fallen over cities in several states in Brazil.

In much of Brazil, fire season usually peaks this time of the year, as farmers set fire to pasture and burn recently deforested plots to clear them of unwanted vegetation. But blazes have unleashed a lot more destruction this year.

Although experts say many of the fires were very likely started by humans, the abundance of dry vegetation fueled immense blazes that grew out of control in extraordinary ways.

Almost half of the fires in the Amazon burned pristine forests, according to data from Brazil’s National Institute for Space Research. That is far from typical. It means fighting deforestation in the Amazon is no longer enough to stop fires.

This shows that fire-control practices in some of the world’s most biodiverse places are not working. And that threatens myriad forms of life, including us. The collapse of the Amazon rainforest could release the equivalent of as much as 20 years’ worth of global carbon emissions into the atmosphere.

A study from 2018 showed that when there is drought in the Amazon, fires can increase even when deforestation goes down. That’s because drier vegetation in the form of standing trees continues to fuel the blazes.

Large parts of South America are under the worst category of drought. That’s partly because of natural climate patterns, such as El Nino, which are associated with scarcer rains in the region. But global warming is probably making matters worse in the background.

Humans are still burning fossil fuels that heat up the atmosphere, so extreme droughts like the current one are likely to become more frequent, scientists say.

“Maybe 2024 is the best year of the ones that are coming, as incredible as it may seem,” said Erika Berenguer, a senior research associate at the University of Oxford. “The climate models show a big share of the biome is going to become drier.”

The forest didn’t evolve to burn like other ecosystems such as the boreal forests, Berenguer said. The bark on its trees is thin, unlike that of redwood trees and sequoias, so even a little fire can kill them.

The types of Amazonian plants that can grow back after fires aren’t the majestic trees we associate with the rainforest, but scrubbier ones that grow and die fast and hold a lot less planet-warming carbon in their trunks.

“What the data shows is that even 30 years after fire, the burned forest still has 25% less carbon than a forest that never burned,” Berenguer said.