In 2023, only a few millimeters of rain fell in the central Amazon rainforest, during the four months from July through October. Normally the region gets close to a half a meter during the same period. The Amazon River sank steadily beginning in June, as it does most years during the dry season. But by mid-October, the river gauge in Manaus, the largest city in the Amazon, reached the lowest level observed since record-keeping began in 1902. Freighters coming up from the Atlantic Ocean—the city’s primary supply line—were blocked by shoals. Factories furloughed workers.
Making matters worse, the drought coincided with a series of weekslong heat waves. In September and October, withering conditions persisted across the Amazon, and temperatures here peaked at 39°C (102.2°F), 6°C above normal. Desiccated jungle set ablaze by farmers enveloped the city in choking smoke. Then, in the season’s most freakish episode, a sandstorm blotted out the sun.
Drought and heat are only half of the story of the changes unfolding in the heart of the world’s largest rainforest. For decades, while dry-season low water has been plummeting, rainy-season high water has been rising. The city has experienced frequent major flooding in recent years because of heavy rains across much of the Amazon Basin, forcing the officials to erect temporary wooden walkways above streets of the historic waterfront.
Researchers expect such changes to intensify as global climate warms. The current drought provided a grim preview, killing river dolphins and fish, and threatening livelihoods for communities along the river. If the combination of higher highs and lower lows becomes the new norm, the ramifications could extend throughout the Amazon Basin and even beyond, threatening the very existence of the forest—which harbors much of the planet’s biodiversity, has a far-reaching influence over regional and global climate, and sustains millions of people.
“We are undergoing massive changes in the hydrological cycle” of the Amazon Basin, says Jochen Schöngart, a forest expert at the National Institute of Amazon Research in Manaus, says.
The question now, he says, is whether its ecosystems and people can adapt.
