'If this is the new normal, then we are in very deep trouble': Brazil's drying aquifers could have ripple effects across the world

Brazil is home to some of the world's largest aquifers, yet many of those groundwater stores — which provide 55% of the country's water — have shrunk so much over the past 25 years that they face irreversible damage. This groundwater depletion has been caused by drought, increased water evaporation due to climate change, and pumping for human consumption, new research suggests.

Most of the world's soybeans, sugarcane, oranges and coffee — as well as a big proportion of the world's cotton and corn — are grown in the areas with the most depleted aquifers, so the dwindling groundwater supply could have ripple effects for food markets around the world, including in the U.S.

The depleted aquifers may also collapse river systems that produce hydroelectric power for Brazil, forcing the country to turn to coal or biomass for electricity, experts told Live Science.

Groundwater declines probably won't lessen total agricultural production in the next 10 to 20 years. "The concern is what happens if these trends persist for several decades," study first author Augusto Getirana, a researcher in the Hydrological Sciences Laboratory at NASA's Goddard Space Flight Center, told Live Science in an email. "Brazil is one of the world's major breadbaskets, so its water security has consequences well beyond the country itself."

A clear geographical contrast

Brazil holds the world's largest renewable freshwater reserves by country, mostly thanks to the Amazon Basin and its rainforest ecosystem. However, compared with countries like the U.S. and India, which have thousands of groundwater measuring sites, Brazil's network of monitoring wells is extremely sparse. Therefore, for the study, Getirana and his colleagues trained artificial intelligence (AI) models to fill in the gaps in the data.

The researchers fed the models measurements from 398 monitoring wells, satellite data showing tiny shifts in gravity resulting from groundwater changes, and information about the geology and land cover in different areas, among other datasets. AI reconstructed monthly groundwater level changes between 2002 and 2023 across different aquifers in Brazil at a resolution of about 6 miles (10 kilometers), Getirana said.

"We then reconstructed groundwater levels to estimate aquifer recharge — how much water reaches and replenishes the groundwater system — throughout the country," he explained.

The results, which were published June 3 in the journal Science Advances, showed severe, persistent groundwater losses in parts of central, northeastern and southeastern Brazil — including portions of the São Francisco, Paraná, Southeast Atlantic and East Atlantic basins, which together cover 760,000 square miles (1.97 million square kilometers), or about 23%, of Brazil's land area.

Some of Brazil's most critical aquifers went years with no recharge. By contrast, the Amazon Basin and parts of southern Brazil showed either no change or localized groundwater gains attributable to shifts in rainfall and natural climate variations, Getirana said.

"There is no single trend for the entire country," he said. "We found a clear geographical contrast."

Climate change is the culprit

The study didn't attribute groundwater changes to specific pressures, but it is clear from the data that climate shifts played a major role in the observed patterns, Getirana said. Several of the sharpest declines in aquifers came after prolonged droughts and major climate events, such as an El Niño cycle between 2015 and 2016.

Due to patchy monitoring, it is difficult to untangle and quantify the impacts of agriculture, industry and households on groundwater levels. However, the results revealed a substantial overlap between groundwater losses and areas with intense irrigation, urban and industrial demands, mining, land conversion and high well density, Getirana said.

"The most scientifically defensible interpretation is therefore that climate creates the underlying water deficit, while extraction and land-use changes are probably amplifying its magnitude and duration in heavily used regions," he said.

Javier Tomasella, an environmental scientist and hydrologist at Brazil's National Institute for Space Research who was not involved in the study, agreed that the main cause of aquifer depletion in Brazil is climate change.

"Droughts are lasting longer and becoming more intense in Brazil, and this is affecting most of the country, particularly the central area and the Northeast of the country," Tomasella told Live Science. Harsher droughts reduce groundwater recharge and create a higher demand for water, meaning people extract more from aquifers during dry spells. "This is why the impact in irrigated areas is much higher," he said.

The findings suggest that if droughts intensify over the next few decades, major agricultural regions in Brazil could run out of water to grow certain crops. Groundwater provides a buffer when rainfall and surface water resources become unreliable, especially for agriculture and municipal water supply, Getirana said.

The worry isn't so much that aquifers will dry up completely but rather that water levels will drop so low that it will become too expensive to pump water compared with the returns from producing crops.

"This is the same type of progression already observed in intensively exploited aquifers such as the High Plains and [Central] Valley systems in the United States and aquifers in northern India and Bangladesh," Getirana said. "The water does not necessarily disappear overnight; it progressively becomes harder, less reliable and more expensive to access."

Supply-chain risks

Farmers will likely adapt to smaller water supplies by switching water-intensive crops, such as soybeans, to less-thirsty ones, such as corn and wheat, Tomasella said. Some may do this during the dry season to save water, as is already common in regions such as northern Paraná that have a "double-crop" system. But if current market conditions hold, farmers' decisions about what to grow will ultimately depend on how much money they can make from crops while covering extra irrigation costs, he said.

The total production of mostly rain-fed crops like soybeans and corn likely won't be affected any time soon, but the balance of these crops may change, Tomasella said. Conversely, the total production of irrigated crops such as coffee, sugarcane and oranges may decline, "but that depends on how droughts will evolve in the next two decades," he said.

Countries that rely on food imports from Brazil might experience supply disruptions, but the scale of these is hard to predict. The most-exposed country is probably China, because it imports roughly 80% of its soybeans from Brazil, Getirana said. The U.S. and Europe may see declines in imports of coffee, sugar and oranges, while Asia and the Middle East could be affected through cotton and corn, he added.

"The United States alone relies heavily on Brazil for coffee and orange-juice imports," Getirana said.

Assuming market conditions don't change, it's unlikely there will be a decrease in Brazilian beef production, because demand for beef is so high, Tomasella said. If anything, he said, beef production will increase, because Brazilian farmers haven't yet maximized the number of cattle per acre of pasture. However, cattle do emit huge amounts of methane, which is a powerful greenhouse gas, he added.

Ripple effects

The study has implications beyond agricultural impacts, because aquifers are connected to river systems. Groundwater declines could cause rivers to dry up, and this would hit Brazil's hydropower network, which supplies 60% of the country's electricity, Tomasella said.

The alternative to hydropower is burning fossil fuels and biomass to produce electricity, he said. This comes with huge carbon dioxide emissions, which would worsen climate change and further amplify Brazil's water issues.

In the short term, groundwater losses are more likely to affect drinking-water supplies in big Brazilian cities like Rio de Janeiro and São Paulo than they are to impact agriculture, Tomasella noted.

"If droughts intensify, it might reach a point where you have to make very tough decisions," he said. "The real question is, 'Is this the new normal?' If this is the new normal, then we are in very deep trouble."