San Francisco Chronicle - (Sunday)
Water survey deepens alarm over extreme drought
RIO DE JANEIRO — The Brazilian scientists were skeptical. They ran different models to check calculations, but all returned the same startling result.
The country with the most freshwater resources on the planet steadily lost 15% of its surface water since 1991. Gradual retreat in the Brazilian share of the Pantanal, the world’s largest tropical wetland, left water covering just one-quarter the area it did 30 years ago.
And the data only went through 2020 — before this year’s drought that is Brazil’s worst in nine decades.
“When we got the first results, we wondered if there was a problem in the equations,” said Cassio Bernardino, a project manager for environmental group WWF-Brazil, which took part in the survey along with Brazilian universities and local partners like the Amazon Environmental Research Institute, plus international collaborators including Google and The Nature Conservancy.
Deforestation of mangroves has left Atafona in Rio de Janeiro state more vulnerable to the encroaching ocean.
They used artificial intelligence to parse some 150,000 satellite images measuring the surface of lakes, rivers, marshes and all surface water across Brazil.
The figures checked out, and the MapBiomas data published last week has heightened an existing sense of alarm. The ongoing drought has already boosted energy costs and food prices, withered crops, rendered vast swaths of forest
more susceptible to wildfire and prompted specialists to warn of possible electricity shortages. President Jair Bolsonaro on Thursday said hydroelectric dam reservoirs are “at the limit of the limit.”
“The prospects are not good; we’re losing natural capital, we’re losing water that feeds industries, energy generation and agribusiness,” Bernardino said. Brazil’s “society as a whole is losing this very precious resource, and losing it at a frighteningly fast rate.”
The study accompanying MapBiomas’s data hasn’t been published yet. Two outside experts consulted by the Associated Press who reviewed the survey’s methodology said the approach appears robust, and its scale offers important insight into Brazilian water resources. They noted, however, use of artificial intelligence to analyze satellite images without on-the-ground verification could increase the margin of error.
Evaporation is a part of the natural cycle that can diminish water resources, particularly in areas with shallower supplies like the Pantanal wetlands, which sprawl across up to 80,000 square miles in three countries. It is a persistent problem in places like Lake Mead and Lake Powell in the Colorado River basin.
The MapBiomas study didn’t establish the extent to which Brazil’s retreating water resources resulted from natural causes. But experts have warned human activity is affecting global weather patterns, causing more frequent extreme events such as severe droughts and floods. The cutting and burning of forest, construction of large hydroelectric plants and dams or reservoirs for crop irrigation, all contribute to shifting natural patterns, said Mazeika Patricio Sullivan, an ecology professor at Ohio State University.
“We’re altering the magnitude of those natural processes,” said Sullivan, a wetlands expert who has studied water systems in the U.S., South America, Eastern Europe, and the Caribbean. “This is not just happening in Brazil, it’s happening all over the world.”
In Brazil’s Amazon rain forest, water that evaporates then travels on air currents to provide rainfall far afield. But some climate experts argue that the Amazon is headed for a “tipping point” in 10 to 15 years: if too much forest is destroyed, the Amazon would begin an irreversible process of degradation into tropical savanna