The Cerrado, a biome sometimes referred to as the South American savanna, accounts for a fourth of Brazil's territory and has no large-discharge rivers, but its springs feed eight of the country's 12 hydrographic regions. For this reason, experts often call it the birthplace of waters. Its three aquifers—the Guarani, the Bambuí and the Urucuia—are responsible for the formation and much of the water supply of major South American rivers.
Scientists heard by Agência Brasil believe that protecting the biome's vegetation is crucial to preserving water levels in most of the country.
“The Cerrado is like an inverted forest, with roots deep and larger than tree crowns. They're responsible for absorbing rainwater and store them in underground reserves—the aquifers,” explains Altair Sales Barbosa, professor at the Catholic University of Goiás (PUC-GO) and director at the Sub-humid Tropic Institute.
According to the expert, deforestation and the loss of native vegetation, which conveys the water down to deeper regions, have brought the water in the aquifers to such low levels that a large number of springs are no longer fed by them.
“Water levels in those aquifers have reached their minimum. It's like a water tank riddled with holes. The holes represent the springs. As long as the tank is full, the water keeps coming out through the holes. As the tanks empties, the water drains out only from holes further and further down, until no more water pours out. We've reached the point where [water] is still coming out, but rather poorly—in amounts considerably smaller than it used to 20 or 40 years ago,” he explains. He goes on to mention that approximately 10 rivers disappear from the region every year.
An older biome
The professor notes that, once degraded, the Cerrado is unable to fully recover. Using it for farming can also be a difficulty. Out of the 13 thousand vegetable species cataloged, only 180 are grown in nurseries.
“The Cerrado is different from the Amazon Rainforest and the Atlantic Forest, for instance. Whereas these biomes are 3 to 7 thousand years old, the Cerrado was fully formed over 45 million years ago. Because of its antiquity, it has already reached its evolutionary climax. Once degraded, it'll never be able to recover its biodiversity to the fullest.”
According to figures from WWF Brasil, the Cerrado is South America's second largest natural formation, home to nearly 5% of the biodiversity on the planet and 30% of that in Brazil. Half of its native vegetation has been eliminated, and less than 3% is fully protected.
“The occupation of the region was fast-paced over the last 60 years, which has brought about problems. Important environments have been lost or shrunk due to urbanization, farming and the construction of hydroelectric power plants,” says forest engineer Julio Cesar Sampaio, coordinator at WWF Brasil's Cerrado Pantanal Program.
Rainfall patterns are shifting
To make things even worse, in the last two decades, rainfall levels in the region have not held steady. Jorge Werneck, a hydrologist at the Brazilian Corporation of Agricultural Research (Embrapa), reports that rainy spells have grown shorter and dry periods longer. Precipitation rates in certain seasons have plunged from 1.5 to 1.2 thousand millimeters.
“That causes a significant impact on the hydrologic cycle. It makes our soils drier, lowers our water tables, and has a direct affect on all of the drainage patterns of our rivers,” he explains.
In Werneck's view, it is still a matter of dispute whether poorer rainfall has been man's doing, or whether or not this reduction is permanent. Barbosa says, however, that one cannot deny the influence exerted by man, not least through the disorderly growth of urban centers, which form heat islands that keep humid air away.
For Marcelo Gonçalves Resende, professor at the Catholic University of Brasília (UCB), everything is connected. In his judgment, problems stem from the inappropriate use and occupation of the land in both rural and urban areas. He believes the land may be occupied sustainably if one takes the environment into account when making plans for agriculture, cattle raising, industry, and housing. “There are techniques, but man forgets about them because of his greed, his urge for easy profit. The environment seems to be the least of his problems,” he concluded.
Translated by Fabrício Ferreira
Fonte: Occupation in Cerrado threatens Brazil's water supply