Climate change threatens water security in South America

Diminishing rainfall and increasing temperatures may impact power generation and agriculture in countries of the region, says the IPCC report.

By Elton Alisson

Agência FAPESP – Changes in climate that have already been seen, as well as those projected for Central and South America, will threaten water security in these regions. These changes will have a direct impact on domestic and industrial supplies and on sectors that are strongly dependent upon water, such as hydroelectric power generation and agriculture.

This warning comes from the Report about Impacts, Adaptation and Vulnerability to Climate Change prepared by the Intergovernmental Panel on Climate Change (IPCC) that was presented on March 30 in Yokohama, Japan and on April 1 at the Brazilian Academy of Sciences (ABC) in Rio de Janeiro.

Chapter 27 of the document, which addresses climate change projections for Central and South America, underscores the fact that the current vulnerability of the water supply in the semiarid zones of these two regions and in the tropical Andes will likely increase further as a result of climate change. According to the IPCC, the problem may be exacerbated by the reduction in the size of Andean glaciers, diminished rainfall and increased evapotranspiration in the semiarid regions of Central and South America.

If these predictions hold true, the supply of water to large cities and small communities in the two regions will be affected. Furthermore, the report says that the generation of hydroelectric power and food production will be jeopardized.

“In the end, the principal impacts of climate change for Central and South America are related to water,” said Marcos Buckeridge, professor of the Biosciences Institute of the University of São Paulo (USP) and one of the authors of chapter 27 of the report, during the publication’s presentation in Rio de Janeiro.

“All sectors that in some way depend on water will be affected,” Buckeridge said. According to the report, water is widely available in Central and South America but is distributed unequally between the two regions.

The document indicates that the principal consumer of water in Central and South America is agriculture, followed by the supply of water to the 580,000,000 inhabitants of the two regions, which does not include the 14% of inhabitants who currently have no access to water.

The publication further states that hydroelectric power is the main source of renewable energy in the two regions, corresponding to 60% of the power grid. In other regions, hydroelectric power contributes only 20% on average.

Because projections indicate increased rainfall in some regions of Brazil, the hydroelectric power systems based mainly on the Paraná River may experience a slight increase in power production.

However, the rest of Brazil’s hydroelectric system – especially that located in the Northeast – could face reductions in power generation, jeopardizing the reliability of the entire system, says the report.

“Imagine if extreme climate events such as extended drought, along with high temperatures like those seen earlier this year in the southeastern region of Brazil, also occurred in the southern region. They could severely affect the operation of hydroelectric plants such as Itaipu,” Buckeridge told Agência FAPESP.

Impact on food

The report indicates that the climate changes predicted for the two regions could have different impacts on the production of some types of food and on the food safety for the population.

Even with the predicted reductions in the availability of water, sugarcane and soybean crops are likely to respond positively to increased carbon dioxide emissions and temperature changes, resulting in higher productivity and yield.

In northeastern Brazil, however, there will likely be a drop in the profitability of subsistence crops, such as beans, corn and cassava, for the region’s population, and the number of areas currently favorable for cultivating cowpeas will decrease.

A 5.8°C warming by 2100 (worst case scenario) could make the harvesting of coffee unfeasible in Minas Gerais and São Paulo – Brazil’s two largest producers of the crop.

“What has been observed in terms of climate change impacts on agriculture in regions of average and tropical latitudes is that, with the exception of soybeans, there will be a reduction in the production of flour, rice and corn grown in these regions,” said José Marengo, researcher at the National Institute for Space Research (INPE) and one of the authors of chapter 27, during the event launching the report in Rio de Janeiro.

“And these agricultural crops basically make up the basic food basket of most developing countries,” he stated.

The report considers that as a result of increasing rates of growth and better efficiency in the use of water, some crops in Central and South America, including soybeans, beans, corn and sugarcane, may respond with increasing productivity.

However, the nutritional quality of these foods is expected to diminish due to the increased sugar content in grains and fruit and the reduced protein content in cereals and legumes, say agricultural researchers.

“Recent studies have shown that increased carbon dioxide in the atmosphere causes plants to grow more and be more robust. Their protein content diminishes by an average of 7%, and this results in a drop in the quality of the food,” Buckeridge said.

Some practices for adaptation suggested by the IPCC report include advances in genetic modification to develop agricultural crops that are better suited to extreme climate events and to meet the global demand for food in the coming decades.

According the report’s projections, by 2040, an increase of at least 70% in the global production of food will be necessary, and South America and South Africa are the only regions in the world that have the available agricultural land to meet part of this demand.

“There will be no way to increase the production of most types of plants through traditional plant breeding,” Buckeridge said. “Biotechnology will have to be used to change the plants so that they produce more food and are better adapted to climate change,” he said.