Study evaluates impact of extreme weather in Amazon

Droughts and floods are becoming more severe in the region, leaving the inhabitants of remote areas more vulnerable to water and food shortages and without access to transportation, health care or schools.

By Karina Toledo

Agência FAPESP – Drought and flooding are natural phenomena in the Amazon, and riverine communities are well adapted to them. In recent years, however, these events have become more extreme, leaving the inhabitants of remote areas increasingly vulnerable to water and food shortages and without access to transportation, health care or education.

These are the conclusions of a study conducted by Patricia Pinho, a visiting professor at the University of São Paulo’s Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) and a member of the Interdisciplinary Climate Investigation Center (INCLINE). The data were presented during FAPESP Week UC Davis in Brazil, an event held in May that brought together 26 scientists from the University of California (UC), Davis, in the United States and from institutions in São Paulo State, Brazil.

“Interannual climate variability in the Amazon basin has increased in recent years, particularly with regard to the beginning and end of the rainy season. We set out to map the extent to which local communities perceive these events as extreme, their adaptive responses, and the limits of their adaptability,” Pinho told Agência FAPESP.

The study focused on the municipality of Silves, located 400 km from Manaus, the capital of Amazonas State, and on the Tapajós National Forest, a conservation unit located in Pará State.

Based on observational data and personal interviews, Pinho assessed how local inhabitants in these areas perceived the extreme droughts recorded for the years 1997, 2005 and 2010, as well as the severe flooding in 2006, 2009 and 2015.

According to Pinho, the 1997 and 2010 droughts were associated with the phenomenon known as El Niño, characterized by unusually warm surface water in the tropical Pacific. In 2005, temperature anomalies were recorded in the tropical North Atlantic.

In previous studies, the floods were associated with La Niña, during which surface water becomes unusually cold in the central and eastern equatorial Pacific. “The point is that both severe droughts and floods are becoming more frequent in the Amazon, and the frequency of hydrologic extremes is set to increase according to the IPCC, INPE and other groups,” Pinho said.

The IPCC, the Intergovernmental Panel on Climate Change, is a UN-sponsored scientific body that assesses the risk of human-induced global warming. INPE is Brazil’s National Space Research Institute.

After analyzing water level gauge data recorded in Manaus between 1900 and 2010, Pinho concluded that the annual peak has been falling, while the trough has risen in recent years, indicating an increase in the interannual variability of this river system.

“The economy of the Amazon Basin, where some 30 million people live, is directly linked to the dynamics of the hydrologic cycle. River flow volumes determine the organization of human settlements, land tenure, production systems and social organization. Any change in ecosystem services causes immediate pressure on this population, for which the poverty level is 42%, well above the national average of 29%,” Pinho said.

The main effects of severe drought observed in the study were high fish and crop mortality, as well as a shortage of clean drinking water. Food security suffered because fish is the main source of protein in the region. River transportation, the sole means of travel for many, was impossible owing to very low water levels, such that the inhabitants could not reach local markets, hospitals or schools.

Curiously, Pinho also observed drinking water shortages during periods of flooding, as well as greater difficulties in fishing due to shoal dispersal. In addition, the flooding destroyed homes, hampered forest production, caused high livestock and crop mortality, and gave rise to outbreaks of diseases such as malaria and diarrhea.

“Local communities in the Amazon cope perfectly well with the normal pattern of rising and falling river levels,” Pinho said. “Up to a point, they know whether droughts or floods will be severe and whether they should move or take other kinds of defensive action, but the extreme events evaluated in the study exceeded their capacity to adapt. Moreover, they happened in rapid succession, making recovery even harder for the riverine population.”

“While these communities are resilient to large variations in river levels, they’re becoming more vulnerable, owing to uncertainty as the events become more extreme and more frequent.”

Lack of support

Another problem highlighted by Pinho was the lack of a prompt government response. Local and federal authorities are too slow to provide any type of support to the inhabitants of the areas studied, she said. Civil defense agencies should prioritize preventive action and hazard assessment, as well as providing assistance when emergencies occur.

“We observed a lack of properly trained personnel and delays in taking action. Preventive measures are non-existent. The local authorities are forced to request help from the state government, which passes on the request to the federal government, and only then is help forthcoming. Mechanisms should be created to speed up this process,” Pinho said.

She stressed the need for public policy measures to improve governance and assure the well-being of these citizens, alongside investment in roads and alternative means of transportation. More schools and clean water wells are also essential.

“Brazilians are accustomed to associating extreme events like drought with the Northeast region, but now the Amazon is also being drastically affected, and we observed a very limited government response,” she said.

More research should be performed to enhance climate models so that they can predict extreme events and help create an early warning system.

“The science is still incipient, and there’s a great deal of uncertainty about how the Amazon will respond to climate change,” she said. “We have a global model, but we must now regionalize it and scale it down. To do this, we’ll have to combine observational data with research done at the local level.”