Reduction in Amazon deforestation avoids 1,700 deaths per year

Estimate comes from a study conducted by researchers in Brazil, England and the United States, published in Nature Geoscience.

By Elton Alisson

Agência FAPESP – Because of decreasing deforestation and emissions from forest fires in the Amazon over the past ten years, the amount of particulate matter (aerosols), ozone, carbon monoxide, nitrogen oxide and other atmospheric pollutants released by burning biomass has fallen by 30% on average during the dry season in southern Brazil, Paraguay, northern Bolivia and Argentina.

This improvement in the region’s air quality may be helping to prevent the premature deaths of some 1,700 adults per year throughout South America.

These estimates come from a study performed by researchers at the University of São Paulo (USP) in Brazil in collaboration with colleagues from the Universities of Leeds and Manchester in England and the Massachusetts Institute of Technology (MIT) in the United States.

Resulting from the projects “GOAmazon: interactions of the urban plume of Manaus with biogenic forest emissions in Amazonia” and “Study of physico-chemical properties of biomass burning aerosols and radiative forcing in the SAMBBA experiment – the South American Biomass Burning Analysis”, both supported by FAPESP, the study was published in September in the online version of the journal Nature Geoscience.

“The study shows for the first time that reducing deforestation results in improved air quality, which in turn leads to a reduction in the number of deaths due to exposure to atmospheric pollution in most of South America,” Paulo Artaxo told Agência FAPESP. Artaxo is a Full Professor of Physics at USP and one of the authors of the paper.

According to the researchers, since 2004, Brazil has achieved substantial reductions in deforestation, as well as in the number of fires deliberately set to clear undergrowth and prepare areas for planting and grazing. Forest fires release large quantities of particulate matter and toxic gas into the atmosphere.

Between 2001 and 2012, deforestation in Brazil fell by some 40%, from 37,800 square kilometers (km²) per year in 2002-04 to 22,900 km² per year in 2009-11, according to the authors of the paper.

“The decrease in deforestation in the Amazon resulted from a combination of several public policies, including restricted access to farm loans for agriculturists who slash and burn and certification of beef and soybeans from areas not cleared by deforestation,” said Artaxo, who is a member of the coordinating committee for FAPESP’s Research Program on Global Climate Change (RPGCC).

To explore whether the reduction in deforestation led to observable impacts on air quality and human health, the researchers analyzed records for 2001-12 showing aerosol volumes from forest fire emissions over southwestern Brazil and Bolivia during the dry season (August-October), when the concentration of particulate matter in the atmosphere is especially high.

Measurements by satellite and ground-based sensors showed that total emissions of particulate matter from fires decreased during the dry season in Amazon forest areas with the largest number of fires during the period 2002-12, especially in years with lower deforestation rates.

When they input these measurements into a global atmospheric circulation model, the researchers found that concentrations of particles with diameters of less than 2.5 microns (μm), which have the worst impact on health, were 30% lower than in years with high deforestation rates during the dry season in southern Brazil, as well as in Paraguay, northern Bolivia and Argentina.

“The sharp fall in Amazon deforestation, which reached 5,000 km² in 2013-14, down from 27,000 km² in 2003-04, led to a decrease of about 70% in greenhouse gas emissions and atmospheric pollutants,” Artaxo said.

“We combined satellite and ground-based measurements with global atmospheric modeling and data on the effects of exposure to particulate matter to estimate the impact on health of this fall in deforestation across the continent.”

Impact on health

To estimate the impact of the particulate matter emitted by forest fires on human health, the researchers calculated rates of premature adult mortality from cardiopulmonary disease and lung cancer due to exposure to aerosols with diameters of less than 2.5 μm in 2002-11.

Mortality rates were calculated for adults older than 30 years in age using consistent epidemiological data from the literature, Artaxo explained.

The study concludes that the greatest risk to health arises close to deforestation fires, but most premature deaths occur outside the Amazon region, owing to atmospheric transport of smoke to more densely populated regions.

Based on their calculations, the researchers estimate that the 40% reduction in deforestation in Brazil in the 2001-12 period prevented some 1,700 premature adult deaths annually throughout South America due to a decrease in forest fire emissions.

“The study points to a new benefit from the fall in Amazon deforestation, on top of the usual ones,” Artaxo said. “Air quality in regions distant from the Amazon improved significantly, and many premature deaths were avoided by the reduced exposure to atmospheric pollution.”

According to the authors of the study, to maximize these benefits, public policy should aim at zero deforestation and the end of slash-and-burn in all moist tropical forest areas.

“Further reducing deforestation until it stops completely will produce extra benefits not just for the environment in the Amazon and worldwide but also for human health,” Artaxo said.

“We must continue with our efforts to protect the Amazon forest because they save lives and mitigate the adverse effects of global climate change.”

The article “Air quality and human health improvements from reductions in deforestation-related fires in Brazil” (doi: 10.1038/NGEO2535) by Artaxo et al. can be read in Nature Geoscience at www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2535.html.