Strong decline in savanna fires due to increasing agriculture

Savannas and grasslands cover a large share of the tropics and harbour unique biodiversity. These grasslands are characterized by frequent fires—a pattern of burning that people have used for millennia to keep the landscape free of trees and shrubs and improve grazing. According to an international team of scientists fires have been disappearing rapidly from these ecosystems, resulting in a global decline in burned area.

06/30/2017 | 11:37 AM

The team analyzed satellite images of fires and vegetation, the results being published in Science. Since 1998, when high quality data became available, global burned area has declined by about a quarter, about 30 times the surface area of the Netherlands. The estimated decrease in burned area remained robust after adjusting for rainfall variability. The decline in fire activity is a result of massive increases in livestock and expansion of croplands that reduce fuel loads and fragment the landscape.

Lower greenhouse gas emissions
Forest fire specialist Guido van der Werf of the Vrije Universiteit Amsterdam (VU Amsterdam) and first author Niels Andela, formerly an employee of VU Amsterdam and now working at NASA, highlight the profound implications of declining fire activity for the Earth System. “Greenhouse gas emissions from fires have dropped, due to the decline in burned area in savannas. However, increasing fires in boreal forest partly offset this decline”, according to the researchers. “Fewer fires also improved air quality in the tropics.”

Human origin
“At the same time we hope our research will create awareness that these incredible ecosystems where humans originate from are rapidly disappearing”, continues Niels Andela. Historic savanna landscapes are being converted into fragmented agricultural areas, where the use of fire by humans is rapidly declining. Increasing population and demand for agricultural suggest that observed declines in burned area may continue or even accelerate in coming decades. The loss of fire threatens the sustainability of remaining tropical savannas, home to lions, rhinos and other iconic species.