Globally, the amount of land being burned by fire is declining and this is largely due to human activities, says a study based on NASA's satellite data.The researchers, however, found that in some parts of the world including in India, China and Brazil, the amount of land being burned by fire has increased.The total acreage burned by fires each year declined by 24 per cent between 1998 and 2015, showed the findings published in the journal Science."Climate change has increased fire risk in many regions, but satellite burned area data show that human activity has effectively counterbalanced that climate risk, especially across the global tropics," said study co-author Doug Morton, a research scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We've seen a substantial global decline over the satellite record, and the loss of fire has some really important implications for the Earth system," Morton said. Shifting livelihoods across the tropical forest frontiers of South America, the Eurasian Steppe, and the savannahs of Africa has altered the landscapes and led to a significant decline in the amount of land burned by fire, NASA's satellites data showed.
The researchers said that the ongoing transition from nomadic cultures to settled lifestyles and intensifying agriculture has led to a steep drop not only in the use of fire on local lands, but in the prevalence of fire worldwide.The decline in burned lands was largest in the savannahs and the grasslands, where fires are essential for maintaining healthy ecosystems and habitat conservation.The impact of human-caused changes in the savannahs, grasslands and tropical forests is so large that it offsets much of the increased risk of fire caused by warming global temperatures, Morton said. Still, the impact of a warming and drying climate is seen at higher latitudes, where fire has increased in parts of Canada and the American west. Regions of China, India, Brazil and southern Africa also show an increase in burned area, the study said. But the expansiveness of the savannahs and grasslands puts the global trend in decline.The international team of scientists analysed the fire data, derived from the Moderate Resolution Imaging Spectrometer (MODIS) instruments on NASA's Terra and Aqua satellites, as well as other sources. They compared these datasets with trends in population, agriculture, livestock density and gross domestic product."Humans are interrupting the ancient, natural cycle of burning and regrowth in these areas," senior author Jim Randerson, Professor at the University of California, Irvine, said of the African savannahs. "Fire had been instrumental for millennia in maintaining healthy savannahs, keeping shrubs and trees at bay and eliminating dead vegetation," Randerson noted.However, there are benefits to fewer fires as well. Regions with less fire also saw a drop in carbon monoxide emissions and an improvement in air quality during the peak of the fire season, confirming the burned area trends using data from other NASA satellites.