Wildfire – nature’s way of turning fallen vegetation into the next season’s nutrients – is a growing hazard. In the last 35 years, the wildfire season has grown longer by a fifth, and wildfire is now a threat to one fourth of all the plant-covered land on the planet.
US researchers report in Nature Communications that since 1970 the number of days without rain has increased by well over one day every decade.
William Jolly of the US Forest Service in Missoula, Montana and colleagues say they examined the fire season worldwide for the study period, taking into consideration all the factors that are used to calculate fire hazard: wind, humidity and temperature, as well as rainfall levels.
They found that the combined changes in the surface weather have meant that the fire season has increased so far by 18.7%
Worldwide, wildfires sear, scorch or incinerate about 350 million hectares of ground cover every year. Changes in the rainfall patterns were a factor, with the number of rain-free days increasing by 1.31 days per decade. The season of smoke and cinders and smouldering stumps had been extended almost everywhere.
The average temperature on land that could support vegetation – for obvious reasons, the researchers did not include Antarctica or Greenland or the most arid desert zones – had increased by 0.185°C per decade and relative humidity, a measure of moisture in the air, had dropped 0.217% per decade.
Read more at Wildfire Threat Spreads Across Warming World
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