"Large-scale seasonal forecasting could help predict fire activity in the investigated areas," José Moreno of the University of Castilla-La Mancha told environmentalresearchweb. "Our findings are important considering the large socio-economic differences between the two areas we analysed and the contrasted changes over time that occurred during the study period."

Moreno and colleagues from Spain, Italy and the US analysed the relationships between summer fires and weather conditions for the period 1985–2011 at three scales in the southern countries of the European Union – Portugal, Spain, southern France, Italy and Greece – and two southern states, California and Oregon, on the US Pacific western coast in the US.

The dependence of fires on weather conditions can be quantified with fire weather indices – estimates of fire risk linked to parameters such as temperature, precipitation, humidity and wind speed. Using the fire weather index of the Canadian Forest Fire Danger Rating System, the researchers found that fire activity – the total number of fires, large fires and area burned by fires – in both southern Europe and the southern Pacific western coast was explained by their seasonal climate. Within any given area, higher fire risks linked to summer weather resulted in higher fire activity, whilst in some areas, dry conditions eight months prior to summer also contributed to more summer fires and larger burned areas.

"Weather conditions carry significant information for predicting fire activity, and this is why this and other similar indices are used by the fire-fighting services," said Moreno. "However, their role is not the same everywhere. Fire-climate relationships were less strong in areas with more amenable conditions for fires. This suggests that, as the climate becomes warmer and drier due to global warming, fires in these regions are likely to become less predictable."

The researchers now plan to analyse the mechanisms behind the fire-climate relationships that they found and to dive deeper into fire forecasting. "The models in this study did not work in the same way across all the areas we examined, thus the role of other factors in fire activity – such as fire ignitions, landscape structure or socio-economic factors – have to be further investigated," Moreno said. "We are also interested in predicting fire activity under future scenarios of climate change, since it can have important implications for fire prevention and planning."

Moreno and colleagues reported their results in Environmental Research Letters (ERL).

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