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Volume 18, issue 3 | Copyright

Special issue: Spatial and temporal patterns of wildfires: models, theory,...

Nat. Hazards Earth Syst. Sci., 18, 935-948, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Mar 2018

Research article | 23 Mar 2018

Modeling anthropogenic and natural fire ignitions in an inner-alpine valley

Giorgio Vacchiano1, Cristiano Foderi2, Roberta Berretti3, Enrico Marchi2, and Renzo Motta3 Giorgio Vacchiano et al.
  • 1Dipartimento di Scienze Agrarie e Ambientali, Università degli Studi di Milano, Milan, 20123, Italy
  • 2Dipartimento di Gestione dei Sistemi Agrari, Università degli Studi di Firenze, Alimentari e Forestali, Florence, 50145, Italy
  • 3Dipartimento di Scienze Agrarie, Forestali e Alimentari, Università degli Studi di Torino, Grugliasco (TO), 10095, Italy

Abstract. Modeling and assessing the factors that drive forest fire ignitions is critical for fire prevention and sustainable ecosystem management. In southern Europe, the anthropogenic component of wildland fire ignitions is especially relevant. In the Alps, however, the role of fire as a component of disturbance regimes in forest and grassland ecosystems is poorly known. The aim of this work is to model the probability of fire ignition for an Alpine region in Italy using a regional wildfire archive (1995–2009) and MaxEnt modeling. We analyzed separately (i) winter forest fires, (ii) winter fires on grasslands and fallow land, and (iii) summer fires. Predictors were related to morphology, climate, and land use; distance from infrastructures, number of farms, and number of grazing animals were used as proxies for the anthropogenic component. Collinearity among predictors was reduced by a principal component analysis. Regarding ignitions, 30% occurred in agricultural areas and 24% in forests. Ignitions peaked in the late winter–early spring. Negligence from agrosilvicultural activities was the main cause of ignition (64%); lightning accounted for 9% of causes across the study time frame, but increased from 6 to 10% between the first and second period of analysis. Models for all groups of fire had a high goodness of fit (AUC 0.90–0.95). Temperature was proportional to the probability of ignition, and precipitation was inversely proportional. Proximity from infrastructures had an effect only on winter fires, while the density of grazing animals had a remarkably different effect on summer (positive correlation) and winter (negative) fires. Implications are discussed regarding climate change, fire regime changes, and silvicultural prevention. Such a spatially explicit approach allows us to carry out spatially targeted fire management strategies and may assist in developing better fire management plans.

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Short summary
Here we show that wildland fires in an Italian alpine region are ignited mainly by human negligence. 30 % of fires stars in agricultural areas, 24 % in forests. Lightning plays a role in 10 % of the cases, but its importance has been increasing recently. Areas under hot, dry climate are more prone to fire. Cattle grazing reduces the fuel for winter fires, but increases ignition risk in summer. The maps of fire risk that we produce can help to support fire prevention and ecosystem management.
Here we show that wildland fires in an Italian alpine region are ignited mainly by human...