Beatriz Duguy

Self-organized criticality of wildfires ecologically revisited

Abstract Wildfire cumulative frequency–area distributions of Mediterranean landscapes are examined for agreement with self-similar (fractal) behavior. Our results support landscape-specific restricted scaling regions of 1.5–3.5 orders of magnitude in size, which are delimited by breakpoints or ‘cut-offs’. By identifying the extent of such regions in the fractal frequency–area distribution of wildfires, fractal statistics may give a deeper insight into the scale-invariant dynamics of fire spread, whereas the observed cut-offs may be related to changes in the process–pattern interactions that control wildfire propagation at the landscape scale.

Modelling the effects of landscape fuel treatments on fire growth and behaviour in a Mediterranean landscape (eastern Spain)

The number of large fires increased in the 1970s in the Valencia region (eastern Spain), as in most northern Mediterranean countries, owing to the fuel accumulation that affected large areas as a consequence of an intensive land abandonment. The Ayora site (Valencia province) was affected by a large fire in July 1979. We parameterised the fire growth model FARSITE for the 1979 fire conditions using remote sensing-derived fuel cartography. We simulated different fuel scenarios to study the interactions between fuel spatial distribution and fire characteristics (area burned, rate of spread and fireline intensity). We then tested the effectiveness of several firebreak networks on fire spread control. Simulations showed that fire propagation and behaviour were greatly influenced by fuel spatial distribution. The fragmentation of large dense shrubland areas through the introduction of wooded patches strongly reduced fire size, generally slowing fire and limiting fireline intensity. Both the introduction of forest corridors connecting woodlands and the promotion of complex shapes for wooded patches decreased the area burned. Firebreak networks were always very effective in reducing fire size and their effect was enhanced in appropriate fuel-altered scenarios. Most firebreak alternatives, however, did not reduce either rate of fire spread or fireline intensity.

Land Cover Change and Fire Regime in the European Mediterranean Region

This chapter presents an analysis of land cover and land cover changes in Southern Europe and its relation to fire regimes. The influence of land cover and land cover changes in fire hazard is presented in the first section. This is followed by a detailed analysis of fire regimes in the study region. Two main parameters, number of wildfires and burned area, are used to study the temporal and spatial variability of forest fires in southern Europe during the last decades. This sets the scene to an in depth analysis of changes in land cover in the areas affected by forest fires. Since the European Mediterranean region is influenced by intense demography and pressure on wildland areas, this section analyzes which areas are most affected by fires, and which are the land cover transitions they lead to. The chapter ends with a comparative analysis of differences in land cover dynamics in fire-affected areas in comparison to the surrounding non-burned areas.

Modelling the Ecological Vulnerability to Forest Fires in Mediterranean Ecosystems Using Geographic Information Technologies

Forest fires represent a major driver of change at the ecosystem and landscape levels in the Mediterranean region. Environmental features and vegetation are key factors to estimate the ecological vulnerability to fire; defined as the degree to which an ecosystem is susceptible to, and unable to cope with, adverse effects of fire (provided a fire occurs). Given the predicted climatic changes for the region, it is urgent to validate spatially explicit tools for assessing this vulnerability in order to support the design of new fire prevention and restoration strategies. This work presents an innovative GIS-based modelling approach to evaluate the ecological vulnerability to fire of an ecosystem, considering its main components (soil and vegetation) and different time scales. The evaluation was structured in three stages: short-term (focussed on soil degradation risk), medium-term (focussed on changes in vegetation), and coupling of the short- and medium-term vulnerabilities. The model was implemented in two regions: Aragón (inland North-eastern Spain) and Valencia (eastern Spain). Maps of the ecological vulnerability to fire were produced at a regional scale. We partially validated the model in a study site combining two complementary approaches that focused on testing the adequacy of model’s predictions in three ecosystems, all very common in fire-prone landscapes of eastern Spain: two shrublands and a pine forest. Both approaches were based on the comparison of model’s predictions with values of NDVI (Normalized Difference Vegetation Index), which is considered a good proxy for green biomass. Both methods showed that the model’s performance is satisfactory when applied to the three selected vegetation types.

Effects of Climate and Extreme Events on Wildfire Regime and Their Ecological Impacts

Fire regime has been affected by climate changes in the past, and is expected to do so in relation to the projected climate warming in the near future. For the Mediterranean Basin, higher fire risk, longer fire season, and more frequent large, severe fires are expected. The projected increased drought for the Mediterranean Basin would make ecosystems more vulnerable to fire, and more difficult to restore after fire. Ecosystem vulnerability is assessed considering soil susceptibility to post-fire erosion, and vegetation capacity to recover after fire.

Predicting wildfire spread and behaviour in Mediterranean landscapes

The use of spatially explicit fire spread models to assess fire propagation and behaviour has several applications for fire management and research. We used the FARSITE simulator to predict the spread of a set of wildfires that occurred along an east–west gradient of the Euro-Mediterranean countries. The main purpose of this work was to evaluate the overall accuracy of the simulator and to quantify the effects of standard vs custom fuel models on fire simulation performance. We also analysed the effects of different fuel models and slope classes on the accuracy of FARSITE predictions. To run the simulations, several input layers describing each study area were acquired, and their effect on simulation outputs was analysed. Site-specific fuel models and canopy inputs were derived either from existing vegetation information and field sampling or through remote-sensing data. The custom fuel models produced an increase in simulation accuracy, and results were nearly unequivocal for all the case studies examined. We suggest that spatially explicit fire spread simulators and custom fuel models specifically developed for the heterogeneous landscapes of Mediterranean ecosystems can help improve fire hazard mapping and optimise fuel management practices across the Euro-Mediterranean region.