Landscape vulnerability to wildfires at the forest-agriculture interface: half-century patterns in Spain assessed through the SISPARES monitoring framework

Abstract

Large-scale socioeconomic changes in recent decades have driven shifts in the structure of Spanish rural landscapes, particularly in those located at the forest-agriculture interface (FAI), as well as in their wildfire regime. Using data from more than 200 16 km 2 landscape plots in Spain surveyed between 1956 and 2008 through the SISPARES monitoring framework, we assessed the FAI vulnerability to wildfires and identified the main landscape structural factors related to an increased number of wildfire events. We found that the most vulnerable landscapes were those with high road density, high diversity of land uses and, most importantly, with fine-grained forest-agriculture mixtures. Ignition frequency was lower in those landscapes where crops and woodlands coexisted but distributed in large and well-separated patches, and much lower where both land uses were combined within an integrated production and management system (''dehesas''). We discuss the geographical distribution patterns and temporal trends of the different FAI types during recent decades. We conclude that such approach is useful to forecast the mutual interactions between land use pattern changes and wildfire regime in the Mediterranean agroforestry mosaics. This would also provide an ecological base for developing a complementary, cost-effective and durable passive strategy of wildfire management targeted to modify the inherent FAI susceptibility to ignition events.

Modelling long-term fire occurrence factors in Spain by accounting for local variations with geographically weighted regression

“…This has a positive influence in many studies (Cardille et al, 2001;Maingi and Henry, 2007;RomeroCalcerrada, 2008;Catry et al, 2009;Sebastian-Lopez et al, 2008;Martínez et al, 2009;Marques et al, 2011;Nunes, 2012) or a negative relationship for some areas in other studies (Narayanaraj and Wimberly, 2012; Sá et al, 2011). Additionally, the previously mentioned variables were also related with the CORINE land use class "agriculture but with significant areas of natural vegetation" (CL 21 PM), showing that fire occurrence was more likely in municipalities where agricultural and forest areas are intermixed, similar to what has been reported by Ortega et al (2012). Recently, when trying to explain the extreme 2007 fires in the Greek Peloponnese, observed that the CORINE land cover category "agricultural land, highly interspersed with significant areas of natural vegetation" was the most affected by fire, reflecting the encroachment of natural vegetation in abandoned fields and also recent patterns of evolution in the wildland-rural interface where agricultural land is increasingly intermixed with natural vegetation.…”

“…6. Another important variable was forest-cultivated land interface (ICFSUP P), which is related to agricultural activities where fire is frequently used in arable and crop lands, , Ortega et al, 2012Gonzalez-Olabarría et al, 2012), which found that the landscapes most vulnerable to fire were those with fine-grained forest-agriculture mixtures or mosaics, where the humancaused fires were more intense than homogeneous and nonfragmented landscapes. Variables DIS 50 91 (population decrease between 1950 and 1991) and DIS SAU (decrease in agricultural area between 1989 and 1999) were positively correlated with the occurrence of at least one fire event.…”

“…On the other hand, more fire density was found in Spanish landscapes with high fragmentation (FRAG7 × 7), especially in the three main river depressions where agriculture dominates (Duero, Ebro and Guadalquivir) and where there is less forest cover. Heterogeneous and interspersed patterns composed by spatially separated patches with different land uses presents higher ignition frequencies (Ortega et al, 2012;Ruiz-Mirazo et al, 2012).…”

The relationship between landscape patterns and human-caused fire occurrence in Spain

“…Among the studies that have dealt with fire occurrence in the literature, many have included geographic or spatial variables (i.e. Padilla and Vega-García, 2011) but only Henry and Yool (2004), Martínez et al (2009) and Ortega et al (2012) have included independent variables measuring landscape pattern. Henry and Yool (2004) calculated landscape metrics (area, shape and diversity indices) in remote sensing images (Landsat TM and SIR-C data) to relate landscape pattern with historical fire occurrence in National Saguaro Park (Arizona).…”

“…Martí-nez et al (2009) considered area, density and fragmentation indices (landscape and cropland fragmentation) with socio-economical and geographical variables to predict human-caused fire occurrence at the municipal scale in Spain. A recent study by Ortega et al (2012) did analyze landscape structural factors (11 metrics) related to increased wildfire incidence in forest-agriculture interfaces within the SISPARES monitoring network (observation size 16 km 2 ), finding that certain landscape configurations were more vulnerable (fireprone) than others.…”