P1.10 USE OF FARSITE SIMULATOR TO PRODUCE FIRE PROBABILITY MAPS IN A MEDITERRANEAN AREA Bachisio Arca* a , V. Bacciu b , P. Duce a , G. Pellizzaro a , M. Salis b , D. Spano b a CNR - IBIMET, Institute of Biometeorology, Sassari, Italy b DESA, Università di Sassari, Sassari, Italy 1. INTRODUCTION Fire is an important, frequent and widespread disturbance in terrestrial ecosystems across the world. This is particularly true in natural vegetation of the Mediterranean basin where the areas burned each year are large and the fire frequency is high (Moreno et al., 1998). In the last two decades of the 20 th century, the annual cumulated burnt area in the Mediterranean European countries was estimated to be about 600,000 ha, almost twice as much as during the 1970s (European communities, 2002). Therefore, the development of fire management policies are required in order to reduce the wildland fire risk by applying methods and models for planning the operational phases of fire management. Although forest fires are predominantly ignited by arson, or by accident, the differences in fire occurrence and fire propagation are a combined effect of the involved environmental components: weather, vegetation, and terrain. The occurrence of fires depends on drought cycles, precipitation amount and timing, temperature reached during drought season and on the amount of fuel biomass (Mouillot et al. 2002). Changes in fire behavior in space and time occur in relation to changes in the environmental components but weather is the most variable component changing rapidly in both space and time (Pyne et al.1996). In this context, relatively few information are available on the interactions between wildfire regimes and frequency and projected climate change in Mediterranean Basin country. Alcamo et al. (2007) in the last report of the IPCC reported that in central west Mediterranean Basin the projected impacts of climate change will create a greater variability and extreme weather events, wetter winters and drier summers and hotter summers and heat waves. The changes in the frequency of extreme events might be the first and most important change registered in the Mediterranean area. At the long-term scale climate changes can affect the overall flammability of the plant material resulting from changes in total biomass, from redistribution of fuel load in the different layers of vegetation or from modification of dead live fuel ratio (Mouillot et al. 2002). At shorter time scale the increase of extreme weather events (heat waves, strong winds ecc.) can directly affect water status of fuel and fire behavior, and it can increase large fires occurrence probability. In this context, identifying areas that are characterized by high probability of large fires occurrence in relation to the projected climatic change could represent an important component of fire management planning. In recent years several authors proposed using fire simulator as a convenient methodology to derive fire probability maps in function of particular weather conditions (Finney 2005, Farris et al. 2000). Given a large enough number of simulations across a landscape under relatively short-term extreme events, areas that have most probability to burn can be quantified and different scenario can be tested (Clarke et al. 1994). FARSITE (Fire Area Simulator, Finney 1998) is one of the main fire simulation systems developed over recent years to describe the temporal and spatial variations of fire spread and behaviour (Rothermel, 1972). The use of the simulator as component of a decision support system for planning the fire management practices involves the assessment of the simulation accuracy under different environmental and vegetation conditions. The aims of this study were to evaluate the capabilities of FARSITE simulator for estimating the probability of burning in a Mediterranean area predominantly covered by shrubland vegetation in relation to different weather conditions. The general goal is to provide basic information that is useful to produce maps of spatial burn probabilities in Mediterranean region in function of projected climate changes. 2. MATERIALS AND METHODS The study area is located in North-East Sardinia, near the village of Budoni (lat. 40° 43’, long. 09° 42’, 50 m a.s.l.). The area (≈ 1976 ha) is affected historically by small and medium (≈ 100 ha) human-caused fires occurred during the summer season, mainly with severe environmental conditions. The area is characterized by the typical sub-arid Mediterranean climate, with a remarkable water deficit from May through September, and most of the annual rainfall amount (approximately 650 mm) occurring in fall and winter. The mean annual temperature is approximately 17 °C, with summer season highs often around 30 °C. The average wind speed is relatively high (≈ 4 m s -1 ) in both winter and summer seasons, with about 50 – 70% of the days showing values between 1.6 and 8 m s -1 . The prevailing wind directions at the sites are typically west and northwest with a cumulative frequency greater than 50%. However, complex terrains typical of the studied areas * Corresponding author address: Bachisio Arca, CNR, Institute of Biometeorology, Section of Sassari, Via Funtana di Lu Colbu 4A, 07100 Sassari, Italy; e-mail: B.Arca@ibimet.cnr.it