Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on socio-economic systems and health4.2.3 Forest firesRelevanceForest fires are an integral part of forest ecosystemdynamics in many ecosystems where they arean essential element of forest renewal. They helpcontrol insect and disease damage and eliminatelitter that has accumulated on forest floors. At thesame time, forest fires are an important disturbanceagent in many forested landscapes. Fire risk dependson many factors such as weather, vegetation(e.g. fuel load and condition), topography, forestmanagement practices and socio‐economic context,to mention the main ones. Extreme fire episodes anddevastating fire seasons of recent years in Europewere in most cases driven by severe fire weatherconditions. Although most of the wild fires inEurope are ignited by humans (either accidently orintentionally), it is widely recognised that weatherconditions and accumulation of fuel play a dominantrole in affecting the changes in fire risk over time.Thus climate change is expected to have a strongimpact on forest fire regimes in Europe.Past trendsHistorical fire series are available in Europe andregularly updated within EFFIS. However, the timeperiod covered is not the same for all countries andonly in a few case series is longer than 25 yearsavailable. A long time series of forest fire data isavailable for five particularly affected countries insouthern Europe (Greece, Spain, France, Italy andPortugal). The total burnt area per year in the fivesouthern Member States since 1980 is shown onFigure 4.3. Since the area of each country is different,and the area at risk within each country is alsodifferent, comparisons among countries cannot beabsolute.The statistics vary considerably from one year to thenext, which clearly indicates how much the burntarea depends on seasonal meteorological conditions.Some multi-annual periodicity in the burned areatrend can also be partially attributed to the deadbiomass burning/accumulation cycle typical of thefire-prone regions. The historical trend of numberof fires is more controversial to analyse becausefire frequency is strongly affected by the significantchanges that occurred in past years in the statisticalreporting systems of the countries. Reported firefrequency in southern European countries hasincreased during the 1990s to then stabilise foraround one decade and slightly decrease duringrecent years.To complement the information from past forestfires, past trends of fire danger have also beenanalysed processing series of meteorological firedanger indices, which are routinely used to ratethe fire potential due to weather conditions. TheCanadian Fire Weather Index (FWI) is used inEFFIS to rate the daily fire danger conditions inEurope. FWI can be transformed with a simpleequation into a daily severity rating index which isdeemed to be linearly related with fire suppressiondifficulties (Van Wagner, 1987). Daily severity valuescan be averaged over the fire season obtaining aSeasonal Severity Rating (SSR) index, which allowsobjective comparison of fire danger from year toyear and from region to region. Although the indexis dimensionless and mainly used for comparisonpurposes, SSR values above 6 may be considered inthe extreme range. Weather input to compute SSRare the same as for FWI (air temperature, relativehumidity, wind, precipitation). Other driving factorsof fire regimes, such as land-use changes or fueldynamics, are not taken into account by SSR whichis based on weather parameters. However, thefundamental role played by weather in affecting theKey messages: 4.2.3 Forest fires• Fire risk depends on many factors, including climatic conditions, vegetation (e.g. fuel load andcondition), forest management practices and other socio‐economic factors.• The number of fires in the Mediterranean region has increased over the period from 1980 to 2000;it has decreased thereafter.• In a warmer climate, more severe fire weather and an expansion of the fire-prone area and longer fireseasons, as a consequence, are projected, but with considerable regional variation.• The impact of fire events is particularly strong in southern Europe on already degraded ecosystems.Climate change, impacts and vulnerability in Europe 2012177