Using unplanned fires to help suppressing future large fires in Mediterranean forests.

Javier Retana,Adrián Regos,Miquel De Cáceres,Núria Aquilué,Lluís Brotons

doi:10.1371/journal.pone.0094906

Abstract

Despite the huge resources invested in fire suppression, the impact of wildfires has considerably increased across the Mediterranean region since the second half of the 20th century. Modulating fire suppression efforts in mild weather conditions is an appealing but hotly-debated strategy to use unplanned fires and associated fuel reduction to create opportunities for suppression of large fires in future adverse weather conditions. Using a spatially-explicit fire–succession model developed for Catalonia (Spain), we assessed this opportunistic policy by using two fire suppression strategies that reproduce how firefighters in extreme weather conditions exploit previous fire scars as firefighting opportunities. We designed scenarios by combining different levels of fire suppression efficiency and climatic severity for a 50-year period (2000–2050). An opportunistic fire suppression policy induced large-scale changes in fire regimes and decreased the area burnt under extreme climate conditions, but only accounted for up to 18–22% of the area to be burnt in reference scenarios. The area suppressed in adverse years tended to increase in scenarios with increasing amounts of area burnt during years dominated by mild weather. Climate change had counterintuitive effects on opportunistic fire suppression strategies. Climate warming increased the incidence of large fires under uncontrolled conditions but also indirectly increased opportunities for enhanced fire suppression. Therefore, to shift fire suppression opportunities from adverse to mild years, we would require a disproportionately large amount of area burnt in mild years. We conclude that the strategic planning of fire suppression resources has the potential to become an important cost-effective fuel-reduction strategy at large spatial scale. We do however suggest that this strategy should probably be accompanied by other fuel-reduction treatments applied at broad scales if large-scale changes in fire regimes are to be achieved, especially in the wider context of climate change.

Highlights

Wildland fires are a major component of disturbance regimes in many regions [1]
Period characterized by strong efforts of firefighters to suppress small fires (Focverd I and II fire suppression programs) Hectares/year to burn in mild years considering an average efforts of firefighters to suppress of small fires Hectares/year to burn in mild years considering relatively little effort of firefighters to suppress small fires Number of years since the last fire after which fire scars can be used as fire suppression opportunities by fire brigades Percentage of adverse years for the simulation period (2000–2050) according to the trends recorded in the period 1980–1999 Percentage of adverse years for the simulation period (2000–2050) factoring in climatic warming
We have shown that relaxing fire suppression efforts under relatively controlled conditions has the potential to substantially reshape fire regimes and decrease the amount of area burnt under undesired, extreme climate conditions

Summary

Introduction

Wildland fires are a major component of disturbance regimes in many regions [1]. While climate and vegetation characteristics have been described as major determinants of fire regimes, in the Mediterranean Basin and similar regions where human influence is widespread, fire regimes emerge as a complex process in which landscape planning, economic activities and fire management can override the influence of natural factors [2,3,4].Despite the huge amount of resources invested in fire prevention and suppression, the impact of wildfires has considerably increased since the second half of 20th century across different Mediterranean regions [1,3,5]. While climate and vegetation characteristics have been described as major determinants of fire regimes, in the Mediterranean Basin and similar regions where human influence is widespread, fire regimes emerge as a complex process in which landscape planning, economic activities and fire management can override the influence of natural factors [2,3,4]. Recent wildfires tend to be larger and more severe as a consequence of an increase in fuel accumulation and continuity (induced mainly by the abandonment of agriculture and livestock, and active afforestation policies) [3,9,10] coupled with drier and warmer climatic conditions [5]. The expansion of populations and the wildland–urban interface has contributed to more fire ignition events [11]

Methods

Results

Conclusion