A Global Index for Mapping the Exposure of Water Resources to Wildfire

François-Nicolas Robinne,Kevin Bladon,Mike Flannigan,Monica Emelko,Carol Miller,Marc-André Parisien,Uldis Silins

doi:10.3390/f7010022

Abstract

Wildfires are keystone components of natural disturbance regimes that maintain ecosystem structure and functions, such as the hydrological cycle, in many parts of the world. Consequently, critical surface freshwater resources can be exposed to post-fire effects disrupting their quantity, quality and regularity. Although well studied at the local scale, the potential extent of these effects has not been examined at the global scale. We take the first step toward a global assessment of the wildfire water risk (WWR) by presenting a spatially explicit index of exposure. Several variables related to fire activity and water availability were identified and normalized for use as exposure indicators. Additive aggregation of those indicators was then carried out according to their individual weight. The resulting index shows the greatest exposure risk in the tropical wet and dry forests. Intermediate exposure is indicated in mountain ranges and dry shrublands, whereas the lowest index scores are mostly associated with high latitudes. We believe that such an approach can provide important insights for water security by guiding global freshwater resource preservation.

Highlights

Wildfires are essential to ecosystem function across the globe [1], influencing a wide spectrum of ecosystem components and natural processes [2], among which is the hydrological cycle
Several key global studies used this approach to underline issues in water security and riverine biodiversity [20], ocean vulnerability to human impact [22] and to identify natural areas of great importance for ecosystem functioning [19]. Inspired by this effective approach, we introduce here the concept of the wildfire water risk (WWR), which we define as the potential for wildfires to adversely affect water resources important for downstream ecosystems and human water needs for adequate water quantity and quality
The highest exposure scores were mostly clustered in the tropical wet forests, whereas intermediate scores tended to be localized in tropical dry forest and shrublands, as well as in several mountain ranges and boreal forests

Summary

Introduction

Wildfires are essential to ecosystem function across the globe [1], influencing a wide spectrum of ecosystem components and natural processes [2], among which is the hydrological cycle. An abundant literature has described the effects of vegetation burning and post-fire recovery on local hydrology in different biogeographic areas [3,4,5,6]. Vegetation cover, litter and soil organic matter can be dramatically reduced by large fires and can lead to higher surface runoff and soil erosion, increasing water quantity, but decreasing water quality. A significant number of studies have examined such second-order fire effects on surface freshwater resources [8], most have been conducted at a local or regional scale [8,9,10,11,12], whereas global-scale studies do not exist. Despite the ubiquitous nature of fire and the potential for adverse consequences on ecosystems and populations [13], large-scale assessments of the risks that fire can pose to water resources are lacking. Several important advancements in natural resources global mapping [14] and the development of innovative methods and global databases make it possible to better understand the intersection of wildfire activity [15,16] and water resource availability [17,18]

Methods

Results

Conclusion