Wildfire and landscape structure: studying links between human activities and natural dynamics to manage fire risk

Abstract

Urban sprawl provides a model of competitive land use where anthropogenic dynamic and wildland dynamic conflict. It creates a threat at the wildland-urban interface, which affects biodiversity. So, we observe more and more wildfires at these interfaces. For example, In Southern France (region of Bouches-du-Rhône), since 1900, natural lands have been abandoned. Then, they have been colonized by forest species most of them very combustible like Pinus halepensis. Urban sprawl has reduced wildland around Marseille since 1960. Development of two crossed dynamics, urban and wildland ones, are making up a new wildland/urban interface. These interfaces are our subject of study, two questions being considered. Management of urban area ecology consequences: In part, urban pattern depends on choices of housing location. People choose their location according to practical reasons (transportation costs, job opportunities like in Marseille or Aix-en-Provence) and characteristics of area (beautiful landscape, green open spaces etc.). Analysis of urban dynamics needs to characterize forest amenities on interfaces. Moreover, urban pattern is linear or mosaic-like along wildland. This creates a growing fragmentation of this area. Our purpose is to determine the links between urban pattern and wildland communities at different scales. Preliminary results reveal disturbances along urban/wildland interface. Our spatial analysis has made possible a description of the structure of exurban landscape and of urban/wildland interfaces. Moreover results in economics show that residential location factors can be included in an economic model as landscape variables. Risk analysis: Interface vegetation usually consists in coniferous stands. However, vegetation constituting the underbrush has different characteristics, which are modified by human activities and urban patterns. Our purpose is to assess underbrush impact on fire vulnerability, i.e. on fire ignition and spread.