A pattern has emerged related to the joint concept of greater precipitation in winter months coupled with greater evaporation in summer months, both driven by a warming climate. A wet winter allows grasses to grow, which dry out during excessively hot summers, and become receptive fuel for fire, especially during offshore wind events like the Santa Ana Winds. The 2017 and 2018 wildfire seasons are examples of escalating property losses from wildfire associated with average to wet winters followed by record-breaking heat during the summer months, which then extend into warm and dry autumn wind seasons, according to Alexander Van Dijk, President U.S. Branches, and Kimberly Roberts, North America Peril Advisory, Guy Carpenter.
While climate change amplifies processes leading to wildfire, increasing exposure and population vulnerability are the root cause of escalating property losses. In 2014, Drs. Walker Ashley (NIU) and Stephen Strader (Villanova University) coined the term “Expanding Bull’s Eye Effect.” Essentially “Targets”— humans and their possessions — enlarge as populations grow and spread. In the case of wildfire, urban areas grow and spread on their fringes, expanding the Wildland Urban Interface (WUI). These areas are often desirable aesthetically, but also risky, as the built environment encroaches on wildlands and vegetation conducive to burning. Significant building into wildlands compounds opportunity for extensive loss scenarios, where the wildland fire can transition into the built environment producing urban conflagration.
Much like an archer shooting their arrows (wildfire) at a target (development), as the target grows in size the odds of the archer hitting a bull’s eye (disaster) is increased. Ashley et al. 2014; Strader and Ashley 2015