Using bioregional variation in fire history and fire response attributes as a basis for managing threatened flora in a fire-prone Mediterranean climate biodiversity hotspot

Abstract

Inappropriate fire-regimes brought about by patterns of human settlement and land-use threaten plant diversity in Mediterranean-type climate (MTC) regions. In south-west Western Australia (SWWA), where there are many threatened plant species distributed across a range of human-modified landscapes, there is a need for approaches to identify where the threat is greatest. This requires knowledge of contemporary fire regimes, how they vary across landscapes, and the sensitivity of threatened species to these regimes. Currently, this information is lacking, and this limits strategic fire management. In this study we compiled fire response information for SWWA’s threatened plant species and undertook a bioregional assessment of variation in fire interval over the last 40 years. We determined the fire response traits of 242 (60%) of the region’s 401 extant threatened species. Over half of the 242 species were obligate seeders and will therefore have population dynamics particularly sensitive to fire interval. Our study highlights large differences in fire interval across nine bioregions in SWWA. The differences were greatest for the heavily cleared and fragmented bioregions compared with more continuously vegetated bioregions. We discuss how variations in the frequency of fire life-history traits and fire interval interact to determine the nature and relative level of threat posed by fire in these landscapes. Survival of many populations of threatened flora in this biodiversity hotspot will depend on developing appropriate fire regimes that match the regeneration requirements of each species.