Could biodiversity loss have increased Australia's bushfire threat?

Abstract

Ecosystem engineers directly or indirectly affect the availability of resources through changing the physical state of biotic and/or abiotic materials. Fossorial ecosystem engineers have been hypothesized as affecting fire behaviour through altering litter accumulation and breakdown, however, little evidence of this has been shown to date. Fire is one of the major ecological processes affecting biodiversity globally. Australia has seen the extinction of 29 of 315 terrestrial mammal species in the last 200 years and several of these species were ecosystem engineers whose fossorial actions may increase the rate of leaf litter breakdown. Thus, their extinction may have altered the rate of litter accumulation and therefore fire ignition potential and rate of spread. We tested whether a reduction in leaf litter was associated with sites where mammalian ecosystem engineers had been reintroduced using a pair-wise, cross-fence comparison at sites spanning the Australian continent. At Scotia (New South Wales), Karakamia (Western Australia) and Yookamurra (South Australia) sanctuaries, leaf litter mass (À24%) and percentage cover of leaf litter (À3%) were significantly lower where reintroduced ecosystem engineers occurred compared to where they were absent, and fire behaviour modelling illustrated this has substantial impacts on flame height and rate of spread. This result has major implications for fire behaviour and management globally wherever ecosystem engineers are now absent as the reduced leaf litter volumes where they occur will lead to decreased flame height and rate of fire spread. This illustrates the need to restore the full suite of biodiversity globally.

Impacts and management of feral cats Felis catus in Australia

“…The volume of flammable surface litter is greater at sites without reintroduced mammals than at matched control sites with them Hayward et al. . Abundant surface litter may increase the frequency and/or intensity of fires (Hayward et al.…”

“…Abundant surface litter may increase the frequency and/or intensity of fires (Hayward et al. ), thus affecting plant and animal communities.…”

Bioturbation by a reintroduced digging mammal reduces fuel loads in an urban reserve

“…Hayward et al. () also found reduced litter mass and litter cover inside large reserves where multiple digging mammal species had been reintroduced. Our results indicate that, within a short time frame (<4 yr since reintroduction, 3 yr since fence construction), the successful translocation of a single digging mammal species can alter surface fuel load characteristics in an urban area.…”

“…The role of digging animals in altering fuel loads and influencing fire has largely been overlooked; but the loss or decline of many native vertebrates may have subsequently altered fire regimes in landscapes (Hayward et al. , Johnson et al. ).…”

“…The FFDI using the Keetch‐Byram Drought Index (KBDI; Keetch and Byram ) for soil moisture component is used for evaluating fire danger in Australia (Lucas , Kumar and Dharssi ) and was previously used to assess fire behavior in a large reserve with reintroduced digging mammals in semiarid habitat (Hayward et al. ).…”