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

Abstract

Digging animals may alter many characteristics of their environment as they disrupt and modify the ground's surface by creating foraging pits or burrows. Extensive disturbance to the soil and litter layer changes litter distribution and availability, potentially altering fuel loads. In many landscapes, including peri‐urban areas, fire management to reduce fuel loads is complex and challenging. The reintroduction of previously common digging animals, many of which are now threatened, may have the added benefit of reducing fuel loads. We experimentally examined how the reintroduction of a marsupial bandicoot, quenda (Isoodon fusciventer), altered surface fuel loads in an urban bush reserve in Perth, Western Australia. Foraging activities of quenda (where they dig for subterranean food) were substantial throughout the reserve, creating a visibly patchy distribution in surface litter. Further, in open plots where quenda had access, compared to fenced plots where quenda were excluded, quenda foraging significantly reduced litter cover and litter depth. Similarly, estimated surface fuel loads were nearly halved in open plots where quenda foraged compared to fenced plots where quenda were absent (3.6 cf. 6.4 Mg/ha). Fire behavior modeling, using the estimated surface fuel loads, indicated the predicted rate of spread of fire were significantly lower for open plots where quenda foraged compared to fenced plots under both low (29.2 cf. 51.4 m/h; total fuels) and high (74.3 cf. 130.4 m/h; total fuels) fire conditions. Although many environments require fire, including the bushland where this study occurred, fire management can be a considerable challenge in many landscapes, including urban bushland reserves, which are usually small and close to human infrastructure. The reintroduction of previously common digging species may have potential value as a complimentary tool for reducing fuel loads, and potentially, fire risk.

Applying Population Viability Analysis to Inform Genetic Rescue That Preserves Locally Unique Genetic Variation in a Critically Endangered Mammal

“…Many threatened wildlife species have highly disjunct distributions with little to no natural gene flow between populations, and translocations are critical for their long-term demographic and genetic stability [21]. Reintroducing populations within the historical range of a species or establishing populations beyond the historical range in low-threat areas (such as predator-free islands or reserves) are increasingly common [30,56,57]. Using predictive models to guide the founding of isolated populations with ongoing translocations is critical to maximising species-wide genetic variation [58].…”

Fire and biodiversity in the Anthropocene

“…Experimental evidence indicates that removal of large grazing mammals in Africa and North America alters ecosystem structure and increases fire activity (57). Indeed, our review of IUCN Red List data indicates that modification of fire activity has contributed to the recent extinction of 37 species, including a suite of fossorial marsupials in Australia whose digging activity influences fire regimes (58).…”

“…Reintroduction of species that have key functional roles offers an innovative opportunity to promote ecological processes that moderate fire regimes (57). For example, the reintroduction of a digging marsupial (Isoodon fusciventer) in an urban reserve in Western Australia led to significant reduction of surface fuel loads and the predicted rate of fire spread (58). Digging animals modify fuels by creating foraging pits and burrows: the reintroduction of previously common digging species is an exciting prospect for restoring fire-prone ecosystems (58).…”

“…For example, the reintroduction of a digging marsupial (Isoodon fusciventer) in an urban reserve in Western Australia led to significant reduction of surface fuel loads and the predicted rate of fire spread (58). Digging animals modify fuels by creating foraging pits and burrows: the reintroduction of previously common digging species is an exciting prospect for restoring fire-prone ecosystems (58). In Africa, reintroducing native grazing animals like White Rhinoceros (Ceratotherium simum) creates patchy fire regimes (57).…”

What can we learn from wildlife sightings during the COVID‐19 global shutdown?

“…Relative to many ecological and evolutionary timescales, the impact of the shutdown may only be a blip on the radar. Perhaps an uptick in movement of urban wildlife will temporarily boost gene flow among wildlife populations or help species re‐establish on isolated islands of urban green space, resetting some equilibria (Ryan et al 2020). If changes in body condition, reproduction, and survival of wildlife occur because animals are better able to exploit the urban environment during the shutdown, this might lead to population‐, community‐, or ecosystem‐level processes in the following year such as increased population sizes or altered trophic dynamics (Shochat et al 2006).…”