Optimising fire and predator management for conservation

Interactions between threatening processes compound and accelerate
biodiversity decline. Conservation managers need to understand how
co-occurring threats interact and account for such interactions when
prioritising when, where, and how to manage landscapes to recover
declining species. Using the Upper Warren region in south-western
Australia as a case study, we develop a framework for identifying optimal
fire age classes while also considering predation by introduced red foxes
(Vulpes vulpes) – two co-occurring processes affecting the recovery of a
threatened faunal community (woylie Bettongia penicillata, chuditch
Dasyurus geoffroii, quenda Isoodon fusciventor, and numbat Myrmecobius
fasciatus). We fitted a multi-species relative abundance model to a
dataset from 548 camera trap sites and tested for associations between
each species’ relative abundance and an interaction between fox baiting
intensity and time since fire. We then used linear programming
optimization to identify the optimal distribution of time since fire
values across the study region that maximizes the abundance of four focal
species under alternative fox baiting intensity and fire severity
scenarios. Fire and baiting both influenced the relative abundance of the
four species in our study, with baiting intensity having a positive
association with woylie relative abundance. The optimal distribution of
time since fire values across the study region varied with the intensity
of fox baiting. The importance of older fire ages increased in some
locations when fox baiting intensity was high, but these results were
highly uncertain and varied spatially. High fox baiting intensities
combined with optimal fire age distributions also led to a higher relative
abundance of three focal species overall, namely woylie, quenda, and
numbat. Our study demonstrates an end-to-end framework for using field
data to derive optimal fire regimes for biodiversity in a way that
explicitly acknowledges uncertainty and remains useful for conservation
decisions. Approaches such as these are essential for managing ecosystems
with compounding threats to biodiversity.