Effects of large herbivores on fire regimes and wildfire mitigation

1. Abandonment of agricultural land is widespread in many parts of the
world, leading to shrub and tree encroachment. The increase of flammable
plant biomass, i.e. fuel load, increases the risk and intensity of
wildfires. Fuel reduction by herbivores is a promising management strategy
to avoid fuel build-up and mitigate wildfires. However, their
effectiveness in mitigating wildfire damage may depend on a range of
factors, including herbivore type, population density and feeding
patterns. 2. Here we review the evidence on whether management with
herbivores can reduce fuel load and mitigate wildfires, and if so, how to
identify suitable management that can achieve fire mitigation objectives
while providing other ecosystem services. We systematically reviewed
studies that investigated links between herbivores, fire hazard, fire
frequency and fire damage. 3. We found that in general, herbivores reduce
fuel load most effectively when they are mixed-feeders, when grazing and
browsing herbivores are combined, and when herbivore food preferences
match the local vegetation. In some cases, the combination of herbivory
with other management strategies, such as mechanical clearing, is
necessary to reduce wildfire damage. 4. We conclude that herbivores have
the capacity to mitigate wildfire damage, and we provide guidance for
grazing management for wildfire mitigation strategies. As areas undergoing
land abandonment are particularly prone to wildfires, the maintenance or
promotion of grazing by domestic or wild herbivores is a promising tool to
reduce wildfire risk in a cost-effective way, while also providing other
ecosystem services. Relevant land-use policies, including fire-suppression
policies, agricultural and forest(ry) policies could incentivise the use
of herbivores for better wildfire prevention.