Fire is a globally important driver of ecosystem composition, structure and function

In fire-prone landscapes, appropriate fire management may help bring native mammals back from the brink of extinction. In a new paper, Shaw et al. use prescribed burning to understand how small mammal populations recover after fire, so that recovery mechanisms can be incorporated into management strategies.

Fire plays a pivotal role in ecosystems around the world, influencing where species are found, their abundance in the landscape, and the life history strategies that evolve.

Population dynamics are shaped by fire. However, we know surprisingly little about the underlying process by which animal populations recover after fire, and how the characteristics of a fire might help or hinder this process. This information is crucial for fire-mediated biodiversity conservation.

Northern Australian mammal populations are collapsing

In the fire-prone savannas of northern Australia, we are seeing the broad-scale decline and local extinction of many mammals that were once common.

The interaction between extensive, high intensity wildfires, predation by feral cats and grazing by introduced herbivores is likely a key factor in this widespread population collapse. Fire management is considered one of the most tractable actions we can take to conserve our mammal fauna.

Shaw image 2
Pale field rat (Rattus tunneyi). Photo: I Garcia Celada / AWC

Exploring the recovery process through fire experiments

In our study, we used a fire experiment to understand the mechanisms that drive population recovery in the pale field rat (Rattus tunneyi), a native rodent that represents the extinction process for many small mammals in Australia’s northern savannas.

We trapped pale field rats across the Australian Wildlife Conservancy’s Mornington Wildlife Sanctuary. Using prescribed burning, we then implemented different types of fire, from patchy, low severity fires (to represent early dry season management burns) to thorough, high severity fires (representing wildfires).

Shaw image 3
Implementing a high-intensity prescribed burn. Photo: G Cary/ AWC

Immediately after fire, pale field rats were only captured in unburnt patches of their preferred vegetation (with almost no animals captured in thoroughly burnt sites).

One year later, both vegetation and pale field rat populations recovered. However, the mechanism driving population recovery was different depending on the spatial characteristics of the prescribed burn.

Recovery after low severity fires stemmed from the animals that survived in unburnt habitat patches, whereas sites that were burnt with high severity fire were recolonised by animals from outside of the burnt area.

Shaw image 4
Aerial photographs of two sites before fire (with vegetation mapping), and after fire (with fire scar mapping). Sites represent a patchy (burn cover 50%) burn.

How can fire management support the recovery of vulnerable populations?

When planning prescribed burns, we need to consider not just the immediate consequences of fire, but how we can use fire to support resilient landscapes that facilitate the recovery process. We can only do this by understanding the mechanisms that drive the recovery process.

Our study suggests that management strategies that help retain unburnt habitat patches within fire affected areas will benefit pale field rats, by supporting the persistence of pale field rats within burnt areas and facilitating population recovery in previously burnt habitat.

Globally, building recovery mechanisms into fire management will be vital for supporting the long-term persistence of fire-affected species

Read the full paper Unburnt habitat patches are critical for survival and in situ population recovery in a small mammal after fire in Journal of Applied Ecology.

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