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Habitat Highways Save Animals from Fire

Credit: Andrés Castañeda

A hazard reduction burn is carried out in mallee vegetation. This is often labelled as “ecological fire management” but hazard reduction and ecosystem management need different burning approaches to protect species. Credit: Andrés Castañeda

By Annabel Smith

Fire can act in a similar way to habitat fragmentation and restrict the movement of animals across the landscape.

Following the “Black Saturday” wildfires in 2009, the Victorian Government introduced a 5% annual controlled burning target to the entire public estate in Victoria. The South Australian Government followed suit, also adopting a 5% controlled burning target for public land at high risk.

However, there is growing consensus among the scientific community that these policies will neither protect lives and property nor conserve biodiversity. There is no scientific justification for the 5% target.

To meet this target, burning programs often occur across large patches within nature reserves rather than focusing on fuel loads within 100–200 metres of houses. As a result, controlled burning will have little impact on housing losses during bushfire. Instead, sensitive ecological communities could be harmed.

Australia has a long history of fire, and many plants and animals are adapted to a particular frequency, intensity, size and timing of fire. This fact is often used to justify hazard reduction burning in nature reserves. Management agencies even state that hazard reduction burning not only protects lives and property but also conserves biodiversity.

Our research, however, suggests that this view is too simplistic. We found that fire can act in a similar way to habitat fragmentation, restricting the movement of animals across the landscape.

Animal Movement after Fire

Understanding how fire affects the movement of animal species requires scientific data from the field. Unfortunately, animal movement is notoriously difficult to study.

GPS and radio tracking systems are great, but their size and weight means they can only be attached to large animals. Most animals in Australia’s ecosystems are tiny. For example, the majority of desert lizards weigh less than 20 grams and tracking these tiny critters is very difficult.

So how can we understand how animals move after fire? Our research took a multi-pronged approach, using the starred knob-tailed gecko (Nephrurus stellatus) as a model species.

The knob-tailed gecko is a fire specialist. It lives in the mallee woodlands of southern Australia, where severe wildfires occur every 40–100 years. The species has a strong response to fire: population density increases for 10–15 years after fire then declines sharply, so populations decline to less than 10% of peak density in habitat that has not been burnt for 30 years.

Knob-tailed geckos are burrowers, so many of them probably survive fire. Recently burnt habitat is ideal as they forage for invertebrate prey in open, sandy spaces. The abundance of their insect food also increases after fire, making burnt habitat prime knob-tail real estate.

Our research on this species examined whether reduced ability to move about as the burnt habitat regenerated also contributed to their decline with time since fire.

We installed hundreds of pitfall traps in the ground to capture geckos in recently burnt and long-unburnt vegetation. When geckos were captured, we implanted a small elastomer mark under the skin that glows under ultraviolet light.

Geckos were then released back into the wild at their capture location. When geckos were recaptured, the glowing mark allowed us to identify the individual and calculate how far it had moved.

Landscape Genetics

Using sophisticated landscape genetics analysis, we looked at how different patterns of fire affected movement. Differences in genetic patterns give insights into how much gene flow and movement occurs between populations.

Theoretical models of movement and genetic diversity were also used to make the findings broadly relevant to other species. Information gathered in the field and the genetics lab was fed into computer-based models to discover how different patterns of fire affected movement. This also gave insights into how fire affected population demographics such as survival, reproduction and population density.

Overall, the study took 11 years to complete, from initial trips to the bush to lab work, analysis and publication in Proceedings of the Royal Society of London B (http://tinyurl.com/h3jahnk). It was the first study to specifically examine how fire affects the movement of animals in a continuous habitat.

How Much Did Fire Affect Movement?

We found that knob-tailed geckos moved further in recently burnt vegetation. Their movement declined as the habitat became more complex with time since fire. In the case of these geckos, a lack of fire would restrict movement, meaning that some level of fire in the landscape is necessary.

The immediate impacts of the fire included mortality, rapid population expansion from a very small number of individuals and reduced survival, all of which shaped genetic patterns very soon after fire.

Our computer-based models suggested that demographic processes drove genetic patterns in the short term (up to 4 years), while movement had a greater influence in the long-term (4–30 years).

The strong response to fire in knob-tailed geckos allowed us to compare movement in different habitats. Unfortunately, many species are adversely affected by fire and are only found in old-growth vegetation. Previous research on these species found that genetic diversity and movement are highest in old-growth vegetation – the opposite pattern to what we observed in knob-tailed geckos.

Overall, this means that ecological fire management is important to ensure that species like the knob-tailed gecko can move through their burnt habitat. However, it’s also critical that different stages of vegetation remain connected via “habitat highways” so that the wide range of species in the ecosystem will continue to move and reproduce after fire.

Habitat Highways

Habitat fragmentation has profound consequences for species. It limits movement, which reduces genetic diversity and the potential for plant and animal species to adapt to environmental change. This means that when hazard reduction burning is carried out across large stretches of vegetation, animals could struggle to move and find breeding partners.

Our findings do not call for an end to hazard reduction burning but they do give us some guidelines about where to go from here.

First, we need to think about hazard reduction for urban protection in a separate category to burning for biodiversity conservation. Controlled burning for asset protection is most effective when it is strategically focused on reducing hazards within 100–200 metres of urban areas.

For biodiversity conservation, careful consideration must be given to the size and shape of controlled burns in addition to their frequency. “Habitat highways” are needed where different stages of habitat remain connected during fire to ensure that species can move through their habitat. Most importantly, controlled burning targets based on area must be avoided in order to protect plant and animal species.


Annabel Smith is a postdoctoral researcher in the Zoology Department at Trinity College Dublin, and Visiting Fellow in the Research School of Biology at the Australian National University.