Altered fire patterns put species at risk
Bush and forest fires are critical to some ecosystems – but not always in a good way. Tanya Loos reports.
History, landscape fragmentation and invasive species interact to influence species distribution decline in landscapes susceptible to fires, say researchers writing in the journal Biological Review.
According to the International Union for the Conservation of Nature (IUCN), more than 1400 animal species are threatened by altered fire regimes, and the new analysis identifies animal movement as a key mechanism.
“We have long tried to understand why species are distributed as they are in fire-prone landscapes, but most of the current theories fall short of explaining these patterns,” explains lead author Dale Nimmo from Charles Sturt University in New South Wales, Australia.
“In this paper we have tried to consider the consequences of animal movement and how patterns of movement might change, and even become harmful, when habitats become fragmented, invasive species such as novel predators are introduced, or fire regimes change abruptly.”
In any given fire-prone ecosystem, parts of the landscape burn, whether due to natural ignition or human intervention, at different times, resulting in what ecologists call a “fire mosaic”. Correctly exploiting an area’s fire history is regarded as a critical component in managing it.
Different parts of a mosaic can be utilised by some species according to diet, habitat preference and other aspects of life history. For instance, zebras (Equus quagga) have been observed foraging in recently burnt areas at night, and then sheltering in unburnt shrubby, complex habitat by day to avoid ambush by lions (Panthera leo).
When fire regimes change – such as when an area is burnt too frequently, or at the wrong time of year, or with blazes that are too large in scale – then even animals that depend upon fire may be adversely affected. The loss of unburnt refuges that offer protection from predators, known as stepping stones, increases the risk of predation.
Inappropriate fire regimes may result in patches of optimal habitat being spread too far apart, increasing travel time for dependent species. The change in the landscape can also induce disorientation in some creatures. Both outcomes mean animals spend more time in the open, placing them at greater risk of predation.
In Australia, indigenous communities used fire to manage landscape for thousands of years, but the practice was almost totally disrupted after the arrival of European colonists in the late eighteenth century.
The loss of such fine-grained mosaic burning has been suggested as the reason for the decline of at least one marsupial species, the mala, or rufus hare-wallaby (Lagorchestes hirsutus), which is now confined to two island populations. Researchers think its mainland extinction was caused, at least in part, by loss of fire-formed habitat.
In compiling the latest review, Nimmo was assisted by a large team of researchers from Australia, the US, the UK and South Africa. The scientists found that firm conclusions regarding the combined effects of altered fire regimes and threats arising from introduced species require the collection of much more data.
They call for the use of emerging technologies such as drones to capture high-resolution spatial fire datasets, luminescent tags to assess small mammal foraging and habitat selection, and remotely triggered cameras and bio-acoustic recorders to capture occurrence data.
“Answering the questions we pose will require fire ecologists and movement ecologists to work together, using both established and emerging technologies to quantify animal movement in relation to fire history,” Nimmo’s team concludes.