JOHN WOINARSKI. Fire and nature

Jan 8, 2020

The future has come – and it is not good for Australia’s natural environments. Drought, heat waves and wildfire, all linked manifestations of climate change, have subverted (and continue to subvert) the viability of many of Australia’s species. Across vast areas, we are losing much of our nature

Impacts of the current drought and wildfires on families, towns, enterprises and the economy have been – and continue to be – devastating. Much less recognised is the cost to Australian wildlife, and the need for a strategic and immediate response to try to staunch and recover from these losses.

Australia’s biodiversity is resilient. Over long evolutionary history, our plants and animals have adapted to recurrent drought and fire. But we have pushed the system now to extremes, likely beyond the limits of many species. Our lamentable rate of extinctions – an ongoing loss of an average of four species per decade since 1788 – is poised to escalate.

Drought has long-lasting impacts on plants and animals. Since at least the Federation drought, observant landholders have noted local losses of many species in drought affected areas, often commenting the ‘bush fell silent’ as bird populations disappeared. The Federation drought contributed to the extinction of the paradise parrot, one of the most exquisite of our birds and the only bird species lost from mainland Australia. Even hardy species such as eucalypts are killed by drought. Many plants and animals need rainfall to trigger reproduction, so long-lasting droughts lead to demographic collapse, as no new recruits enter the population. As the intervals between successive droughts diminish, and droughts last longer, sustained or repeated lack of recruitment will lead to local extirpations and failure to recover. Where drought extends over large areas, as is the case now, these local losses compound. The impacts of drought may be especially evident for aquatic species – witness massive fish kills over the last year – but the losses are also far more insidious and unseen.

Much of Australia has experienced record maximum temperatures over the last year. Such heat wave conditions are beyond the thermal tolerance of many species. The most startling example was in 2018, when two days of plus-40oC temperatures in the Cairns area caused the death of about one-third of Australia’s population of the threatened spectacled flying-fox. Similar examples of mass die-offs in extreme heat have been recorded now for many species, including ring-tailed possums and black-cockatoos.

And now, largely as a consequence of long-lasting drought, we have fire, fire and more fire. This season’s wildfires are exceptional in their timing, extent, intensity and impacts on nature. Images of singed and fire-killed koalas have horrified the global community. But the tragic fate of these koalas is also symptomatic of losses of Australian wildlife more generally.

How much wildlife has been lost? One plausible estimate is that about 480 million individual native animals have been ‘affected’ by the fires in New South Wales alone, with this estimate based simply on average densities of birds, mammals and reptiles multiplied by the area burnt. Many to most of these ‘affected’ animals will have been killed immediately by the fire; many of those that somehow survived the fire will have died soon afterwards as their blackened territories are left with no food or shelter. And the ferocity of these fires has meant that, unlike ‘normal’ fires, there will be few unburnt patches (refuges) in which some fragment of the local population may have persisted within otherwise burnt areas. Not so self-evidently, these fires also affect wetland species, such as the threatened barred galaxias, as flow of rainwater across burnt areas leads to greatly reduced water quality.

These impacts are not short term only. Many of the habitat features needed by various animal species, such as tree hollows, hollow logs and a deep layer of leaf litter and mulch, may take many decades to be restored after fire. Furthermore, the impacts of fires also compound other threats: cats and foxes hunt more effectively in burnt areas, and the ‘green pick’ of post-fire regrowth may facilitate the spread and impacts of deer and other pests.

It is not the scale of wildlife mortality alone that is of concern. Of even more significance for conservation is the high degree of overlap between the distribution of many species and the extent of drought and wildfire. Koalas have extensive distributions. But many Australian plants and animals are much more restricted, and it is for these species that impacts may be most perilous. The entire range of more than 100 threatened species is now drought-affected. It is premature to derive comparable assessments for population-level impacts of the wildfires, given that the burnt area is continuing to increase. But there are some disconcerting examples. The long-footed potoroo exists only in small populations thinly scattered across a restricted area of east Gippsland, the nearby mountains and the far south coast of New South Wales. Many have worked with care and love for the conservation of this species over decades, through establishment of parks and intensive control of its predators. Its parlous state had been gradually improving. But these wildfires have been their nemesis – almost to have targeted the potoroo’s populations. It is unlikely to survive in burnt areas and its continued existence has suddenly become far more tenuous. There are many comparable cases, such as the Kangaroo Island dunnart, Kangaroo Island glossy black-cockatoo and silver-headed antechinus.

We should acknowledge and lament the losses of wildlife arising from drought, heat and fire. But tallying the deaths is not sufficient. There is an immediate need also for strategic response. Priorities may differ between areas and species, but actions should include a mix of fine-scale assessments to identify refuge (unburnt) areas, targeting the vicinity of these for pest animal control, monitoring, captive breeding, translocations, and conserving unburnt areas. These are remedial and responsive actions. But there are deeper causal issues that need to be addressed to minimise the risks of similar future disasters. Casting around for someone to blame, some authorities have named national parks as the scapegoat and claimed that these wildfires are due to the lack of hazard reduction burning. But evidence suggests that more fuel reduction burning would not have stopped these fires, that many wildfires originate from such control burns, and the season available for such controlled burning is rapidly diminishing. There is a role for fine scale and expert use of preventative fire, but there is a far more fundamental problem that needs to be addressed: climate change.

Many Australians choose to live in the bush, within nature. Following these fires, we must avoid the temptation to see our forests and woodlands as a menace. We cannot live well in this land with such an attitude.

John Woinarski is a professor of conservation biology at Charles Darwin University. He lost all his belongings in the Ash Wednesday fires.

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