Many of our plants and animals have adapted to fires, but now the fires are changing



Eucalypt seeds don’t fall far from the tree, meaning repopulating large areas of forest will be difficult.
from http://www.shutterstock.com

Cris Brack, Australian National University

Australia is a land that has known fire. Our diverse plant and animal species have become accustomed to life with fire, and in fact some require it to procreate.

But in recent decades the pattern of fires – also known as the fire regime – is changing. Individual fires are increasingly hotter, more frequent, happening earlier in the season and covering larger areas with a uniform intensity. And these changes to the fire regime are occurring too fast for our native flora and fauna to adapt and survive.




Read more:
Some say we’ve seen bushfires worse than this before. But they’re ignoring a few key facts


Our fire-adapted plants are suffering

Many of Australia’s iconic eucalypts are “shade intolerant” species that adapted to exist within a relatively harsh fire regime. These species thrive just after a major fire has cleared away the overstory and prepared an ash bed for their seeds to germinate.

Some of our most majestic trees, like the alpine ash, can only regenerate from seed. Those seeds germinate only on bare earth, where the leaf litter and shrubs have been burnt away.

But if fire is so frequent the trees haven’t matured enough to produce seed, or so intense it destroys the seeds present in the canopy and the ground, then even these fire-adapted species can fail.

The current fires are re-burning some forests that were burnt only a decade ago. Those regenerating trees are too young to survive, but also too young to have started developing seed.

With the disappearance of these tree species, other plants will fill the gap. Acacias (wattles) are potential successors as they mature much earlier than alpine ash. Our tall, majestic forests could easily turn into shrubby bushland with more frequent fires.

Wattles mature early and could take over Eucalypts.
from http://www.shutterstock.com

Even within a burnt area, there are usually some unburnt patches, which are highly valuable for many types of plants and animals. These patches include gullies and depressions, but sometimes are just lucky coincidences of the terrain and weather. The patches act as reserves of “seed trees” to provide regeneration opportunities.

Recent fires, burning in hotter and drier conditions, are tending to be severe over large areas with fewer unburnt patches. Without these patches, there are no trees in the fire zone to spread seeds for regeneration.

Eucalypt seed is small and without wings or other mechanisms to help the wind disperse it. Birds don’t generally disperse these seeds either. Eucalypt seed thus only falls within 100 – 200 metres of the parent tree. It may take many decades for trees to recolonise a large burnt area.

That means wind-blown or bird-dispersed seeds from other species may fully colonise the burnt area well before the Eucalypts. Unfortunately many of these windblown seeds will be weed species, such as African Love Grass, which may then cover the bare earth and exclude successful Eucalypt regeneration while potentially making fires even hotter and more frequent.

Animals have fewer places to hide

Young animals are significantly more vulnerable to disturbances such as fire than mature individuals. So the best time to give birth is a season when fire is rare.

Spring in the southern zones of Australia has, in the past, been wetter and largely free from highly destructive fires. Both flora and fauna species thus time their reproduction for this period. But as fire seasons lengthen and begin earlier in the year, vulnerable nestlings and babies die where they shelter or starve as the fires burn the fruits and seeds they eat.

Australian fauna have developed behaviours that help them survive fire, including moving towards gullies and depressions, climbing higher, or occupying hollows and burrows (even if not their own) when they sense fire.

Many native animals have learnt to sense fire and take cover, but with greater areas burning, there are fewer places to hide.
from http://www.shutterstock.com

But even these behaviours will fail if those refuges are uncharacteristically burning under hotter and drier conditions. Rainforest, marshes and the banks of watercourses were once safe refuges against fire, but we have seen these all burn in recent fires.




Read more:
Animal response to a bushfire is astounding. These are the tricks they use to survive


What can be done?

All aspects of fire regimes in Australia are clearly changing as a result of our heating and drying climate. But humans can have a deliberate effect, and have done so in the past.

Indigenous burning created a patchwork of burnt areas and impacted on the magnitude and frequency of fires over the landscape. These regular burns kept the understory under control, while the moderate intensity and patchiness allowed larger trees to survive.




Read more:
There’s no evidence ‘greenies’ block bushfire hazard reduction but here’s a controlled burn idea worth trying


There have been repeated calls of late to reintroduce Indigenous burning practices in Australia. But this would be difficult over vast areas. It requires knowledgeable individuals to regularly walk through each forest to understand the forest dynamics at a very fine scale.

More importantly, our landscapes are now filled with dry fuel, and shrubs that act as “ladders” – quickly sending any fire into tree canopies to cause very destructive crown fires. Given these high fuel conditions along with their potentially dangerous distribution, there may be relatively few safe areas to reintroduce Indigenous burning.

The changed fire conditions still require active management of forests, with trained professionals on the ground. Refuges could be developed throughout forests to provide places where animals can shelter and from which trees can recolonise. Such refuges could be reintroduced by reducing forest biomass (or fuel) using small fires where feasible or by mechanical means.

A Kangaroo Island landscape devastated by fire.
David Mariuz/AAP

Biomass collected by machines could be used to produce biochar or other useful products. Biochar could even be used to improve the soil damaged by the fires and excess ash.

Midstory species could be cut down to prevent the development of fire ladders to tree crowns. Even the overstory could be thinned to minimise the potential for crown fires. Seed could also be collected from thinned trees to provide an off-site bank as ecological insurance.

Such active management will not be cheap. But using machinery rather than fire could control biomass quantity and distribution in a much more precise way: leaving some biomass on the ground as habitat for insects and reptiles, and removing other patches to create safer refuges from the fires that will continue to come.The Conversation

Cris Brack, Associate Professor, Fenner School of Environment and Society, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia’s threatened bats need protection from a silent killer: white-nose syndrome



Three North American little brown bats with signs of white-nose syndrome, which is virtually certain to hit Australian bats without further action.
KDFWR/Terry Derting, CC BY-SA

Christopher Turbill, Western Sydney University and Justin Welbergen, Western Sydney University

We already know how deadly this summer’s fires have been for mammals, birds, and reptiles across Australia. But beyond this bushfire season, many of those same species – including our bats, which make up around a quarter of all Australian mammal species – are facing another devastating threat to their survival.

White‐nose syndrome has recently decimated bat populations across North America. While the fungal pathogen responsible for this disease, Pseudogymnoascus destructans, currently doesn’t occur in Australia, the fungus is virtually certain to jump continents in the next decade.

Our recent research, published in the journal Austral Ecology, attempted to quantify this risk – and the results are not encouraging. Up to eight bat species occupy caves in south-eastern Australia that provide conditions suitable for the fungus to grow.

Large parts of southern Australia provides cave habitat suitable for growth by the cold-loving fungus responsible for white-nose syndrome.
Turbill & Welbergen 2019

Even before this summer’s fires, seven of those types of bats were listed on state or federal legislation as threatened with extinction. This includes the critically endangered southern bent-winged bat (Miniopterus orianae bassanii), a species whose caves would all provide optimal conditions for growth of the fungus.

All caves occupied by the critically endangered southern bent-winged bat provide ideal thermal conditions for white-nose syndrome.
Dr Lindy Lumsden

Millions of bats wiped out in North America

White-nose syndrome was first detected in the United States in 2006 at a popular tourist cave in the state of New York. Since then, the disease has spread across North America, killing millions of bats in its wake, with many local populations experiencing 90 to 100% mortality.

The novel pathogen hypothesis explains why P. destructans has such catastrophic impacts on North American bats: the immune system of these species is evolutionarily naive to this fungal attack. Accordingly, in Europe and Asia, where P. destructans is endemic and widespread, few bats exhibit white‐nose syndrome and mortalities are rare.

Australia’s unique wildlife is inherently at risk from invasive novel pathogens because of its long‐term biogeographical isolation. Thus Australian bats, like their distant North American relatives, probably lack an effective immune response to P. destructans and would be susceptible to developing white-nose syndrome.

Since its detection in the United States in 2006, white-nose syndrome has received extensive media attention globally.

Hibernation is the key risk period

Most fungal pathogens grow best at cool temperatures, and a high body temperature in mammals and birds provides an effective barrier against fungal diseases. The fungus causing white-nose syndrome is also cold-loving, ceasing to grow at temperatures above 20°C. The only time it can infect and kill bats is when they hibernate.

Bats go cold (use torpor) during hibernation to prevent starvation over winter in temperate climates. Hibernating bats that are infected by P. destructans rewarm more frequently than normal. These unscheduled bursts of metabolic heat production prematurely burn up the body fat of overwintering bats. Hence, despite the damage caused by white-nose syndrome to the bat’s skin tissue, they apparently die due to starvation or dehydration.

The infection is easily visible under UV light.
Turner et al. 2014

Hibernation is key to predicting the susceptibility of bat populations to mortality from white-nose syndrome: those with less energy to spare over winter are more at risk. Consequently, white-nose syndrome has fuelled a large research program on the winter ecology and hibernation physiology of North American bats.

Bats in south-eastern Australia do enter a period of winter hibernation, but that is about the extent of what we know. This knowledge gap makes it impossible to predict how they will respond if exposed to P. destructans. Even non-lethal impacts, however, will worsen the extinction-bound trajectory of several cave-roosting species, most notably the eastern and southern bent-winged bats.

What can Australia do?

Given the impending arrival of P. destructans in Australia, and our study’s findings of widespread thermal cave suitability in south-eastern Australia, we urge immediate action. This includes tightening biosecurity measures and gaining missing information on bat biology so we are better prepared for a possible white-nose syndrome epidemic.

The importance of this threat has not been missed by Wildlife Health Australia, which has produced guidelines for reporting and response to incursion. Advice is also available from the Commonwealth. Just recently, white-nose syndrome was listed in the national priority list for exotic environmental pests and diseases, ranking in the top five of native animal diseases and their pathogens.

Cave enthusiasts have also been proactive in alerting members to white-nose syndrome and the risk of accidentally introducing P. destructans, especially when returning from overseas caving adventures. And the Australasian Bat Society – a strong advocate for bat conservation – has alerted the public and government agencies to this potential new threat.

Action now is critical

At present, there is little that would prevent P. destructans from making it its way to Australian caves, despite two years passing since experts assessed the risk of incursion as almost certain.

We need effective measures at all levels, from requiring incoming visitors to identify contact with cave environments, to decontamination procedures at caves popular with international tourists.

The US Fish and Wildlife Service’s White-nose Syndrome Response Team produced this infographic, including what you can do to help bats.

Predicting the impact of white-nose syndrome on Australian bats is currently not possible because we know so little about their winter biology. We urge the Australian government to fund specific research to gain this information.

The US Fish and Wildlife Service has injected more than US$46 million since 2008 into research and fieldwork to address the threat. Australian researchers can use this work to focus on the critical data needed to inform models that predict the vulnerability of local bat populations.

Why we need bats to survive

Bats are incredibly valuable in their own right. But the world needs healthy bat populations: a single insectivorous bat can eat up to half its body mass in insects each night, and together colonies of bats provide a service with an estimated value to the agricultural industry alone in the billions of dollars per year.

We hope this terrible disease will not threaten Australian bats. But the precautionary principle dictates we should plan and act now, assuming the worst-case scenario. Alarm bells are ringing.


Read more: The importance of Australia’s weird and wonderful batsThe Conversation


A selection of Australia’s bat diversity. Top row from left: grey-headed flying-fox; orange leaf-nosed bat; common blossom bat; large-footed myotis. Bottom row: golden-tipped bat; eastern horseshoe bat; common sheath-tailed bat; ghost bat.
Justin Welbergen (grey-headed flying-fox, eastern horseshoe bat); Nicola Hanrahan (ghost bat); Bruce Thomson (golden-tipped bat); Steve Parish & Les Hall for remainder of species

Christopher Turbill, Senior Lecturer in Animal Ecology, Western Sydney University and Justin Welbergen, President of the Australasian Bat Society | Associate Professor of Animal Ecology, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.