Mega fires mega study: Deakin leads huge research effort into the impact on biodiversity after a bushfire

A mega study involving over 100 scientists has uncovered some startling findings into how the megafires that tore through Australia's forests in 2019-2020 impacted animals and plants.

As per The Conversation, the world-first research - published today in the journal Nature - is led by Deakin University's School of Life and Environmental Sciences Professor Don Driscoll.

'The reality of those megafires is that they burnt more than ten million hectares,' said Professor Driscoll. 'This tragedy prompted a massive research effort to understand how one single fire season affected the biodiversity of those animals and plants, including why some species declined, while others increased after the fires.'

Data of more than 1300 animal and plant species was gathered and analysed over three years.

Importantly, the results depended strongly on the condition of the land before the fire – especially how frequently it had been burned before the megafires occurred.

'These findings have profound implications for how Australia manages its natural environments,' said Professor Driscoll. 'Authorities often use frequent fuel-reduction burning to prepare for bushfires – however our findings suggest this primes ecosystems for major disruption when the next wildfire hits.'

After Australia's 2019-20 fires, an estimated 900 plant and animal species were severely impacted or put at heightened extinction risk from future fires. In response, government and non-government organisations allocated hundreds of millions of dollars for field-based monitoring and recovery.

'We collated 62 sets of data involving 810,000 records of the presence, absence or abundance of species in burnt and unburnt sites,' said Professor Driscoll. 'It covered 1380 species including frogs, reptiles, birds, mammals, insects, land snails and plants.'

The records were collected along more than 1000 kilometres of Australia's east coast, plus sites in South Australia and Western Australia. The researchers found 55% of species declined after the 2019-20 megafires – either because they were less abundant overall or occupied fewer sites.

'Species in areas exposed to frequent or recent past fires struggled the most,' said Professor Driscoll. 'Sites that experienced three or more fires in the 40 preceding years experienced declines up to 93% larger than with sites not burnt or burnt once over the same period.

Too-frequent bushfires can mean plants don't have enough time between fires to set seeds. They can also wipe out valuable habitats such as logs, dead trees and tree hollows. Among the animal and plant groups that we examined, mammals were the most sensitive, showing average declines twice as large as other groups.

They may be too large to shelter in small places, cannot fly to escape the flames, and naturally require more food because they are warm-blooded.'

However, some 45% of species were more commonly found in burnt sites after the megafires. The size of increases generally mirrored the size of declines in other species under the same conditions.

The most important example relates to fire frequency. Sites burnt frequently experienced both the largest declines and largest increases after the 2019-20 fires.

'There are several ways frequent fire before the megafires could allow species to increase,' said Professor Driscoll. 'Species that re-establish quickly after a fire could have large populations before the next fire. And if individuals do survive a fire, their living conditions may become easier if, say, their predators did not survive, or there is less competition from other animals for resources.

Also, some plants may become increasingly abundant after each successive fire, such as grasses, benefitting animal species that eat or shelter in them.

This is not to say that megafires are good for biodiversity overall, or that more abundant species balance out the losses.

The species that do well after fire will continue to thrive as recently burnt areas become more common. That's great, but the declining species will become an increasingly severe problem for conservation.'

The research team says a rethink of bushfire management is urgently needed.

'Bushfire management agencies aim to reduce fire risks through frequent fuel-reduction burning,' said Professor Driscoll. 'This involves deliberately burning blocks of native vegetation at relatively short intervals, to reduce flammable materials such as plants, fallen branches, logs, twigs, leaves and bark.

Our research suggests this practice, which increases fire frequency, may create larger disruptions to ecosystems when big bushfires occur. Even if a bushfire is not particularly severe, the harm to plants and animals can be extreme when sites have been burnt three or more times over 40 years, or within the ten preceding years.

So frequent fuel-reduction burning, combined with any other preceding bushfires, condemns many plants and animals to large, potentially catastrophic declines in the next bushfire.'

This could include developing the skills and technologies to rapidly detect and suppress bushfires. It may also involve supporting Indigenous "right-way fire" - a culturally informed method of fire management.

'In good news, we found severe bushfire impacts could be moderated if a lot of unburnt habitat exists within 2.5 kilometres. This allows plant seeds and animals to move from unburnt to recently burnt habitats, helping the damaged area to recover.

Fire managers should protect remaining unburnt patches after fire, rather than the current practice of burning them, to prevent later flare-ups.

At the end of the day, the alternative fire management approaches we suggest will likely fail if climate change continues unabated.'

The full TC article can be read here: ‘Catastrophic declines’: massive data haul reveals why so many plants and animals suffer after fire