In a paper published in the international journal Diversity & Distributions, researchers from the Department of Biological Sciences looked at over 50 years of bushfire data to discover how long it takes plant species to bounce back from being burnt. They found that shortening intervals between fires are threatening the survival of 595 plants, including iconic banksia, wattle and grevillea species only found in Australia.
While many Australian plants species have adapted to regenerate after fire given enough recovery time, frequent burning disrupts this cycle. Following the 2019-2020 megafires, which impacted the habitat of 69 per cent of all plant species in Australia, for 257 plants, the interval since the previous fire was predicted to be too short to allow them to recover effectively. For a further 411 species, fires in coming summers will be too soon to allow regenerating or immature plants to set new seed.
For annual species – like many grasses and herbs – fires within the last five years are considered too soon to allow regeneration, whereas for perennials – such as shrubs and trees – at least a 15-year window is required to allow effective regrowth. Some trees will need up to 50 years free from fires to recover.
Lead researcher, Dr Rachael Gallagher from the Department of Biological Sciences, says prescribed burning regimes need to be designed to consider the different timeframes required for plants to recover in order to protect threatened species.
“Frequent fires are creating conditions that could completely change the type of vegetation and wipe out some of the oldest lineages of plants we have – and we found that this threat is widespread across the country,” says Dr Gallagher.
“Although we’re seeing reshooting from the burnt trunks of eucalypts across the fire grounds, many plants can’t recover in this way and require seedlings to germinate in the rich, post-fire soil to maintain their populations.
Frequent fires are creating conditions that could completely change the type of vegetation and wipe out some of the oldest lineages of plants we have.
“For these species, a fire that burns the immature recovering plants is a major concern. Resprouting species like eucalypts are also vulnerable to short intervals between fires, as they need time to build up the resources needed to withstand the next fire.”
“Different fire regimes are required to maintain ecosystems across the country; there is no one-size-fits-all approach to the use of management approaches like prescribed burning. However, using information such as the likely recovery window of species when we plan and carry out prescribed burning will be vital to protecting species from extinction, especially as we expect to see increasing fire activity due to the changing climate.”
The paper High fire frequency and the impact of the 2019–2020 megafires on Australian plant diversity can be openly accessed here: https://onlinelibrary.wiley.com/doi/full/10.1111/ddi.13265