A team of researchers from La Trobe University has found more than 60 billion invertebrates living in temperate rainforests were incinerated during catastrophic bushfires in NSW and Victoria 2019-2020.
The Black Summer fires burned over 10 million hectares of land in southern Australia but devastated the ecology of rainforests and forest floors.
In Australia, rainforests account for only 1% of all forests and approximately 70% of invertebrates in these ecosystems are undescribed by science. This means the extent of the disruption caused by natural disasters such as fires often goes unknown.
La Trobe University’s Professor Heloise Gibb said the findings of major invertebrate loss were significant because insects were a vital food source for many other species.
“Iconic birds like lyrebirds, as well as lizards and small mammals heavily rely on litter invertebrates for sustenance,” Gibb said.
“Furthermore, invertebrates facilitate decomposition by breaking down litter, making it easier for microbes to decompose.”
Gibb noted that without vertebrates the process of breaking down litter to facilitate decomposition potentially set the stage for more dangerous fires in future. This was because it allowed longer-lasting combustible litter to accumulate.
The study surveyed 52 sites in East Gippsland and southern NSW, encompassing rainforest areas in gullies along the coast.
Gibb explained various methods were used in the study to compare burnt and unburnt areas to assess the effects of the bushfires on invertebrate populations. This included using traps to extract insects from the litter to undertake a “comprehensive examination” of the invertebrate community.
“Due to the exceptionally intense nature of recent fires, many of these rainforests were severely affected.
“Even a year after the fires, we observed distinct changes in habitat composition, with a significant decline in litter invertebrates in the severely burnt sites,” she said.
Because of the nature and distribution of invertebrates in Australia’s rainforests, estimating the impact of fires at the species level is incredibly complex. These environments typically are not subject to severe burns like those of the summer of 2019-2020.
The research team estimate approximately 75% of invertebrate abundance in rainforests was affected by severe bushfires.
“This loss has far-reaching implications for the persistence of species in these areas and poses a significant threat to the functioning of ecosystems in the short term,” Gibb said.
“Invertebrates play a crucial role in decomposition and nutrient cycling, and their absence can disrupt these essential processes.”
The observational study was published in the journal Austral Ecology.
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