Jess Marsh
Bulletin

Small animals, big consequences: the impacts of bushfires on Australia’s invertebrate species

Jess Marsh (Charles Darwin University and South Australian Museum), Payal Bal (University of Melbourne ) and John Woinarski (Charles Darwin University)

Much attention has been given to the impacts of the recent bushfires on Australia’s iconic vertebrates. Species such as the koala and the mountain pygmy possum have become the public image for the impacts of fire on Australia’s wildlife. However, far less coverage has been given to the plight of invertebrates, the little powerhouses of Australia’s biodiversity. Yet this group contains some of Australia’s most threatened species and those that are at highest risk of extinction following fire. 

Fire impacts on invertebrates 

Over 90% of the world’s animal species are invertebrates. They are highly diverse, abundant and perform crucial functional roles in the ecosystem—as detritivores, pollinators, herbivores, food for vertebrates, and food for each other. Invertebrates are essential for ecosystem function, and it is important to understand the impacts of the fires on them, and which species are now at most risk of extinction. 

Ecological or life history traits significantly impact a species’ susceptibility to fire. Species at particular risk of extinction are short range endemic taxa whose highly restricted distributions, reliance on specialist habitat and low dispersal abilities mean that a fire event could feasibly impact a species’ entire range and population. 

The Kangaroo Island micro-trapdoor spider (Moggridgea rainbowi) is endemic to Kangaroo Island, the species known range was heavily impacted by fire. (a) adult female; (b) pre-fire, young spider in a burrow (which they share with the female); (c) burnt burrow. Credit: Jess Marsh.

This unfortunately happened with the Kangaroo Island Assassin Spider, only known from one conservation reserve on Kangaroo Island, and that reserve was burnt in 2020 in its entirety by high severity fire.

Specific ecological traits, for example living in litter or vegetation, can increase a species’ vulnerability to fire. However, to add to the challenges of understanding fire impact on invertebrates, traits can vary with life stage. Take for example the cicada, which as larvae may spend years underground, protected from fire; but as adults, live on vegetation and are more vulnerable. Surviving the initial fire impact is also only one element in post-fire survival. Fire-induced changes to the ecosystem, such as incineration of the understorey, are likely to alter food supply, increase exposure to predation, to fluctuations in temperature and relative humidity, and therefore to desiccation (to which many invertebrates are highly vulnerable). 

The task of elucidating the impact of fires on invertebrates is large and complex. A key challenge is the vast number of undescribed species – for these species we have no robust way of knowing how many may have gone extinct, or are on the verge of extinction. Even for described species, the challenges are formidable. A shortage in funding for invertebrate research, a paucity in surveys and a scant taxonomic workforce has resulted in a shortfall in scientific knowledge on what species we have, their diversity, distribution, ecological roles, or conservation risk. This coupled with the sheer number and diversity of species means that pre-fire baseline data for many species is patchy and based on limited, often historical records. 

A way forward: prioritising species and assessing fire susceptibility 

With funding from the Australian government, a new National Environmental Science Program project was developed to tackle some of these challenges, elucidate the impact of the 2019 / 2020 bushfires on Australia’s invertebrate species, and help recover the affected species. Our project is a continuation of a preliminary post-fire impact project, which developed a list of nearly 200 priority invertebrate species for bushfire recovery. Species distribution data, drawn from a range of private and public data sources, will be compiled to identify invertebrate species occurring in bioregions impacted by fire. Species that have not been formally described, but are classified to morphospecies and linked to a physical specimen will be included in analyses, increasing the range of species to be assessed. Distributions will be mapped and modelled (where possible) and overlaid with estimated fire extent and severity. The insights drawn will be further improved by incorporating ecological and life-history trait analyses and expert assessments. 

The Kangaroo Island robust fan-winged katydid (Psacadonotus insulanus). IUCN listed and endemic to Kangaroo Island, most of its known range was impacted by fire. Credit: R. Glatz.

In order to achieve the best conservation outcomes this project will be highly collaborative, seeking crucial input from experts and relevant ecological and entomological societies in Australia, working closely with state and federal bodies and data holders. To aid protection of the most vulnerable fire-affected species, support will be provided for the submission of nominations for eligible species to be assessed for listing as threatened under the EPBC act. 

Key outcomes of the project will be a justified and prioritised list of invertebrate species impacted by fire, the identification of post-fire threats to recovery, and the development of advice on threat management actions most needed for priority species to achieve recovery. Mapping will be used to identify fire-impacted ecological communities that are likely to be of importance for invertebrate endemism or diversity. In some cases, these data will be used to inform listings of ecological communities as priorities for protection and thereby conserving the range of species within. The findings of the project will lead to a greater understanding of the impact of fire and the subsequent conservation needs of Australia’s fire-impacted invertebrates. 

For more information, contact Jess (jess.marsh@cdu.edu.au).

Read more from the September 2020 edition of the ESA Bulletin.