New paper: we don’t know how extreme fire impacts Australian invertebrates

Really happy to see our new paper is now published at Insect Conservation and Diversity.

We present an evidence-based perspective to show how invertebrates, and the ecosystems they support, face major threats as fire severity and frequency intensifies in response to global climate change. Our capacity to make effective decisions about ecosystem recovery and restoration funding after bushfires is hampered by the lack of knowledge on how invertebrates are impacted by fire, directly and indirectly, and how invertebrate communities influence ecosystem recovery.

After last year’s catastrophic megafires, the world’s attention rightly turned to the devastating impacts on our ecosystems and wildlife.

Unfortunately, invertebrates were often overlooked in media coverage and conservation policy responses. Other than a few charismatic threatened invertebrates, the discourse focused on the tiny proportion of animals that are most well-known and loved – vertebrates.

This is largely because there simply isn’t enough information or baseline data about most of our invertebrate species to talk with any certainty about how many invertebrates were lost or impacted by the fires. Listed threatened invertebrates are a rare thing, mostly an artefact of the taxonomic expertise and recommendation activity that was available for the relevant committee, rather than knowledge of new threats facing invertebrates.

Only 30% of Australia’s invertebrates have a name, and most of these haven’t had enough targeted research to know about their ecology, distribution, or how they respond to extreme events. If we don’t know anything about them, we can’t prioritise actions to support them in times of crisis.

Invertebrates are 95% of animal species on Earth and are critical to ecosystem function. Most of the ecosystem services we depend on come from invertebrate activity and interactions. They drive ecological processes generally in all terrestrial and aquatic systems, and in some contexts they may help ecosystems recover from fire.

So we wanted to shift the conversation. To do this effectively, we needed some data to highlight how little we know and to identify where to prioritise future research.

Using a structured repeatable literature review method, we collated published peer-reviewed studies that measured some aspect of fire effects on an invertebrate group in Australian ecosystems.

This is not an exhaustive review of all published and unpublished data. That wasn’t our aim. It’s an expert perspective, with replicable data to back up our argument.

Some editors and reviewers rejected our paper simply because we may not have found ALL the data ever collected (published or unpublished), even though they recognised it was an important topic! This is an unreasonable expectation for any article, let alone an expert opinion article, which aren’t even required to include data. No lit review will find all knowledge – that’s not the purpose of a good review. It’s to provide a replicable and representative snapshot of the literature that guides future research.

We included data because we believe it makes our case stronger, and too many opinion articles are getting published without any evidence justification. We used Sysrev, a systematic open source platform, to review our literature (see our public project page) and our data table is published at Open Science Framework.

Here are the key knowledge gaps and issues we found

  1. Taxonomic breadth. Many studies provided limited taxonomic information on samples, grouping samples as broad general unnamed invertebrates, or identifying mostly to morphospecies. Most studies that did identify to a suitable taxonomic level were on arthropods, predominantly ants. This matters because ecological responses can vary greatly between groups, even among closely-related species.
  2. Marine systems. Most studies were done on land, a handful on freshwater systems. Our search found no studies on fire impacts on marine invertebrates, which is concerning, as ash falls and post-fire runoff can have huge impacts on marine and coastal systems.
  3. Ecoregions. 75% of studies were from only two ecoregions in southern Australia: Mediterranean Forests, Woodlands and Scrub and Temperate Broadleaf and Mixed Forests. Two ecoregions were not represented at all (Montane Grasslands and Shrublands and Tropical and Subtropical Moist Broadleaf Forests), both of which have been facing increased fire risk in recent years.
  4. Fire severity. Most studies measured impacts of managed or experimental burns. These results may not be relevant to understanding the impacts of extreme fires that are increasing in severity and risk with climate change.
  5. Methodological limitations. Many studies, especially older ones, did not provide enough details to be repeatable, or used sampling methods that didn’t match the study aims. For example, many studies stated their aims were to measure invertebrate communities generally, but used a sampling method that targeted a small proportion of invertebrates that use a particular habitat (e.g. pitfall traps). Some studies had confounded the fire effects with land management (e.g. forestry harvesting), further limiting the relevance of those results to policy.

In a nutshell, the literature on how Australian invertebrates are affected by fire is fragmented and ambiguous. Unlike key native vertebrate and plant species (e.g. eucalypts), for which there are decades of scientific knowledge on fire interactions that can inform policy, we have little understanding of how the increasing risk of extreme fire events will impact Australia’s invertebrate diversity. This means it limits our capacity to inform effective conservation policy in response to extreme fire events. Without this evidence, invertebrates will continue to be overlooked.

Not only do we need more public and political acknowledgement of invertebrate conservation issues, but we also need the scientific community and publishers to understand the broader value of invertebrate research. As a related anecdote, our paper was finished almost 12 months ago, when the fires and their impacts were still very topical. Our first submission to a ‘high impact’ journal was desk rejected for not being ‘novel’ enough. That week, the very same journal published an opinion article on the impacts of the Australian megafires on vertebrate animals… Another high impact journal rejected our paper after review because reviewers were worried we didn’t find ALL POTENTIAL data and because the editor “was expecting” a meta-analysis. This is another unreasonable expectation that too often seems to be used as a reason to unfairly reject conceptual papers. It would have been irresponsible for us to do a meta-analysis with the limited data available from our review.

I’m also really grateful that we were able to include in the paper (with permission) this amazing photo of insects washed up on the beach during the megafires, taken by Caitlin Brown (bluebowerstudio on Instagram). Caitlin found the insects at Bermagui beach in southern New South Wales, when the Currowan megafire was burning into a pyrocumulus about 100 km to the north. We still know very little about insect washups generally, but this anecdotal evidence of how fires move invertebrate biomass across ecosystems is super interesting and we hope to explore this question further.

We hope our contribution starts an important discussion about invertebrates and fire – how we do research, how we fund research, and how we prioritise conservation policies and actions targeted at biodiversity.

© Manu Saunders 2021

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