Dr Nicholas Porch, Deakin University 

All ecologically literate people know that the vast majority of animals are invertebrates. When it came to estimating how many animals died in the 2019/2020 fires, instead of referring to vertebrates or ‘vertebrate animals’, much of the communication regarding this estimate, from both scientists and the media, referred to the less specific ‘animals’. This promotes the impression – although I don’t think it’s on purpose – that the only animals that matter are those with backbones. It helps entrench the idea amongst the wider public that invertebrates are somehow second tier animals. This idea flows through ecology and conservation science and education and, implicitly, into policy. 

Similarly, discussions regarding threatened species rightly focus on the species that we know are threatened. The reality, however, is that only an extremely small, and highly taxonomically biased, part of our biodiversity has been assessed for conservation status. Given the status quo of not considering survey and taxonomy of lesser well-known groups a priority, other than as disaster response, this is unlikely to change soon. This is a real shame for a wide range of reasons, notwithstanding the likelihood large numbers of terrestrial invertebrate taxa will disappear from our landscapes without anyone even knowing that they existed.

In other words, caring about the biggest chunk of animal biodiversity – invertebrates – has become important.

There is good reason to be concerned about terrestrial invertebrates. There is increasing evidence for insect declines, even talk amongst experts of an insect apocalypse, but the lack of widespread monitoring makes it difficult to quantify trends and assess the scale of population declines where they may be occurring. Palaeoecological evidence from oceanic islands, however, is damning. Fossil records that span the last several thousand years and include the period of human arrival, show that many islands have lost much – or in some cases most – of their indigenous land snail and beetle faunas to extinction. 

Why is the fossil record of islands relevant to a continent like Australia? 

It’s informative from two perspectives. Firstly, a large part of our invertebrate fauna is insular in its distribution (i.e. short-range endemic species living in habitat islands like mountain ranges and peaks), and restricted by inimical habitat from movement, much like the taxa of oceanic islands. Secondly, the fossil record demonstrates the genuinely long-term outcomes of habitat clearance, changed fire regimes and invasive species, taking into account extinction debt that is very hard to quantify in modern landscapes. Add to this mix the long-term consequences of climate change and there’s a perfect storm coming for insular invertebrates, especially those of the high mountains.

To provide context, let’s consider some recent survey work conducted in a small part of Australia’s high southeastern mountains. This work, funded by the federal government as part of the bushfire response, revealed in the invertebrate bycatch hundreds of records of pill millipedes, charismatic Acanthanura springtails and specimens of the lace bug subfamily Cantacaderinae. All this material represents undescribed species, many of them never previously sampled.

Taking this to its logical conclusion, there are hundreds, likely thousands, of species at risk of decimation under future climate and fire regimes. There are almost certainly landscapes where, with careful management, we could see many of these species through. However, without investment in finding out what is where, not only will the conservation of these species be less likley, we won’t even be aware of what we have lost. 

Let’s wrap up by considering a circumstance where your favourite taxonomic group (e.g. mammals, frogs, eucalypts or orchids) is almost completely unknown; our understanding of their diversity, distribution and ecology is based on imperfect knowledge of widespread and common species. Knowledge of the less common and range-restricted species is almost non-existent. Would you consider it imperative that we develop knowledge regarding this component of the biota so we can better manage them into the future? I’m pretty certain that you’ll answer ‘of course’. 

It doesn’t have to be this way for our wonderful invertebrates. We make that choice.

For more information, follow Dr Nicholas Porch on Twitter. 

Images (all credited to Nicholas Porch):

1) Lissotes furcicornis stag beetle (Lucanidae) from the Dandenong Ranges, Victoria. You would think that this that genus of large and conspicuous beetles would be well-known in Victoria, but recent bushfire recovery research discovered two new species in eastern Victoria.

2) An Acanthanura springtail. This group has many species distributed across the wetter parts of eastern Australia, yet only a single Tasmanian species has been formally described. There are seemingly endemic species at high altitude along the Great Dividing Range and their future under climate change is uncertain.

3) Like springtails, mites are both incredibly abundant and very poorly known. This beautiful long-legged mite belongs to the genus Eriorhynchus (Eriorhynchidae) which is found in the wetter forests of eastern Australia.

4) An undescribed galerucine leaf beetle (Chrysomelidae) from Dinner Plain in the Victorian mountains. Invertebrates like this, that are relatively large and colourful, are increasingly being recorded by citizen scientists and this species is now known from more citizen science records than specimens from scientific collections.