Case studies

Dr Kevin Thiele, Taxonomy Australia

The discovery, naming and documentation of Australian species by western scientists has been ongoing for about 3 centuries. A high point in the number of new species named each year was reached just before World War 1, followed by a decline until recovery of Australia’s biodiversity science effort after the end of World War 2 (Figure 1). The establishment of the Australian Biological Resources Study in 1972 saw an increase in rate until a plateau was reached in the 1990s. Since 2000, the annual rate of naming of new species has declined, likely due to a reduction in investment in taxonomy in real terms.

Figure 01 Annual rate of naming, and the accumulation of new species of animals, plants, fungi and protists since 1753

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Figure 01 Annual rate of naming, and the accumulation of new species of animals, plants, fungi and protists since 1753

a Dotted section of line (after 2010) indicates extrapolated values.

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Current knowledge of Australia’s biodiversity is very incomplete. The best estimate is that 70% (or 420,000) of all Australian species of plants, animals, fungi and other organisms have yet to be discovered, documented, named and classified (Cassis et al. 2017). At the current rate, it will take more than 4 centuries to document Australia’s biodiversity.

Of course, some groups of organisms are better documented than others. In general, species that are prominently visible (e.g. vertebrates, flowering plants) are well known, and groups that are rarely noticed (e.g. most invertebrates, fungi) are poorly known.

But noticeability is not a good surrogate for ecological, economic or environmental importance. Fungi and insects, for example, are very poorly documented (less than 5–10% of Australia’s species are likely to have been named) yet they provide critical ecological functions and ecosystem services, sometimes pose risks to natural and agricultural systems, and may provide important opportunities for industry and the economy.

This substantial gap in our knowledge of Australia’s species hinders effective management, conservation and the sustainable use of Australia’s biodiversity. Although unnamed species can at times be conserved effectively through conservation of habitats, monitoring of conservation effectiveness is severely limited with so many species effectively invisible. Similarly, many unnamed species are likely to be rare and threatened, and many of these will become extinct before they can be recognised.

New technologies, including high-throughput DNA sequencing and machine learning, mean that a substantial acceleration in the discovery, naming and documentation of Australia’s biodiversity is achievable. The Australian Academy of Science has proposed an ambitious mission to discover and document all remaining Australian species in a generation. A cost–benefit analysis has shown that the returns to society of achieving this goal could be 35 times greater than the investment, with benefits for biodiversity conservation as well as for biosecurity, biodiscovery, and agricultural research and development (Deloitte Access Economics 2020).

Reporting on the state and trend of threatened species in past state of the environment reports has relied primarily on simple changes in the number and status of threatened species and communities. This has been largely because there are very few national datasets that measure actual trends in the abundance and distribution of threatened species, or the extent and condition of threatened ecological communities. In addition, there is no system to capture reporting of this type in Australia, even where adequate data and knowledge collection do exist (Latch 2018a).

The Australian Government’s National Environmental Science Program (NESP) Threatened Species Recovery Hub has developed a national Threatened Species Index by aggregating datasets from a range of programs monitoring population trends.

The NESP Threatened Mammal Index, Threatened Bird Index and Threatened Plant Index provide measures of population trends across a subset of Australia’s best monitored threatened species.

The index shows the average change in population size compared with a base year, which is assigned a score of 1.0. A score below 1.0 reflects a decrease in population size compared with the base year. For example, a score of 0.5 indicates an average 50% reduction in population size. Grey shading around the trend line shows the range of trends for the individual species that make up the overall multispecies score. The shading is created by randomly sampling species trends from all possible trends in the dataset 100 times and dropping the 5 trends that are furthest from the average, resulting in a 95% ‘confidence interval’.

Accurate detection of individual animals is integral to the conservation of threatened wildlife species, but is often difficult and costly for species that occur over wide or inaccessible areas. In addition, many animals are cryptic (camouflaged) and are therefore difficult to detect and monitor effectively by traditional monitoring methods.

Technology to support the use of drones (also known as unmanned aerial vehicles or UAVs, and remotely piloted aircraft systems or RPAS) is rapidly improving and being implemented in wildlife surveys, largely because drones can cover larger areas than ground survey methods. The inclusion of thermal (heat-detecting) imaging cameras in drones offers a major advance in survey methodology, because they have the potential to provide more precise data at lower cost and with little impact on wildlife.

For example, drones have successfully been combined with thermal camera technology to detect and count koalas (Phascolarctos cinereus) (Beranek et al. 2021), and have been more efficient than on-ground surveys. When drones detect infrared koala-size signals, a GPS point can be collected, as well as detailed images that are then checked for accuracy.

The Australian Wildlife Conservancy is also using thermal imaging and drone technology to improve monitoring of reintroduced mammals on the Faure Island Wildlife Sanctuary. The sanctuary is a feral-free haven off the coast of Western Australia and home to critically important populations of burrowing bettong (Bettongia lesueur), banded hare-wallaby (Lagostrophus fasciatus), Shark Bay bandicoot (Perameles bougainville) and Shark Bay mouse (Pseudomys fieldi). Initial estimates of population size from drone footage are comparable to those generated from standard spotlight surveys (Australian Wildlife Conservancy).

Nicki Mitchell, University of Western Australia

A well-recognised response to climate change is the poleward shift of species’ range limits. However, many terrestrial species are unable to shift their distribution because of the loss of connecting habitats. In south-western Australia, a marked decline in winter rainfall began in the 1970s, and this climatic shift, coupled with extensive habitat loss and fragmentation, threatens species that depend on wetlands and are incapable of migration. Consequently, some species might only persist if they can be introduced to wetter areas. This form of conservation introduction is termed ‘assisted colonisation’ because species are translocated beyond their native range to mitigate a major threat.

A world-leading trial of this conservation strategy as a response to climate change began in 2016 for the Critically Endangered western swamp tortoise (Pseudemydura umbrina) – one of Australia’s rarest reptiles. In its habitat north of Perth, declining winter rainfall has shortened the period in which swamps hold water, which coincides with when tortoises grow and reproduce. Eventually, wet periods may be too short for successful recruitment of juveniles. Further, as the only viable natural population of the species at Ellen Brook Nature Reserve is threated by urbanisation and infrastructure development, translocation sites that can support additional swamp tortoise populations are urgently needed.

Wetlands near the south coast of Western Australia have longer wet periods than those near Perth, and predictive models suggest they are likely to provide ideal microclimates for swamp tortoises within 30 to 50 years (Mitchell et al. 2013, Mitchell et al. 2016). With the support of the species’ recovery team, assisted colonisation trials began in 2016, aimed at testing whether wetlands more than 300 km south of the natural range could provide suitable food and microclimates for tortoise growth. Captive-bred juveniles raised at Perth Zoo were released into 2 wetlands near the south coast, as well as into an existing northern translocation site to provide a comparison. Encouragingly, at one of the southern wetlands, tortoises grew at a similar rate to those in the north in spring–summer (Bouma et al. 2020).

In 2018, a year-long trial of assisted colonisation commenced. In this trial, captive-bred tortoises were again released, and researchers focused closely on postrelease behaviour. Based on analysis of data recorded by biotags attached to tortoises, it became clear that lower water temperatures and solar radiation in the south limited tortoise activity, and consequently their opportunity to forage. However, overall, the research suggests that tortoises can grow well in southern wetlands, provided that energy-rich food sources such as tadpoles are abundant when tortoises are warm enough to be active. The longer-term suitability of southern sites will become more evident as juveniles reach maturity, which depends on them surviving annual summer aestivation – a period when they are susceptible to predation by foxes and impacts from fire.

Selection of translocation sites for the western swamp tortoise is multifaceted (Dade et al. 2014), and an important factor to consider is the possible impact of tortoises on recipient ecosystems that support other threatened species such as the salamanderfish (Lepidogalaxias salamandroides) and black-stripe minnow (Galaxiella nigrostriata).

Current research is now focusing closely on tortoise activity and diets in southern wetlands, aided by the largest ever release of more than 70 juveniles into wetlands in the East Augusta region – including the site of the successful 2016 trial. Ultimately, due to their slow maturation and long lifespan of at least 80 years, decades of monitoring will be required to understand whether western swamp tortoise populations can establish and ultimately flourish in novel habitats.

The Wildlife and Threatened Species Bushfire Recovery Expert Panel, which was established in January 2020 to help inform the Australian Government’s response to the 2019–20 bushfires, identified the northern corroboree frog (Pseudophryne pengilleyi) as 1 of 119 animal species in need of urgent management intervention (Figure 19).

The northern corroboree frog was considered Critically Endangered before the fires and the recent drought left the tiny frog particularly vulnerable. The frog depends on the Alpine Sphagnum Bogs and Associated Fens threatened ecological community, which was significantly impacted by the fires, and the remaining populations are at high risk of extinction. Taronga Zoo has been working to protect the frog for more than a decade, and setting up additional captive colonies was deemed critical for its recovery. The first 100 frog eggs were collected from the wild in March 2020 and were hatched successfully at the zoo.

A purpose-built facility to support conservation breeding of the species opened in March 2021. The zoo’s captive breeding program will allow the experts to plan ahead, manage the production of many more eggs, and deliver offspring for translocation trials once the habitat is healthy again.

Figure 19 Northern corroboree frog

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Figure 19 Northern corroboree frog

Photo: Taronga Zoo

The NSW South Coast was hit hard by the January 2020 bushfires. Heavy rains immediately after the fires resulted in ashy sediment flowing rapidly into the estuaries.

With a bushfire recovery grant, Local Land Services and the Mogo and Batemans Bay Local Aboriginal Land Councils joined forces to fortify areas of high run-off in the catchments of the Clyde and Deua rivers. The team installed 300 ecologs made from 100% coconut fibre compacted into an outer mesh of bristle coir twine and jute mesh (Figure 23).

This successful project has helped alleviate damage to aquatic ecosystems, including valuable areas such as saltmarsh, mangroves and seagrass beds that provide fish habitat and are a food source.

Figure 23 Batemans Bay Local Aboriginal Land Council Ranger Group working in the Clyde Catchment to reduce effects of sedimentation on waterways

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Figure 23 Batemans Bay Local Aboriginal Land Council Ranger Group working in the Clyde Catchment to reduce effects of sedimentation on waterways

Photo: James Cornwell, Local Land Services, New South Wales

Victoria’s high country suffered badly in the summer bushfires of 2019–20. The region has more than 4,000 hectares of Alpine peatlands – an endangered ecological community. Alpine peatlands are crucial for providing habitat and for modulating water flow. The health of the peatlands influences the health of water further down the catchment and is therefore important for the whole community – people, plants and animals.

One bushfire recovery project in the region is working to control feral animals, to protect the peatlands from trampling and overgrazing. Invasive weeds are being removed in the Alpine National Park to protect endangered communities from further impacts. This project is being delivered by the North East Catchment Management Authority in partnership with Parks Victoria, Mount Hotham Alpine Resort Management Board and HVP Plantations, with support from the Australian Government.

The Kangaroo Island dunnart (Figure 29) was listed as endangered before the 2019–20 bushfires, with only a few hundred estimated on the island. The bushfires were the largest in the island’s recorded history – more than a third of the island and approximately 95% of the dunnart’s range was burned.

Figure 29 Dunnart

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Figure 29 Dunnart

Photo: Peter Hammond

The Wildlife and Threatened Species Bushfire Recovery Expert Panel, which was established to help inform the Australian Government’s response to the bushfires, identified the dunnart as one of 119 animal species in need of urgent management intervention.

With bushfire recovery funding from the Australian Government, Natural Resources Kangaroo Island and the South Australian Government have been working with several partners, including Kangaroo Island Land for Wildlife, Australian Wildlife Conservancy, WWF Australia and the Foundation for Australia’s Most Endangered Species, to monitor native species and put management projects in place.

A fenced safe haven and shelter tunnels were constructed on the island’s west to help protect the remaining dunnart populations from feral cats. In April 2020, more than 70 infrared cameras were set up across the island to monitor both dunnart and predator movements.

Teams have now recorded the dunnart at 60 sites across the western end of the island. They have also noticed an increase in the number of smaller dunnarts, which may coincide with successful breeding during spring and summer followed by dispersal of the youngsters across the fire scar in autumn.

Although it is still a mystery how dunnarts survived in areas that were severely burned, the fact that they are returning to some of the worst affected areas is a promising sign for the future of the species, and is providing valuable information for future recovery efforts.

Source Woinarski et al. (2020)

Since cats arrived in Australia in the early 1800s, the combined population of feral and domestic cats has grown to more than 6.5 million and they are now present across 99.9% of the Australian landmass.

Both feral and pet cats continue to have an extensive and harmful impact on Australian fauna. Cats are known to eat over half of Australian mammal species, including 50 threatened species. Nearly half of all Australian bird species have been recorded as being eaten by cats, including 71 threatened species.

Feral cats in the bush kill an estimated 2,414 million animals annually – mostly native species – including:

• 769 million invertebrates
• 815 million mammals
• 466 million reptiles
• 272 million birds
• 92 million frogs.

In built environments, cats that roam kill an estimated 714 million vertebrates annually, including:

• 338 million mammals
• 162 million birds
• 213 million reptiles
• at least 1 million frogs.

Most of these kills are made by pet cats.

Figure 35 Cats have a significant impact on Australia’s biodiversity

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Figure 35 Cats have a significant impact on Australia’s biodiversity

Management and abatement of the threats posed by feral predators, in particular feral cats, has continued to improve with the ongoing development of novel baits. Currently, 2 types of bait have been developed – Eradicat® and Curiosity® – with a third in progress (Hisstory®) (Legge et al. 2020). All baits are dried meat lures. Eradicat® contains 1080 poison, Curiosity® has an encapsulated pellet (hard shell delivery vehicle, or HSDV) that contains the toxicant para-aminopropiophenone (PAPP) (Johnston et al. 2020) and Hisstory® has 1080 within an HSDV (Algar et al. 2015). Eradicat® is registered for use in south-west Western Australia, Curiosity® was registered for use in Australia in 2020 and Hisstory® is yet to be registered.

Ongoing research to quantify the potential benefits of feral cat baiting is required, especially to determine the impact on nontarget species in new areas and any mitigation required (Hohnen et al. 2019). Results from recent studies indicate little impact of Eradicat® baits on northern quolls (Dasyurus hallucatus) (Cowan et al. 2020). However, the mitigation options for the potential impacts on goannas and dingoes from cat baiting, in particular, warrant further consideration given the customary, cultural and spiritual values ascribed to these species by Traditional Owners.

The Felixer™ grooming trap is a novel control method for invasive red foxes and feral cats (Moseby et al. 2020). It is designed to target individual animals. Felixer™ achieves target specificity (meaning it only affects the target species) through a discriminatory sensor arrangement and algorithm, and a dosing pathway that make feral cats and foxes more vulnerable to treatment than nontarget species (Read et al. 2019). Felixer™ works by ejecting a dose of 1080 poison onto the fur of a target animal, which it subsequently ingests through grooming. Felixer™ is particularly effective in areas with limited predator immigration and has proven to be safe for nontarget threatened species such as the numbat (Myrmecobius fasciatus) (Chambers et al. 2020) and northern quoll (Dunlop et al. 2019).

The Australian Government led the $5.9 million project to develop the Curiosity® bait for feral cats and is leading the development of the Hisstory® bait.