Australia's biodiversity crisis and the need for the Biodiversity Council

Abstract

Australia's Rich Biodiversity is in Crisis

Australia is a mega-biodiverse region. Millions of years of geographical isolation have resulted in high species diversity and endemism. So far, >21 000 species of plants, 8000 species of vertebrates, and 110 000 species of insects and other invertebrates have been described (Chapman 2009). An exceptionally high percentage are endemic; 93% of flowering plants, >80% of invertebrates, 87% of mammals, 93% of reptiles, 94% of frogs, 74% of freshwater fishes and >50% of temperate marine fishes in Australia are found nowhere else (Lintermans 2013; Cresswell & Murphy 2017).

Since European colonisation, Australia's rich biodiversity has been in rapid decline. This decline has been driven by habitat destruction and fragmentation due to land clearing for agriculture and urbanisation; the introduction of invasive plants, animals, and diseases; the disruption of First Peoples practices in caring for Country, including fire management; and the extraction of water including the modification and regulation of freshwater ecosystems. These pressures are now being exacerbated by climate change.

One hundred Australian species have been formally recognised as extinct including 34 mammal species, representing 10% of Australia's endemic mammals at the time of European arrival. Twenty-two freshwater fish species are at high risk of extinction within the next 20 years (Lintermans et al. 2020). One thousand, nine hundred and ninety-five taxa are nationally listed as threatened with extinction (Australian Government 2023) and hundreds more at State and Territory levels. Many once widespread species that are important ecosystem engineers, such as digging mammals, now persist only in small fragments of former natural ranges.

The situation is likely far worse than reported, due to unresolved taxonomy (new species being discovered that are already extinct), a lack of systematic and rigorous monitoring of most species and ecosystems, and under-reporting of extinction. Declines are not abating. Population sizes of threatened birds have declined to half (47%), and threatened plants to almost one quarter (73%) of their populations, on average, since 1995 (Threatened Species Index 2022). Three vertebrate species have been declared extinct in the last fifteen years: the Christmas Island PIPISTRELLE (Pipistrellus murrayi), Christmas Island FOREST SKINK (Emoia nativitatis) and Bramble Cay melomys (MELOMYS rubicola). There is a > 50% likelihood that a further 16 vertebrate taxa, for which there have been no recent verified records, are already extinct, with four almost certainly extinct (Garnett et al. 2022).

Mass mortality events are increasing. These include an estimated 3 billion vertebrate animals and 60 billion invertebrate animals which were killed or displaced in the Black Summer fires; four mass coral bleaching events on the Great Barrier Reef in the past seven years; multiple major fish kills in the Murray-Darling Basin; and extensive heat-related mortality in flying foxes and cockatoos which are important forest pollinators and seed dispersers (Legge et al. 2023). Feral and free-roaming cats and foxes kill more than 2.6 billion vertebrate animals every year, with the vast majority being native species (Stobo-Wilson et al. 2022).

Most ecosystems are in decline and 17 are showing signs of collapse (Bergstrom et al. 2021), including mangroves critical for fish spawning in the Gulf of Carpentaria, and the tall wet forests of Victoria that store more carbon than any other forest on the planet (Keith et al. 2009). Since giant kelp forests were listed as Endangered in 2012, declines have continued and less than 5% of this ecosystem, that was widespread in coastal waters of southeastern Australia, remains. Ninety-five per cent of Australian shellfish reefs (Gillies et al. 2018) and half of our total seagrass area have been destroyed. Ecosystem processes are being eroded rapidly, with pollination by native species, soil turnover through digging, water filtration, and carbon sequestration all much depleted (Bergstrom et al. 2021). Extreme climatic events (2011 to 2017) have led to abrupt and extensive mortality of key marine habitat-forming organisms—corals, kelps, seagrasses, and mangroves—along over 45% of the Australian coastline (Babcock et al. 2019).