Australia is in the middle of one of the world’s most severe biodiversity declines. Over the past forty years, populations of the country’s threatened wildlife have collapsed by roughly three-quarters — a statistic captured most precisely in two government-grade datasets that are usually read in isolation. Combined, the Threatened Species Index and the EPBC Act’s list of threatened species make the trajectory unambiguous: the crisis is broad, persistent, and uneven.
When most Australians picture the threatened-species crisis, they picture koalas in bushfires or the platypus on the new $20 note. But the long arc is captured most clearly in numbers, not images. The Threatened Species Index (TSX) — Australia’s equivalent of the global Living Planet Index — is the country’s most comprehensive measure of how monitored populations of threatened wildlife are tracking through time. Curated by the Threatened Species Recovery Hub at the University of Queensland, it aggregates more than 1,500 individual population time series collected by ecologists, parks staff and citizen scientists across the continent. The resulting index combines population counts for 47 threatened bird, mammal, frog, plant and reptile species and tracks them, year by year, against their 1985 levels. When the index sits at 100%, populations are at their baseline level. At 25%, three-quarters have been lost.
The Environment Protection and Biodiversity Conservation Act 1999 — the EPBC Act — adds a second, complementary view. It is the federal law that determines which species the Australian government has formally accepted are in trouble, listing them as Vulnerable, Endangered, Critically Endangered, or Extinct, with smaller categories for species that survive only in captivity or under active human protection. A species is listed only after a formal scientific assessment by the Threatened Species Scientific Committee, and the list is updated continually as new evidence emerges. Where TSX measures populations, EPBC measures recognition: how many species the Commonwealth has, on the record, accepted are at risk of being lost.
The two datasets have different blind spots. TSX only covers species with enough monitoring data to model a credible time series — roughly 5% of Australia’s listed species. Most invertebrates and many plants don’t yet qualify. EPBC, conversely, covers every species that has been formally assessed, but says nothing about how those populations are moving within a listing category. Read in isolation, each tells half the story. Read together, they trace both the trajectory and the scale of the same crisis — and that combination is the point of this article.
What follows walks through both datasets in five charts. The first sets the national headline: a single trend line that aggregates every monitored species into one number. The second and third break that figure down by taxonomic group, asking which animals are recovering, which are stable, and which are essentially gone. The fourth pivots to the EPBC list to ask, of the thousands of species formally counted as at-risk, how is the burden distributed across plants, mammals, birds, reptiles and amphibians — and how many sit in each severity category. The final chart places both datasets on a single canvas, so the reader can see at a glance where each taxonomic group sits on both measures of the crisis at once.
If you want to know how serious the situation actually is, start with a single number. The Threatened Species Index does exactly that — it bundles every monitored population of every threatened species into one figure and tracks it year by year, from 1985 to today. It’s the closest thing Australia has to a stock-market ticker for its threatened wildlife. The chart below is the ticker tape.
The red line is the aggregated index, anchored at 100% in 1985. The faint pink band around it is the 95% confidence interval — the range of plausible values once you account for the noise in the underlying counts. The dashed line at the top is the baseline, drawn so you can see at a glance how far below it the index has dropped. The shape of the drop is itself revealing: the steepest losses come in the first decade, when the index falls from 100% to roughly 65%. The next two decades extend the decline more slowly, ending in a recent flatline that isn’t reassuring — it likely reflects populations already too depleted to lose much more. By the late 2010s, the line sits below 30% and stays there. Even at the widest part of the uncertainty band, the conclusion holds: three-quarters of the populations being monitored have, on average, vanished within a single human generation. For context, WWF’s global Living Planet Index — the international equivalent of this measure — fell by 73% between 1970 and 2020 (WWF, 2024). Australia’s threatened-species index is steeper still over a shorter window. We are losing biodiversity faster than the planet as a whole.
That single national number hides an uncomfortable truth. Not every type of animal is losing at the same speed. Some are in freefall. Others are merely declining. Splitting the same index by taxonomic group reveals which Australian wildlife is bearing the brunt of the crisis — and which groups have, so far, escaped the worst of it.
Each coloured line is one group’s own TSX trajectory, indexed to the year it entered the dataset. Hover over a line to read the exact value, or click a legend item to isolate a single group. The pink line for amphibians collapses early and hard, falling below 10% of baseline by the late 1990s — a near-total loss of indexed frog populations. Species like the southern corroboree frog, once common in the alpine wetlands of Kosciuszko National Park, are now functionally extinct in the wild and survive only through captive-breeding programs; that single line on the chart hides hundreds of similar local collapses. Mammals (orange) drift downward more gradually, weighed down by long-running declines in marsupials like the mountain pygmy possum. Birds (blue) — the group the public most often notices — sit closer to the baseline than any other, suggesting that public visibility correlates with public protection. But even inside that comparatively mild line sit individual emergencies: the regent honeyeater, for instance, has lost more than 95% of its population over the same period. Plants (green) and reptiles (yellow) entered the index later, but both lines head firmly downward. The shaded bands behind each line are per-group 95% confidence intervals — wider where there are fewer monitored populations, tighter where the data is richer.
The previous chart showed the journey. This one shows the destination. By 2022, every group has lost ground — but the size of the loss varies wildly. To make the magnitude visible at a glance, we use a dumbbell chart: a single horizontal line per group, running from the 100% baseline on the right to wherever that group sits today on the left. The longer the line, the worse the loss.
The hollow grey dot on the right of every line is the baseline. The filled coloured dot on the left is the current position. The line between them is the loss. Amphibians have the longest line, ending at roughly 3% of baseline — meaning 97 in every 100 indexed amphibian individuals are gone. Reptiles aren’t far behind. Plants sit at around 27% of their baseline — a 73% decline that’s easy to overlook when public attention focuses on charismatic animals. Birds retain roughly 44% of their numbers, the smallest loss in the group. The thin horizontal lines through each coloured dot are the 95% confidence intervals: a quiet reminder that “current position” is itself an estimate, not a precise count.
TSX is about how populations are moving. It cannot tell you how many species the federal government has actually accepted are in trouble. For that question, we need a different dataset entirely: the EPBC Act’s list of threatened species — the legal register that determines which species qualify for recovery plans, habitat protection, and federal funding. The list is updated continuously, and as of February 2026 contains roughly 2,200 entries.
Each horizontal bar shows the total number of EPBC-listed species in one taxonomic group, broken into segments by conservation status. The colour ramp runs from black (Extinct) through dark red (Critically Endangered) and bright red (Endangered) to faint pink (Conservation Dependent) — severity reads left to right within each bar. Several things stand out. First, plants dwarf every other group: there are more individual plant species on the EPBC list than every animal group combined. Iconic listings like the Wollemi pine — a species so rare it was thought extinct until rediscovered in a Blue Mountains canyon in 1994, with fewer than 100 mature trees known in the wild — sit inside that bar. Second, mammals carry a disproportionate share of the “Extinct” category: Australia has already lost more mammal species in the past 200 years than any other continent on earth. Third, the chart now splits out Fish and Invertebrates, two groups that were previously buried inside “Other” — and both carry substantial listing counts that warrant separate attention.
The final chart is where the two datasets meet. TSX answers the question “how steeply is the population trend going?” EPBC answers the question “how many species are in the system?” Plot one against the other and you get a map of the crisis from two different angles in a single frame — a kind of cross-validation that no individual chart can produce.
Each dot is a single taxonomic group. The horizontal axis is the group’s TSX decline since baseline — further left means a worse trend. The vertical axis is the number of EPBC listings on a log scale, with dot size reinforcing the same measure. The geography of the chart matters. Plants sit high — a moderate-to-deep TSX decline, but by far the largest formal listing count. Amphibians sit far to the left — the steepest TSX decline, but a comparatively small formal list (in part because many Australian frogs simply aren’t monitored or assessed at the same intensity as birds and mammals). Birds, mammals and reptiles cluster in the middle. Read together, the chart resolves what neither dataset alone can: a single shared answer to “where does each group sit on both measures of the crisis at once?”
Forty years of monitoring lead to the same conclusion no matter which dataset you read. Australia’s threatened-species populations have shrunk by three-quarters. The formal list of threatened species has more than doubled since 2000 and is still climbing. Different taxonomic groups face different fates — but every one of them has declined, and no group is recovering at anything close to the scale of the loss.
What changes this trajectory isn’t found in the data. It’s found in policy. Funding for recovery plans, habitat protection enforced under the EPBC Act, and the long-term monitoring investment that produces datasets like TSX in the first place — all of these have shrunk relative to the scale of the crisis they are meant to address. The federal government’s Threatened Species Strategy commits to a goal of zero new extinctions by 2030. On the evidence of these five charts, that goal is currently not on track. The charts make plain the floor we are starting from: a continent already three-quarters into a biodiversity decline, with the formal recognition of that loss still growing every year. The crisis is no longer a forecast. It is a record — and the next decade will decide whether the record keeps thickening, or stops being written.
Bayraktarov, E., Ehmke, G., O’Connor, J., Burns, E. L., Nguyen, H. A., McRae, L., Possingham, H. P., & Lindenmayer, D. B. (2019). Do big unstructured biodiversity data mean more knowledge? Frontiers in Ecology and Evolution, 6, 239. https://doi.org/10.3389/fevo.2018.00239
Department of Climate Change, Energy, the Environment and Water. (2026). EPBC Act list of threatened species [Data set]. data.gov.au. https://data.gov.au/data/dataset/threatened-species
Department of Climate Change, Energy, the Environment and Water. (2022). Threatened Species Strategy 2021–2031. Australian Government. https://www.dcceew.gov.au/environment/biodiversity/threatened/strategy
Threatened Species Recovery Hub, & University of Queensland. (2025). Threatened Species Index for Australia (TSX 2025) [Data set]. https://tsx.org.au/
World Wide Fund for Nature. (2024). Living Planet Report 2024: A system in peril. WWF International. https://livingplanet.panda.org/
In preparing this assignment I used Anthropic’s Claude as a coding collaborator. Claude assisted with suggestions for improving the charts and visualisations, and with fixing errors in the R code. The choice of topic, story angle, data sources and final editorial decisions are my own.