Environment & Ecology · Data Feature

 ·  June 2026

Australia carries the heaviest burden of modern mammal extinctions on the planet. Yet inside the country’s most extensive threatened-species monitoring programme, a quieter story is emerging: where active management is applied, population declines can slow and, in some cases, reverse. The challenge is not whether conservation works it is whether investment is reaching the species that need it most.

The Threatened Species Index 2025 brings together more than 2,000 long-run monitoring series spanning 1985 to 2022, covering birds, mammals, reptiles, plants, amphibians and invertebrates across all Australian states and territories.

Chart 1 · Four Decades of Change by Taxonomic Group

Three variables: year (x), smoothed median abundance index (y), taxonomic group (colour). Click a group in the legend to isolate it.

Source: TSX 2025, TERN/NESP/University of Queensland. Each line is a 3-year rolling median of the group abundance index (baseline = 100).

What the data shows: Mammal populations have remained consistently below the 1985 baseline across the full period. Bird abundance started declining sharply from around 2000. Plant counts fluctuate widely, reflecting sensitivity to rainfall variability. Amphibians dropped steeply in the late 1980s, a pattern consistent with the global spread of chytrid fungus.

Chart 2 · Monitoring Coverage Across States and Taxa

Four variables: state (x), taxonomic group (y), typical abundance level (colour intensity), and monitoring detail (tooltip). White = no recorded data.

Source: TSX 2025. Colour intensity reflects log-transformed median survey count. White cells indicate no monitoring data recorded for that state-group combination.

What the data shows: Invertebrates have almost no monitoring presence across all states. Amphibian coverage is near zero in the Northern Territory and ACT. Birds and mammals dominate monitoring effort in the larger eastern states, leaving large taxonomic and geographic blind spots in the national picture.

Chart 3 · Active Management vs No Management Across Threat Categories

Three variables: EPBC threat status (x), survey-count distribution (y), and management category (colour).

Source: TSX 2025. Violin widths show the distribution of log-transformed mean survey counts per species-management group.

What the data shows: Actively managed species record higher median population counts at every threat level. The difference is most pronounced for Critically Endangered species, where the gap between managed and unmanaged populations is widest. The data supports the case for targeted investment not broader monitoring coverage alone.

Chart 4 · Change Over Time by Functional Group and State

Five variables: state (x), abundance index (y), functional group (colour), survey count (bubble size), and year (animation frame). Press Play to run.

Source: TSX 2025. Bubble size = number of surveys that year. Dotted line = baseline of 100.
What the data shows: Migratory shorebirds show consistent downward pressure across most states through the full animation. Some ground-dwelling functional groups in WA and SA hold above baseline for extended periods, suggesting localised conditions or management practices that deserve closer study as potential low-cost success cases.

Chart 5 · Monitoring Quality and Population Change

Four variables: monitoring completeness (x), population change over the monitoring period (y), taxonomic group (colour), and years monitored (bubble size). Each bubble is one species.

Source: TSX 2025. Each point represents one species; bubble size reflects years monitored. Population change is the percentage difference between mean count in the first three years and mean count in the last three years of each series.

What the data shows: A large cluster of species sits in the bottom-right quadrant — well monitored but still declining. This confirms that observation alone does not halt population loss. Species in the upper-left quadrant, recovering despite limited monitoring, represent an important area for investigation: understanding what is driving those recoveries could inform scaled, lower-cost conservation strategies.