The five previous mass extinctions — and the one we're in
Earth's geological record carries five clear mass-extinction signals: the end-Ordovician (~440 million years ago), the late Devonian (~370 Ma), the end-Permian (~252 Ma — the largest, killing roughly 90% of marine species), the end-Triassic (~200 Ma), and the end-Cretaceous (~66 Ma — the asteroid that ended the non-avian dinosaurs). Each event is defined by a sudden, geologically rapid loss of species across many taxonomic groups. The sixth — the Holocene or Anthropocene extinction — is the one currently underway, and its proximate cause is unambiguously human activity.
The rate, with numbers
Background extinction is the steady, slow turnover that happens between mass-extinction events: roughly one species per million per year (E/MSY) for vertebrates, based on the fossil record. Current estimates of the human-driven rate range from 100 to over 1,000 E/MSY depending on the taxonomic group and the calculation method. Even the conservative end of that range is two orders of magnitude above background. We are, measurably, in the middle of a mass extinction.
SpeciesRadar's contribution to that picture is granularity. The IUCN Red List flags 55,738 species in immediate at-risk categories. We layer national red list assessments on top — and the divergence between them often reveals that the global rate understates the local crisis.
What's driving it
The IUCN classifies documented threats across roughly a dozen top-level categories. The patterns are consistent across taxa and continents:
- Habitat conversion — agriculture, logging, urban expansion. The single largest cause across vertebrates and plants.
- Direct exploitation — hunting, fishing, harvesting. Particularly acute for large mammals, sharks, reef fish, and tropical timber species.
- Climate change — range shifts, phenology mismatch, sea-level rise. Increasingly the dominant pressure on cold-adapted and island species.
- Invasive species — accelerated by global trade. The leading cause of bird extinctions on islands.
- Pollution — agricultural runoff, plastics, pharmaceuticals. Underestimated for invertebrates and freshwater species.
The counterintuitive findings
Aggregate threat-record analysis often surfaces patterns that defy the headlines. Insect populations are crashing globally, yet insects are dramatically under-assessed by IUCN — the threatened-species count is a floor, not a ceiling. Plants face habitat threats comparable to vertebrates but receive a fraction of the conservation funding. Marine species are harder to monitor and likely have higher real-world rates than terrestrial ones. The spoke posts below dig into each of these.
What can be done
The data also shows the levers that work: conservation success is real, measurable, and replicable. Recovery is slow — measured in decades — but the species-by-species evidence is stronger than the gloomier headlines suggest. The sixth extinction is ongoing; whether it reaches the magnitude of the previous five is still, in part, a matter of choice.
Data sourced from SpeciesRadar (speciesradar.org), drawing on IUCN Red List 2025-2, GBIF, and national red list assessments from 200+ countries. See our Methodology for how each figure is computed.