RedList: IUCN Conservation Status Guide
Understand how conservation biologists assess global extinction risk across the 6-tier IUCN Red List spectrum—from Least Concern (LC) to Critically Endangered (CR) and Extinct (EX)—and explore 196 profiled organisms.
🐾 The 6-Tier IUCN Red List Conservation Spectrum
The IUCN Red List of Threatened Species evaluates wild populations using quantitative thresholds across five criteria (Criteria A–E): rate of population reduction, geographic range size (Extent of Occurrence & Area of Occupancy), small population size and decline, very small/restricted populations, and quantitative extinction probability analysis.
Widespread, abundant taxa with stable or increasing global wild populations, or formerly imperiled species that have achieved strong recovery under legal protection.
Populations experiencing habitat fragmentation, climate stress, or localized decline (typically 20–29% over 3 generations), or species dependent on ongoing conservation management to prevent entering Vulnerable status.
High risk of extinction in the wild: ≥30–50% population decline over 10 years or 3 generations, Extent of Occurrence <20,000 km2, or fewer than 10,000 mature individuals.
Very high risk of extinction in the wild: ≥50–70% population reduction, Extent of Occurrence <5,000 km2, or fewer than 2,500 mature individuals across fragmented habitats.
Extremely high risk of imminent extinction in the wild: ≥80–90% population collapse, Extent of Occurrence <100 km2, or fewer than 250 mature wild individuals remaining.
Exhaustive surveys across historic and prehistoric ranges confirm that no surviving individuals exist anywhere on Earth (including Pleistocene megafaunal extinctions and historical insular wipeouts).
🧪 The Captive–Wild Paradox
The Axolotl (Ambystoma mexicanum, CR) and Golden Hamster (Mesocricetus auratus, EN) number in the millions in laboratories and homes worldwide, yet IUCN assessments evaluate wild populations only—where the Axolotl is restricted to remnant canals of Lake Xochimilco.
🌍 Invasive Abroad, Imperiled at Home
The European Rabbit (Oryctolagus cuniculus, EN) and Monterey Pine (Pinus radiata, EN) are abundant introduced species across Australia and New Zealand, yet suffer severe declines from viral hemorrhagic disease and pitch canker in their native ranges.
📈 Landmark Conservation Recoveries
International bans on commercial whaling and organochlorine pesticides (DDT) enabled the Humpback Whale (LC), Bald Eagle (LC), and Peregrine Falcon (LC) to rebound from the brink of extinction, while habitat restoration downlisted the Giant Panda from EN to VU.
🦴 Pleistocene & Insular Extinctions
Apex hypercarnivores like the Saber-toothed Cat (Smilodon fatalis, EX) vanished at the Pleistocene–Holocene transition (~10,000 BP) when megafaunal prey collapsed, whereas flightless island endemics like the Dodo (EX, c. 1662) and Great Auk (EX, 1844) succumbed to human overhunting and invasive predators.