Rarity or decline: Key concepts for the Red List of Australian eucalypts

Abstract

The 822 eucalypt species (Angophora, Corymbia, Eucalyptus) within Australia were assessed using IUCN Red List Categories and Criteria. Overall, 193 (23%) eucalypts qualified as threatened and 36 were considered Data Deficient. One hundred and thirty-four threatened species qualified under criterion A2, representing a past and irreversible population decline of >30%. The remainder were narrow-range species with ongoing threats (mostly mining or urbanisation), or naturally rare. Habitat conversion to crops and pastures was the cause of decline for most threatened eucalypts. Threatened species were concentrated where deforestation and high eucalypt richness coincide, especially south-western Western Australia. Corymbia or Angophora species, and relatively few tropical eucalypts are threatened. Fire, timber harvesting and disease were rarely sufficient threats to eucalypts to warrant a threatened status. Sheep grazing limits regeneration in temperate woodlands, but requires further quantification for individual species. Prior to this study, 89 eucalypts were listed as threatened under Australian environmental law. This assessment recommends that 32 of these species be downgraded to Near Threatened or Least Concern. A further 11 species were identified as Data Deficient, while an additional 147 species were proposed for listing as threatened. This systematic assessment of Australian eucalypts emphasises the importance of decline rather than rarity when compared with previous listings, with broad implications for listing long-lived plants in deforested landscapes.