4. Heritage values

The Reef supports tens of thousands of marine and terrestrial species, many of which are of global conservation significance. The assessment of the Reef’s habitats for conservation of biodiversity comprises all habitat values (Chapter 2) on a property-wide scale. 

The Outlook Report 2019 identified that widespread loss and degradation of key habitats (coral reefs and seagrass meadows) had occurred in that reporting period and found the overall condition grade for habitats to support species was poor. In 2024, coral reefs and seagrass meadows show improved trends, including the grade for coral reefs shifting from very poor to poor borderline good. Multiple other habitats remain in good condition, noting confidence in some grades is broadly inferred due to limited data. However, overall, habitats to support species remain in poor condition.

The most immediate and priority threat from climate change is thermal extremes that cause mass mortality of corals and other organisms. Since 2019, further research has increased understanding of the effects of ocean warming on the condition of habitats, and the marine and terrestrial species they support. The present-day frequency and severity of climate change-related impacts are increasing and interacting with the other key factors influencing the values of the Region (Sections 6.4, 6.5 and 6.6), compounding their effects. 

At the time of inscription in 1981, some 400 species of corals in 60 genera were known to occur in the Region.¹⁰⁹⁶ It is now known that these numbers are likely to be much higher. New techniques, such as genomic sequencing, are providing new insights into biodiversity and the ability of species to cope with climate change (Sections 2.1 and 2.3.5). 

While the condition of some values at the Region-wide scale have improved (seagrasses, corals and crocodiles) since 2019, others have declined (some populations and species of marine turtles and dolphins). This range reflects the vast size of the ecosystem, being unparalleled in latitudinal extent. However, human-induced climate change continues to challenge the integrity of the World Heritage Area; its size is becoming a less effective buffer against global impacts. The potential implications on the Reef’s intactness are assessed in Section 4.2.6 and Appendix 4. The Region’s long-term outlook is discussed in Chapter 10.