GREAT BARRIER REEF
// Outlook Report 2014
2.5.3 Overall summary of biodiversity
The Great Barrier Reef remains one of the world’s most unique and biologically diverse ecosystems. At the scale of the whole Region, the majority of its habitats are assessed to be in good to very good condition, however an increasing number are assessed as being in poor condition. This includes the two key habitats of coral reefs and seagrass meadows in the southern two-thirds of the Region. The condition of a number of species has deteriorated since the assessment in the Outlook Report 2009, with some important species now assessed as being in poor condition. On a regional scale, the habitats and species north of the Port Douglas–Cooktown area are in better condition than those further south. Also, habitats further offshore and in deeper water are typically subject to fewer threats and are therefore presumed to be in better condition, including the lagoon floor, shoals, Halimeda banks, deeper reefs and the continental slope. A range of past and current threats, including pollutants in land-based run-off, crown-of-thorns starfish outbreaks, death of discarded species, incidental catch of species of conservation concern and recent extreme weather, have caused declines in the biodiversity values of the southern two-thirds of the Region, especially in inshore and mid-shelf areas. For some species, such as sharks and rays, corals, some marine turtles and dugongs their condition is assessed as poor and deteriorated. Two species of inshore dolphins are also considered at high risk and in decline. There are few examples of recovering populations. Those that are recovering are species that declined as a result of human-related impacts which are now eliminated or reduced, for example commercial whaling for humpback whales and incidental drowning of marine turtles in trawl nets. These populations have yet to recover to their original size and, as they tend to be long-lived species, full recovery is likely to take decades. Biodiversity is critical to the outstanding universal value of the world heritage property. While both criteria are assessed as being in good condition, the current trends for 14 of the 27 components are assessed as deteriorated since 2009. This has meant that the grade of ‘good’ is borderline with ‘poor’ and is likely to deteriorate further in the future. A lack of comprehensive information means the assessment of many habitats and species or groups of species is principally based on limited evidence and anecdotal information. Understanding of the less accessible habitats, such as the lagoon floor and continental slope, is poor and often based on oneoff surveys — there is little or no trend information. Key gaps in knowledge include understanding of deeper reefs and deep-water seagrass meadows, islands, and identification of new biodiversity hotspots. Biological and ecological information is lacking on inshore dolphins and populations of seabirds that breed in the Great Barrier Reef as well as some targeted ‘at risk’ fishery species and populations of bycatch species. Sea snakes and some shark and ray populations are poorly understood as are turtle populations after migration out of the Marine Park.
The Great Barrier Reef remains one of the world’s most diverse ecosystems
© Matt Curnock