Update on Scientific Consensus Statement and GBR Risk Assessment - Jon Brodie, Jane Waterhouse

Our building of towns, cities and roads and use of land for farming or mining has a major impact not only on the land itself but on our fresh water environments, and the marine ecosystems downstream, including the Great Barrier Reef World Heritage Area (GBRWHA). Fresh water carries suspended sediments, nutrients and pesticides down to the GBRWHA, impacting the health and survival of all organisms living there; the reef itself, the seagrass beds and all the other plants and animals that depend on those ecosystems for survival.

This issue has been recognised for some time, and in 2003 State and Federal Governments endorsed the Reef Water Quality Protection plan (Reef Plan), put in place to “halt and reverse the decline in water quality entering the Reef”1 An update on progress towards that goal was published in 2009, with another due this year.

The development of the Reef Plan has been guided by Scientific Consensus Statement which involved a review and synthesis of significant advances in scientific knowledge on water quality issues in the Great Barrier Reef. The Statement, developed by a multidisciplinary group of scientists with oversight from the Reef Plan Independent Science Panel, is expected to be presented to the Great Barrier Reef Ministerial Forum on 10th July.

The Statement’s lead author, Jon Brodie (TropWATER2) discussed the continuing decline in coral cover and seagrass, and dependent turtles and dugongs. Coral cover on some reefs is estimated to have been around 50% in the 1960’s, and has declined from 27% in 1985 to less than 14% now, with a projection to drop to less than 5% by 20253.

There is unanimous acceptance that increased loads of suspended sediment, nutrients (nitrogen and phosphorus) and pesticides, particularly PSII herbicides, pose an unacceptable risk to some parts of the GBRWHA. Jon Brodie reiterated the role of enhanced nitrogen inputs in crown-of-thorns-starfish (COTS) outbreaks, macroalgal dominance over corals on near-shore reefs, coral bleaching susceptibility and interactions with suspended sediments to smother corals.

He considers the outlook for the GBR to be poor, with an outlook of continued COTS outbreaks, extreme weather and increased coastal development, and emphasised the need to do the things we can do; manage terrestrial runoff and improve management of coastal developments and agricultural land uses.

1  http://www.reefplan.qld.gov.au/about.aspx
2  https://research.jcu.edu.au/research/tropwater
3  http://www.nerptropical.edu.au/publication/project-51-journal-27-year-decline-coral-cover-great-barrier-reef-and-its-causes

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