Great Barrier Reef Outlook Report 2009 – In Brief

9LONG-TERM OUTLOOKThe outlook for the Great Barrier Reef ecosystem, alongwith most other coral reef ecosystems, is at a crossroad,and it is decisions made in the next few years that are likelyto determine its long-term future. Unavoidably, futurepredictions of climate change dominate most aspects of theGreat Barrier Reef’s outlook over the next few decades. Theextent and persistence of the damage will depend to a largedegree on the extent to which climate change is addressedworldwide and on the resilience of the ecosystem in theimmediate future.Climate change Many ecosystem components are alreadyshowing some effects from climate change (for exampleincreased frequency and severity of coral bleaching anddecreased density of coral structures). It is only withatmospheric concentrations of carbon dioxide betweencurrent levels and about 400ppm that the key groups ofspecies and habitats of the Great Barrier Reef have low ormoderate vulnerability to climate change. If the atmosphericconcentration of carbon dioxide increases beyond theselevels then there will be serious consequences for the GreatBarrier Reef. At a concentration of 500ppm, it is predictedthat many components of the Great Barrier Reef ecosystemwould be highly vulnerable, including seabirds, fish, marinereptiles and plankton. At about this concentration of carbondioxide, hard corals would likely become functionally extinctand coral reefs would be eroding rapidly. It is predictedthat the progress of degradation will not be linear, ratherecological responses to climate change will likely occur ina series of abrupt steps separated by intervals of relativelyminor change.Catchment runoff The Great Barrier Reef, especially muchof its inshore area, is being affected by increased sediments,nutrients and pesticides in catchment runoff mainly fromdiffuse agricultural sources. With recent advances inagricultural practices and additional government programs,there has been a reduction in sediment and nutrient inputsinto some coastal river systems, but a long lag time isexpected before there are positive effects on marine waterquality.Most of the sediments and nutrients entering the Great BarrierReef are delivered during ood events such as here at Taylors Beach(the outlet for the Herbert River) near Ingham. Recent ooding fromthe Great Barrier Reef catchment has resulted in elevated nutrientconcentrations in river plumes reaching mid-shelf reefs.Coastal development Coastal development significantlyaffects the Great Barrier Reef. A main driving factor is theincreasing human population in the Great Barrier Reefcatchment. Current projections estimate that nearly 1.5million people will reside in the Great Barrier Reef catchmentby 2026, a 40 per cent increase from the current population.Without adequate planning and careful environmentalmanagement, this growth could increase pollution andsedimentation, decrease water quality and change thenatural drainage channels. The growth in human populationis likely to substantially increase use of the Great Barrier Reef,particularly in areas close to population centres.Coral reef habitats are particularly vulnerable to climate changeand are likely to be severely impacted in coming decades.Many coastal habitats, such as those at the location for this re nerynear Gladstone, have been affected by industrial development.19GREAT BARRIER REEF OUTLOOK REPORT 2009 IN BRIEF