A way forward for the Great Barrier Reef
With back-to-back bleaching events and the looming prospect of another warm summer for 2017-18, the Great Barrier Reef is dramatically displaying its inability to acclimatize to the stresses imposed by the current rapid rate of global climate change. Alongside global efforts to slow warming, we need to find new science-based ways forward for the Reef and the communities and industries that depend upon it.
Reef Havens as a conceptual framework
Managing climate change refugia for local-scale persistence of valued ecological communities while longer-term bigger-picture solutions are enacted is a well-accepted approach for conservation management of terrestrial ecosystems. Corals have considerable natural capacity to acclimatize and adapt to gradually increasing temperatures (e.g. through genetic adaptation, acclimatization, and symbiont shuffling), but these processes are unlikely to be able to keep pace if stressful conditions occur every year. Even conservative IPCC forecasts show that another >20 years of rapid global warming is now inevitable. If the Great Barrier Reef is to have a future, potential refugia (“havens”) not only need to be identified and prioritised, but actively defended using a range of science-based management interventions that reduce coral stress, promote coral survival, reduce bleaching severity and promote recovery after bleaching.
Developing active defences
In recent years, a more interventionist style of management has been trialled on the Great Barrier Reef in the form of the Targeted Control Program for outbreaks of the coral-eating crown-of-thorns starfish. Additional science-based defensive interventions that reduce coral stress and promote recovery after bleaching need to be developed, trialled and evaluated.
Coral species differ significantly in their tolerance/resistance to stress, but local environmental conditions are also a significant factor: reefs that are near upwellings, or experience cooler currents or wind mixing, tend to experience less severe bleaching, and those with few other pressures tend to recover better. Could science-based localised interventions that mimic these natural stress-reducing phenomena (for example by incrementally increasing water movement, reducing water temperature by 1-2 °C, or disrupting the water’s surface) reduce coral stress, bleaching severity and/or promote recovery on key reef sites, potentially providing time and space for natural acclimatization and adaptation processes to occur?
There is no suggestion that even an extremely effective and coordinated Reef Havens program could save the Reef as a whole from climate change. However, this science-based Reef Havens approach will provide data and field trials to inform a way forward for the Great Barrier Reef through the next >20yrs of already inevitable rapid climate change.