Resilience of Great Barrier Reef marine ecosystems and drivers of change
Recent extreme weather – heavy rainfall, floods and tropical cyclones – have severely impacted marine water quality and Great Barrier Reef ecosystems. Climate change is predicted to increase the intensity of extreme weather events.
The prediction that weather events (rainfall variability and tropical storms) may become more intense in the future as a consequence of climate change has severe implications for water quality and Great Barrier Reef ecosystems. Extreme weather events (drought and flooding rain) will increase runoff and physically disturb ecosystems.
Summary of evidence:
- In 2010, a historically strong La Niña weather pattern developed, replacing an El Niño pattern. Between 2009 and 2012, seven cyclones affected North Queensland which produced substantial physical damage to shallow water ecosystems and record flooding. Extreme rainfall in 2010-2011 and 2012-2013 resulted in extensive flood plumes along most of the coast and across much of the continental shelf in some regions.
- Recent loss of seagrass habitat as a result of severe weather events and degraded water quality has led to increased mortality of dugongs and green turtles.
- The cumulative pressure of multiple stressors determines the state of marine ecosystems and the trajectory of recovery after disturbance. A 50 per cent decline in Great Barrier Reef coral cover over the past three decades shows that the natural resilience of the ecosystem has been compromised by impacts from extreme rainfall and associated runoff from agriculture, thermal stress, salinity stress, light stress, cyclone damage and crown-of-thorns starfish outbreaks.
- Reducing end-of-catchment loads of nutrients, sediments and pesticides will help enhance reef resilience in the face of continuing climate change pressures. For example, if the impacts of crown-of-thorns starfish were reduced following nitrogen load reduction from the Wet Tropics, coral cover is predicted to either recover or at least stabilise.