6.3 Climate change

Climate change due to human activities is a global issue that affects all ecosystems and the services and benefits they provide. Climate change is the most pervasive and persistent influence on the Region. The most immediate and current threats from climate change are ocean warming resulting in thermal extremes that cause mass mortality and sublethal impacts in corals and other organisms and extreme rainfall events that reduce water quality.540,1535 Other impacts of climate change, such as sea-level rise and ocean acidification, are also increasingly affecting the Region, but they are not having the same immediate and Region-wide impact as increases in sea temperature. The present-day frequency and severity of climate change-related impacts are increasing and interacting with the other key threats (Sections 6.4 to 6.6), compounding their effects.

In 2016 and 2017, the Reef experienced 2 consecutive summers of severe mass coral bleaching towards the end of the most severe, widespread, and longest-lasting global-scale coral bleaching event on record (Section 2.3.5).1536 These bleaching events caused widespread mortality of corals across the Region.1537 Between 2018 and 2022, coral cover in offshore reefs recovered rapidly, led by fast-growing plating and branching corals.182 Further recovery was also facilitated by limited cyclone activity and flood impacts, and mitigation of further coral losses from the ongoing crown-of-thorns starfish outbreak through targeted control actions across much of the Marine Park.182 Recovery occurred despite a further, albeit less severe, mass coral bleaching event in 2020 and continued until the trend plateaued in response to the cumulative effects of the 2022 mass coral bleaching event and localised crown-of-thorns starfish impacts.161 Another widespread mass coral bleaching event unfolded in the Region in early 2024 (Box 2.3 and Section 3.2.6).  

Of the 4 main factors influencing the Region’s values in the Outlook Report 2024, climate change is assessed as having the highest negative impact, with impacts on natural and heritage values already apparent and expected to increase. 

  • 161. Australian Institute of Marine Science 2023, Long-Term Monitoring Program Annual Summary Report of Coral Reef Condition 2022/23, Townsville.
  • 182. Australian Institute of Marine Science 2022, Long-Term Monitoring Program Annual Summary Report of Coral Reef Condition 2021/22.
  • 540. CSIRO and The Bureau of Meteorology 2022, State of the Climate 2022.
  • 1535. Babcock, R.C., Bustamante, R.H., Fulton, E.A., Fulton, D.J., Haywood, M.D., et al. 2019, Severe continental-scale impacts of climate change are happening now: Extreme climate events impact marine habitat forming communities along 45% of Australia’s coast, Frontiers in Marine Science: 411.
  • 1536. Eakin, C.M., Sweatman, H.P. and Brainard, R.E. 2019, The 2014–2017 global-scale coral bleaching event: insights and impacts, Coral Reefs 38(4): 539-545.
  • 1537. Hughes, T.P., Kerry, J.T. and Simpson, T. 2018, Large-scale bleaching of corals on the Great Barrier Reef, Ecology 99(2): 501.