Climate change is the greatest threat to the Great Barrier Reef and coral reefs worldwide.

Climate change is caused by global emissions of greenhouse gases, such as carbon dioxide from the burning of fossil fuels (coal, oil and natural gas), agriculture and land clearing.

Not only has the current concentration of carbon dioxide in the atmosphere reached record levels in the last 800,000 years, the climate is changing at a rate unprecedented over decades to millennia.

For the latest science, monitoring and modelling information to describe variability and changes in Australia’s climate, both from natural events and human activities, view the 2018 State of the Climate report.

• Climate change can affect many aspects of the marine environment, including:
• sea temperature
• storms and cyclones
• floods
• ocean acidity
• sea level
• ocean currents

Position statement

On 18 July 2019, the Authority released our position statement on climate change. Our position is:

Climate change is the greatest threat to the Great Barrier Reef. Only the strongest and fastest possible actions to decrease global greenhouse gas emissions will reduce the risks and limit the impacts of climate change on the Reef. Further impacts can be minimised by limiting global temperature increase to the maximum extent possible and fast-tracking actions to build Reef resilience.

The position statement explains what is causing the climate to change, why it’s the greatest threat to the Reef, and that caring for the Reef requires actions at all levels.

Caring for the Reef is a shared responsibility. We recognise the critical importance of strong and effective implementation of all government programs, policies and tools supporting action on climate change. We encourage others to take action to reduce the risks and limit the impacts of climate change on the Reef and coral reefs globally. Actions everyone can take can be found on our website and the Department of the Environment and Energy’s website.

Building the resilience of the Reef is central to ensuring it can withstand threats. Our approach to managing the Marine Park is adaptive and future-focused and we are committed to strengthening partnerships to build the capacity of Marine Park managers, industries and communities to adapt their activities to a changing climate.

Impacts on the Marine Park and our oceans

The Great Barrier Reef is already experiencing the consequences of climate change. The cumulative impacts of recent coral bleaching events and multiple severe tropical cyclones since 2005 have caused an unprecedented decline in the health of the Reef.

During the 2016 bleaching event, an average of 30 per cent of shallow-water corals (at depths between two and 10 meters) were lost across the Reef, with the majority of mortality occurring in the northern third where heat exposure was the most extreme. Bleaching and mortality of coral generally declined with depth, however, severe bleaching and some mortality of corals were also observed on northern reefs along the outer shelf at 40 metres deep.

In 2017, the spatial extent of severe bleaching was estimated by aerial surveys. Given the severity of bleaching observed, it is certain that the 2017 event caused a further decline in coral cover across the northern two thirds of the Marine Park. Global analyses show climate change has contributed to a fivefold increase in the frequency of severe coral bleaching events over the past 40 years. Increasing global temperatures will cause the health of the Reef to decline further and has serious implications for the communities and industries that depend on a healthy Reef for recreation and their livelihoods.

Climate change is also likely to increase the proportion of severe tropical cyclones and the frequency and severity of heavy rainfall events. Severe weather events have various impacts on the Reef — floodwaters can cause flood plumes and reduce the salinity of reefs, and cyclones can cause extensive damage to both individual corals and coral structures.

If the current rate of greenhouse gas emissions continues, global average temperature will continue to increase rapidly, which will have further negative impacts on the Reef. A report by the Intergovernmental Panel on Climate Change advised that coral reefs worldwide are projected to decline by a further 70-90 per cent at a 1.5°C increase in temperature, with greater losses at a 2.0°C increase.

A healthy Reef is naturally resilient to disturbances, however the rapid increase in sea temperature presents significant challenges for the Reef to adapt to a changing climate. More frequent and more intense bleaching allows less time for coral reefs to recover and adapt, and reduces their ability to withstand other impacts such as disease. Loss of corals leads to a reduction in the fish and associated species they support, and have major implications on the whole Reef ecosystem. These affects are likely to have far-reaching consequences for the Great Barrier Reef and its outstanding universal value as a World Heritage Area.

The impacts of climate change are outlined in our 2009 and 2014 Outlook Reports, as well as our strategic assessment.

Management actions

There is an urgent need to accelerate actions to decrease global greenhouse gas emissions if we are to secure a better future for the Reef and the communities and businesses that depend on it. Even with immediate and strong action to reduce global emissions, increasing temperatures will continue to affect the Reef due to the greenhouse gas already in the atmosphere.

Further impacts on the Reef can be minimised by limiting global temperature increase to the maximum extent possible under the Paris Agreement (and ideally less). The Paris Agreement aims to strengthen the global response to climate change by keeping the global temperature increase this century to well below 2°C, while pursuing efforts to limit the increase to 1.5°C.

• The Authority encourages:
• the strongest and fastest possible actions to reduce global greenhouse gas emissions
• partnerships, plans and actions that reduce cumulative impacts on the Reef
• actions that build Reef resilience and protect key species for reef recovery
• actions that enable adaptation and restoration of reef habitats.

Climate change and communities and industries

Climate change is likely to affect the way people interact with the Great Barrier Reef region and the social and economic benefits they derive from it.

Climate change poses one of the greatest risks to the future economic value of Reef-dependent industries such as tourism, fishing and recreation. Below are some examples.

Tourism and fishing industries

The health of the Reef and the sustainability of its $5+ billion tourism industry are inextricably linked.

The tourism industry is concerned about how climate change will affect its businesses and livelihoods. This includes the impact of reef site degradation, poor recovery of bleached sites as a result of other stresses, and a loss of marketing appeal as a high-quality reef destination.

It is likely fishing activities will also be highly sensitive to climate change because of projected changes in fish abundance, survivorship size and distribution, disruptions to shallow-water nurseries and loss of coral reef habitats, as well as changes in cyclone and storm activity.

Physical changes in the regional environment will affect fisheries differently. For example, south-east fisheries are most likely to be affected by changes in water temperature, and northern fisheries by changes in rainfall.

The vulnerability of commercial fishers and tourism operators to climate change will depend on their exposure and sensitivity to the associated impacts, as well as the ability of the individuals or operators to anticipate and adapt to change.

Extreme weather may provide a window into future potential climate change impacts on coastal communities, especially the flow-on effects of major disturbances to the Reef ecosystem.