Current efforts to protect the Great Barrier Reef from land-based pollution are unlikely to be enough, according to our scientific review published in Global Change Biology.
Poor water quality – along with climate change, fishing, coastal development – is one of the major threats to the reef. Due to the cumulative impacts of these threats, the condition of the Great Barrier Reef has deteriorated over past decades.
This is despite its protection under federal law, its global recognition as a World Heritage site, and the ongoing efforts and investment by the Queensland and Australian governments and many other sectors of the community, including landholders. In 2014, the UN threatened to list the reef as “in danger”, but efforts by the Australian and Queensland governments managed to avoid this.
Poor water quality is driven by material washed off the land. So we looked for examples in Australia and overseas that could help improve the reef’s situation.
The Great Barrier Reef is the world’s largest coral reef system, extending more than 2,000 km along the northeast coast of Australia. It includes 20,000 square km of coral reefs, around 43,000 square km of seagrass meadows, and extensive mangrove forests.
The reef currently contributes about A$5.6 billion to the Australian economy. This includes tourism (A$5.2 billion), commercial fishing (A$160 million) and recreational use (A$244 million), and supports around 69,000 full-time jobs.
Poor water quality has come about largely from excess sediment, nitrogen and pesticides flowing from the land into the reef’s lagoon. This has a significant impact on reef health.
Fine sediments from soil erosion reduce availability of light for corals and seagrasses to grow. Nitrogen discharge from fertilised land and from erosion promotes the growth of various types of algae, some of which compete with corals. Other algae are associated with outbreaks of the coral-eating Crown-of-thorns starfish.
Herbicides can reduce the productivity of seagrass, which ultimately affects the dugongs and turtles that feed on seagrass.
To protect the Great Barrier Reef from land-based pollution, the Queensland and Australian governments jointly released the Reef Water Quality Protection Plan in 2003, with updates since. The 2013 update set water quality targets for reductions in river loads of dissolved inorganic nitrogen (50%), sediment (20%) and pesticides (60%) by 2018.
The plan focuses on voluntary plans for farmers, known as best practice management. After more than ten years of dedicated effort and substantial investment to improve reef water quality, the 2014 report card shows only modest changes in agricultural management practices. Indeed, while some progress has been made made, previous 2013 targets were not met and current 2018 targets are unlikely to be met.
Recent economic analyses indicate that progress towards the 2018 targets can be accelerated by, for example, focusing investment in areas that can deliver the greatest improvement in water quality at the least cost.
Even so, recent studies show that even if all farmers adopted best practice under current land uses, the 2018 sediment and nitrogen targets are still unlikely to be met.
We need to look at other options to improve water quality and protect the Great Barrier Reef. This has become even more critical in the face of more stringent water quality targets stated in the Reef 2050 Long-Term Sustainability Plan. This plan, released by the Queensland and Australian governments in 2015, was part of a response to the UN’s request to show how Australia would protect the reef over coming decades.
Looking overseas for solutions
The situation in the Great Barrier Reef is not unique and there are international examples of how to reduce sediment and nitrogen runoff. These case studies show measurable reductions in sediment and nutrient levels at river mouths, and declines in nutrient concentrations and amounts of algae in the marine environment.
These approaches centre around two mechanisms: first, identifying the management practices and/or land uses that have low pollutant runoff; and second, establishing effective incentives and regulation for their adoption. They also need long-term political commitment.
In the case of the Great Barrier Reef, several studies have emphasised the lack of effective law and regulation of agricultural land uses and management. Effective regulation has the potential to provide the stick that will support other voluntary and incentive-based approaches.
More broadly, our review identifies the opportunity to more completely harmonise federal and Queensland policies, regulations and laws that affect the reef’s water quality, and to better align land-based pollution and water quality initiatives.
Experience both globally and in the Great Barrier Reef suggests that even with continued improvements to best practice farming systems, some land use will need to change to protect the reef’s ecosystems. This could include realising the value of other products, such as carbon derived from current agricultural lands, or replacing crops that need large amounts of fertiliser such as sugarcane with other crops that need less, such as grains and cereals.
Finally, retirement of high-risk agricultural land has been used as a tool for reducing land-based pollution and can be a cost-effective measure to improve water quality.
These options presented in our paper are intended to support the ongoing discussion on managing land-based pollution to protect the Great Barrier Reef from poor water quality.
Only by looking at a large range of additional solutions will we be able to achieve the water quality targets stated in the Reef 2050 Long-Term Sustainability Plan.
Frederieke Kroon, Principal research scientist, Australian Institute of Marine Science and Britta Schaffelke, Research Program Leader – A Healthy and Sustainable Great Barrier Reef, Australian Institute of Marine Science