Pollution in the Great Barrier Reef

Our beautiful Great Barrier Reef is threatened by water pollution from land-based activities like agriculture.  

Our Reef needs to be strong in the face of rapidly warming oceans. Land-based pollution is a preventable problem entirely in our control.

We must stop water pollution and give our Great Barrier Reef the clean water it needs to restore its health.


What is ‘runoff’? 

Runoff refers to the excess water flows across the surface of the land and into nearby creeks and rivers after rainfall or irrigation. Runoff can often wash chemicals, fertilisers, pesticides and sediment from the land into bodies of water.

All waterways and creeks eventually lead to our oceans. And so, sediment and chemical runoff from agriculture and land-based activities is a major threat to inshore coral reefs and seagrass meadows in our Great Barrier Reef. 

Water Quality and Land-based Runoff

When inefficient fertiliser is applied to crops, like sugar cane, excess fertiliser washes into rivers and waterways, where it is carried out to the Great Barrier Reef. Nitrogen from these fertilisers are linked to harmful algal blooms, which is a food source for juvenile crown-of-thorns starfish. These starfish destroy vast amounts of coral and pose a huge threat to our Great Barrier Reef. Algal blooms can also reduce the amount of light available required for seagrasses to grow and be healthy.

Pesticides and herbicides have been detected in high concentrations in inshore areas of the World Heritage Area and pose a further risk to marine plants and animals. Herbicides are applied to crops to kill weeds by inhibiting their ability to grow. But when they wash into the Reef, they also inhibit the growth of other non-target plants, such as seagrasses, on which dugongs, turtles and fish depend.

Tree clearing and overgrazed grasslands cause soils to erode and wash into creeks and rivers that run into the Great Barrier Reef.

Sediment discharged from rivers reduces sunlight available to seagrasses and corals, which can smother coral growth. To reduce the sediment smothering our Reef, we need to maintain grass cover and protect and restore the bush, especially along our rivers.

Satellite image of Fitzroy River flood plume, Queensland on the 8th of April 2017.
Photo credit: European Space Agency Sentinel 2 Mission

Crown-of-thorns starfish (COTS) are marine invertebrates that feed on coral. Whilst they occur naturally on our Reef, when conditions are right outbreaks can occur. COTS outbreaks can cause widespread damage to our Reef, including loss of coral cover and decline in biodiversity.

Many scientific studies have investigated what causes outbreaks of COTS and have found it is likely to be a combination of factors. A study found that the survival of COTS larvae increases dramatically when algae, their food source, becomes more abundant. Nutrient pollution from land-based run-off can cause algal blooms and provide the required boost in food source for COTS.

We can stop nutrient pollution and give our Great Barrier Reef a fighting chance.

Read more

What problems does water pollution cause?

When sediment and excess nutrients runoff lands into Reef waters they can cause harmful algal blooms, reduce the amount of light available to seagrasses and smother marine ecosystems.

These ecosystems are critical habitats for threatened dugongs, turtles and juvenile fish.

While climate change remains the biggest threat to our Great Barrier Reef, cleaning up the water that flows from the land reduces further pressure and helps our Great Barrier Reef to restore its health.


What is being done about pollution in our Great Barrier Reef?

We have an incredible opportunity to help our vulnerable Great Barrier Reef.

In 2019, the Queensland government strengthened Reef laws after decades of inaction by farmers and graziers to stop water pollution. The majority of farmers follow water pollution laws and do the right thing, however, a small minority of farmers have not changed their practices so the last resort is law enforcement with strong monitoring and penalties.  Together, we can keep the Reef healthy but we need farmers to do the right thing by adopting cleaner, more profitable practices, and for those who don’t change, we need to enforce pollution laws.


How water pollution enters our waterways and reaches the Reef

Poor water quality and our Great Barrier Reef infographic


How fertiliser enters waterways from farms and industrial agriculture infographic



Water pollution is an entirely preventable problem. The solution to it is to start making changes on our land before it ends up in our waterways. 

Climate change requires an international effort and cooperation (of which Australia and Queensland should play its part!) Tackling water pollution in runoff that’s entering our Reef, on the other hand, is entirely in Queensland’s control. Meaning, we have the power to fix this easily and quickly. 

After decades of incentives for voluntary management practices, water quality of our inshore Reef has remained in poor condition

In 2019, the QLD government passed a historic bill designed to improve the quality of the water that flows from farming and grazing properties in northern Queensland into our Reef. 

So meeting sensible fertiliser use requirements and minimum practice standards for agriculture on land, as well as, restoring cleared land, waterways and coastlines with vegetation, are some of many solutions that will reduce water pollution from reaching our Great Barrier Reef.

More Info about Water Pollution

We Support Sustainable Agricultural Practices

We all support our farmers and graziers. The new regulations target those practices that pose the greatest risk for water quality, such as farmers who are overusing fertiliser and polluting our Reef. 

There needs to be strong laws against all forms of pollution on our World Heritage listed Great Barrier Reef. The last water quality report card showed that we have a long way to go to meet the targets laid out by the Queensland and Federal governments. With that in mind, these regulations are crucial for the future of our Reef, the wonderful wildlife it is home to and the thousands of jobs it supports in Queensland.



¹ https://www.reefplan.qld.gov.au/tracking-progress/reef-report-card