James Cook University TropWATER scientists are major contributors to the most comprehensive and rigorous review of water quality and the Great Barrier Reef – confirming that elevated levels of fine sediments, nutrients and pesticides continue to have detrimental impacts on the Great Barrier Reef, especially inshore ecosystems.
Scientists say hitting water quality targets in the next decade is imperative. To succeed we need to work closely with regional communities, like growers and graziers.
The 2022 Scientific Consensus Statement is led by C2O Consulting and funded by the Australian and Queensland governments. It addresses 30 questions by 78 expert authors, with policy or management to make decisions based on consideration of the full synthesis of the evidence.
Eighteen James Cook University (JCU) experts contributed to the report, with eight lead authors including Associate Professor Nathan Waltham, Dr Stephen Lewis, Dr Shelley Templeman, Dr Aaron Davis, Dr Len McKenzie, Dr Catherine Collier, Dr Maxine Newlands and Dr Ciemon Caballes.
Scientists provided expertise on land-use, wetlands, pesticides, sediments and nutrients and ecosystem health and connectivity.
Lead author of two chapters, Dr Stephen Lewis, said evidence shows extensive land use changes is documented from 1860 to 2019 with associated sediment erosion and nutrient loads increasing. Recent modelling also indicates that sediment loads have more than tripled in some regions since European settlement.
“The increase of sediment and particulate nutrients is largely due to land modifications for livestock grazing, cropping, urban development, and mining, along with climate variability causing larger river discharge events,” he said.
“The evidence of changes in pollutant exposure is most pronounced in the estuarine and nearshore environments just offshore from river mouths but can be seen as far out as 100 km alongshore from the source river.
“Excess sediments are a major threat to the health of the Great Barrier Reef, especially those closest to the coast. The most damaging sediments cause prolonged reductions in water clarity during river floods.
“Our research has contributed to identifying the hot spot areas within the Great Barrier Reef catchment that contribute the highest amount of sediments. We work with local communities and Natural Resource Management bodies to help guide catchment remediation in these catchment sediment hot spots.”
Lead author of two chapters, Dr Aaron Davis, said the Great Barrier Reef’s health is closely linked to what happens on land, and effective protection of the reef requires managing both land and sea together.
“The highest water quality risks from land use occur close to exposure from pesticides, nutrients, and sediment—such as freshwater areas, estuaries, and nearshore marine environments,” he said.
“While the mid and outer reef are less affected by these land-use issues, the reef is a highly connected system where water, matter, and organisms move between catchments, floodplains, and the outer reef.”
Dr Davis, who also led a chapter on pesticides, said it was important to remember growers need pesticides in most farming systems, to keep away pests like grubs and weeds.
“While pesticides are needed to maintain a viable crop, extensive monitoring has shown that certain pesticides are often found in freshwater waterways, sometimes at levels that exceed ecosystem protection guidelines,” he said.
“Our monitoring programs are seeing growers adopting innovative methods to reduce off-paddock pesticide losses through careful product selection and application techniques.
“The good news is we now have recent results showing decrease in some pesticides, which is likely a testament to growers adopting improved farming practices.”
Associate Professor Nathan Waltham led two chapters on wetlands. He said natural and near natural wetlands need healthy water quality conditions, but these systems are understudied in the Great Barrier Reef.
“There are few studies from the Great Barrier Reef wetlands that measure or model the efficacy or cost of wetlands maintenance and protection, particularly in terms of water quality improvement,” he said.
“Most research on the services that wetlands provide in terms of improving water quality have been conducted overseas, with limited studies in Australia, and only a few focused on the Great Barrier Reef catchment.”
Associate Professor Waltham said TropWATER was undertaking research and working with communities, Traditional Ranger groups, industries and governments to better understand the roles different types of wetlands play, as part of a broader whole-of-ecosystem based approach.
“Different types of wetlands will have different abilities to process nutrients and protect important biodiversity,” he said.
“We must determine which types perform best for future protection and management opportunities for Great Barrier Reef wetlands.”
Director of JCU TropWATER Professor Damien Burrows said good water quality starts on the land. By improving runoff from catchments, the Great Barrier Reef can build its resilience to better handle threats like coral bleaching, cyclones and diseases.
“Providing evidence on land-use impacts is a crucial step toward driving meaningful changes for water quality improvement,” he said.
“TropWATER has a unique role, we combine scientific expertise in water quality with on-ground engagement. Not only do we conduct critical research on water quality but we also work directly with farmers, Traditional Owners, industry, and government.
“Our focus is on delivering science-based solutions to water quality challenges and actively apply these solutions within communities, including growers.”
Comments