Herbicide Fate and Transport in the Great Barrier Reef: A Review of Critical Parameters

Herbicides used for weed management on agricultural land in Australia's Great Barrier Reef catchments are a key concern for its ecosystem, including the lagoon's marine plants and corals, whose productivity has been found to decline. The most reliable way to assess herbicide risk is by monitoring a site regularly, but this is costly and time-consuming, so numerical simulations and computer models are an alternative method. Despite the availability of low-cost and less labor-intensive modelling methods, they have been limited in their effectiveness due to a lack of specific herbicide usage data and an inadequate understanding of the breakdown and transport processes of herbicides after application. This paper reviews current findings regarding herbicide risk in all Great Barrier Reef catchments according to their agricultural land use, and the most recent Reef Water Quality Protection Plan recommendations. The various pathways for fate and transport of the herbicides were also examined, and a list of critical parameters was developed to help with computer simulations. The accuracy and reliability of modelling can be improved by including aerial drifts, interceptions by crop residues, mechanisms within the root zone, and subsurface and groundwater contributions to the herbicide load in the GBR lagoon. Moreover, the findings will provide new directions for management practices adoption data with the fate and transport model from paddock to reef and improve the reliability of model results.

Automated summary

Herbicides used for weed management on agricultural land in the Great Barrier Reef catchments have negative impacts on the ecosystem, including marine plants and corals. Numerical simulations and computer models can be used to assess herbicide risk, but their effectiveness is limited by a lack of specific herbicide usage data and understanding of herbicide breakdown and transport processes. This paper reviews herbicide risk in the catchments, provides recommendations from the Reef Water Quality Protection Plan, and examines the fate and transport pathways of herbicides to improve modelling accuracy and reliability.