Reduced fertilizer use linked to cleaner water flowing to Great Barrier Reef

Cleaner waters are flowing to the Great Barrier Reef, with scientists identifying a strong link to changes in how farmers fertilize their crops. Two comprehensive studies, drawing on decades of data, suggest that reduced synthetic fertilizer use has led to measurable improvements in water quality across multiple river catchments.

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We've been able to document those substantial fertiliser reductions that they've undertaken over the last 30-odd years. We're also now able to tie that into improvements in water quality with real data and significant downward declines in dissolved inorganic nitrogen concentrations at the end of catchment with real data.

Researchers from CSIRO and James Cook University (JCU) analyzed extensive datasets. One study documented significant reductions in synthetic nitrogen and phosphorus fertilizer application, with declines ranging from 25 to 50 percent in many areas over the past one to two decades, especially in sugarcane-growing regions. This shift in farming practices is seen as a crucial factor in improving the health of the reef's environment.

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The fertiliser records we compiled [show] the amount of synthetic nitrogen and phosphorus fertiliser application for all river catchments across the entire Great Barrier Reef catchment area. What that showed was there was a marked reduction by up to 25 to 50 per cent reductions in nitrogen and phosphorus fertiliser application across the vast majority of basins for the Great Barrier Reef catchment area, and this occurred over the past one to two decades.

The second study focused on water quality itself, analyzing nearly 40 years of data from nine key sites, representing an area comparable to New Zealand. This analysis revealed that 75 percent of these sites showed improvements in water quality over the recorded period. Scientists noted that landholders played a significant role in achieving these positive outcomes, which are vital for the reef's ability to recover from the escalating impacts of climate change, including coral bleaching.

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We evaluated water quality at nine sites. That doesn't sound like a lot, but it actually represents an area the same size as New Zealand, so a really big catchment area. At those nine sites, 75 per cent of them showed improvements in water quality over about a 40-year record.

While the studies highlight progress, the Great Barrier Reef continues to face significant challenges from climate change. However, the findings offer a hopeful outlook, demonstrating that targeted changes in agricultural practices can yield tangible benefits for the reef's ecosystem. The improved water quality is believed to bolster the reef's resilience, providing a better chance for recovery amidst ongoing environmental pressures.

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It's well established that climate change