A group representing dairy farmers believes the latest Land Air Water Aotearoa (LAWA) water quality report shows the huge amount of work farmers have put in.
LAWA's National River Water Quality 10-year Trend Summary report, released Thursday, found a "mixed bag" of trends across the country's freshwater ecosystems.
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The report said while the decline in macroinvertebrates is a concern, for every other parameter LAWA measures there were more sites improving than declining.
Dairy NZ says the report confirms that all the hard work underway to improve water quality is on the right trajectory.
"The sector has already undertaken a huge amount of work over the past 10 years to improve dairy's environmental footprint including fencing cows out of waterways through the Sustainable Dairying Water Accord with 97 percent of all dairy accord waterways now fenced off ," said Dairy NZ's Dr David Burger.
He said thousands of farmers are carrying out extensive planting alongside waterways to filter runoff from land.
"Much more work is underway, including science into better ways to mitigate contaminant runoff from the land before it leaves the farm gate, and whole of catchment projects to adopt improved farming practices at scale, and demonstrate those outcomes through monitoring and modelling," he said.
Dr Burger acknowledges that there is still work to be done.
"We are very concerned at the LAWA finding that macroinvertebrates are under pressure," he said.
For sites where 10-year MCI (Macroinvertebrate Community Index) trends were evaluated, two out of five sites were reported as likely or very likely degrading for macroinvertebrate health.
"This is not acceptable and the dairy sector is committed to doing everything it can alongside other land users to continue to contribute to improving the health of waterways including the health of macroinvertebrates," said Dr Burger.
Report authors praised farmers saying it was particularly encouraging to see ammoniacal nitrogen improving at many sites given the work of councils in reducing point source discharge and farmers keeping stock out of waterways.
"They've cleaned up waterways, they've taken rubbish out, they've improved the banks, put a lot of planting in, made sure that it's well fenced-off so dogs can't get near the streams," said LAWA's river water quality lead Tim Davie.