New water policy a concern
The amended National Policy Statement on fresh water management introduced on August 1 has fishermen and scientists concerned.
Massey University's senior lecturer of environmental science/ecology Dr Mike Joy said the NPS sets the future of freshwater health in New Zealand.
The amended statement requires the overall water quality to be maintained or improved within a region. It also requires councils to safeguard the "life-supporting capacity, ecosystem processes and indigenous species (including their associated ecosystems) of fresh water", and New Zealand Fish & Game Council chief executive Bryce Johnson does not believe it will do that.
Scientists and fishermen are viewing it with suspicion and Joy said it weakens the protection of fish.
"It affects all fish, native and non-native fish alike. The biggest impacts are loss of habitat and increases of nutrients that drive algal growth that then impacts on all life by blanketing stream-beds and causing swings in oxygen affecting all stream life.
"None of the aspects of freshwater ecosystem health are included in the accompanying national objectives framework (NOF), only nitrogen toxicity and algal biomass are included," Joy said.
A Ministry of Environment spokesperson said when setting water quality standards that have to apply nationally, the best approach was to manage nutrients (nitrogen and phosphorus) by managing periphyton (slime).
"The framework does not specify nutrient concentrations for rivers but specifies objectives in terms of the amount of periphyton and algae found on the bed of gravel in streams and rivers, which comprise a large proportion of New Zealand's rivers."
In most cases nitrogen levels for managing periphyton will be much lower than the 6.9mg/litre nitrate toxicity bottom line.
"In rivers where periphyton is not a problem, the nitrate toxicity bottom line provides a backstop for ensuring the water is safe for aquatic species. This level protects aquatic species from toxic effects."
Joy disagreed and said the statement's primary goal to maintain or improve water quality could not be achieved because it was not supported by the measures and their thresholds in the NOF.
The crucial flaw was that ecosystem health, the key factor for freshwater biodiversity, had somehow been subverted into nitrogen toxicity and periphyton biomass.
He said that was not scientifically sound and would continue to encourage poor practice and inevitably lead to further degradation and consequent biodiversity decline.
The Timaru Herald