Ian McLean Spokesperson for the Green Party

The declining water quality in our rivers and lakes can be attributed to two primary pollutants, nitrogen and phosphorous. Both are a by-product of intensive farming of animals. The equation is simple. More animals on the land, and more land with animals, mean more pollution in our waterways.

Once upon a time, New Zealand was overrun with sheep, while dairying and beef farming were niche activities. Large areas of land that had failed to support profitable sheep farming were covered in scrub or pine forest. The waterways remained reasonably clean.

Then, in the 1990s, we discovered irrigation; the Chinese discovered milk protein, and on-farm methods allowing more cows per hectare were developed.

News from the Parliamentary Commissioner for the Environment is that our waterways are bearing the environmental costs of the shift from wool and meat to intensive production of milk protein. And they are not coping.

It is true that farmers are responding with mitigation. New management techniques include stand-off areas, such as feed pads and herd homes (where effluent can be collected), recycling of captured effluent using spray equipment, fencing of waterways, and planting of riparian strips.

Riparian strips capture phosphorous, but the highly soluble nitrogen waste easily slips through. Water quality is still in decline, and the PCE sees little hope that mitigation is the solution.

Fundamentally, the shift to more cows on our landscape has raised the bar. Grass-fed cows are a key point of international difference for NZ milk products, but mitigating their effects on water is proving challenging, expensive, and perhaps impossible.