Green Co-Leader Jeanette Fitzsimons says farmers should stop seeing environmental concerns as a threat and recognise that it is essential to their economic interests to clean up their act.
She was commenting on the sector's reaction to the Parliamentary Commissioner for the Environment's warning that intensive agriculture is damaging New Zealand's fresh water and soil.
"This is not a message that farmers are bad guys, but that we must work as a community to fund research into sustainable strategies, help farmers adopt them and insist that they do.
"Ultimately the measure of how successful farmers are at cleaning up their act is not how hard they are trying but how clean the water in our rivers and lakes actually is.
"Project Green, stream fencing and planting, shed effluent management and nutrient budgeting are all good initiatives. Those who have adopted them should be congratulated and the laggards encouraged to hurry up. Unfortunately every time such schemes are launched some farmers resist them.
"The dissenters from Fonterra's Clean Streams Accord, for instance, should view pollution prevention and control as an infrastructure cost that is as basic as their milking shed and accept that Fonterra is acting in their best interests in attempting to introduce such measures.
"As a society we must face the possibility that some limits will have to be put on the rapid growth of dairying. The faster and better farmers respond to the need for changing methods, the more likely it is that we can postpone or avoid this.
"The agriculture sector is still the cornerstone of our export economy, but the fundamental advantage it enjoys today springs from the historical accident of New Zealand's clean, green image. Customers are not going to continue to accept food from a system that is degrading water quality, overusing water quantity, losing soil into the sea 10-times faster rate than the rest of the world.
"It also has to be recognised that New Zealand agriculture is dependent on non-renewable energy that is a major source of the greenhouse gases that is changing the very climate on which our farming depends.
"If farming is to be become sustainable it must be rethought on the basis of ecological systems, not just on the basis of short-term economics. It cannot be economic if it is destroying its resource base and destroying the natural capital on which our future depends," said Ms Fitzsimons.