That warning comes from Massey University ecologist Dr Mike Joy, who has received the 2013 Charles Fleming Award for Environmental Achievement from the Royal Society of New Zealand.
The award, made every three years, honours people achieving distinction in aspects of the sustainable management of New Zealand's environment.
Dr Joy, of Palmerston North, was presented with the award medal at a recent function at the Otago Museum by the award's previous recipient, University of Otago botanist Emeritus Prof Sir Alan Mark.
Dr Joy also gave the latest in a national series of lectures linked to the award.
In his lecture, titled ''The Demise of New Zealand's Freshwaters: Politics and Science'', he focused on a sharp decline in the country's freshwater quality.
And it was ''past time'' for scientists to ''come out from behind their microscopes, binoculars and computer screens and make a stand on the many environmental issues facing us and our children''.
In an interview, he added that New Zealand was no longer the cheapest producer of dairy produce but was now competing on the high quality of our exports and relied on our clean green environmental reputation.
But, given rising dairy production, New Zealand's freshwaters- ''our lakes, rivers and groundwater outside of the conservation estate'' - were in a ''perilous state''.
The Otago Regional Council was helping by tightening nitrogen leaching controls through its 6A regional water quality plan, and individual farmers were also taking positive action by better protecting waterways, including by fencing.
But plans to further increase dairy production would damage our waterways and ''strong leadership'' was needed to avoid the loss of further ''natural capital'', he said.
