A Green Government would hugely expand protected areas for Maui's dolphin and ban lethal fishing methods, while compensating fisheries for some of their losses, the party revealed this morning.
The Greens' third major environment policy, announced in Wellington this morning, was designed to reverse the decline in Maui's dolphin numbers.
Co-leader Metiria Turei said the dolphin - the smallest and most endangered in the world - was part of New Zealand's natural heritage.
"Scientists across the world are united in their call for much greater protections for Maui's dolphins than National is offering, but National is promising oil drilling and mining over Maui's protection," she said.
If in power, Greens would seek to ban all set nets, trawl nets, mining and oil exploration within the established Maui's sanctuary on the West Coast of the North Island.
The ban would not apply to existing oil wells.
The party would also extend the ban on these lethal fishing methods to the extent of the dolphins' range - from Maunganui Bluff to the Whanganui River on the West Coast, out to 100 metres' depth.
The ban would be a massive increase in protection for the species. At present, set netting is banned in 40 per cent of this region, and trawling in less than 10 per cent of it.
Government estimated that this level of protection would cost commercial fisheries around $13.5 million a year.
To soften the blow, Greens said they would invest $20 million over three years to help fishing companies shift to non-lethal methods.
The Maui's dolphin is endemic to New Zealand, and its habitat is limited to the West Coast. A Marine Mammal Sanctuary has been established around this coastline, though some commercial fishing is still permitted.
Government's latest oil and gas block offer also opened up some of the coastline for mineral exploration, including a 3000 sq km portion of the sanctuary.
Ms Turei said this made the protected area a "sham sanctuary".
The most recent survey of Maui's dolphin numbers, in 2012, estimated that around 55 remained, down from 111 in 2004 and 2000 in the 1970s.
A risk assessment in 2012 estimated that under current protections for the dolphins, five would be killed a year by commercial or recreational boating.
Government responded to this assessment by adding some protection, which would reduce this mortality rate to three or four dolphins a year. A sustainable level is believed to be around one dolphin every 10 to 23 years.
The International Whaling Commission (IWC) said in June that current regulations were inadequate to reverse the decline in the Maui's population.
The proposal was the third part of Greens environmental policy, which also included making all New Zealand rivers safe to swim in and a complete ban on deep-sea oil drilling.
The Labour Party supports increased protection for Maui's.