Up to 90 per cent of seabird populations in northern New Zealand are at risk of extinction, scientists say, with emerging threats like climate change adding extra pressure.
A major review, to be publicly released over the weekend, found "rapid action" was needed to tackle six key threats: invasive species, fisheries, climate change, disease, pollution and direct human impacts like coastal development.
"We must first understand what threats these seabirds are up against before we can establish a baseline from which to work on researching and conserving them," said the review's lead author, Edin Whitehead, a doctoral student at the University of Auckland.
Northern New Zealand was a seabird biodiversity hotspot with more than 28 species breeding in the region, five found nowhere else in the world.
Yet little is known about the status of, and threats to, many of these birds, the Northern New Zealand Seabird Trust report found.
"Some seabird species we have really only just discovered, such as the New Zealand storm petrel breeding on Te Hauturu-o-Toi/Little Barrier Island," report co-author and trust project co-ordinator Chris Gaskin.
"It's quite possible that if the eradication of rats and cats on the island had not happened, we may never have known they were there."
Some of the most vulnerable seabirds include black petrels, threatened by fisheries by-catch, and the fairy tern, New Zealand's most endangered bird, down to around a dozen breeding pairs restricted to an area between Whangarei and Auckland.
The tern was intensively managed during the breeding season, its population directly threatened by human impacts.
While some threats to seabird populations are well known, such as introduced mammalian predators and fisheries, others are only just appearing, such as climate change, pollution and disease.
"Although there has been some progress in eradicating invasive species from islands to restore seabird populations, this isn't enough when they are facing multiple threats both on land and at sea," said report co-author Associate Professor James Russell, of the University of Auckland.
The report was being released at the Birds New Zealand conference in Wellington this weekend.