Great Barrier's future is in islanders' hands

by Tim Higham,
Manager Hauraki Gulf Forum

Kiwis are the most unlikely birds: Pinocchio-beak, Lomu-legs and a Keira Knightley breast. I watched one on Motutapu recently, blinking, whiskers twitching, taking in the helicopter-assisted adjustment from the Coromandel, among the first to be returned to the island.

Who is behind such a moment, when news cameras whir, children gasp and hairs on the backs of necks stand on end? Literally thousands of people: political champions, business partners, supportive iwi, careful managers, technical experts, tireless workers, volunteer crews and supportive public – early adopters, main streamers and last-on-boarders … Successes like this take time and Motutapu’s kiwis are the latest reason to celebrate in a chain of island milestones.

In the 1970s there was no shortage of nay-saying when junior lecturers John Craig and Neil Mitchell suggested pest-plagued, sun-addled Tiritiri Matangi might become a forested wildlife sanctuary. Today it supplies and exchanges native birds and reptiles with a growing network of copycat and sister projects: Motuihe, Motuora, Hauturu/ Little Barrier, Motukorea/ Browns, Rakino, Rangitoto-Motutapu, Mokohinau, Tawharanui, Waitakere’s Ark in the Park as well as islands and sanctuaries outside the Hauraki Gulf.

The restoration of islands is a bright spot in an otherwise underwhelming story of environmental management around the Hauraki Gulf Marine Park.

The Hauraki Gulf Forum’s 2011 State of our Gulf assessment compiled monitoring information from land and fishery management agencies and found most indicators showed ongoing decline or levels associated with poor environmental condition. It is easy to look out over the Gulf on a fine day, marvel at its natural beauty, unaware of the changes and stressors wrought upon it.

Around Barrier it can be hard to find a decent patch of legal-sized paua. I’ve heard it suggested they don’t grow that big in these waters (perhaps justifying the taking of a few smaller ones?) Rather, remaining paua are likely to be relic populations (there are a few carefully hidden ones well over 125 cm around) and the attitude is known as using a sliding baseline: each generation sees as normal a reduced environmental state without memory of, or reference to, historical benchmarks.

Others might be surprised that hapuku – now caught at carefully-guarded GPS co-ordinates in deep-water – was once a top predator of inshore reefs. But left alone for a decent while, paua and hapuku would find their way back to their original densities and habitats.

Like at the Leigh marine reserve, where large snapper are nine times more abundant than surrounding areas, and at Tawharanui where the reserve’s 3.5 km of reefs hold as many crayfish as 40 km stretches either side. Kelp forest and associated reef communities are markedly healthier in the reserves as the abundance and size of top predators keeps species like kina in a natural equilibrium.

To the west of Great Barrier the habitat type which once covered much of the Firth of Thames and Tamaki Strait has all but disappeared. Dense beds of sub-tidal green-lipped mussels were dredged until uneconomic in a 30-year period until 1967. Then the last few beds were heavily poached through the 1970s to sell in pub raffles.

With them went one of the most productive ecosystems of the Gulf. Mussel reefs provide shelter for algae, small invertebrates and juvenile fish. Densities of fish are 10 times higher than surrounding sandy areas. And at their prime mussel reefs could have filtered the entire water of the Firth in a day compared to the two years it would take the remaining patches today.

Mussel spat has not been able to re-establish on the bare substrates left after dredging and the muddy sediments accumulating from land run-off. The cycle of natural regeneration has changed, and passed a tipping point. The beds won’t return now without active intervention.

Shifting baselines and tipping points are important in understanding Great Barrier Island’s future.

The big picture first: Since their arrival, humans have eliminated nearly half of New Zealand’s original native bird species and, of the remainder, a large proportion are threatened.

Great Barrier has fared a little better than most places, as its isolation meant some of the country’s most voracious predators, like Norway rats, stoats and possums, were excluded. But ship rats and cats did make it and have thrived. Populations of birds, reptiles and insects that may be taken for granted and viewed as common, are slowly, sometimes suddenly, less abundant: kokako, whiteheads and riflemen are the most recent disappearances from the island; bitterns, kakariki and tomtits are noticeably scarce; and kaka, black petrels and wood pigeons are likely to be next.

At a recent seminar organized by the Hauraki Gulf Forum the Prime Minister’s Science Advisor Sir Peter Gluckman suggested we focus resources on preserving whole ecosystems. “We need to get cleverer at looking at species before they reach their tipping points.”

Windy Hill and Glenfern Sanctuary enable comparison between environments where predatory pressures vary from intense to light. Where rodents, cats and pigs are kept at very low densities, plants such as nikau and puriri seedlings, insects such as weta, and birds like wood pigeons, kaka and tui are more abundant. Re-introduced New Zealand robins can survive and breed successfully.

Outside the sanctuaries, the island is noticeably quieter, and will become more so, as rats and cats work their way through fauna at a rate faster than it can reproduce.

Once a population is pushed past a tipping point it is lost from the island and won’t come back, unless through active intervention (assuming a sanctuary exists elsewhere) and to an environment where the stressors are contained.

Glenfern and Windy Hill sanctuaries are proof of the possible. Critical to their success has been the regular application of predator control methods, including trapping and a range of toxic baits – carefully monitored for environmental impacts – and, in the case of Glenfern, a predator-proof fence. But surrounded by cat and rat infested land they have to deal with constant re-invasion and re-application of the control methods. If you want a battleground analogy think the Balkans conflict compared to the Battle of Britain. Rather than being called upon to fight incursions from multiple sides, an island with a moat proved more successful in defense.

If eradication was done once, everywhere, there would be no need for ongoing application of costly control measures and, for some people, concern about environmental effects.

By using a range of techniques Glenfern and Windy Hill are building knowledge about whether a complementary mix and match approach might be possible at broader scale, according to environmental factors and community preferences.

Another lesson has been that economic benefits accrue for investments in enhancement. Windy Hill has created 18 jobs over the last 13 years and currently provides eight jobs for islanders, while guided walks and accommodation support Glenfern’s mission.

A whole island as a lived in, worked in sanctuary, with regenerating and thriving native flora and fauna, is likely to create similar opportunities in biodiversity and tourism related business.

At the Hauraki Gulf Marine Park scale, a recent stock-take of economic activity commissioned by the Hauraki Gulf Forum showed tourism and marine recreational activity providing the lion’s share of earnings and jobs. These sectors also have much greater capacity to grow than extractive uses, suggesting enhancement and economic development are broadly compatible and identifying the potential for an industry cluster with environment at the heart of its business case.

Great Barrier Island can gain from a “blue-green” economic growth agenda, increasingly recognized and promoted in business, local and central government circles. The Great Barrier Local Board’s recent commitment to community consultation about the island’s environmental future is timely and significant.

Like the cast of thousands that made Motutapu a place of celebration and wonder, there’s a similar opportunity for the people of Great Barrier to think carefully and find their mojo.