Why doesn’t everyone want to get
rid of rats, rabbits and feral cats on Great Barrier Island? What are
the perceived downsides to an eradication campaign?
1. Cost. It is a huge task – where will the money come from? Is it worth
2. More ‘trouble’ for residents (e.g. more biosecurity at wharves, more
controls imposed over activities on private land).
3. A strongly held belief that toxins are bad for the environment.
All of these important concerns are being addressed by other island
communities throughout the world (see item on Recent Progress on
Eradications on Inhabited Islands) and currently on Stewart Island,
where a Technical Feasibilty Study was completed by Brent Beavan in 2007
with support from the Stewart Island Rakiura Community Environment Trust
(GBICT can provide this as a PDF, see also item from Brent Beavan in
In different ways all these questions have come to the fore in 2010. Our
State of the Environment Report for Great Barrier demonstrates the
‘worth’ of the island. It outlines the history of environmental changes
on the island, emphasising the National significance of the remaining
biota and the potential of the natural environment to form the focus of
the island’s economy in future. The Report calls for the production of a
Technical Feasibility Study to explore methods, issues, costs and
benefits of island-wide eradication of rats and feral cats. This call
has had a positive response from potential funders. Given stronger
support from the Great Barrier Island Community a feasibility study
could almost certainly get started next year.
Biosecurity is clearly an issue for some residents, who imagine it will
be very difficult to keep rats off the island in future. But, there are
plenty of examples throughout the world where residents have opted for biosecurity measures to keep rats out – for example rats have been
eliminated from, and subsequently kept out of, the landlocked state of
Alberta in Canada since 1950, despite their presence in surrounding
states (Google: rat control Alberta Canada for articles). The Pribilof
Islands, Alaska (U.S.A., c.700 inhabitants), have implemented a strict
rat prevention program, which includes laws barring infested ships from
entering the harbor and requiring onshore industries to establish rat
prevention measures (Ebbert & Byrd 2002; Fritts 2007). On Great Barrier
a possum was recently thought to have jumped off a freight boat in
Tryphena – demonstrating both the risks to our environment, and the need
for more effective controls. The rapid response by Auckland Biosecurity
staff to this event was re-assuring, but the possum should never have
got to Great Barrier in the first place. The re-invasion of Motu
Kaikoura (since 2008) by rats from ‘mainland’ Great Barrier also
provides a salutary lesson: we need to do the research and listen to all
points of view before we write the cheque. Good intentions are not
enough. From the biosecurity perspective this local example, and the
continued efforts needed to keep rats out of Glenfern Sanctuary, are all
part of the learning process. But isolated islands, such as Tiritiri
Matangi, are more relevant to Great Barrier as a whole. Rats were
eliminated from Tiritiri using an aerial brodifacoum drop in 1993.
Thousands of visitors go to Tiritiri every year to witness the
indigenous biodiversity. However, despite this influx of people, plus
many others coming ashore and picnicking at Hobb’s beach from private
boats anchored in the bay, there has not yet been a re-invasion by rats.
Preventing colonisation by rodents is not impossible.
Mammalian toxins also came to the fore on Great Barrier in 2009 and
2010. The film on 1080 by the Graf brothers made compelling viewing, but
was in my view barely relevant to an island with neither possums nor
deer, and with no conceivable use of that toxin. However, the boundaries
between different toxins were blurred, and many people clearly felt
strongly that the risk of ‘contaminating the environment’ with any sort
of poison outweighed the advantages that might come from rat
elimination. We pointed out the misleading way in which some of the New
Zealand research on the effects of toxins on bird populations was
presented in the film (see Environmental News Issue 20, Spring 2009),
but of course science cannot answer all the questions with certainty.
The debate over mining on Te Ahumata also included toxins in the
environment, but centred mainly on the nature of the island’s economy in
the future. The vehemence of the island’s rejection of the inappropriate
mining proposals was reassuring – mining of Schedule 4 land on Great
Barrier was stopped primarily by opposition from residents. The island
residents and the ‘off-islanders’ spoke with one voice on this issue.
Moreover, with a few individual exceptions, all segments of the Great
Barrier Community were united.
In 2011 the island’s links with Auckland will be in some ways
strengthened by the new structure of the Community Board, but also the
island may have more autonomy and ability to make decisions relating to
island issues. The debate over toxins and the mining issue both
generated public meetings, which were well run by the Community Board.
Opposing points of view were put forwards, and listened to. However, the
new board may have more capacity to lead debates, and to influence and
implement decisions. In congratulating the new Board Members on their
election (Scott Mabey and Sue Daly) and the re-elected members (Izzy
Fordham Paul Downie (Chair) and Richard Somerville-Ryan), the Trust also
expresses the hope that public participation in environmental issues
will be seen as core business, and incorporated into a Strategic Plan
for Great Barrier Island.