A 50 year history of rodent eradications in NZ
reviewed by Emma Waterhouse
A recent paper published in the New Zealand Journal of Ecology
reviews the past half century of rodent eradications on New Zealand
authors document development and implementation of rodent eradication
technologies and look at the major challenges to expansion onto
inhabited islands throughout New Zealand.
The eradication of Norway rats from Maria Island/Ruapuke
was the first rodent eradication in New Zealand, and 50 years later,
about a third of our islands larger than five hectares are rat –free.
These islands tend to be small and uninhabited, and account for only 10%
of the area of offshore islands. Looking ahead, the eradication of
introduced mammalian predators from Rakiura/Stewart Island and
Aotea/Great Barrier would make 50% of the offshore island estate
Not surprisingly then, the authors acknowledge that
the next challenge for eradication is engaging communities on these
inhabited islands to work towards ‘a
common conservation goal such as pest eradication’.
Resident human communities add complexity, and
moving beyond islands considered within current capability (20,000
hectares?) will also require a change in methods to avoid logistics and
costs overwhelming a project. To this end, scientific evidence of
species and ecosystem recovery is increasingly in demand to justify
further investment in new eradications. Other trends noted are the
increasing number of eradications being achieved on mixed-tenure islands
with multiple partners and agencies.
Reinvasion risks are also addressed. Following
mammal eradications, Rangitoto-Motutapu Islands were considered a
high-risk site for human-mediated reinvasion given their location near
Auckland. The joint agency ‘Treasure Islands ‘programme in the Hauraki
Gulf has meant that rodent incursions here, and on other island, are now
intercepted to the extent that very few lead to full island
Going forward, the authors assert that only with
ongoing improvement in eradication and barrier technology will permanent
predator removal from any site in New Zealand be possible.
Russell, JC and Broome, KG. 2016. Fifty years of rodent eradications in
New Zealand: another decade of advances. New Zealand Journal of Ecology
(2016) 40(2): 197-204