In the “Ecosystem restoration on Mainland New Zealand”
Tuatara on Cuvier Island
Many of the species that have survived these onslaughts are scattered amongst the hundreds of islands that surround the main North and South Islands. They often represent the fragments of species and systems once widespread on the mainland. But despite this fragmentation, we still have most of our flora (over 80% endemism in most groups); over 100 species of endemic flightless crickets; a huge fauna of endemic land snails; the largest fauna of lizards on any temperate archipelago; the tuatara (sole representative of a Triassic group of reptiles); the flightless kiwi; the world’s heaviest and most peculiar parrot (the kakapo); and endemic bats. The islands also provide breeding grounds for 75% of the world’s penguin species, 54% of the world’s albatrosses and half of the world’s petrels, shearwaters and prions (Daugherty et al. 1990).
These diverse remnants represent an enormous challenge. We are not only faced with conservation of our own unique biodiversity, we are also the custodians of species such as seabirds that we share with other nations.
At first the challenge seemed beyond us. Early conservationists could only watch helplessly as more pests, including stoats and ferrets, were introduced to control other introduced pests such as rabbits. Desperate attempts by Richard Henry in the 1890s to shift vulnerable birds including kiwi and kakapo off the mainland and onto islands failed as the stoats swam to the island sanctuaries. History repeated itself in 1962 when ship rats reached Big South Cape Island off Stewart Island. Despite attempts to translocate them to nearby islands, a species of bat, a snipe and a wren failed to establish and are now extinct. Only the South Island saddleback was saved (references in Towns et al. in press). So not only mainland habitats were at risk, all islands were also threatened by the accidental spread of predators such as rats. And this spread seemed inexorable.
Rather than view the situation as hopeless, however, government conservation agencies took a bold pragmatic view. For any island species to survive in the long term we would have to:
- Undertake aggressive, co-ordinated intervention to remove pests - especially introduced predators - from islands.
- Overcome the mindset that such removals were not possible.
- Ensure that the pests could not get back.
Successful removals of cats from islands have been achieved since early this century. Progressively, the more technically difficult problems were attacked. In the last 15 years Department of Conservation staff have successfully cleared many islands of rodents. Yet as recently as 1978 our scientists met in a workshop to consider the problem of rodents on islands and considered that efforts to remove them would be futile. I will shortly give examples to illustrate how technical advances have made these kinds of operations possible. Before I do, however, such achievements have raised some hitherto unexpected philosophical possibilities that should be explored.
Consider what might be achievable if ALL problem pests could be removed from a selection of islands. We could:
- Shift gear from preservation of the last populations of threatened species to their reintroduction to islands previously unsuitable.
- Seek permanent solutions to threatened species problems with very low pest prevention costs.
- Set recovery goals that would realistically see species removed from threatened species lists.
- Knit threatened species recovery into the restoration of whole ecosystems.
The restoration of whole ecosystems could thus be seen as a logical progression from a focus on individual species. The Department of Conservation now has the following strategic goals and policies that encourage the practical application of ecosystem restoration.