Source: Auckland Council
Te Kawau Tūmaro ō Tōi / Kawau Island’s forests are showing strong signs they can recover – when long-standing pressures from introduced mammalian pests are removed.
A new baseline forest monitoring report, prepared ahead of a major pest eradication programme, paints a clear picture of both the damage done by browsing animals such as wallabies and possums, and the hopeful future that could follow their removal.
Once the programme is fully completed, Kawau could become one of the largest permanently inhabited islands in the Hauraki Gulf to be free of pest mammals.
Introduced to Kawau Island in the mid-to late-1800s, the four remaining species of wallabies have had a profound impact on the island’s forests. Alongside other pest mammals, they have heavily eaten seedlings and saplings, creating what ecologists describe as a “recruitment bottleneck”– where young plants struggle to grow into the next generation of forest.
Despite this, the forests have not lost their resilience.
Auckland Council’s Principal Specialist for Natural Environment Operations Lisa Tolich says the really encouraging thing is that the building blocks for recovery are still there.
“We’re seeing a dominance of native plants, plenty of seedlings waiting for their chance to grow, and bird communities that are still relatively intact. That tells us these ecosystems are ready to respond once the pressure is lifted.”
Kawau Island has been identified as a strategic priority area under Auckland Council’s Regional Pest Management Plan. The ‘working towards a pest-free Kawau Island’ programme is a collaborative effort led by Auckland Council with funding through the Natural Environment Targeted Rate as well as funding from central government and third-party philanthropic donations. The project is supported by the Manuhiri Kaitiaki Charitable Trust, the Department of Conservation and developed alongside the local community.
The programme is being rolled out in stages. Stage one, which began in autumn 2025, focuses on removing wallabies and possums – the primary browsing pests. A second stage, subject to feasibility, approvals, funding and further community engagement, would target mammalian predators such as rats and stoats.
Before any eradication work began, a network of forest monitoring plots was established across the island to capture a detailed snapshot of current forest health. This baseline allows scientists and land managers to track changes over time, understand how different forest types respond, and adapt management as needed.
The recent findings show recovery is unlikely to look the same everywhere.
Broadleaved forests with existing diversity are expected to bounce back more quickly, while kānuka-dominated areas and exotic forests may take longer to diversify. There is also a note of caution: removing browsing pressure could allow some invasive weeds, currently kept in check by pests, to spread rapidly if not closely monitored.
“Eradication isn’t the end of the story, it’s the beginning of a new phase of stewardship,” says Tolich.
“Ongoing monitoring will be critical so we can spot emerging issues early and respond before they become major problems.”
To do this, the report recommends re-measuring forest plots every two to three years in the short term, then every five years over the longer term. It also suggests targeted monitoring of high-value native species to better understand how individual populations respond to a pest-free future.
Chair of the Policy, Planning and Development Committee Councillor Richard Hills says the findings offer a hopeful message.
“While decades of browsing have destroyed native flora and held Kawau Island’s forests back, the potential for recovery is strong.
“With sustained effort, careful monitoring and community support, Te Kawau Tūmaro ō Tōi forests will once again grow, regenerate and thrive which is promising news for the biodiversity of all of our Hauraki Gulf islands not just Kawau.”
Read the full report on Knowledge Auckland.