How the restoration project began
The first version of the Tiromoana Bush Restoration Management Plan was prepared in 2004. This plan and subsequent plan focused on using plant and animal pest control, and strategic restoration plantings, to facilitate the natural development of Tiromoana Bush to a state where native forests and wetlands, and their associated fauna, dominate the site. This plan has been updated approximately every five years, and a detailed review of restoration progress over the first 18 years was undertaken in 2022.
Vision
Tiromoana – He Kitenga O Te Wāheke (A View To The Future)
Take a moment to imagine… standing here 300 years from now you will see before you a mosaic of forest and wetland. New Zealand’s tallest tree – kahikatea – towers above wetlands, their buttressed roots holding firm. Mighty tōtara clothe the hillsides leading down to the coast, with patches of tawhai/black beech on the dry ridges. Trees echo with the voices of korimako/bellbird, tūī and the whirr of kererū wings. Wildlife flourishes and people visit to learn, recreate and enjoy.
Mō tātou, ā, mō kā uri, ā muri ake nei (For us and our children after us)
At the outset of the project, domestic livestock (sheep and cattle) were removed from Tiromoana Bush and a QEII National Trust Open Space Covenant gazetted on the property’s title. This covenant provides protection for the area for future generations irrespective of any change of ownership.
Management has focused on facilitating the natural regeneration of forest and wetland to achieve the vision through:
- Reducing the numbers of exotic grazing animals (deer and pigs) to levels that do not impact natural regeneration or restoration plantings.
- Controlling exotic animals that prey on native fauna (cats, possums, stoats, rats, hedgehogs) to enable native birds and lizards to become more abundant.
- Focusing plant pest control on those species with the potential to limit natural regeneration and restoration plantings.
- Using strategic restoration plantings to enhance connectivity, increase food resources for birds and reintroduce locally extinct species.
- Monitoring how the fauna and vegetation responds to this management.
- Providing public access to the site for education and recreation.
Deer and pig control
The deer fence was completed in 2017, and a major deer cull was undertaken after that. Pigs are a more recent arrival in the wider landscape and are more difficult to control as they can go under fences. However, regular pig culls have been successful at keeping numbers down. The occasional deer remaining within the deer fence, or able to get through it, are usually eliminated during pig culls.
Small mammal predator control
An assessment of exotic carnivores was completed in 2018 and showed the presence, in moderate to high numbers, of a suite of small mammals including mice, rats, mustelids (weasels, stoats and ferrets), cats, hedgehogs and possums. A predator control programme began in 2019 based on a network of 200 paired DOC200 and Timms traps spread through the bush. As a result of trapping, mustelid, possum, hedgehog and cat numbers have declined with time, indicating the suppression of these species, but rodent numbers have been less impacted, perhaps because their predators (cats and mustelids) have been suppressed and also because of the abundance of grass seed in the area. Small mammal predator control will continue to be a major priority for management at Tiromoana Bush as reinvasion is constantly occurring from surrounding areas and numbers can increase rapidly if control stops.
Plant pest control
Annual weed control is undertaken focusing on species such as wilding conifers, willows, and old man’s beard that have the potential to smother native vegetation. Gorse and European broom are not controlled as they act as a nursery for native forest regeneration and the cost and potential damage to native vegetation associated with their control outweighs any biodiversity benefits. As the native plants become established and successfully compete for water, nutrients in the soil and light the gorse dies out and is replaced by native forest.
Annual programme of restoration planting
Strategic restoration plantings are undertaken annually to increase the area of native forest and wetland vegetation, as well as providing nesting sites and food resources for native birds. Approximately 1 hectare of restoration planting takes place each year, with all plant species sourced either from Tiromoana Bush or from elsewhere in the Motunau Ecological District. A key focus has been on enhancing linkages between existing areas of regenerating forest and re-establishing rare ecosystems, such as wetlands and coastal forest. Restoration plantings have been primarily located on the floor of Kate Valley and in the coastal zone of lower Kate Stream, although some enrichment of regenerating kanuka forests has been undertaken (mainly with tōtara). One of the major focuses of restoration plantings in the last few years has been to establish a kahikatea forest-wetland complex on the floor of Kate Valley.
Monitoring is essential and important
Regular monitoring and photographing of vegetation and landscape, birds and animal pests over the last 20 years has enabled progress to be assessed. Monitoring has focused on biodiversity outcomes, rather than management actions and shows a marked improvement of the condition and abundance of native species in Tiromoana Bush. The photo-monitoring shows some very encouraging results. In particular there has been a marked increase in native woody cover right across Tiromoana Bush, including both natural regeneration into previously pasture areas and from restoration plantings. In addition, native shrublands appear to be becoming more diverse with mahoe invading into matagouri-mingimingi shrubland. The photos also clearly show the expansion of wetlands and wetland vegetation
Vegetation monitoring has focused on both the existing areas of regenerating native forest and on restoration plantings. Permanent 10 x 10 metre monitoring plots have been used to quantify change in species composition through time. The results from this monitoring show both the amazing growth of the restoration plantings and how the regenerating kānuka forest has recovered with grazing exclusion and now has a healthy developing understory of species that will eventually replace the kānuka when it dies.
Bird monitoring shows an increase in the diversity of native forest birds and the presence of nationally threatened or at risk species in the wetlands (marsh and spotless crake and grey duck). Three rare or absent forest birds (tomtit, kereru and shining cuckoo) are now present. Exotic birds have declined. A combination of weather and food availability is likely driving these changes, coupled with the small mammal pest control.
What has been achieved?
Considerable progress has been made towards meeting the 35-year outcomes for the Tiromoana Bush restoration project which even now 20 years into the project gives considerable confidence the project is tracking in the right direction.
- From an ecological perspective this can be seen in the strong biodiversity outcomes achieved – restoration of rare ecosystems, healthy forest understories, abundant natural regeneration in pasture areas, presence of native birds including some species that were rare or absent at the start of the project.
- From a recreational perspective, the walkway is well used, especially following the substantial upgrade that occurred in 2016-2019. And since the start of the project, Tiromoana Bush has been regularly used for university education especially by students from the University of Canterbury.
Looking ahead
There is much that still needs to be done to both consolidate what’s been achieved to date and to ensure the project continues to move forward and eventually fulfills the vision. Key areas where more focus will be given over the next ten years include:
- Continuation of animal pest control, especially keeping small mammal predators including feral cats at low levels, eradicating the final few deer and if possible, exterminating pigs from the site.
- As well as the current focus on kahikatea forest restoration, more emphasis will be given in restoration management to expanding black beech and to facilitating succession within the existing restoration plantings and in naturally regenerated shrubland and forest areas towards a more diverse forest state.
- While some locally rare or absent native bird species appear to be returning to the site (such as tomtit/miromiro and tui), and some species are becoming more abundant, several bird species are unlikely to return without a formal re-introduction programme. Such a re-introduction programme, including fish and lizard species as well as birds, will be an exciting component of future management.
- There is always the opportunity to boost the popularity of the walkway with local and regional communities in Canterbury, as is their potential to increase use by schools and universities.
- Further engagement with Ngāi Tūāhuriri must be positive for the long-term future of the Tiromoana Bush project.
To achieve all these outcomes, it is important the current biodiversity monitoring is continued and where appropriate expanded (for example to include reptiles) and takes advantage of new technologies (such as acoustic bird recorders).