Case study: Opportunities for indigenous biodiversity gains within sand dune plantation forestry in Manawatu/Rangitikei: Retained plantation forests, duneland habits
- Author
- Peterson, P.; Simcock, R.
- Year
- 2020
- Publisher / Organisation
- Manaaki Whenua Landcare Research
- Month
- September
- Pages
- 63
- Summary
- Project and Client This report is an internal case study investigating options to achieve indigenous biodiversity gains within a sand dune plantation forest in the Manawatu/Rangitikei. Objectives Identify options that achieve biodiversity gains within the Tangimoana production forestry landscape. Determine the relative financial costs and indigenous biodiversity benefits of each option and use to prioritise options. Methods Information on the natural and human history of the Tangimoana dunelands was collated from websites, reports, modelling, and papers found using google/google scholar searches. A field trip involving Graeme La Cock, David Havell, and Samantha Gale (Department of Conservation), Paul Horton (Rangitaane o Manawatu), Pat McCarthy (Ernslaw One Ltd), Robyn Simcock and Paul Peterson (Manaaki Whenua – Landcare Research) was held at Tangimoana forest to discuss past, present, and potential future activities, focusing on biodiversity. Expert advice was sought from botanist Dr Jill Rapson (Massey University) who has decades of experience working on sand dune country and its restoration within the Foxton Ecological District. Estimates of costs of different options for promoting indigenous biodiversity were determined in consultation with James Sinclair, Ernslaw One Ltd. Results and Conclusions The case study identified four options to enhance native biodiversity within, or adjacent to, Tangimoana forest. Tabulation of costs and benefits considered indigenous biodiversity management and production implications, and ongoing financial costs, allowing options to be ranked. Restoration within currently retained 250-ha of plantation forest (the coastal shelter belt) was ranked highest. This includes the creation of pockets of duneland habitats by promoting wetland/swampland, scrubland and native forest, mainly by planting and/or natural regeneration following selective killing of pines to increase light levels. This approach provides medium to longer-term indigenous biodiversity benefits with low management and production implications and costs. This option would incur a one-off cost of ~$8K in the 1 st year for tree removal ($4,200), conversion of fire ponds ($2520) and weed and pest control ($4.56/ha) + $15,000/ha for restoration planting. The ongoing cost would be $4.56/ha/yr ($1,140/yr) for weed and pest control. The second-ranked option involves connecting the current retained coastal plantation forest to the inland Pukepuke lagoon with a 160-ha ecological corridor. For landscape- scale benefits, connectivity over space and time needs to be considered alongside creation and protection of a range of dune habitats. This option requires a significant reduction in production forest (with associated lost opportunity costs) but offers - 6 - landscape-scale benefits that may be unique in the area. Given the depauperate native seed sources, much of the corridor would likely be established by restoration planting once the pine plantation is felled. This option would incur a one-off cost of ~$300,000 in the 1 st year for lost opportunity cost ($2000/ha) and weed and pest control ($4.56/ha) + $15,000/ha for restoration planting (unless volunteer). The ongoing cost would be $2000/ha+$4.56/ha (~$300K/yr) for lost opportunity cost and weed and pest control. The third ranked option is to refine harvesting methods and replant areas for biodiversity benefits within the productive forest. While this option has relatively low management, production and financial costs, longer-term biodiversity benefits are limited to those species that can move or disperse quickly when areas are harvested. Total ongoing costs are already being spent, for those activities that are practical, but were not defined by Ernslaw One. The final option is to facilitate protection and enhancement of the adjacent 152-ha Tawhirihoe Scientific Reserve. Ernslaw One machinery and expertise could be used to assist this neighbouring area where the priority is conservation. However, Ernslaw One prefer to undertake any ‘equivalence work’ within their own estate. This option would incur a one-off cost of ~$5000 in the 1 st year for earthworks, tree felling, barrier and signage placement and weed and pest control. Plan preparation and resource consent applications may also be required for earthworks (estimated $20-$50,000). The ongoing cost would be $4.56/ha/yr ($693/yr) for weed and pest control.