The uncontrolled spread of introduced conifers (wilding conifers) presently threatens over 210,000 hectares of land administered by the Department of Conservation (DOC) in the South Island. Wilding conifers threaten native plant communities, endangered species, and important wildlife habitat. In some cases plant communities and species, such as bog pine shrublands, the rare Hebe cupressoides and the Cromwell chafer beetle, are threatened with local extinction. Wilding conifers also threaten the distinctive expansive landscapes of the South Island, historic and cultural sites, and recreation opportunities.
Wilding conifers are defined, for the purposes of this strategy, as introduced species of the Class Coniferopsida (Gymnospermae) that are self-sown or growing wild (i.e. naturalised). Typically wilding conifers have spread from planted trees, and these plantings often provide a continuing seed source for further wilding spread. Eighteen species of wilding conifer threaten DOC-administered land in the South Island, five of which comprise most of the spread (contorta pine, Corsican pine, Douglas fir, radiata pine and larch).
These wilding conifer species are characterised by their ability to disperse, and the vigour of their growth. They can produce cones at between eight and thirteen years of age, and produce vast quantities of seed that can be dispersed for distances of over 10 kilometres in favourable conditions. Wilding conifers are long-lived and can out-compete other plant species in nearly all communities except dense forest. Dense infestations will reduce water yield from stream catchments, reduce the profitability of pastoral farming, restrict access for recreation, and transform scenic landscapes.
There are at least 245 DOC-administered sites threatened by wilding conifer spread in the South Island, from regenerating native forest in the Marlborough Sounds to dunes on Stewart Island, and from estuary margins on the West Coast to areas above the natural timberline in the eastern Southern Alps. The Department spent at least $236,000 and 3686 hours of staff time controlling wilding conifer infestations in the South Island in the 1999/2000 financial year. An additional $112,000 has been allocated to new wilding conifer control projects in the 2000/2001 financial year. Not all infestations are controlled as, at present, there are insufficient funds to do so. If wilding conifer control was neglected for just a few years many important conservation sites would be damaged beyond repair and the cost of removing new infestations would rise exponentially.
This strategy covers all wilding conifer spread that threatens DOC-administered land in the South Island. The purposes of the strategy are to describe the present wilding conifer problem, to outline the conservation values at risk from wilding conifer spread, to identify the Department's wilding conifer control obligations, and to propose options for the control of wilding conifers. Control priorities proposed have been determined using the methodology of Department's Strategic Plan for Managing Invasive Weeds. The strategy is compatible with the Department's Conservation Management Strategies and with Area Weed Strategies.
Wilding conifers affect large parts of the South Island, are the most significant weed threat in many areas, and do not discriminate between land tenures and property boundaries. Control of wilding conifers must be targeted at the most important sites, coordinated between land management agencies and landowners, and be sustained for as long as there is a risk of re-infestation. This Wilding Conifer Strategy aims to help ensure that this will occur.
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