Key principles for management of threatened species within plantation forests
The following is a summary of key conservation management actions that can be undertaken to protect threatened plants and animals that occur within and adjacent to plantation forests. Further species-specific recommended management actions are given within each species text, as are sources of information and recommended reading.
Protection of existing habitats is the easiest and most cost-effective option to protect indigenous biodiversity. Indigenous forest remnants within and adjacent to plantations should be protected, including patches, corridors, riparian margins, and wetland buffers, and any areas supporting threatened plant species. Many threatened species of plants and fauna will be largely restricted to these areas of indigenous vegetation, while others will benefit from the availability of a greater diversity of food sources and habitat types provided by maintaining indigenous remnants. Indigenous vegetation can also provide refuges when forest is being felled. Fencing may be appropriate in some situations where grazing should be avoided (such as wetlands and their margins). Other habitat types such as rocky areas (e.g. outcrops, cliffs) should not be disturbed as they may provide habitat for lizards.
In addition to the protection of riparian margins, a number of further actions can be undertaken to protect streams and threatened fish and invertebrate species. Fish passage should be provided through artificial barriers within streams such as building up the downstream side of overhanging culverts or providing other routes for climbing species. Water abstraction should be managed, particularly from areas of important habitat. The fishing of threatened species such as longfin eel should be regulated or prevented altogether. Lastly, exotic fish and aquatic weed species should be prevented from establishing in all waterways (including wetlands).
Forest harvest management
Plantation forest should be harvested in a manner that causes the least damage to indigenous remnants, particularly riparian vegetation and wetlands, and any areas that support threatened plant populations. Discharges of sediment-laden run-off from harvested areas into wetlands or other waterways should be avoided. Many species that occur in plantations are able to escape during felling operations, as long as escape routes to other suitable habitat are maintained; staging harvesting to keep escape routes open as long as possible is important for species such as kiwi and weka. Falcon nests will survive harvest if a buffer of 100-200m is maintained around a nesting site.
Avoid grazing, burning or spraying in order to encourage recovery of vegetative cover and higher ground moisture levels. The use of herbicides and pesticides should be minimised near waterways, especially if an area may, or is known to, support native frog populations (specialist advice should be sought if chemical use is unavoidable in areas with frogs). Kiwi use habitat such as slash piles and these microhabitats should be left if possible (or removed/burnt at night when birds are active).
Pest animal control
Introduced mammals such as cats, mustelids (stoats, ferrets, and weasels), hedgehogs, and rats are a key threat to the survival of the majority of threatened fauna on the New Zealand mainland. Mammalian predation affects an array of species including native and endemic invertebrates, reptiles, bats and birds. It is not yet confirmed whether introduced mammals are a threat to endemic frog species. Different threatened species benefit from targeted predator control regimes, tailored to their requirements. For example, North Island kokako require highly intensive possum and rat control, kereru will benefit from slightly less intensive possum and rat control, and North Island brown kiwi primarily require intensive mustelid and cat control. A predator control regime can be purpose-designed to protect a number of threatened fauna species present within an area. Exclusion of dogs should be considered in areas with kiwi or weak, or requirements for kiwi-aversion training for dogs. In coastal areas, black-backed gull predation may be a problem for shore-nesting birds such as New Zealand dotterel.
Many threatened plant species are severely impacted by browsing of pest mammals such as goats, deer and possums, and also wandering stock. Control of pest species and removal or fencing of stock can improve survival of individuals and increase regeneration potential of a number of threatened plant species, as well as improve general vegetation condition and long-term sustainability.
Pest weed control
A wide variety of invasive weeds have the ability to compete with indigenous plants, including threatened species, for light, space, and nutrients. Control of these can help ensure the persistence of these plant species in remnants of indigenous vegetation. Weed species in wetlands, such as willows, can completely change the appearance and function, and viability, of these threatened ecosystems. However, weed control in wetlands can be more complex than in other habitats, and may require the help of a specialist in wetland weed control, particularly in regard to the use of herbicides in these environments. Weeds can also transform sand dunes, and their control will ensure natural dune formation processes are able to continue, benefiting indigenous plants and animals.
Survey and monitoring
Surveys for threatened plants and fauna may need to be undertaken by specialists, particularly those for threatened plant species, lizards, frogs, and invertebrates. Liaison with staff from the Department of Conservation (DOC) will help to clarify the best methods for surveying. Records of threatened species should be passed on to DOC. Certain methods of monitoring are standard for some species such as kiwi and weka. The implementation of a monitoring regime will evaluate whether management actions (such as predator control, weed control for threatened plants) are improving the status of the species in question. Raising the awareness and knowledge of forestry staff will greatly benefit threatened species management.
Community groups can be involved in the conservation management of threatened species in and adjacent to plantations in many ways. These include management of coastal nesting areas, construction and placement of nest boxes, predator control initiatives, weed control initiatives, and monitoring.