This indicator provides information on the population status of selected forest-associated species that are considered to reflect the genetic diversity present in forest ecosystems. Some forest species support or rely heavily on particular forest structures, patterns, associations and processes and can therefore be used to describe the status of genetic diversity in forests as a whole.
The National Biodiversity Monitoring and Reporting Programme (NBMRP), recently implemented by the Department of Conservation, is providing improved information on the population status of selected forest-associated species or species groups (weeds, ungulates, possums, palatable tree species, birds) that are considered to influence the diversity (including genetic diversity) of forests on public conservation land.
Results from the assessment of forest bird community show that indigenous forests support at least twice as many native bird species as introduced ones. This pattern is consistent across forest types (both beech and non-beech). It does not differ between national park and other conservation land. The most abundant and widespread species in indigenous forests include some of New Zealand’s main avian pollinators and seed dispersers (bellbird, tūī, silvereye) and cavity nesting birds such as tomtits, riflemen and kākāriki, which are susceptible to mammalian predation. Of concern is the relatively low occupancy estimates for kererū (about 35 percent), New Zealand’s primary large- seed disperser, and mohua or yellowhead (about 5 percent), a cavity nesting species known to be highly susceptible to mammal (rat and stoat) predation.
Indigenous plant species greatly outnumber exotic weeds in number and abundance in forests on conservation land, and this has not changed over recent years. Introduced ungulates (goats and deer) and possums are widespread in forests. Both are less abundant in beech than in non-beech forests. Palatable tree species such as kāmahi, māhoe and broadleaf continue to regenerate across public conservation land, although there are local sites where pest mammals are preventing their regeneration. While the population size structures of these palatable tree species have been maintained over the last decade, mortality rates have exceeded the rate of recruitment, so current regeneration patterns may not be maintained.