Forests, and particularly indigenous forests, support a substantial proportion of the planet’s biological diversity and terrestrial species. The biological diversity and sustainability of forest ecosystems may depend on forest size, diversity, ownership stability and the values placed on ecosystem services.
The sustainability and stability of forest ecosystems may depend on their size and diversity. Human activities and natural processes can reduce biological diversity by altering and fragmenting habitats, introducing invasive species, or reducing the population or ranges of species.
The total forested area of New Zealand is a little over 10 million hectares:
Plantation forests expanded steadily through to the early 2000s, but have since shown a small (about 3 percent) decline as some existing plantations are converted to agriculture, notably dairy farming. Decline in forest area may mean forests become vulnerable to habitat degradation and loss.
Over the last decade areas of some forest species have declined:
Conversely the area of Douglas-fir has increased marginally (2.4 percent), and there has been a substantial (about 70 percent) increase in cypress plantings, albeit from a low base.
While most tall indigenous forests (76 percent) remain in public ownership, large areas of plantation forest have shifted from publicly listed companies to various forms of private ownership over the last decade.
New Zealanders recognise a wide range of values associated with both indigenous and plantation forests including: