Biodiversity

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. 

Forest size and diversity

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:

  • 6.8 million hectares tall indigenous forest
  • 1.2 million hectares regenerating forest
  • 2.1 million hectares plantation forest.

Forest area and percentage by forest class

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:

  • radiata pine by 4.7 percent (76 700 hectares)
  • eucalypts by 38 percent (13 400 hectares)
  • other exotic hardwood species by 35 percent (6800 hectares)
  • other exotic softwoods by 13 percent (3700 hectares).

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.

Forest ownership types

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.

Ecosystem services

New Zealanders recognise a wide range of values associated with both indigenous and plantation forests including:

  • biodiversity at the species and ecosystem levels, and the ability of ecosystems to function in a healthy state
  • access to non-polluted drinking water catchments and waterways
  • the contributions forests make to soil conservation and carbon sinks
  • wild animal hunting and the cultural harvest of plant species.

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