thumb|300px|[[Clematis vitalba (old man's beard) smothering a cabbage tree (Cordyline australis) in the Port Hills of Christchurch]]

A number of introduced species, some of which have become invasive species, have been added to New Zealand's native flora and fauna. Both deliberate and accidental introductions have been made from the time of the first human settlement, with several waves of Polynesian people at some time before the year 1300, followed by Europeans after 1769.

Almost without exception, the introduced species have been detrimental to the native flora and fauna, but some, such as farmed sheep and cows and the clover upon which they feed, now form a large part of the economy of New Zealand. The possibility of introduced herbivores (deer) to serve as ecological proxies for extinct moa has been questioned.

Biosecurity New Zealand maintains registers and lists of species that are invasive, potentially invasive, or a threat to agriculture or biodiversity. They also manage a small number of species under the National Interest Pest Responses (NIPR) programme. The rainbow lorikeet is the one animal that has been covered by the NIPR, and was eradicated in 2014. All the other species covered by the NIPR, past or present, are weeds.

Some of the invasive animal species are as follows.

Mammals

  • Cat
  • Dog
  • European hare
  • European hedgehog
  • European rabbit (Oryctolagus cuniculus)
  • Fallow deer
  • Ferret (Mustela putorius furo)
  • Goat
  • Himalayan tahr
  • Horse (Equus ferus caballus)
  • House mouse (Mus musculus)
  • Least weasel
  • Pig
  • Stoat (Mustela erminea)
  • Red deer
  • Rusa deer
  • Sambar deer
  • Sika deer
  • Wallaby
  • Wapiti (elk)
  • Whitetail deer

Reptiles

  • Plague skink or rainbow skink (Lampropholis delicata)

Birds

  • Common myna
  • Common redpoll
  • Mallard
  • Mute Swan

Fish

  • Koi
  • Gambusia affinis
  • Common rudd
  • Brown trout

Invertebrates

  • Argentine ant (Linepithema humile)
  • Asian paddle crab (Charybdis japonica)
  • Asian paper wasp (Polistes chinensis)
  • Australian paper wasp (Polistes humilis)
  • Carpet sea squirt (Didemnum vexillum)
  • Common wasp (Vespula vulgaris)
  • European paper wasp (Polistes dominula)
  • German wasp (Vespula germanica)
  • Varroa mite (Varroa destructor)

Spiders

  • there are 73 known introduced spiders, of which 50 are Australian, including

:*Philoponella congregabilis Additionally, as at 2024 the Department of Conservation lists 386 vascular plant species as environmental weeds.

Some of the better-known invasive plant species are:

  • Acacia species (mostly Australian) especially wattle
  • Acanthus - bear's breeches
  • Agapanthus
  • Arrowhead (Sagittaria sagittifolia)
  • Arundo donax - giant reed (or elephant grass)
  • Asiatic knotweed (Reynoutria japonica or Fallopia japonica)
  • Boneseed (Chrysanthemoides monilifera)
  • Boxthorn (Lycium ferossimum)
  • Broom (Cytisus scoparius)
  • Buckthorn (Rhamnus alaternus)
  • Californian thistle (Cirsium arvense)
  • Cape sundew (Drosera capensis)
  • Castor oil plant (Ricinus communis)
  • Caulerpa brachypus
  • Caulerpa parvifolia
  • Moth plant (Araujia sericifera)
  • Old man's beard (Clematis vitalba)
  • Oxygen weed (Egeria)
  • Oxygen weed (Lagarosiphon major)
  • Pampas grass (Cortaderia selloana)
  • Tree privet (Ligustrum lucidum)
  • Chinese privet (Ligustrum sinense)
  • Purple loosestrife (Lythrum salicaria)
  • Queen of the night (Cestrum nocturnum)
  • Rhododendron ponticum
  • Royal fern (Osmunda regalis)
  • Salix cinerea (gray willow)
  • Salix × fragilis (crack willow)
  • Scotch thistle (Onopordum acanthium)
  • Smilax (Asparagus asparagoides)
  • Spikemoss
  • Sycamore (Acer pseudoplatanus)
  • Tradescantia fluminensis
  • Water pennywort (Hydrocotyle umbellata)
  • Woolly nightshade (Solanum mauritianum)
  • Yellow flag (Iris pseudacorus)
  • Zantedeschia ("Arum Lily")

Auckland has been declared to be the weediest city in the world.

See also

Animals in New Zealand

Plants in New Zealand

References

Further reading

;Publications