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New Zealand’s beech forests are made up of five species of southern beech. Beech forests are the largest remaining indigenous forest type in New Zealand, mainly because beech forests are found on mountainous land not generally regarded as the best for agriculture.

Bumper beech seed triggers pest plague

The heaviest beech forest seedfall in more than a decade is happening now in 2014. It is expected the increased seedfall will lead to an explosion in the numbers of rats, mice and stoats, who will turn to our native birds for food once the seeds disappear.

Without help many native species will suffer dramatic declines over the next year. This massive beech mast event requires quick decisive action to protect populations from further depletion.

Facts about beech trees in New Zealand

  • A bit less than a quarter of New Zealand is still covered in native forest (6.4 million ha)
  • Of these forests, about two thirds have some beech in them (4 million ha)
  • About half of these have almost nothing but beech trees (2 million ha)
  • Beech trees can produce millions of seeds, and during a heavy seed fall about 50 million seeds (about 250 kg of seeds) will fall per hectare.

Bumper seed or 'mast'

Beech trees generally seed every four to five years but weather conditions over the last two summers - a cool summer followed by a warm one - appear to have triggered a bumper seed or 'beech mast' event. Intense and widespread flowering throughout North and South Island beech forests during spring and early summer has prompted the need for urgent action.

Past experience has shown that when a beech mast occurs, it leads to a dramatic rise in mice and rat populations, who feast on the plentiful seed all winter. A single female rat can potentially produce 10 offspring every eight weeks.

Mountain beech flowers. Photo: Herb Christophers.
Mountain beech flowers

Predator explosion

An explosion in rodent numbers leads to a sharp rise in the number of stoats, which also pose a lethal threat to many species.

In spring, when the seed runs out, germinates and rots, these predators will then prey on native birds and their eggs, as well as other critically endangered critters such as native bats and snails.

View predator plague cycle diagram

Species at risk

Beech mast 2014 logo.

This will put some of our most threatened species at risk of extinction. South Island populations at risk include two types of kiwi (great spotted kiwi and Haast tokoeka), yellowhead/mōhua, orange fronted parakeet/kākāriki karaka, kea, kākā, blue duck/whio, rock wren, long and short tailed bats/pekapeka and powelliphanta land snails.

Find out more about species at risk

Battle for our Birds programme

The Department of Conservation is preparing a major pest control campaign in 2014 to protect vulnerable native species from an expected surge in rat and stoat numbers. DOC will extend the South Island forest areas targeted for aerial protection with biodegradable 1080 pesticide and boost ground based trapping networks.

Find out about DOC’s largest-ever species protection programme ‘Battle for Our Birds’.

Beech species

New Zealand has five species of beech, each prefer different soil and climate conditions.

  • Hard Beech (Nothofagus truncata) and black beech (Nothofagus solandri) are found in the lowland areas of the North Island and northern South Island.
  • Red beech (N. fusca) prefers the foothills and inland river valley floors particularly where soils are fertile and well drained. Silver beech (N. menziesii) prefers higher, wetter conditions.
  • Silver beech is the most widespread tall tree in Fiordland.
  • Mountain beech (N. solandri var cliffortioides) grows in the mountains and on less fertile soils than silver beech, often forming the tree line at high altitudes.

Reproductive cycle

Beech trees flower in spring and are wind pollinated. After fertilisation, beech flowers produce seeds in the form of small winged nuts which fall in autumn. The seeds rarely blow more than a few metres before falling to the forest floor where they germinate the following spring. The half light of the forest floor stunts the growth of seedlings until a mature tree falls and light floods in. Once established, a beech tree can grow over 30 metres tall and can live for more than 300 years.

Mistletoe and fungi dependent on beech trees

Three species of native mistletoe depend on beech forests for their survival. Korukoru or crimson mistletoe (Peraxilla colensoi) has scarlet, sometimes yellow, flowers and can reach three metres across. This mistletoe grows almost exclusively on silver beech. Pirirangi or red mistletoe (Peraxilla tetrapetala) has bright red flowers and grows on black, mountain and silver beech. Alepis flavida, has orange-yellow flowers, and is found mainly on mountain and black beech. All three species of mistletoe are threatened with extinction from possum browse.

The beech strawberry fungus (Cyttaria gunnii) has distinctive orange-yellow golf-ball-like fruiting bodies and is only found on silver beech.

A group of fungi, known as mycorrhizae, enjoy a mutually beneficial relationship with beech trees. Living on the tree roots, the fungi take sugars while in return the beech tree absorbs minerals, which the fungus has transported from the surrounding soil.

Beech forest, Eglinton Valley, Fiordland National Park.
Beech forest, Eglinton Valley, Fiordland National Park


The beech scale insect plays a vital role in the food supply for a range of native bird and insect species. The native insect lives in the bark of beech trees drawing off the sap. The insect then excretes sugary liquid drops, known as honeydew.

Beech scale insects infest all species of beech tree except silver beech. They are particularly common on beech at the foothills of the Southern Alps. The honeydew drops have a high sugar content and are an important energy source for birds including tui, bellbirds and kaka. Lizards, possums, rats, honeybees and wasps have also been recorded feeding on honeydew.


  • Possums do enormous damage to native New Zealand forests. Apart from damaging the trees and other flora, they compete with native animals and birds for food, and prey upon birds, their eggs and nestlings.
  • The high wasp numbers in some forests, such as Nelson Lakes National Park, have depleted the honeydew and dramatically reduced the abundance of insects and spiders. This has had flow on effects on birds that eat the honeydew and insects. Trees have been seen with around 400 wasps crawling over them. 
  • Land clearance has reduced the size of our native beech forests, particularly in the foothills of the Southern Alps.
  • Browsing by introduced mammals such as deer and sheep seriously limit the capacity of a beech forest to regenerate.
  • Fire is an obvious threat to beech forest and fire restrictions apply all year round to many areas of land managed by the New Zealand Department of Conservation.

How can you help?

When enjoying beech forests, take note of any signs warning of poison and other Department of Conservation signs. Do not interfere with native birds or the traps and bait stations that are there to protect them. Dogs are not allowed in national parks and restrictions may apply elsewhere. In places where they are allowed, dogs must be under control.

When enjoying the outdoors, pay attention to fire warnings and local weather conditions. Trampers, hunters, fishers and other explorers of the backcountry are asked to carry in personal cooking equipment and only operate stoves well clear of vegetation. Land owners should be aware that in New Zealand permits are required to light fires within one kilometre of public conservation land. It is important to remember that fire authorities can seek to recover costs if a fire gets out of control.

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DOC's 24 hour emergency hotline:

0800 DOC HOT (0800 362 468)

Call to report sick or injured wildlife, and whale or dolphin strandings.