The Convention on Biological Diversity and associated New Zealand Biodiversity Strategy define biological diversity as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems”. Section 2 of the Resource Management Act 1991 (RMA) provides a simplified and similar definition, as follows: “the variability among living organisms, and the ecological complexes of which they are a part, including diversity within species, between species, and of ecosystems”.
Components of biological diversity include:
- genetic diversity: the variability in the genetic makeup among individuals within a single species
- species diversity: the variety of species – whether wild or domesticated – within a particular geographical area
- ecological (ecosystem) diversity: the variety of ecosystem types (eg, forests, grasslands, streams, lakes, wetlands and oceans) and their biological communities that interact with one another and their non-living environments. This includes the manner in which the ecosystem functions, which in turn is directly linked to its diversity.
Biological diversity is often shortened to biodiversity, and it is this common terminology that is used in this guidance note. Biodiversity is sometimes interpreted narrowly as a synonym for species richness based on the total number of species present. This interpretation is not consistent with the definitions in the Convention on Biological Diversity, the New Zealand Biodiversity Strategy or the RMA.
A variety of scientific disciplines study different aspects of biodiversity. These disciplines include ecology, population biology, taxonomy and genetics. A scientist may specialise in particular environments (eg, lakes, estuaries, wetlands, forests, scrub) and/or particular groups of biota (eg, vascular plants, insects, freshwater or marine fish, seabirds). Ecologists study the interaction between organisms and their environments.
What is indigenous, endemic and introduced biodiversity?
An indigenous or native species is one that occurs naturally in New Zealand. That is, they have evolved or arrived here without any assistance from humans. Indigenous species include migratory species that travel to or from New Zealand or to or from other parts of the world, to either breed or feed. Some indigenous species occur naturally in other countries (eg, pukeko also occur naturally in Australia).
An endemic species is an indigenous species that breeds exclusively in a specific country or locality. Endemic New Zealand species are of high conservation importance as they are unique to our country and the survival of natural populations can only be ensured in New Zealand.
An introduced species (also known as exotic, adventive or alien species) is one that has been brought to New Zealand by humans, either by accident or intent. Naturalised or acclimatised species are introduced species that breed in the wild and are able to maintain populations in competition with New Zealand’s indigenous biodiversity. Invasive species are introduced species that are considered pests because they negatively affect biodiversity or other values. Cultivated species are those maintained in gardens, horticulture and agriculture.
Why is indigenous biodiversity important and vulnerable?
New Zealand is one of 34 priority global terrestrial biodiversity hotspots. Biodiversity hotspots are defined quantitatively as those areas where:
- there are more than 1500 species (greater than 0.5 per cent of the world total) of endemic vascular plants
- at least 70 per cent of the original habitat has been lost.
Biodiversity hotspots hold especially high numbers of endemic species, yet their combined area of remaining habitat covers only 2.3 per cent of the Earth’s land surface. Each hotspot faces extreme threats and has already lost at least 70 per cent of its original natural vegetation.
New Zealand has an extraordinary number of endemic species. As the New Zealand Biodiversity Strategy points out, this is a result of a long period of isolated evolution and the diversity of New Zealand’s landscapes and seascapes. All three species of New Zealand bat are endemic, as are all four frogs, all 60 reptiles, more than 90 per cent of insects and a similar percentage of marine molluscs, about 80 per cent of vascular plants, 87 per cent of terrestrial birds and 44 per cent of all breeding seabirds.
This level of endemism is remarkable internationally. By comparison, Great Britain, which separated from continental Europe only 10,000 years ago, has only two endemic species – one plant and one animal.
Many New Zealand animal species are endemic at taxonomic levels above that of genus or species. This means that, internationally, they are highly distinctive. For example, there are two orders of birds (one containing 10 extinct species of moa and one containing five kiwi species) and one order of reptiles (containing two species of tuatara) that are found only in New Zealand.
The uniqueness of much of New Zealand’s indigenous biodiversity means that responsibility for its continued existence is entirely ours. It cannot be conserved in nature anywhere else in the world.
New Zealand’s long geographic isolation from other land masses has meant that indigenous species have evolved without terrestrial mammalian species (with the exception of bats). The introduction of mammalian predators and competitors by people has contributed to the extinction of many species and numerous others becoming threatened. Non-mammalian animal pests, such as koi carp and magpies, and thousands of introduced plants also threaten native flora and fauna.
New Zealand’s biodiversity is also vulnerable because of habitat destruction and invasive introduced species. Habitats continue to be destroyed through vegetation clearance, wetland drainage, seabed dredging, dam construction and other habitat degradation.
Potential climate change impacts on indigenous biodiversity
In the future, it is very likely that these existing threats to biodiversity will be exacerbated by the impacts of climate change.
Climate change is projected to affect individual organisms, populations, species distributions and ecosystem composition and function both directly (eg, through increases in temperature and changes in precipitation regimes) and indirectly (eg, through changes in distributions of both native and introduced invasive species).
District and regional councils need to work together to respond to climate change. See the Climate change guidance note for more information.
National, regional and local identity
Many of the New Zealand national emblems are based on our indigenous biological world – such as the koru, silver fern and kiwi. New Zealanders are known around the world as ‘kiwis’.
New Zealand’s indigenous biodiversity is an integral aspect of the Māori world view, and Māori have special roles and responsibilities as ‘kaitiaki’ (guardians). At the local and regional level, New Zealanders often have a strong bond with the landscapes and ecosystems of their region and local area.
Indigenous biodiversity provides a variety of often unrecognised ecosystem services. These services, which can be provided directly or indirectly, include:
- regulation of atmospheric carbon levels and temperature, including sequestration of atmospheric carbon by growing forests
- the retention of soil by catchment vegetation, thereby reducing erosion and downstream sedimentation
- catchment vegetation and wetland moderation of run-off peaks (potentially flooding) and the provision of more consistent water flows in dry conditions
- wetland sediment trapping
- nutrient filtering by riparian and wetland vegetation to improve downstream water quality
- waste decomposition and nutrient recycling
- habitat for native species and ‘taonga’ (treasures)
- provision of resources for medicinal use (traditional and western medicine)
- provision of resources for cultural use
- provision of food (eg, fish, honey) and resources for commercial use
- providing the backdrop and essence of much of New Zealand’s tourism industry
- opportunities for recreational activities
- natural character, aesthetic values and sense of place.
The New Zealand Biodiversity Strategy describes the provision of ecosystem services. The International Union for Conservation of Nature (IUCN) (PDF 4.9MB) published Building Biodiversity Business in 2008, which provides a comprehensive overview of ecosystem services from a business perspective. Information on carbon sequestration in different land covers is available from the Ministry for Primary Industries.
New Zealand’s ecosystems
New Zealand has a great diversity of ecosystems for its land area. Most indigenous terrestrial and freshwater ecosystems are unique to New Zealand although some are structurally similar to ecosystems found in land masses that were once part of the ancient southern continent, ‘Gondwanaland’.
Unique ecosystems include:
- mature kauri forests
- kahikatea swamp forests
- pohutukawa forests
- tall tussock grasslands
- multi-tiered subtropical podocarp/mixed broadleaved rain forests
- mature red beech forests
- scrub dominated by divaricating species
- Fiordland marine ecosystems
- marine environments of the northern offshore islands
- certain seamounts
- geothermal seep ecosystems.
New Zealand ecosystem types
The following are general descriptions of selected ecosystem types in New Zealand:
- shrublands and scrub
- lowland grasslands
- alpine and mountain
- rare ecosystems.
Councils should obtain a better understanding of the specific ecosystems within their boundaries.
The RMA defines wetlands as permanently or intermittently wet areas, shallow water and land water margins that support a natural ecosystem of plants and animals that are adapted to wet conditions. This is a broad definition that includes:
- swamps, marshes, bogs and seeps
- lakes, ponds, rivers and streams
- estuaries and intertidal areas
- geothermal pools, splash zones and wet terraces.
The agreed classification of wetlands in New Zealand includes the full range of wetland types covered by the Ramsar Convention on Wetlands.
Shallow, freshwater wetlands with emergent vegetation (rooted below water or wet soil) are technically referred to as palustrine wetlands. They range from permanently saturated or flooded land (as in marshes, swamps, bogs and lake shores) to land that is wet only seasonally (as in vernal pools).
Wetlands are now one of New Zealand’s rarer ecosystem types, supporting a greater diversity of native species than most other ecosystems, yet nationally they continue to be drained and modified. Over 90 per cent of New Zealand’s freshwater wetlands have been drained, with a 99 per cent loss of the palustrine wetlands in the Bay of Plenty. The loss of large areas of wetland habitat and the introduction of plant and animal pests have threatened the survival of many native species of plants and animals.
Wetland biodiversity values are often vulnerable to:
- vegetation clearance, burning, spraying and discing
- land drainage, humping and hollowing and other re-contouring
- channelising, diverting or piping waterways
- impoundment and damming flows
- barriers to fish passage
- discharges contaminated with sediment, nutrients or toxins
- grazing by stock or feral animals
- predation by feral and domestic animals
- invasion by plant or invertebrate pests.
Wetlands can have very high recreational, cultural and spiritual values and they also perform vital ecosystem services such as improving water quality and reducing flood risks. Peat bogs can be year-round sinks for 2–5 tonnes of carbon per hectare – making them potentially a more important environment for mitigating climate change than native forests.
The diverse range of threats to wetland biodiversity values, the potential for activities far removed from wetlands (eg, up-catchment topdressing) to impact on those values and the often delayed impact of land development changes (eg, hydrological or biosecurity) mean that biodiversity maintenance provisions for wetlands in council planning frameworks need to be comprehensive, complementary and catchment-wide.
Wetlands have been identified as being vulnerable to the impacts of climate change, particularly changes to precipitation. Projected impacts of climate change on wetlands include changes in salinity, primary production and species composition.
Riparian areas are generally defined to be those linear strips of land along the edge of a river or stream over which either the water influences processes on the land (eg, deposition of silt onto a floodplain), or the processes and structures on the land influence attributes of the water (eg, vegetation shading the water surface). Hence riparian strips are as wide as those processes and influences extend, and may vary from 2 to 200 metres in width depending on topography and hydrology.
Current practice is to manage riparian areas for the intrinsic biodiversity values that they can sustain. These include specific plantings to restore spawning habitat quality for whitebait species in intertidal riparian areas; sequential planting of indigenous species of shrubs and trees to catalyse the successional evolution of riparian forest corridors for indigenous wildlife; and control of riparian predators, such as stoats and rats, to restore habitat quality for ground dwelling and nesting waterfowl, such as the endangered brown teal (eg, Northland) and blue duck (eg, Taranaki).
Because of the diverse range of functions and values of riparian areas it has been difficult to reach agreement between different sector interests about how they should be managed and the extent to which damaging activities should be constrained.
The management issues and main options for their resolution are relatively straightforward when addressing potential planning provisions and proposals for new uses or development of riparian areas with existing indigenous vegetation or habitats. Generally, there is substantial support for quite restrictive protective provisions and development setbacks. Often, encouragement for restoration initiatives is provided to offset residual adverse effects of development potentially impacting on riparian or aquatic biodiversity.
However, a major challenge is in applying the sustainable management tests to the continuation of ongoing land use practices and activities in or near to riparian areas that have cumulative adverse impacts on riparian and aquatic habitats and other biodiversity values. While s85 of the RMA constrains the extent to which a plan or proposed plan may restrict activities in such a way that “renders any land incapable of reasonable use”, the definition of the term ‘reasonable use’ would exclude use of the land for an activity whose potential effects on the environment would be significant. Therefore, plan provisions to constrain specified ongoing activities adversely impacting on the biodiversity of riparian and aquatic systems would not necessarily render the land incapable of reasonable use.
Whether or not the establishment of a restrictive rule within such plan provisions could actually constrain existing use activities that were established before the provisions came into force does depend upon whether the intensity of the activity and its effects have increased (s10(1)) in relation to any district plan rule. However, if the provisions and restrictive rules were made in a regional plan for which the use of land was controlled under s30(1)(c) for the purposes of soil conservation, or maintaining or enhancing ecosystems or water quality in water bodies then the existing use rights to continue such activities are effectively negated by s10(4)(a).
Few councils have seriously wrestled with this issue, apart from contributing funding to landowner-initiated riparian retirement projects. However, Environment Waikato has negotiated a package of provisions for Lake Taupo and its tributary streams and catchment that does include progressive restrictions on existing agricultural uses of land and riparian areas. These restrictions are complemented with substantial contributions of funding from central and local government. Environment Bay of Plenty is part-way through a similar process to protect the water bodies of the Rotorua Lakes. It did have a head start in terms of comprehensive riparian retirement and planting programmes for several of the lake catchments, but this component of the Upper Kaituna Catchment Control Scheme of 1974 was highly subsidised by central government.
Most lowland riparian vegetation in developed landscapes is in the form of thin linear strips so is highly vulnerable to ‘edge effects’.
Dunelands are coastal ecosystems based on accreted sediments of low cohesiveness (and conversely high erodibility) with quite variable drainage. Most are composed of sequences of sand dune ridges with finer silts and clays accumulating in the intervening swales, often forming poorly drained linear wetlands and sometimes lakes. They are formed by and evolve through the action of wind on the sand supply delivered to the adjoining drying beach berm.
Other similarly profiled coastal depositional ecosystems are composed of shingle ridges with intervening wetter hollows. These are common where there are very high rates of erosion and transport of coarse sediment and are often associated with braided river systems. These shingle systems are formed by (and conversely removed through) high energy wave action, with only a relatively small amount of finer material reworked by wind action.
Dunes are naturally stabilised by specialised indigenous sand-binding plants. These form the basis of relatively fragile duneland communities. These biological communities include the pioneering plants (such as pingao and spinifex) of ‘active’ fore dunes through to the tall forests that have evolved on stable back dunes over thousands of years. Many indigenous animals that depend on duneland habitats are quite specialised and often have restricted distribution. These include indigenous snails (PDF) such as Succinea archeyi , spiders such as the iconic katipo, shorebirds such as the threatened New Zealand dotterel as well as many species of threatened plants.
Active dunelands owe their natural character to the ongoing movement of sand by wind. These have declined in area by about 80,000 hectares or 70 per cent since the early 1900s. Dunelands are an ecosystem type particularly vulnerable to the impacts of climate change. Dune systems provide a natural defence against coastal erosion and are valued for this ecosystem service.
The main cause of decline has been the stabilisation/afforestation of active dunelands using marram grass and plantation conifers, but agricultural development, uncontrolled grazing by stock, sand mining and urbanisation have caused localised losses. Historically, coastal landfill sites (with their leachates, rats and gulls), military manoeuvres and off-road recreational vehicles have also caused widespread degradation. However, only off-road recreational vehicles are still a major issue. River impoundments and coastal structures can potentially affect sediment supply to beaches.
Weeds threaten the biological integrity of dunelands and affect dune shape. Without effective control, weeds will continue to invade dunelands and replace native vegetation communities.
Tall forests covered around 80 per cent of the land when people first came to New Zealand. The only areas without tall forests were the upper slopes of high mountains, active dunes, frost flats, the margins of rivers with aggrading beds, recently disturbed sites, some areas of wetland and the driest parts of Central Otago.
Indigenous forests have been reduced to around 23 per cent of the country because of clearance, burning and logging. Clearance has concentrated on the favourable land for agriculture and settlement in the lowlands and around the coast. There is a useful series of maps showing the progressive deforestation across New Zealand from the time before people first arrived around 1200 AD, to the beginning of European settlement in 1840 AD and in more recent times at 2000 AD.
New Zealand forests can be divided into two main types. The first is dominated by one or more species of beech, the second by one or more species of native conifer. These two elements are not mutually exclusive. Conifers including the podocarps, native cedars (Libocedrus) and even kauri can grow with beech.
The beeches are the major element in New Zealand forests today. They either totally dominate a forest to form ‘pure beech forest’ or they occur in mixtures with any, or all, of kauri, the podocarps or broadleaf species to form ‘mixed beech forest’. Pure beech forest covers about 46 per cent of the area of indigenous forest in New Zealand today. Thirty-two per cent of indigenous forest has little or no beech.
The beech element tends to be associated with southern latitudes and mountain areas, with 84 per cent of the total indigenous forest area of the South Island being pure or mixed beech forest. Click here to view a map of the extent of beech forests.
New Zealand lowland conifer and broadleaf forests, especially in the north, are structurally like the forests of the tropics. The conifer kahikatea is the tallest tree in New Zealand and can reach heights of 50 metres. It towers, along with the other emergent podocarps (rimu, totara, matai, miro), above the broadleaved hardwood canopy, giving the forest its characteristic layered appearance. Instead of bearing seeds in cones like other conifers, the podocarp seeds are either in a dry nut (eg, rimu), on a fleshy stalk or within a fleshy ‘berry’ (eg, miro). The fleshy ‘berries’ are distributed by large forest birds such as kereru.
Totara, matai and kahikatea favour fertile soils. Where soils are dry, especially at lower altitudes, totara predominates (eg, Horowhenua). Kahikatea prefers the wet soils of alluvial flood plains (eg, Waikato, South Island West Coast). Matai is most abundant on fertile alluvial or volcanic ash soils. Rimu is the most widespread podocarp and is present on a wide range of reasonably moist sites including flats, slopes and ridges around New Zealand.
Dense podocarp stands are not common today. Examples include sites with thick volcanic ash deposits from major volcanic eruptions (eg, parts of Whirinaki Forest in the Central North Island); sites subject to flooding and other alluvial plain processes (eg, flood plains in the Waikato); and some sites of poor drainage (eg, parts of West Coast lowlands).
Several flowering tree species can also be emergent including northern rata, which is present in some North Island and northern South Island podocarp and broadleaf forests.
Kauri grows naturally north of a line from Kawhia to Tauranga and reaches its southern limit at about 38 degrees South. The loss of kauri forest has been immense. In pre-European times New Zealand kauri forests extended over 1,500,000 hectares. Today mature kauri forest occupies only approximately 0.5 percent of its pre-European extent, that is, only approximately 7,500 hectares.
Most of New Zealand’s land birds inhabit native forest or scrub. Many of the uncommon and threatened species (eg, kokako, brown creeper, mohua and saddleback) are completely dependent on quality native forest habitat. Even those species that visit gardens (eg, tui) usually require native forest habitat at times. The tall lowland conifer and broadleaf forests and lowland beech forests are of most value to wildlife as these forests have a diverse habitat structure and complex food webs. Aside from kauri, it is this type of forest that has been most reduced in extent since human arrival in New Zealand.
Today the major threats to indigenous forest ecosystems include:
- damage of sensitive forest vegetation by introduced herbivores (species such as rata, pohutukawa and mistletoe are particularly vulnerable to damage by browsing)
- predation of native forest bird species by a wide range of introduced animal species
- fragmentation of lowland and coastal forests, especially on private land.
A functioning forest ecosystem includes a range of plant species of a wide variety of sizes and the fauna they support. Many smaller plants specialise in growing in the groundcover tier and will never be tall. Sustaining a functioning forest ecosystem involves ensuring that these smaller species are protected. It also means allowing small seedlings of future canopy trees to grow to replace the existing forest canopy when it reaches the end of its natural life. In addition, the dead wood, rocky outcrops, leaf litter and soil that provide specialised habitats required by a vast array of species need to be protected.
In New Zealand, fragmented native forests of drier lowland areas (Northland, Waikato, Manawatu) and in the east (from East Cape to Southland) are likely to be most vulnerable to the impacts of climate change.
Atkinson defines scrub as woody vegetation in which the cover of shrubs and trees in the canopy is greater than 80 percent and in which shrub cover exceeds that of trees. Shrubs are woody plants with a trunk diameter of less than 10 centimetres at chest height.
Shrubland is a plant community in which the cover of shrubs in the canopy is 20–80 per cent and in which the shrub cover exceeds that of any other growth form or bare ground.
New Zealanders generally think of native scrub as either manuka (North Island) or matagouri (South Island), but there are many different types of scrub, falling into two main categories: short-lived (temporary) and long-lived (persistent).
Scrub covers some 7.5 million hectares – 28 per cent of New Zealand. It is often much maligned, considered as wasteland or as invasive in paddocks or plantations. Much of it is still cleared in New Zealand, particularly for plantation establishment.
Scrub plays a valuable role as:
- a climax vegetation type in environments that favour its persistence, such as geothermal, alpine, coastal and wetland areas
- a nursery for regenerating forest
- habitat for many native plants and animals, including threatened species such as kiwi, lizards and rare orchids, some of which only live in scrub
- habitat for unique species such as divaricating plants – a small-leaved, twiggy growth form that possibly evolved in response to moa browsing. These are an important food source and hiding place for lizards
- habitat for around 445 native shrub species (more than twice the number of tree species), just over a third of which are uncommon or threatened
- corridors between other areas of natural vegetation
- buffers to native forest, wetlands and waterways
- land stabilisers, preventing slips and minimising erosion
- storage for greenhouse gases – New Zealand scrub could be accumulating about 1 million tonnes of carbon dioxide per year
- a storehouse of commercial products, such as honey and essential oils, and traditional products, such as medicines.
Most people are familiar with short-lived scrub, usually comprising manuka and common shrubs like five-finger, coprosmas, young pittosporums and wineberry. Short-lived scrub is nature’s ‘band-aid’, covering bare land or abandoned paddocks. It is the early successional stage that allows cleared land to develop back into native forest, usually within 30–50 years in suitable sites.
Long-lived (persistent) scrub occurs where the conditions are too harsh for native forest to establish, such as on mountains, in wetlands, along exposed coastlines, on poor soils and in geothermal areas. Highly specialised plants often grow in long-lived scrub, including prostrate kanuka, marsh ribbonwood, mountain neinei, coastal tree daisy, snow totara and whip-cord hebes.
Scrub is mainly threatened by clearance, but can also be susceptible to weed invasion (particularly wilding pines) and fire, and most areas of scrub will have animal pests such as rodents and mustelids.
A description of scrub and shrubland types in New Zealand including maps showing the national distribution of shrubland is available.
At the time of European settlement, much of the eastern side of the South Island as well as the Southland Plains was in native grassland. Short tussock grassland was on the driest sites and tall tussock grassland was on the moister Southland Plains and eastern Otago Hills. Until relatively recently it was assumed that the short tussock grassland was the original vegetation cover although recent research has shown that this landscape was originally forest.
Short tussock grasslands grow where the annual rainfall is from 350 millimetres to 1000 millimetres. It is likely that the only significant areas of temperate lowland grasslands existing before Polynesian settlement were in the intermontane basins in central Otago, McKenzie and Marlborough where annual rainfall was less than 500 millimetres.
The early European sheep farmers burnt the grasslands and extended them at the expense of forest and scrub communities. Initially the fire killed the speargrasses and much of the matagouri scrub and provided fresh tussock growth for the stock. Eventually the fire weakened and killed the snow tussocks. Their replacements were hard and blue tussocks that were then depleted by the fire and grazing regime.
Rabbits quickly became a plague after their introduction in the 1870s. The settlers soon realised that the European grasses and clovers were more productive and tolerant of grazing than the native grasses. Oversowing using the introduced grasses became common. The depletion of the native vegetation assisted the establishment and spread of introduced plant species, including weeds like Hieracium.
Tall lowland tussock grasslands are dominated by red tussock. Normally red tussock is a species of wetter soils, but following the extensive forest destruction by fire within 200 years of the arrival of Polynesians in Southland, it spread to a wider range of sites in places such as the Southland Plains.
Today the main threats to tussock grassland include:
- oversowing with pasture grasses and topdressing, thereby converting an area to pasture dominated by introduced species
- burning and grazing by domestic stock
- grazing by animal pests
- invasion by weed species (introduced tree species as well as ground species such as Hieracium), especially in areas of degraded grassland.
The ‘invasion’ of grassland by native shrub and tree species is a natural process in areas that were formerly forest.
New Zealand indigenous alpine ecosystems have generally been spared the destruction resulting from human settlement that has occurred to many other New Zealand ecosystems. Thus, their extent has not been significantly reduced in comparison with many lowland ecosystems.
Many alpine areas are relatively small and physically isolated from other alpine areas. This isolation has led to the evolution of endemic species with a limited distribution. Climate change is likely to have a significant effect on small isolated alpine areas because species are unlikely to migrate naturally to alternative environments as the climate warms.
Species with limited climatic ranges and/or restricted habitat requirements are typically the most vulnerable to extinction. Many mountainous areas have endemic species with narrow habitat requirements that could be lost if they cannot move up in elevation. Changes in the duration and depth of snow cover, the location of the upper tree line, reduced glacier extent and a potentially shortened snow-melt period will all affect alpine biodiversity.
There has, however, been damage resulting from introduced animals especially deer, Himalayan thar, chamois and goats. This damage has altered plant species composition led to accelerated erosion where vegetation cover has been significantly reduced. These effects were particularly pronounced in the 1940s to 1970s when deer and thar numbers reached their peaks. While major animal control programmes have reduced numbers of pest animals in the alpine zone, the harsh conditions mean recovery can take a long time. In some places, pest animal numbers may still be too high to allow full recovery of indigenous plants and animals.
Some eastern alpine areas have been used for pastoral farming. Often these areas were burnt deliberately and/or accidentally. As a consequence the alpine vegetation has been degraded and the area is more prone to erosion. Species composition has often been significantly changed as those species sensitive to fire and grazing (especially when the grazing immediately follows fire) are replaced by less sensitive species.
It is projected that 200–300 indigenous New Zealand alpine plant species may become extinct by 2080.
The protection of indigenous vegetation associated with originally rare ecosystems has been identified as one of the four national priorities for biodiversity protection by the Department of Conservation and Ministry for the Environment (PDF 1.39 MB). Rare terrestrial ecosystems are defined as having a total extent of less than 0.5 per cent of New Zealand’s total area and having been rare since before humans colonised New Zealand. The Landcare Research list of 72 rare terrestrial ecosystem types can be used to guide protection at national and regional scales. An equivalent list has not been developed for aquatic ecosystems.
New Zealand vegetation classification
New Zealand vegetation classification: The mostly widely used system is the Atkinson system for New Zealand terrestrial vegetation classification.
New Zealand ecologists commonly use the terrestrial vegetation classification system developed by Ian Atkinson. It includes two components:
- the structural form of the vegetation (eg, forest, grassland)
- the floristic composition as determined by the dominant species (eg, mountain beech forest, manuka scrub).
These standard definitions of structural classes such as forest, scrub, shrubland and treeland can be helpful when writing definitions or criteria in policy, as follows.
- Forest is defined as woody vegetation in which the cover of trees and shrubs in the canopy is more than 80 per cent and in which tree cover exceeds that of shrubs.
- Treeland is defined as vegetation in which the cover of trees in the canopy is 20–80 percent, with tree cover exceeding that of any other growth form, and in which the trees form a discontinuous upper canopy above either a lower canopy of predominantly non-woody vegetation or bare ground, for example, mahoe/bracken treeland.
(Note: Vegetation consisting of trees above shrubs is classified as either forest or scrub depending on the proportion of trees and shrubs in the canopy.)
The system is relatively complex for non-woody vegetation. In palustrine wetlands (particularly where there is a range of species), it may be useful to use the LCDB2 structural class ‘herbaceous freshwater wetland’ rather than distinguishing between rushland, reedland, sedgeland and tussockland.