Key points
- New Zealand straddles two tectonic plates whose edges are crunching
against each other. The resulting earth movements have produced hilly
and mountainous terrain over two-thirds of the land, with frequent
earthquakes in most parts of the country and a zone of volcanic and
geothermal activity in the central North Island.
- Three quarters of New Zealand's land mass consists of geologically
young sedimentary rocks which tend to be erodible. The known mineral
resources are dominated by coal, gold, silver, and beach sand deposits
of iron and titanium. Large amounts of sand, gravel and rocks are
used for building, and limestone for fertiliser, building and other
purposes. Economic exploitation of other minerals has been slight,
though deposits of aluminium, uranium, halloysite clay, potassium
and sulphur exist in recoverable amounts.
- New Zealand's soils, which mostly evolved under forests, tend to
be thin and acidic with low levels of nitrogen, phosphorus, and sulphur.
As a result, nearly all soils used for crops and pasture need to be
'developed' and maintained with nitrogen-fixing legumes (e.g. clover),
significant inputs of fertilisers, and often lime. In some areas,
exotic planted forests also require fertilisers.
- Since human settlement approximately 700-800 years ago, the indigenous
forests, which once covered about 85 percent of the land area, have
been reduced from some 23 million hectares to approximately 6.2 million
(23 percent of the land area)-mostly confined to mountain areas and
to some low-lying parts of the West Coast, Southland and Northland.
In most areas lowland forests have been reduced to fragments and will
need considerable expansion if the biodiversity within them is to
be sustained.
- Of the surviving indigenous forests, 4.9 million hectares are Crown-owned
and 1.3 million hectares are privately owned. Most of the Crown forests
are on fully protected conservation land (except for 150,000 hectares
set aside for timber production on the West Coast). Most of the private
indigenous forests are unprotected from conversion to other land uses,
but timber production from them is subject to the sustainable management
provisions of the Forests Act 1949 (except for 60,000 hectares set
aside for economic purposes under the South Island Landless Māoris
Act 1906, the management regime for which is currently under negotiation).
- The biggest threat to the remaining forests comes from tree and
seedling destruction by possums, goats and deer. These pose a serious
risk to biodiversity on some 1.8 million hectares of Department of
Conservation land. The Department runs pest control operations over
about 1.3 million hectares and its pest control funding has been increased.
Invasive weeds are also a threat and are subject to control operations.
- Duneland ecosystems cover about 50,000 hectares, most of which have
been heavily modified by grazing, fires, drainage, coastal development
and introduced trees and grasses. A further 250,000 hectares of sand
dunes are covered in pasture, pine forests or scrub. The inter-dune
wetlands are among our most threatened ecosystems.
- Grasslands covered 1-2 million hectares (roughly 5 percent of the
land area) before humans arrived but expanded to almost 8 million
hectares as a result of deforestation by early Māori fires. Further
deforestation in the past 100 years by farmers and timber millers
has extended the grassland area to 14 million hectares-over 50 percent
of the total land area.
- As introduced pasture grasses have expanded, the native grasses
have contracted. Today, there are about 3.3 million hectares of 'tussockpredominant'
grassland and nearly one million hectares of mixed scrub and tussock.
Virtually all of this surviving tussock has been grazed, at least
1.5 million hectares have been degraded by sheep, rabbits and invasive
weeds, and at least half a million hectares have been oversown with
introduced grasses.
- The proportion of New Zealand converted to farmland is large by
world standards (52 percent compared to the world's 37 percent in
1993). Although our human population density is comparatively low
(13 per square kilometre compared to the world's 43) our livestock
density is high (180 sheep per km2 compared to the world's
14, and 35 cattle per km2 compared to the world's 10).
This amounts to 13 sheep and 3 cattle for every person, and makes
pastoral agriculture the country's main land use.
- Although 14 percent of our land is physically able to support crops
or horticulture, standing crops of all sorts (e.g. arable grain and
fodder crops, market gardens, orchards and vineyards) cover less than
2 percent of this area (compared to the world's 11 percent). Conversely,
the area devoted to pasture is twice the world average (50 percent
compared to 25 percent).
- Besides pastoral farming, the other major land use is forestry based
on plantations of exotic conifers. These planted forests cover approximately
1.6 million hectares and are expanding over former farmland at a rate
of about 70,000 hectares per year.
- Because two-thirds of New Zealand consists of hills and mountains,
areas of highly fertile soil and flat to gently rolling terrain are
limited. Only about 31 percent of the land can sustain pastoral farming
(grazing animals) without significant erosion controls. This includes
the 14 percent which could also sustain cultivation. A further 28
percent can support restricted livestock grazing combined with tree
planting, farm forestry or other erosion control measures.
- Soil erosion has been accelerated in many areas since human occupation,
by deforestation and inappropriate land use. National survey data
collected in the 1970s, and more recent local studies, indicate that
over half the country is affected by moderate to slight erosion. Nearly
10 percent has severe to extreme erosion, mostly concentrated in a
few high risk areas (i.e. the eastern North Island, from Wairarapa
to Gisborne, plus parts of Taranaki and the South Island high country).
- No national data exist on other types of soil degradation, though
carbon depletion, nutrient depletion and acidification may be widespread,
and compaction and contamination appear to be common but localised.
- An estimated 7,800 urban and industrial sites may be chemically
contaminated, some 1,500 seriously. Sites associated with contaminating
activities include landfills, service stations, sawmills, timber treatment
plants, railway yards, engine works, metal industries and chemical
manufacturers.
- Several thousand of the nation's 80,000 farms, orchards and market
gardens may have contaminated sites (e.g. old sheep dips, farm landfills),
though no instance of extensive and serious contamination is known.
In addition, some orchard soils have heavy metal residues from fungicides
and some farms have DDT residues. The latter are well managed and
rarely enter the livestock or human food chain.
- Among the main land-use issues in New Zealand are:
- the decline in ecological processes and biodiversity caused
by habitat fragmentation in agricultural and urban areas;
- the impacts of pests and weeds, especially possums, on ecosystems,
crops and livestock;
- the loss of agricultural soils for productive use in North Island
hill country and South Island high country;
- the degradation of 'elite' soils by the impacts of intensive
farming;
- the loss of 'elite' soils to urbanisation;
- the loss of wetlands to land drainage; and
- the degradation of waterways by run-off from farms, urban streets
and subdivisions, and industrial discharges.
- The main laws controlling the environmental effects of land use
are the Resource Management Act 1991 and the Conservation Act 1987,
the former requiring sustainable management and the latter conferring
protection on gazetted areas. Other legislation requires sustainable
logging in native forests, coherent strategies for pest control and
the safe handling of hazardous substances and toxic sites.
- Land users, with assistance from regional councils, the Government's
Public Good Science Fund and environmental grants, are playing an
increasingly active role in developing sustainable land management
programmes and codes of practice (e.g. through community-based organisations,
including 'landcare' groups, Federated Farmers, and the Forest Owners'
Association).
- Although much of the information on the national state of our soils,
vegetation, and land ecosystems is out of date, incomplete, fragmented
or poorly referenced, initiatives are under way to redress some of
these deficiencies. They include:
- the Ministry for the Environment's National Environmental Indicators
Programme which includes the development of a core set of "state
of the land" indicators;
- the National Sustainable Land Management Strategy being coordinated
by the Ministry for the Environment;
- the National Science Strategy for Sustainable Land Management
being developed by the Ministry of Research, Science and Technology
(MoRST);
- the updating of the New Zealand Land Resource Inventory by Landcare
Research;
- the collation of existing data in Landcare Research's Spatial
Database Index;
- the Biodiversity Assessment Programme being developed by Landcare
Research; and
- the development of a national land cover database derived from
satellite imagery by Terralink NZ Ltd (formerly part of the Department
of Survey and Land Information).
- Initiatives are also under way to improve the information base for
land managers at ground level. Monitoring programmes and extension
services of regional councils play a key role, as do the information
networks developed by land user organisations. In addition, the Ministry
of Agriculture is developing sustainability indicators to assist farmers.
Other research and information projects for better land management
are funded through the Government's Public Good Science Fund, the
Ministry for the Environment's Sustainable Management Fund and the
Ministry of Agriculture's Sustainable Agriculture programme.
