Chapter 9: Land

At a glance

Land use and our economy

Land underpins a significant part of our economy. Seventeen per cent of New Zealand’s gross domestic product depends on the top 15 centimetres of our soil.

Land plays an integral part in supporting New Zealand’s top two export earners: tourism and primary production. In 2007, agriculture, forestry, horticulture, and viticulture generated $16.1 billion, $3.6 billion, $2.5 billion, and $662 million respectively in export earnings. In 2006, tourism generated $8.3 billion in export earnings.

Land cover

Reflecting changes in land use, land cover in New Zealand continues to change as our population grows, land prices change, and international commodity prices fluctuate.

In 2002, natural land cover (native forest, native vegetation, and other native land cover, for example, rivers, lakes, snow, ice, and scrub) was New Zealand’s largest land cover at 50 per cent of New Zealand’s total land area. Pasture was our second largest land cover at just over 39 per cent. Exotic forest covered 7.31 per cent of New Zealand’s land area.

Between 1997 and 2002, satellite measurements showed that:

• pastoral land cover decreased by 125,200 hectares (or just over 1 per cent)

• human settlements increased by just over 5,300 hectares (or 3 per cent)

• native vegetation and native forest decreased by 17,200 hectares (or 0.15 per cent)

• exotic forest cover increased by 139,500 hectares (or about 8 per cent)

• horticultural land area increased by 4,500 hectares, with the total area of horticultural land remaining at just under 1.6 per cent of New Zealand’s total land area.

In 2006, the total land area of planted forestry was estimated to be 1.8 million hectares. From 1990 until 2003, a trend of increasing land area in exotic forestry was observed.

Land use

In 2004, pastoral land use (for example, sheep, beef, and dairy farming) was New Zealand’s largest human land use at just over 37 per cent of New Zealand’s total land area.

Although the total area of New Zealand land in pasture has been decreasing since 1972, the area of land in dairy pasture has increased. Between 1996 and 2006, the national dairy herd has grown by 24 per cent. This intensification of agricultural land use has occurred as farmers have responded to economic signals by converting suitable dry-stock pasture, exotic forestry, and existing dairy farms into more intensive dairy farms.

A change to more intensive farming in some regions has resulted in:

• further reduction of freshwater quality in lowland rivers and waterways

• changes in soil health

• increases in some greenhouse gases, for example, methane.

Over the past 10 years, greater diversification of land use has been evident, especially for horticultural land including vineyards, orchards, and perennial crops. As an example, the area of land in vineyards increased by 28 per cent between 1997 and 2002.

From the mid-1990s, there has been a significant reduction in the amount of new exotic forestry plantings. In 2005, the rate of new exotic forest plantings declined to its lowest level since 1959. In 2004, a new trend of not replanting exotic forestry after harvesting became apparent. In addition, some planted exotic forest planting has been converted to pastoral land use before maturity.

Hill-country erosion

Hill-country erosion is estimated to cost New Zealand between $100 million and $150 million each year through the loss of soil and nutrients; loss of production; damage to houses, fences, roads, phone and power lines; and damage to waterways and aquatic habitats. About 10 per cent of New Zealand is classed as severely erodible.

During the 1990s, hill-country erosion eased in some regions. Satellite measurements between 1997 and 2002 showed that 36,400 hectares of land on erosion-prone hill country was converted from pasture to other land covers during this period. The large majority of this (36,300 hectares) was converted to exotic forestry or retired and left to revert to scrub.

Land use affects the environment

Land use puts many different pressures on our environment.

• Urban and rural run-off pollute our waterways and coasts.

• Urban expansion can lead to the loss of land for food and fibre production or the loss of plant and animal habitats.

• Intensive farming (with high animal stocking rates and increased use of fertilisers) can have detrimental effects on groundwater and surface water quality.

• Intensification of agricultural activity can also increase greenhouse gas emissions from animals.

Land use and soil health

Intensively cropped soils (such as market gardens) have lower organic content and poorer soil structure compared with pasture soils, and very high nutrient levels. High levels of available phosphate were also observed under some croplands, reflecting application of fertilisers.

Soils under exotic pasture generally have higher nutrient levels and are less acidic than forestry soils, reflecting the use of lime and phosphate fertilisers to develop agricultural land. Under some dairy farming soils, phosphate levels are high and some forms of nitrogen may be reaching saturation point. When nitrogen levels reach saturation point, excess nitrogen can be leached from soils, affecting water quality. Nitrogen and potentially mineralisable nitrogen were highest under pastoral land use than any other land use.

Monitoring found moderate soil compaction on a large proportion of monitored pastures and some cropping land uses. Soil compaction is caused by farm animals treading on pastures, and vehicle traffic and cultivation on croplands. Compaction can reduce pasture growth and increase rates of nutrient run-off to waterways.

Soil pH (acidity or alkalinity) under exotic forests was found to be similar to that under native forests. Other agricultural land uses exhibit higher pH values (are more alkaline).

Past uses have contaminated some land

New Zealand soils generally contain low levels of contaminants, but past industrial, domestic, or agricultural activities have contaminated some sites. Local government is working to identify these sites and ensure they are appropriately managed.

Our understanding of the extent of land contamination in New Zealand has improved, but a substantial amount of work is still required:

• to assess sites identified as potentially contaminated

• to record information about contaminated sites in a consistent format.

Legislation such as the Hazardous Substances and New Organisms Act 1996 has been enacted to prevent the present-day contamination of land.

Past, present, and future management

Historically, environmental management of land in New Zealand has focused on:

• managing hill-country erosion

• minimising flood risk

• improving the health of pasture soils.

More recently, greater focus has been placed on:

• protecting riparian stream margins

• excluding stock from waterways

• minimising nutrient enrichment of our waterways, including through nutrient budgeting and use of nitrification inhibitors

• protecting our land-based primary production sector from pests and diseases from overseas.

Looking ahead, focus is likely to sharpen on how best to:

• manage the impacts of intensified land use on our soils and waterways

• identify and manage land contaminated by historical agricultural and industrial activities

• continue to manage hill-country erosion

• continue to manage biosecurity risks to New Zealand’s primary production sector and native species

• meet growing consumer demand for sustainably produced agricultural, horticultural, and forestry products.