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Topic 5: Land use

Land includes soil and rock, plant and animal communities in the soil, and the landforms and vegetation that cover it. Our lifestyle and economy, particularly farming, depend on good quality land. Land use decisions require social, economic, and environmental needs to be balanced. A growing population requires more space for housing, recreation, and economic development, but land use changes for these purposes will affect the environment.

There are three main land uses in New Zealand: production, conservation, and urban development. Over one-third of land is legally protected for conservation purposes, with the remaining majority being used for primary production (agriculture, forestry, and horticulture). Urban and rural residential developments, and artificial surfaces such as transport infrastructure, landfills, and mines, cover a small but growing area.

Although it is difficult to predict future needs with certainty, current development decisions should not limit options for future generations. Some activities, such as expanding cities and creating new landfills, may lead to environmental changes that are irreversible over human timescales.

Main results

Between 2002 and 2007, the total area of land used for farming in New Zealand decreased, including that used for sheep, beef cattle, and deer farming. However, land used for dairy farming increased.

In contrast to the target trends, between 1979 and 2002 the stock of soil with the most versatile uses decreased, and between 1990 and 2004 the excess of nitrogen and phosphorus in soil increased. However, between 1997 and 2002 the area of hill country land at risk of erosion was reduced.

Table 5.1
Land use indicators – key results

Land use indicators - key results.

What the indicators tell us

Area of land used for farming (indicator 5.1)

Much of New Zealand’s economy is based on farming activities, with the agriculture and forestry sectors making a significant contribution to export earnings. This contribution in turn, influences farming decisions, and about half the total land is used for primary production. However, different production activities have differing environmental effects on factors such as soil erosion, water use, nutrient leaching, organic waste generation, and greenhouse gas emissions.

This indicator shows the total amount of land used for farming, by type – pasture, horticulture, production forestry, and all other uses of land on farms.

At June 2007, farmland made up 54.8 percent of the total New Zealand land area, with three-quarters of this being pasture. Figure 5a shows that between 2002 and 2007 land used for farming decreased 5.7 percent, or 889,000 hectares. The largest decrease was for pasture (575,000 hectares).

The amount of pastoral land used by farms with sheep, beef cattle, and deer declined 5.9 percent between 2002 and 2007. Conversely, the amount of pastoral land used by farms with dairy cattle increased 5.1 percent.

Forestry is the second-largest primary production land use after livestock farming. Forests do more than supply wood products. They also provide important environmental services such as soil stabilisation, water filtration, and acting as a carbon sink (see indicator 3.1).

 Farm land as a proportion of total land, by land use type.

Soil health (indicator 5.2)

Soils can take thousands of years to develop. Production is directly affected by soil health, and land management practices affect the biological, physical, and chemical composition of soils.

Changes in soil health can have positive and negative environmental effects. For example, small increases in soil carbon content can reduce atmospheric levels of CO2 (see topic 3), but an excess of other nutrients may leach into waterways and contribute to algal blooms (see topic 4).

This indicator reports the percentage of soil samples, between 1995 and 2001, with soil health indicator scores outside recommended targets for fertility, acidity, organic resources, and physical composition.

Over 80 percent of the soil health indicators fell within target ranges for maintaining soil quality. However, as figure 5b shows, across all farmland uses, over two-thirds of soils tested had at least one soil quality indicator outside the target range.

Pasture soils, which cover over 40 percent of New Zealand’s land, have a higher nitrogen content (organic resources) than that for all other soil use types. The soils with the highest proportion of samples outside the target range for fertility were those used for crops and horticulture. The phosphate content of these soils is high, due to regular application of fertiliser over many years (see also indicator 5.3).

 Proportions of soils not meeting target range, by soil health indicator.

Nitrogen and phosphorus content in soil (indicator 5.3)

New Zealand’s soils tend to be thin and acidic with low levels of the nutrients necessary for the production of the grasses and crops grown today. Nitrogen and phosphorus are two nutrients applied to land, in fertilisers, to grow more productive pasture or crops. Nitrogen-fixing plants (usually white clover) and stock excrement also add these nutrients to the soil.

This indicator reports on the surplus or deficit of nitrogen and phosphorus content in soils. A surplus means a high potential for nutrient loss, to the atmosphere as nitrous oxide (a greenhouse gas, see topic 3), or through leaching from soils that contaminates aquifers and waterways (see topic 4). A deficit may be detrimental to soil fertility and agricultural production (see also indicator 5.2).

Ideally, the addition of nitrogen and phosphorus should be balanced by removals. Figure 5c shows that between 1990 and 2004, the nitrogen surplus in soils increased 41 percent and the surplus for phosphorus increased 128 percent.

Nearly all nutrient removal is from pasture growth. The main source of both nitrogen and phosphorus in New Zealand soils is livestock excrement. The high density of grazing stock on dairy farms delivers more nutrients to the land than other forms of farming (Ministry for the Environment, 2007a). Between 1990 and 2004, the number of dairy cattle increased 50 percent.

 Soil nitrogen and phosphorus balance, 1990–92 and 2002–04 December years.

Contaminated soil sites (indicator 5.4)

Industrial, domestic, and farming activities have all contributed to the contamination of land in New Zealand. Most land contamination has been caused by historical practices not known to be hazardous at the time. In particular, contaminated sites have often resulted from the past manufacture and use of pesticides and fertilisers, production of coal and gas, mining, timber treatment, and sheep dipping.

In 2007, 10 of the regional councils in New Zealand reported that 1,238 sites had been confirmed as contaminated, with 545 of these having been cleaned and 301 being managed to ensure they do not significantly affect the environment. In 2009, 11 councils reported a total of 1,895 contaminated sites, with 663 having been cleaned and 760 being actively managed (see figure 5d).

 Identified contaminated sites by management category, 2007 and 2009 June years.

Versatile soil extinction (indicator 5.5)

Versatile soils are fertile, well drained, and have slopes of less than 12 degrees. They are an important natural resource and valuable for food production. Versatile soils need to be managed to ensure a variety of land-use options remain for future generations and that the production needs of current generations can be met.

Urban expansion typically reduces versatile soil stocks either by reducing the total area or impairing the remaining soils. Such changes are effectively irreversible, because top soils can take thousands of years to develop.

Versatile soils cover about 10 percent of New Zealand. Between 1997 and 2002, the amount of land covered by artificial surfaces increased 2.5 percent (5,500 hectares). Figure 5e shows that since the late 1970s the types of soils with the highest rate of conversion to urban land use are the most versatile ones. Over this period, the total area of the most versatile soil class decreased by 2.3 percent.

 Extinction of versatile soils since 1975–1979, by land use class.

Hill country erosion (indicator 5.6)

Hill country with slopes greater than 21 degrees is classified as severely prone to erosion and makes up about 10 percent of New Zealand. Every year, erosion results in an estimated 200 million tonnes of soil being lost (Landcare Research, 2006). The resulting sedimentation can damage freshwater and marine ecosystems, and increase flooding risk.

The risk of erosion is affected by land use, with pasture-covered hills being most vulnerable. Strategies to reduce erosion, such as planting trees or reverting land to native cover, can prevent nutrient loss and soil slippage.

Between 1997 and 2002, the area of hill country with pasture cover and most at risk of erosion reduced by 3.1 percent (36,400 hectares). This was achieved by converting pasture to exotic forestry or allowing it to revert to scrub. Across the North Island, there was a 3.7 percent reduction in pasture-covered erosion-prone soils, and a 1.7 percent decrease in the South Island (see figure 5f).

There is no recent data for the total area of land at risk of erosion. However, the Ministry of Agriculture and Forestry (2009) estimates that erosion control measures are currently being undertaken on approximately 15,000 to 20,000 hectares per year.

 Erosion-prose soil, 1997 and 2002.

About the indicators

The land use statistics for indicators 5.2 and 5.3 come from the New Zealand Land Cover Database (administered for the Crown by the Ministry for the Environment). This was last updated in 2002.

Area of land used for farming (indicator 5.1)

The information is from Statistics NZ’s Agricultural Production Censuses, data being as at 30 June and from Statistics NZ 2002a, 2003b, 2008a, 2008b.

There was a change in the collection methodology for production forestry in 2007, therefore, care needs to be taken in interpreting the 2007 result.

Soil health (indicator 5.2)

The health of soils was determined from the collection and analysis of over 500 soil samples between 1995 and 2001. The soils tested represented all land types across three dominant land use classes (cropping, pasture, and forestry). The target ranges for each soil health indicator allow for both production and environmental impacts. The indicators of soil health used (see also figure 5b) are:

  • fertility – represented by measures of phosphate content
  • acidity – measured by pH in water
  • organic resources – such as the presence of carbon and nitrogen
  • physical composition – such as bulk density or ability to absorb water.

Nitrogen and phosphorus content in soil (indicator 5.3)

The indicator measures ‘gross nutrient balance’, which shows the difference between the nutrient inputs, such as fertiliser and manure, and outputs leaving the system in the form of crops and pasture growth. Data is from the OECD (2008b).

Contaminated soil sites (indicator 5.4)

The 10 regions with data for 2006–07 were Auckland, Waikato, Bay of Plenty, Hawke’s Bay, Taranaki, Wellington, Tasman, Marlborough, Canterbury, and Otago. In 2009, data for Manawatu-Wanganui was also included. Data is collected by the regional councils and territorial authorities with the assistance of the Ministry for the Environment.

The Resource Management Act was amended in 2005 to include a definition of contaminated land. However, there are no national environmental standards that set maximum levels for contaminants in soil. Therefore councils may have used different guidelines.

As more historically contaminated sites are identified, the number is likely to rise in the medium term. However, the desired long-term trend is a decrease in the number of sites yet to be dealt with or actively managed.

Versatile soil extinction (indicator 5.5)

Soils across New Zealand have been classified according to their suitability for cropping, general pastoral production, or forestry, to yield eight land use classes, with class 1 being the most versatile and class 8 the least. Classes 1 to 4 are suitable for multiple purposes, and are the only soils that crops can grow on. These are least abundant, and made up only 26 percent of the stock of non-urbanised soil in 1979. Classes 5, 6, and 7 are only suitable for pasture and forestry (Molloy, 1998). Class 8 is unsuitable for production, but important for water catchment.

The base period over which the soil classes were assessed was between 1975 and 1979.

This indicator uses provisional information and analysis from Landcare Research, which may be subject to further peer review.

Hill country erosion (indicator 5.6)

The data is from the Ministry for the Environment (2007a), sourced from Landcare Research.

Table 5.2
Land use indicators – defining principles

Land use indicators - defining principles.

See part C for the complete list of defining principles for all indicators.

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