Northland is a long narrow peninsula with a land area of approximately 1.25 million hectares, making it the eighth largest region in NZ based on land area. The region consists of a wide variety of landforms, soil types and associated land uses. Landforms range from young active sand dunes along the coast to relatively old greywacke, and volcanic peaks and hills in inland areas. There are no mountain ranges in Northland, with all ranges less than 800 metres above sea level.
The low relief, absence of ash deposits from recent ash showers, warm moist climate and the original vegetation, have resulted in Northland soils being dominated by strongly leached, mature, heavy clays. Generally, topsoils are thin and subsoils are of low fertility. The main exceptions are the fertile volcanic soils, young alluvial deposits and the young soils developing on unstable steep slopes.
The cover of the original indigenous forest has strongly influenced soil properties. Trees with acidic litter, such as kauri, totara and rimu, have produced strongly leached soils, while broadleaf trees, such as puriri, kohekohe and taraire, have returned the nutrients to the soil through rapid decomposition of leaves and branches to give fertile top soils.
Northland's economy is largely agricultural with approximately half of the region's land used for dairy, beef and sheep farming. Therefore as a region, Northland is heavily dependant on the environment and the state of soil and land resources for its economy.
The objectives relating to Northland's land and soils resources in the Regional Policy Statement (RPS) for Northland (NRC 2002) are:
· The maintenance, and where possible, enhancement of the life-supporting capacity of soils, especially those which have potential to support intensive primary production.
· The protection of the soil resources, including soil quality and soil quantity, from degradation or loss as a result of unsustainable land uses and land use practices.
· The safeguarding of the life-supporting capacity of water and ecosystems from the adverse effects of unsustainable land uses and land use practices.
· The avoidance, remedying or mitigation of the adverse effects of plant and animal pests on the use of land, including its potential for primary production and natural ecosystems.
The following are the anticipated environmental results after the implementation of the policies for soil conservation and land management in the Regional Policy Statement:
· Continued availability of highly versatile soils for primary production.
· Reduction in the damage caused to soils and natural features from pest animals and plants.
· Safer use, storage and disposal of pesticides and other agricultural chemicals and reduced risk of soil contamination.
· More widespread adoption of soil conservation practices within land use and subdivision proposals.
· Reduction of erosion in high risk areas.
· Reduction in the volumes of soil and other contaminants entering surface water bodies.