Land Cover

Overview:

Canterbury has the largest land area of all the regions in New Zealand.  It extends from the Kaikōura coast near Kēkerengu in the north to the Waitaki River catchment in the south, from the coast in the east to the Main Divide in the west.  The Canterbury region comprises 45,226 square kilometres.

Canterbury’s long Pacific coastline is distinguished by sweeping sand or mixed sand and gravel beaches, rocky peninsulas, and lagoons and estuaries.  Urban areas and small settlements range in size from towns and cities to bach and hut communities.  Christchurch is the largest urban area.  Timaru, Ashburton, and Rangiora are of medium size, followed by smaller towns such as Culverden, Darfield, and Temuka.

The Canterbury Plains, with their mountain backdrop, slope gently from the foothills to the sea.  The Plains are crossed by braided rivers.  Large basins have formed within the upper catchments of several braided rivers.  Land cover in these basins was fire-induced tussock grasslands.  Land cover has changed since pastoral farming became the predominant land use.

Large parts of North and South Canterbury consist of steep to rolling hill country, and immediately west of the Plains, the ‘foothills’ area.  Hill country areas include areas of native forest, relatively unmodified tussock grassland, and remnant scrub and shrubland.  High country, at a greater altitude than hill country, lies eastward of the alpine zone, including the Main Divide.  In the high country there are areas of indigenous (beech) forest, shrub, and tussock grasslands.

The Southern Alps/Kā Tiritiri o te Moana are a distinctive boundary for Canterbury with their extensive natural bare/lightly vegetated surfaces (screes interspersed with alpine vegetation, bare rock, permanent icefields and glaciers).  Land cover here is largely unmodified, except for skifields and state highways.

The Seaward Kaikōura Range rises from the Pacific Ocean to Mt Manakau (2608 m).  The Inland Kaikōura Range includes the highest peak outside of the South Alps in Canterbury (Mt Tapuae-o-Uenuku at 2885 m).  The Kaikōura area is characterised by distinctive natural bare/lightly vegetated surfaces (rocky sea coast in close proximity to high mountains).

Banks Peninsula’s volcanic landforms, valleys, and harbours created an outstanding landscape and diverse land cover.  Remnants of the original forest vegetation remain, including indigenous beech forest, scrub and shrubland, and tussock areas, with sub-alpine shrubland at higher altitudes.  Land cover changed to mostly grassland as pastoral farming became the dominant land use on the peninsula.

Canterbury’s land cover in 2018 is characterised by:

• Extensive areas of grassland (over half of the total land area), of which three quarters is exotic.
• A substantial area of naturally bare/lightly vegetated surfaces, of which most is natural sand or gravel or rock, landslide, alpine grass or herbfield, and permanent snow and ice.
• Fragments of scrub/shrubland on the Plains, with remnants in the foothills and more extensive areas in the high country. More than three quarters of scrub and shrubland is predominantly indigenous.
• Forest cover of which more than two thirds is indigenous.

The major changes in land cover between 1996 and 2018 in the Canterbury region are that:

• Exotic forest increased in area by just under 12,000 hectares, matched by a similar size decrease in area for exotic scrub/shrubland at just over 10,200 hectares.
• Cropland, and urban areas (including artificial bare surfaces), increased in area, with urban areas increasing by about 6,000 hectares.
• Water bodies (lake or pond) increased in area, by about 4,000 hectares.
• Exotic grassland decreased in area by just over 8,000 hectares.
• There was a decrease in area for indigenous vegetation land covers combined - the largest decrease being for tussock grasslands at about 2,500 hectares.

The likely drivers and potential implications of these changes are:

• Good export log prices from 1996 until about 2002, and the introduction of the New Zealand Emissions Trading Scheme c. 2000, encouraged forest planting and allowed eligible foresters to earn New Zealand emission units (NZUs) as their trees grew and absorbed carbon dioxide. Exotic forest cover increased in response. This included conversion of grassland/other herbaceous vegetation, and exotic scrub and shrubland into forest cover.
• In 1996 the national dairy herd continued to expand. Farming patterns were changing at a regional level as farmers moved away from sheep and beef to dairy, deer, and forestry.
• Milk product prices and the growing international demand for processed milk products such as milk powder and casein drove conversion from sheep and beef farming into dairy cattle farming. The number of dairy cattle in Canterbury in 1996 was 246,230, and by 2018 dairy cattle numbered 1,246,299.
• With an increase in dairy cattle numbers in Canterbury, and the shift to more intensive pastoral farming, fodder production increased the area of cropland. Arable harvest area increased (e.g., wheat and barley) as a result of good international grain prices and the domestic demand for grains as stock feeds.  In 2018 Canterbury also grew two thirds of the national harvest of barley.  The area of potatoes in Canterbury also increased and accounts for almost half of the national harvested area.
• With demand for water and the shift to more intensive pastoral farming and irrigated land area, water storage ponds increased in area. In Canterbury, the total area of land equipped for irrigation by 2007 was 385,271 hectares, increasing to 467,315 hectares by 2019.
• The Canterbury earthquake on 22 February 2011 damaged or destroyed dwellings within Christchurch City. As a result, urban areas on the fringe expanded to accommodate shifting residential populations (e.g., Waimakariri and Selwyn districts). Artificial bare surfaces increased also with the provision of transport infrastructure, surface mines or dumps to service new areas of urban settlement, and support the Christchurch rebuild.
• Conversion of tussock grassland for pastoral farming, including more intensive farming in hill and high country, reduced tussock grassland area. Practices such fire, spraying, ploughing, and over sowing with exotic grasses and fertiliser, combined with ongoing grazing, decrease tussock grassland area. Conversion brought exotic pasture grasses and more recently fodder crops, ongoing grazing degrades tussock grassland communities, together with introduced pests and weeds.

Sources:

Statistics New Zealand. 1996; 2007; 2012; 2020. Agricultural Production Statistics.  Wellington. 

Environment Canterbury. 2017. Canterbury Regional Policy Statement. Canterbury.  

Land Cover Database 1996; 2012; 2018.