Land Cover

The Auckland region encompasses a diverse range of ecosystems and landforms.  The region comprises about 4520 km² of land-based ecosystems on the mainland and 500 km2 on the islands.  An impressive variety of habitats ranges from dunelands and wetlands in lowland and coastal areas to extensive tracts of native forests on the rugged hills and 'mountains' of Te Waonui a Tiriwa and Te Waonui a Mataaoho (the Waitākere and Hunua ranges), and Aotea (Great Barrier) and Hauturu (Little Barrier) islands.  Some of the best agricultural soils in the country are found in Auckland — mostly in the south.  Croplands cover about 2% of the region, and exotic grasslands cover almost half.  More than a quarter of Auckland is forested; more than half of which is indigenous forest (or 16% of the region’s total).  The third most significant land cover, at 11%, is urban area, reflecting Auckland’s status as New Zealand’s major metropolitan centre hosting of the country’s population.  Between 1996 and 2018, the areas of urban settlements, exotic forests, and croplands increased, whereas exotic grassland decreased.

 

 

Auckland’s land cover profile is characterised by:

  • The Auckland region hosts New Zealand’s largest city (Auckland), and its wider metropolitan areas, extending from Pukekohe to Warkworth. of New Zealand’s population lives in the region. Urban area represents a relatively sizeable proportion of the regional land area (11%); another 1% of land area is covered by other transport infrastructure and bare areas (both natural and constructed).
  • The Auckland isthmus sits at the centre of the region and consists almost entirely of urban area. The metropolitan area extends south and north from the isthmus. An urban corridor is developing through the extension and connection of satellite towns and smaller enclaves, from Pukekohe in the south to Warkworth in the north.
  • Grassland/other herbaceous vegetation is the largest land cover category (comprising 46% of the region), almost all of which is exotic grassland.
  • A substantial area of forest cover (26% of land area), of which more than half is indigenous forest. Most of this indigenous forest is located in Te Waonui a Tiriwa and Te Waonui a Mataaoho (the Waitākere and Hunua ranges) ranges and on the islands, with small forest remnants also found throughout the region, including within the urban corridor.
  • Scrub/shrubland cover (11% of the region) is predominantly comprised of indigenous scrub/shrubland.
  • Cropland and horticulture comprise 2% of the region’s land area, which in part supports 25% of New Zealand’s vegetable production.

 

The key changes in land cover between 1996 and 2018 in the Auckland region are:

  • Urban area, exotic forest , scrub/shrubland, and cropland increased in area.
  • Grassland/other herbaceous vegetation (primarily exotic grassland) decreased in area.
  • The area of urban settlements increased between 1996 and 2018, with the highest rate of increase in the 1996-2001 period (closely followed by the 2012-2018 period) and the slowest in the 2008-2012 period. Urban areas covered 15% more area in 2018 than 1996, comprising the largest area increase (7,259 ha) of any land cover category over the period.
  • Exotic forest area increased by 5%, comprising the second largest area increase (2,242 ha) over the period The area of exotic forests increased rapidly between 1996 and 2001, reached a peak in 2008, and has declined since then.
  • The third-largest increase in land cover in terms of area (590 ha) was cropland, 5% higher in 2018 than in 1996. The area of cropland expanded from 1996 to 20082012, with a marked increase between 2001 and 2008. Cropland area has subsequently decreased since 2008.
  • A 21% increase in artificial bare surfaces comprised the largest proportional change in land cover area (300 ha) during the period.
  • The area of exotic grassland decreased between 1996 and 2008, increased slightly between 2008 and 2012 and decreased again between 2012 and 2018.

 

The likely drivers and potential implications of the changes are:

  • Between 1996 and 2018, Auckland's population grew from an estimated 1,115,800 to 1,654,800, and increase of 539,000 at an annual average of 23,400.
  • Between 1996 and 2018 (the year ending 30 June 1997 to year ending 30 June 2018) there were 196,678 buildings consented in Auckland region.  There were 175,828 dwellings consented for the same period (these serve as a proxy for building activity, as there is insufficient data on actual builds or net change in number of structures over the period at present, but recent analysis by Stats NZ found that on average "97 percent of consented new dwellings get built").
  • Consequences of the Global Financial Crisis resulted in a slowdown of building in the 2008-2012 period.
  • The expansion of urban areas onto surrounding rural land corresponds to decreases in exotic grasslands. The land area available for primary production can be reduced and, in some areas, could result in the loss of highly productive and versatile land from productive uses (e.g., commercial vegetable production).
  • The increase in exotic forest area between 1996 and 2018 may reflect national activity in the forestry industry, driven by increased confidence in the industry and the introduction of the Emissions Trading Scheme (ETS), followed by reactions to implemented policies. The afforestation of hillslopes at risk of erosion (e.g., steep or with fragile soils, or both) under grassland cover can be beneficial in terms of improving slope stability and reducing the incidence of soil erosion.
  • The increase in area of cropland between 1996 and 2018 may be driven by growth in both the cropping and horticultural industries. Soil cultivation, more commonly associated with short-rotation cropping, can result in increased losses of soil carbon, sediment, and nutrients, and soil structural degradation over time.

 

 

 

 

 

 

 

 

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