The video shows the successive waves of urban growth from 1990 to 2008. The urban extent of the city in 1990 (pale yellow) is taken as a baseline. Watch the growth on low (purple) and on high-class land (red).
An interactive, full-screen version of this map is also available.
Auckland is facing the challenge of accommodating a growing population. A significant growth in house numbers is needed and various proposals have been made as to how this could be achieved. One proposal is to expand the city into the rural land that surrounds it. But all land is not equal. Some parts of the rural land – where the soils and climate support thriving produce, dairying, and bloodstock sectors – are more valuable than other areas. Such high-class land is a precious and limited resource. A change in the use of that land is therefore an important decision with many consequences.
Urbanisation on agricultural land is essentially an irreversible process. Dividing agricultural land into relatively small parcels for housing produces a sharp rise in land value, making it difficult for farmers to buy back; and many of the qualities of high-class land require centuries to return to their initial state.
The importance of urban growth over high-class land
The diagram below shows that over a period of 18 years, 15% of the available high-class land around Auckland has been lost to urbanisation.
A comparison of urban growth on low- and high-class land around Auckland over the same time period shows that the expansion onto high-class land has drastically surpassed the expansion onto low-class land.
Sources of this analysis
Information on the impact of housing planning on high-class land can be accessed in a 2012 study led by Robbie Andrew and John Dymond from Landcare Research.
High-class land has been mapped nationally as part of the Land Use Capability database.
LUC classes 1 and 2 were used in this analysis. LUC class 1 is the most versatile multiple-use land with minimal physical limitations for arable use. LUC class 2 is very good land with slight physical limitations to arable use, readily controlled by management and soil conservation practices.
The urban areas have been extracted from the Land Cover Database of New Zealand (1996, 2001 and 2008), and from the 1990 urban areas layer (1990).
All the data used in this analysis are open and available on the LRIS portal under the Landcare Data Use Licence. The data have been processed in GRASS GIS. The figures have been produced in the R statistical environment, and the maps have been rendered using TileMill.
Any further discussion, perhaps a 3-way Lync?