Where and how we collect the data
The New Zealand Census of Population and Dwellings provides complete coverage of the Waikato region at the Census meshblock level. The meshblock is the smallest geographic unit for which statistical data is collected and processed by Statistics New Zealand1. Meshblocks vary in size from part of a city block to large areas of rural land, depending on the number of households included.
The productive capability of land in the Waikato region is assessed from the Land Use Capability (LUC) classification in the New Zealand Land Resource Inventory (NZLRI) (NWASCO, 1979). There is complete coverage of the Waikato region.
The New Zealand Census of Population and Dwellings is collected every five years. The latest information is from the 2013 Census.
The rural subdivision indicator is developed from data in the 1991, 1996, 2001, 2006 and 2013 New Zealand Census of Population and Dwellings.
The NZLRI LUC was mapped in the 1970s and 1980s. The LUC classification is unchanged although attributes such as vegetation and soil characteristics are being updated.
Areas of rural land in the Waikato region under pressure from subdivision are obtained by interpreting information in the New Zealand Census of Population and Dwellings.
The LUC classification is a measure of the land’s capacity for sustained productive use, taking into account physical limitations, soil conservation needs and management requirements. This is a national database administered by Landcare Research Limited, and should not be confused with recommended land use or present land use.
The LUC classification includes eight classes of productive capability ranging from Class I – ‘the most versatile multiple use land with virtually no limitations to use’ through to Class VIII – ‘land with very severe to extreme limitations or hazards which make it unsuitable for arable, pastoral or production forestry’ (NWASCO, 1979). In this indicator, we report subdivision on LUC classes I through IV (flat to strongly rolling slopes – 0 to 20degree slopes). These classes are reported because they represent land with a high productive capability that is well suited to agricultural or horticultural use but also land that would appeal for urban and lifestyle block development.
Developing the rural subdivision indicator requires three major analysis steps:
1. Identifying areas of rural land that are likely to have been subdivided into more intensive uses
A study in the Western Bay of Plenty (Scarrow, 1997 and Western Bay of Plenty District Council, 1996) found that when rural land was subdivided, the average property size after subdivision was 4.4 hectares.
In this indicator, we use the Census meshblock data to identify where the area of land available per dwelling has decreased below 4 hectares, for instance where low-density rural land has been subdivided into more intensive land uses. The Western Bay of Plenty study found that properties less than 4 hectares were most likely to have decreased in overall production compared to the pre-subdivision production levels. This land has effectively been removed from large scale, low-density agricultural enterprises and forces large-scale enterprises onto land with a lesser productive capability.
Properties below 4 hectares can also be put into more intensive agricultural and horticultural uses that generally require much more fertiliser, water and energy than large-scale agricultural enterprises.The area of each Census meshblock is calculated and divided by the number of dwellings present. A query is used to identify which meshblocks had less than one dwelling per 4 hectares in 1991 but more than one dwelling per 4 ha in 1996. We then repeated the process for the 1996, 2001 , 2006 and 2013 Census data. The meshblocks identified as undergoing subdivision are checked that they agree with local knowledge of subdivision and intensification trends.
2. Extracting the Land Use Capability (LUC) classifications for subdivided land
The meshblocks indicating probable subdivision in the 1991-1996 and 1996-2001 periods are overlain on the LUC classification. The area of each LUC class within the meshblocks is extracted.
3. Summarising the subdivision LUC results for the Waikato region and territorial authorities.
The areas of land in each LUC classification for each period are analysed using geographical information system (GIS) technologies. Database queries are used to summarise the area of land by the LUC class for the Waikato region and territorial authorities. This information is finally exported to a Microsoft Excel spreadsheet for presentation and graphing.
To produce this indicator we have used the Census meshblocks to indicate rural subdivision rather than examining information on individual properties. This means that we cannot identify exactly which properties have been subdivided and what the LUC class of that land is. However, using Census meshblock data has a number of advantages over examining individual properties for subdivision:
This indicator may be modified in subsequent reporting to follow national guidelines for reporting of rural subdivision currently under development.
Statistics New Zealand has in place a Quality Management Strategy (QMS) to ensure data from the census is fit for use.
The NZLRI classification has been extensively checked and applied by Landcare Research and other agencies.