The conservation status of New Zealand's indigenous grasslands

Abstract

The conservation status of New Zealand's indigenous grasslands was assessed against an 1840 baseline, immediately prior to European settlement, when they were of maximum extent. Five major types were recognised, four of them tussock grasslands. The assumed baseline extent of areas with at least some grassland dominance was mapped on the basis of the best available information. Their current extent was derived from the “tussock” category in Land Cover Data Base 1 map (typed as for the baseline map) and the areas formally protected (as at September 2002) from Department of Conservation records. Ecological region boundaries were added and the map information scanned and compiled using ArcGIS. North Island areas were also assessed as one unit while South Island was divided into three geographic regions based on general land use patterns: western wet non‐rangeland, rain‐shadow rangeland, and eastern lower altitude non‐rangeland regions. Of the total baseline extent of indigenous grasslands (82 432 km2 or c. 31% of the land area), about 13% was low‐alpine snow tussock grassland, 18% montane to subalpine snow tussock grassland, 23% montane to low‐alpine tall red/copper tussock grassland, 44% montane to subalpine short‐tussock grassland, and c. 2% lowland sward grassland. Most grassland (57%) was in the South Island rangeland region which also had the greatest extent of all four major tussock grassland types. Remaining areas of each grassland type vary largely with altitude and climate, the drier lower‐elevation grasslands showing the greatest reduction. Protection of the remaining indigenous grasslands, with various degrees of modification and/or degradation, is greatest in the South Island wet western region (89% of the 98% which remained as of September 2002), with less in the North Island (40% of the remaining 17%), and eastern South Island non‐rangeland region (11% of the remaining 3%). Grassland protection in the rangelands (12% of the remaining 76%) is currently increasing through tenure review of the Crown‐owned pastoral leases in this region. Indigenous temperate grasslands, claimed to be the world's most beleaguered biome (currently 4.59% protected), attain about 12.3% protection of the baseline area in New Zealand (or 28% of the 44% of remaining baseline extent), though biased towards the uplands. Data sets are available as ArcGIS shape files for indigenous grasslands at both 2002 and 1840, on an ecological region basis, as well as for high‐alpine and nival areas for the same periods and regions.