Marlborough’s land cover profile is characterised by:
- A predominance of grassland/other herbaceous vegetation cover (39% of land area), of which most is exotic grassland but also includes a substantial area of tussock grassland (10% of land area).
- A substantial area of forest cover (about one third of land area), of which most is indigenous forest but also includes a substantial area of exotic forest (9% of land area).
- Scrub/shrubland cover is predominantly comprised of indigenous scrub/shrubland.
- Cropping/horticulture comprises a relatively small proportion of the regional land area overall (3%).
The key changes in land cover between 1996 and 2018 in the Marlborough region are:
- Grassland/other herbaceous vegetation (primarily exotic grassland) and scrub/shrubland (both exotic and indigenous scrub/shrubland) have decreased in area.
- Cropland and exotic forest have increased in area.
The likely drivers and potential implications of the changes are:
- The increase in the area of cropland may be largely driven by growth in horticultural industries such as viticulture (most of the change in area was in ‘orchards, vineyards or other perennial crops’ rather than ‘short-rotation cropland’). 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.
- The increase in exotic forest area over the last 30 years has been driven by withdrawal of government subsidies for pastoral production, and afforestation grants in the 1980’s and 1990’s. 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. Although there are benefits during the growing phase of reducing soil erosion, the harvesting of forests has resulted in significant soil erosion and silting up of estuaries and sheltered coastal waters. Habitat damage and destruction has been documented in the Marlborough Sounds.
- The decrease in area of tussock grassland and indigenous scrub/shrubland could have implications for the conservation of indigenous biodiversity.
