- Tairāwhiti’s land cover profile reflects the interaction the people of the land have had with it. Modification of the natural environment by people has resulted in the landscape we see today.
- Wrapped in coastlines and its western ranges, this isolated region of much natural beauty supports vibrant farming, forestry, and tourism opportunities across an area of 8391 km2 (3% of New Zealand land area) for some 50,000 residents, and numerous visitors. The majority of the region’s land (90%) consists of erosion prone hill country, interspersed with areas of flat arable land in alluvial valleys which generally increase in size towards the coast.
- As of 2018, land cover data broadly shows about 65% of the region’s total land area is being actively used by people (for pastoral farming, forestry, and cropping uses) and is highly modified from its pre-human state. Passive use is inferred over the region’s indigenous forest (22%) and indigenous scrub/shrubland (9%) which covers the rest of the region’s main land cover types, with the remaining 2% classed as urban, bare or lighted vegetated surfaces.
- Grassland/other herbaceous vegetation cover (41%, predominantly exotic grassland) is the region’s farming heartland. It has been decreasing in area as the region’s exotic forest, indigenous forest, and indigenous scrub/shrubland areas have grown. Exotic forest now covers 22% of mostly steep eroding hill country that can be found throughout the region.
The key changes in land cover between 1996 and 2018 in the Gisborne region are:
- The area of exotic forest increased by about 43,400 ha. Coupled with the almost 2,000 ha increase in indigenous forest and the 1,000 ha increase in indigenous scrub/shrubland, these changes were largely accounted for by a decrease in the area of exotic grassland of almost 47,000 ha.
- Urban/bare/lightly-vegetated surfaces (predominantly comprised of natural bare/lightly vegetated surfaces), and cropland comprise relatively small proportions of regional land area overall, covering just 2% each. These areas are mostly concentrated around the region’s main service centres on the broad alluvial valleys near the coast.
Likely drivers and potential implications of the changes are:
- Supplementing well established state forests as well as commercial exotic forests, most large-scale afforestation occurred as a result of the implementation of forestry schemes made available to landowners to control erosion post Cyclone Bola in 1988. A common afforestation treatment was to plant the land at risk of further erosion with Pinus radiata as it is known to be beneficial in terms of improving slope stability and reducing the incidence of soil erosion.
- Further increases in area of exotic forest have been driven by:
- The Emissions Trading Scheme (ETS);
- Confidence in New Zealand forest products industry and markets;
- The Ministry of Primary Industries Erosion Control Funding Programme (ECFP); and
- Land and water management requirements of the Tairawhiti Resource Management Plan, in particular land classified in the plan as Land Overlay 3A (the region’s most erosion prone land).
- Large areas of Tairāwhiti’s Pinus radiata-dominated exotic forest are being harvested with completion of first rotation harvesting anticipated by the early 2020’s. Pressures on natural ecosystem services, land suitability and availability, and civil infrastructure continue to grow. Further research and development of low impact forest management techniques requires continued support, in particular managing the land through the ‘window of vulnerability’ of harvest and post-harvest activities.
- The Ministry of Primary Industries Erosion Control Funding Programme (ECFP) targets erosion prone land providing financial support for property owners to implement slope stability and soil loss controls. Under this scheme, careful consideration is required to determine the exotic grassland unsuitable for commercial afforestation, or other land uses such as Manuka or Kanuka. A maturing Manuka and Kanuka products industry may be driving some of this change providing alternative revenue streams as opposed to drystock or arable farming systems. The ECFP also targets areas of both exotic grassland and plantation forest to retire and allow to revert to indigenous scrub/shrubland. Spaced erosion-control planting of coppicing species was also a treatment option under the ECFP and has been used successfully to reduce erosion of gullies and highly erodible slopes in the hill country on land kept in exotic grassland.
- Increases in indigenous forest and indigenous scrub/shrubland are likely to have positive effects on the conservation of indigenous flora and fauna, help to improve indigenous biodiversity, and provide a platform for the re-establishment of ecosystems that were once present before the land was cleared.
- A lack of flat arable land constrains opportunities for further expansion of the strong cropping/horticulture industry in the region. A small increase in cropping/horticulture cover may reflect an opening up of easier hill country and high country alluvial flats to more intensive forms of land use, pressuring ecosystem services of the land and receiving environments.
- A nominal increase in urban area presents a real threat to Tairāwhiti’s most versatile and valuable land and soils.
- Suitable management of the regions sensitive land and water resources, particularly under typical exotic grassland, exotic forest, and cropping/horticultural land covers/uses, is vital to ensuring regional ecosystem and economic health and requires the right tree in the right place.
Sources:
The Tairawhiti Resource Management Plan recently superseded previous Gisborne Regional and District Plans.
MoH, https://www.health.govt.nz/new-zealand-health-system/my-dhb/tairawhiti-dhb/population-tairawhiti-dhb
