Environmental risks from extensive forestry clearcuts on steeplands in Tairāwhiti remain elevated two years after Cyclone Gabrielle

Abstract

The on-site and off-site impacts of widespread slash-laden, storm-initiated landslides within plantation forests during Cyclone Gabrielle led to a Ministerial Inquiry and changes to national forestry regulations. In this paper, we analyse the six resource consent applications submitted to Gisborne District Council (GDC) by four companies, together with associated resource consent decision documents, where granted, after the National Environmental Standards for Commercial Forestry (NES-CF) were amended in late 2023. We asked whether foresters: (1) were limiting the harvesting within catchments to reduce the size of clear-fell areas during the window of vulnerability; (2) whether any convergent landforms (e.g. headwater basins, incised gullies) were to be retired without harvesting; and (3) what geospatial landslide modelling tools they were using to manage safe storage of slash in areas of elevated risk. We found that for five of the six resource consent applications, clear-fell operations were to be staged over multiple years, but only one application stated that there would be a three- to five-year gap between adjoining areas in a catchment. The exemption under the NES-CF to remove slash where it was unsafe or impracticable to do so might partly explain why harvesting continues to occur in headwater basins and steep gullies along with potential liabilities under the New Zealand Emissions Trading Scheme (ETS). All four companies used a morphometric model to identify areas of least susceptibility to shallow landslides and connectivity to streams where, with consent from the GDC, greater volumes of slash than permitted by the NES-CF could be stored safely. We argue that the landslide susceptibility and connectivity model should underpin the coupe size and timing of harvest restrictions in high-risk areas. Also, that the exemption to remove slash from these areas needs to be more tightly constrained to disincentivise the harvesting, or repeat establishment and harvesting of further rotations, of exotic species in steep and very steep landforms. Our study shows that changes to harvest practices in plantation forests in Tairāwhiti are needed to reduce vulnerability to increasingly intense storms outside of land-use transitional areas