Effectiveness of vegetative mitigation strategies in the restoration of fluvial and fluvio-mass movement gully complexes over 60 years, East Coast region, North Island, New Zealand

Background: Early (1957–1997) remediation strategies, predominantly Pinus radiata D.Don afforestation and indigenous shrubland reversion, proved effective in treating gully erosion the East Coast region, North Island, New Zealand. However, expansion of untreated gullies initiation new ones necessitated additional investment land-use change (1997– 2017) to reduce their on- off-site impacts. Methods: Gullies were digitised from aerial photography flown ~1957 (before reforestation) again 1997. The region was re-flown 2017, providing an opportunity assess successes failures. For hill country areas, location size recorded by vegetation type, for major catchments, two contrasting geological terrains, land designated Gisborne District Council’s Combined Regional Plan as Land Overlay 3A (LO3A). Results: Between 1997 601 treated fully re-stabilised 315 formed. There remain 1864 gullies, comprising 5347 ha. This represents a 13% reduction numbers 31% decrease area during this 20-year period. Over longer 60-year period, across all uses, 2942 successfully stabilised. with 1446 there are currently ha requiring further treatment, largest affected equally distributed pastoral reforested primarily located within Tertiary terrain, Waiapu catchment, areas LO3A. Conclusions: Although attempts at since early 1960s have resulted 45% number, current gullying is only 5% less than 60 years ago. During development outstripped mandated control targets set Forestry Project (ECFP), LO3A, ‘Restoration Catchment’ 2020-22. Addressing ongoing impacts will require significant long-term prioritisation completion these unfulfilled targets. identified National Environmental Standard Plantation (NES-PF) high risk (orange zone) or where very (red zone), we recommend: (i) revision strategies larger more actively eroding destined future afforestation, (ii) exotic production forests, replanting species (exotic indigenous) better suited stabilisation, post-harvest.