Ecology and long-term history of fire in New Zealand

Fire is a complex physical and ecological process and one that has dramatically affected New Zealand’s landscapes and ecosystems in the post-settlement era. Prior to human settlement in the late 13th century, the Holocene palaeoenvironmental record suggests that fire frequencies were low across most of New Zealand, with the notable exception of some wetland systems. Because few of New Zealand’s indigenous plant species show any real adaptation to fire, the greatly increased fire activity that accompanied human settlement resulted in widespread, and in some cases permanent, shifts in the composition, structure and function of many terrestrial ecosystems. The combined effects of Maori and European fire have left long-lasting legacies in New Zealand’s landscapes with the most obvious being the reduction of forest cover from 85–90% to 25% of the land area. Here we review the long-term ecological history of fire in New Zealand’s terrestrial ecosystems and describe what is known about the fire ecology of New Zealand’s plant species and communities, highlighting key uncertainties and areas where future research is required. While considerable emphasis has been placed on describing and understanding the ‘initial burning period’ that accompanied Maori arrival, much less ecological emphasis has been placed on the shifts in fire regime that occurred during the European period, despite the significant effects these had. Post-fire successional trajectories have been described for a number of wetland and forest communities in New Zealand, but in contemporary landscapes are complicated by the effects of exotic mammalian species that act as seed and seedling predators and herbivores, reduced pollination and dispersal services due to declines in the avifauna, and the presence of pyrophyllic exotic plant species. Many invasive plant species (e.g. Pinus spp., Acacia spp., Hakea spp., Ulex europaeus) are favoured by fire and now co-occur with indigenous plant species in communities whose long-term composition and trajectory are unclear. On the other hand, some highly-valued ecosystems such as tussock grasslands may require recurrent fire for their long-term persistence. Combined, the direct and indirect effects of the introduction of anthropic fire to New Zealand may have shifted large areas into successional ‘traps’ from which, in the face of recurrent fire, escape is difficult. Developing appropriate management strategies in such a context requires a nuanced understanding of the place of fire in New Zealand’s ecosystems.