Knowing when native regeneration is for you, and what you should do about it. The Aotearoa New Zealand context

Forest restoration is an activity that can be readily undertaken to address both the climate and biodiversity crises. In Aotearoa New Zealand, aspirations for large-scale native forest restoration are growing across governmental and private sectors and a considerable focus to date has been on forest establishment by actively planting native trees. In contrast to actively planting trees, considerable proportions of Aotearoa New Zealand have a demonstrated potential for passive tree establishment through natural regeneration processes, subsequent to land use change away from pastoralism or exotic forestry. At a policy and land manager level, knowledge is lacking over the main considerations that should determine whether native restoration will most efficiently be achieved by active tree planting or by natural regeneration. Whether restoration follows active or passive establishment methods (or an intermediate point along the active-to-passive continuum), adequate forest management is essential to achieve high levels of native forest health, functionality, and permanence. We describe a step approach for assessing at a site scale whether forest restoration can most efficiently be achieved via active or passive methods, or combinations of the two. Our assessment covers the main biotic and abiotic factors which explain the probability of native tree establishment. These factors are mean annual rainfall, mean annual air temperature, proximity and composition of adjacent seed sources, landform type, slope aspect, slope, topographic exposure, and the presence of existing woody cover. We then describe the main management interventions that will be required to support successful natural regeneration outcomes and highlight the importance of strategic natural regeneration for achieving large scale restoration for the betterment of both our climate and biodiversity.