Large-scale tree planting initiatives as an opportunity to derive carbon and biodiversity co-benefits: a case study from Aotearoa New Zealand

Planting trees is widely regarded as an important part of climate change mitigation and adaptation efforts. As a result, large-scale tree planting projects have been initiated around the world. However, a number of these initiatives have unintentionally opened up risks to native forests and biodiversity while increasing exotic tree cover. Using the Aotearoa New Zealand One Billion Trees programme as a case study we reflect on what trees are being incentivised by these projects and the downstream impacts of how these projects are realised. We suggest ten recommendations for how these initiatives could be adapted to avoid perverse outcomes for native species while jointly achieving our carbon and biodiversity goals: (1) Diversify strategies—protect first, restore second, plant third; (2) Consider net change in trees—do not just count trees planted; (3) Consider the co-benefits of carbon and biodiversity from the outset; (4) Consider the broader landscape; (5) Consider the carbon and biodiversity benefits of soil; (6) Consider the importance of existing carbon stocks; (7) Consider potential impacts to non-tree ecosystems; (8) Consider the longevity of the future forest; (9) Support landowners in planting and maintaining native trees; (10) Remember that climate goals cannot be achieved by planting trees alone. We believe these recommendations are critical for improving the outcomes of the One Billion Trees programme in Aotearoa New Zealand, while providing important insights relevant to other tree planting initiatives around the world.