Evaluating the role of biodiversity in delivering sustainable nature-based solutions to climate change

In the wake of missed climate targets and failed technological fixes, the concept of "Nature-based Solutions" (NbS) has emerged as a prominent alternative in climate policy. It has been forecast that forest growth can provide a third of the climate action needed by 2030, leading to high-profile endorsements in the corporate sector, as well as by many national governments. Under the Bonn Challenge, 62 countries have pledged to restore 170 million ha of deforested or degraded land and intend to meet nearly half of these commitments with tree plantations. At an even larger scale, the Trillion Tree Campaign was announced at the World Economic Forum in Davos, 2020, based on plans to plant a trillion trees worldwide by the end of the decade.

Although broadly welcomed, these initiatives are risky. In particular, their potential to deliver the intended benefits has not been rigorously assessed, leading to concerns over reliability and cost-effectiveness. Indeed, many previous tree planting or reforestation programmes have failed, seemingly because they paid little attention to factors such as disease prevention, water supply, seed dispersal and pest control, all of which may be delivered at much reduced cost in natural systems with high levels of biodiversity.

The goal of this project is to assess the role of biodiversity in maximising positive outcomes for tree planting schemes, agroforestry and plantation forestry. To achieve this, the student will focus on published and unpublished datasets from established study systems in Europe, Africa and South America. They will assess the effect of landscape-level variation in natural vegetation and biodiversity on seed dispersal, pollination, pest control, and the recruitment and growth of tree seedlings, including comparison with hand-planted systems. Traits of seed dispersing birds and tree fruits are available through the Tobias lab global trait dataset and the TRY plant trait database, respectively, allowing an investigation of trait diversity, trait matching between trophic levels, and their effects on reforestation. A second theme will focus on evaluating the role of biodiversity in regulating populations of insect pests and pollinators. The student will conduct lab-based meta-barcoding of flower-visiting insects and faecal samples from the dominant insectivorous bird species at each study site, and use these to build interaction networks. Finally, the extent to which different management strategies improve socio-economic outcomes will be investigated, with particular focus on cost-effectiveness, carbon uptake and yield (timber or crops).

The results will improve understanding of best practices in building biodiversity-based resilience into multifunctional landscapes, a key step towards ensuring that NbS can achieve their potential to tackle both climate and biodiversity crises while also contributing to sustainable economic development.