Potential Biodiversity and Climate Benefits of Voluntary Carbon Market Tree-Planting Projects

This research explored the potential for voluntary carbon markets to benefit forest biodiversity and climate change by directing funding to tree-planting projects. This research topic is important because voluntary carbon markets are rapidly expanding and have the potential to drive great financial resources to nature-based climate change solutions such as tree-planting projects. In addition, tree-planting projects are gaining attention internationally and may gain prominence among nature-based climate solutions. Tree-planting projects can simultaneously provide climate change mitigation and biodiversity benefits. There also may be opportunities to maximize both benefits within a single tree-planting project. However, there has been a lack of research on this subject. There is particularly a lack of research on potential optimization by influencing the carbon sequestration rate. Tree-planting project type and design affect the potential biodiversity and carbon sequestration benefits of tree-planting projects. Organizations may be able to optimize biodiversity and carbon sequestration benefits through their project type and design choices. However, the biodiversity benefits of tree-planting projects are context-dependent, and there are risks inherent in large-scale tree-planting efforts. Tree-planting projects not conducted according to best practices can significantly harm biodiversity and contribute to climate change through carbon emissions. There is currently a knowledge gap on the types and designs of tree-planting projects gaining funding through voluntary carbon markets. For this project, I created an extensive dataset on all the tree-planting projects that applied to the VCS and CCB Standards (and were included in Verra's registry as of September 2021). I conducted a two-part study on the dataset. First, I extensively researched the activities and carbon sequestration benefits of tree-planting projects certified to the rules of the Verified Carbon Standard (VCS) and the Climate, Community, and Biodiversity Standards (CCB). To do this, I summed the reported carbon sequestration values of the projects. I calculated the extent and prevalence of project types and designs among projects that have been certified to the rules of the Standards. Second, I explored the potential for tree-planting projects to optimize both carbon and biodiversity benefits. To do this, I researched the following questions: (1) How does planting higher numbers of tree species affect the carbon sequestration rate of tree-planting projects? (2) How does planting native species affect the carbon sequestration rate of tree-planting projects? (3) How do the carbon sequestration rates of various tree-planting project types compare? I used simple linear regression, one-way ANOVA, the Kruskal-Wallis Rank Sum Test, and the post hoc Dunn’s test to answer these questions for the set of projects that have been certified to the rules of the VCS. I did not find a significant relationship between the number of tree species planted and the carbon sequestration rate. I also did not find a significant relationship between the use of native species and the rate of carbon sequestration. However, I found that project type significantly affects the carbon sequestration rate of a tree-planting project. The carbon sequestration rate of monoculture commercial forestry (planting one species) was significantly higher than that of commercial forestry projects planting two or three tree species. In addition, the carbon sequestration rate of a type of tree-planting project in China was significantly higher than that of commercial forestry projects planting two or three species. The project types and designs favorable for biodiversity were not prominent among the projects certified to the rules of the VCS. My results indicated that projects certified to the rules of the VCS, on average, better resemble commercial plantations of few species than species-rich native forest restorations. In addition, I found that native forest restorations were not a large component of projects registered to the CCB Standards, although the CCB Standards are intended to identify projects benefitting local biodiversity. My results indicated that the VCS could be conserving or harming biodiversity by directing funding to tree-planting projects. Since the VCS is the market leader among voluntary carbon standards, this suggests that voluntary carbon markets could be conserving or harming biodiversity by directing funding to tree-planting projects.