Improving the Outcomes of Tree Growing Efforts
Research Description
Countless tree planting programs have been established in the past decade as part of a growing global movement that has promoted tree planting as a solution for myriad social and environmental problems. There are at least three initiatives to promote one trillion trees on the planet and numerous other initiatives to plant hundreds of millions of trees in different countries and regions. These ambitious tree planting efforts have numerous potential benefits, such as conserving biodiversity, improving water quality, providing shade in urban areas, and sequestering carbon. Nonetheless, tree planting can have negative consequences, such as reducing water supply in arid areas and displacing agricultural activities into remaining forests, and many of these tree planting efforts have failed due to poor planning, lack of long-term commitment, and failure to meaningfully engage of local stakeholders. Pedro Brancalion (University of São Paulo) and I have worked to promote outline key steps that need to be taken to improve tree growing outcomes, namely tailoring tree growing strategies to clearly stated project goals; planning, adaptively managing, and evaluating success over a sufficiently long timeframe; and including local stakeholders throughout the process. More recently, postdoctoral fellow Spencer Schubert, a team of students, and I have been evaluating how well intermediary reforestation organizations and companies have been following best practices. We recently launched a public Global Reforestation Organization Directory in collaboration with Mongabay. We score how well 127 global tree-growing organizations commit to following permanence, ecological, social, and financial best practices. Our goal with this site is to: (i) help potential funders identify organizations that share similar priorities and commit to the highest standards. This work is funded by the Center for Coastal Climate Resilience at the University of California, Santa Cruz and the University of California Macarthur Foundation Chair. Below are links to publications, interviews, and talks on this work.
General Audience Publications
Kimbrough, Liz. 2025. New directory helps donors navigate the complex world of global reforestation. Mongabay
Holl, K.D. and S.C. Schubert. 2024. From promise to practice in improving tree growing outcomes. Summary of Schubert et al. 2024 Conservation Letters article for Terraformation blog.
Holl, K.D. and P.H.S. Brancalion. 2022. Which of the plethora of tree growing programs to support? One Earth. You can also read a summary in English in Climate and Capital Media. Leer en español. Leia uma versão em Português
Holl, K.D. and P.H.S. Brancalion. 2021. Arbor Day should be about growing trees, not just planting them. The Conversation. 27 April.
Holl, K.D. & Brancalion, P.H.S. 2020. How can we improve tree planting outcomes. This blog provides a summary of our 2020 Journal of Applied Ecology paper on how to improve tree growing outcomes.
Cook-Patton, S., R. Chazdon, N. Harris, and K.D. Holl. 2020. The best way to restore our forests is to let nature takes its course. This World Economic Forum blog builds on Cook-Patton et al. 2020.
Scientific Publications
Spencer C. Schubert, Katherine E. Battaglia, Christina N. Blebea, Cole J. P. Seither, Helena L. Wehr, Karen D. Holl. 2024. Advances and shortfalls in applying best practices to global tree-growing efforts. Conservation Letters. Short overview of paper
Holl K.D., and P.H.S. Brancalion. 2022. Which of the plethora of tree-growing projects to support? One Earth 5:452-455
Holl, K. D., M. S. Ashton, J. J. Bukoski, K. A. Culbertson, S. R. Curran, T. B. Harris, M. D. Potts, Y. L. Valverde, and J. R. Vincent. 2022. Redefining “abandoned” agricultural land in the context of reforestation. Frontiers in Forests and Global Change 5.
Brancalion, P. H. S. and K. D. Holl. 2020. Guidance for successful tree planting initiatives. Journal of Applied Ecology 57: 2349-2361.
Holl, K.D. & Brancalion, P.H.S. 2020. Tree planting is not a simple solution. Science 368: 580-581. Download pdf.
Holl, K.D. 2017. Restoring tropical forest from the bottom up. Science 355:455-456.
Senior theses
Seither, C. J. P. 2024. Global agroforestry initiatives and carbon credits: balancing diverse priorities while preserving community benefits.
Battaglia, K. 2023. Monitoring socioeconomic indicators for reforestation success.
Mammo, T. 2023. Opportunities and challenges to the Ethiopian Green Legacy Initiative.
Selected Talks and Interviews
Improving outcomes of tree growing and forest restoration efforts. 40 minute talk by K. Holl followed by Q&A.
Do we really need to plant a trillion trees? Science podcast. Interview with K. Holl starts at 14 minutes.
Does the world need another trillion trees? World Economic Forum House on Fire podcast interviews with Tom Crowther, Forrest Fleischman, Karen Holl and others. December 2020.
Mejorando las campañas de cultivo de árboles. Radio de la Universidad Nacional de Mar del Plata. Entrevista en español con K. Holl empieza a las 21:30 minutos.
Keys to improving tree growing campaigns. SER-IUCN Webinar in October 2020 by Karen Holl, Matthew Fagan, and Pedro Brancalion.
Planting trees sounds like a simple climate fix. It's anything but. by Kyla Mandel. Huffington Post.
Countless tree planting programs have been established in the past decade as part of a growing global movement that has promoted tree planting as a solution for myriad social and environmental problems. There are at least three initiatives to promote one trillion trees on the planet and numerous other initiatives to plant hundreds of millions of trees in different countries and regions. These ambitious tree planting efforts have numerous potential benefits, such as conserving biodiversity, improving water quality, providing shade in urban areas, and sequestering carbon. Nonetheless, tree planting can have negative consequences, such as reducing water supply in arid areas and displacing agricultural activities into remaining forests, and many of these tree planting efforts have failed due to poor planning, lack of long-term commitment, and failure to meaningfully engage of local stakeholders. Pedro Brancalion (University of São Paulo) and I have worked to promote outline key steps that need to be taken to improve tree growing outcomes, namely tailoring tree growing strategies to clearly stated project goals; planning, adaptively managing, and evaluating success over a sufficiently long timeframe; and including local stakeholders throughout the process. More recently, postdoctoral fellow Spencer Schubert, a team of students, and I have been evaluating how well intermediary reforestation organizations and companies have been following best practices. We recently launched a public Global Reforestation Organization Directory in collaboration with Mongabay. We score how well 127 global tree-growing organizations commit to following permanence, ecological, social, and financial best practices. Our goal with this site is to: (i) help potential funders identify organizations that share similar priorities and commit to the highest standards. This work is funded by the Center for Coastal Climate Resilience at the University of California, Santa Cruz and the University of California Macarthur Foundation Chair. Below are links to publications, interviews, and talks on this work.
General Audience Publications
Kimbrough, Liz. 2025. New directory helps donors navigate the complex world of global reforestation. Mongabay
Holl, K.D. and S.C. Schubert. 2024. From promise to practice in improving tree growing outcomes. Summary of Schubert et al. 2024 Conservation Letters article for Terraformation blog.
Holl, K.D. and P.H.S. Brancalion. 2022. Which of the plethora of tree growing programs to support? One Earth. You can also read a summary in English in Climate and Capital Media. Leer en español. Leia uma versão em Português
Holl, K.D. and P.H.S. Brancalion. 2021. Arbor Day should be about growing trees, not just planting them. The Conversation. 27 April.
Holl, K.D. & Brancalion, P.H.S. 2020. How can we improve tree planting outcomes. This blog provides a summary of our 2020 Journal of Applied Ecology paper on how to improve tree growing outcomes.
Cook-Patton, S., R. Chazdon, N. Harris, and K.D. Holl. 2020. The best way to restore our forests is to let nature takes its course. This World Economic Forum blog builds on Cook-Patton et al. 2020.
Scientific Publications
Spencer C. Schubert, Katherine E. Battaglia, Christina N. Blebea, Cole J. P. Seither, Helena L. Wehr, Karen D. Holl. 2024. Advances and shortfalls in applying best practices to global tree-growing efforts. Conservation Letters. Short overview of paper
Holl K.D., and P.H.S. Brancalion. 2022. Which of the plethora of tree-growing projects to support? One Earth 5:452-455
Holl, K. D., M. S. Ashton, J. J. Bukoski, K. A. Culbertson, S. R. Curran, T. B. Harris, M. D. Potts, Y. L. Valverde, and J. R. Vincent. 2022. Redefining “abandoned” agricultural land in the context of reforestation. Frontiers in Forests and Global Change 5.
Brancalion, P. H. S. and K. D. Holl. 2020. Guidance for successful tree planting initiatives. Journal of Applied Ecology 57: 2349-2361.
Holl, K.D. & Brancalion, P.H.S. 2020. Tree planting is not a simple solution. Science 368: 580-581. Download pdf.
Holl, K.D. 2017. Restoring tropical forest from the bottom up. Science 355:455-456.
Senior theses
Seither, C. J. P. 2024. Global agroforestry initiatives and carbon credits: balancing diverse priorities while preserving community benefits.
Battaglia, K. 2023. Monitoring socioeconomic indicators for reforestation success.
Mammo, T. 2023. Opportunities and challenges to the Ethiopian Green Legacy Initiative.
Selected Talks and Interviews
Improving outcomes of tree growing and forest restoration efforts. 40 minute talk by K. Holl followed by Q&A.
Do we really need to plant a trillion trees? Science podcast. Interview with K. Holl starts at 14 minutes.
Does the world need another trillion trees? World Economic Forum House on Fire podcast interviews with Tom Crowther, Forrest Fleischman, Karen Holl and others. December 2020.
Mejorando las campañas de cultivo de árboles. Radio de la Universidad Nacional de Mar del Plata. Entrevista en español con K. Holl empieza a las 21:30 minutos.
Keys to improving tree growing campaigns. SER-IUCN Webinar in October 2020 by Karen Holl, Matthew Fagan, and Pedro Brancalion.
Planting trees sounds like a simple climate fix. It's anything but. by Kyla Mandel. Huffington Post.