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Where will we plant a Trillion Trees?

We propose to evaluate the feasibility, at regional and local levels, of planting a trillion trees world-wide, and the implications in terms of the resulting carbon sequestration.

In 2019 it was proposed that tree planting remains the most effective strategy for climate change mitigation. A group led by Thomas Crowther at ETH-Zurich estimated the potential global area available for tree planting, excluding existing forest and developed areas, was 0.9 billion hectares, enough for approximately 1.2 trillion trees (Bastin et al. 2019; Crowther et al. 2015). Inspired by the potential of growing trees to contribute to control of climate change, in 2020 the World Economic Forum, held in Davos, announced the One Trillion Tree Initiative, Several world leaders have endorsed the idea.


Figure 1: World Resource Institute: (a) Potential Forest Coverage, (b) Human Pressure

The location of each of those trees will be determined by a multitude of local determinations of ownership, economics and land suitability. While large areas could be planted in Russia, Canada, Australia, Brazil, China and the United States, there remains large potential in the aggregated contributions of smaller countries, and in the municipalities and rural areas of all countries. Designers and planners decide where to put the trees while reconciling all the alternative uses for that land; to determine the land-use strategies that connect the local actions of planting individual trees to the global goal of containing climate change, while maximizing the potential benefits to environment and people. Figure 1 demonstrates the challenge. We propose to use the global network of universities participating in the International Geodesign Collaboration (IGC) to evaluate that potential by designing allocations of land to tree planting while addressing human and ecological system constraints, and to demonstrate how those local initiatives aggregate into regional, national and global.


Geodesign is a systems-oriented approach to design that couples model projections and feedback mechanisms to enable design at geographic scale (Steinitz, 2012. The International Geodesign Collaboration (IGC), has already conducted a global array of geodesign projects (Figure 2). This breadth and depth provides a framework for addressing global sustainable development goals that include the climate, food, water and fiber ecosystem services that would flow from such a tree-planting initiative.


Figure 2: International Geodesign Collaboration partner locations

While there are numerous “top-down” descriptions of how to achieve global-scale goals, there are few that focus on how local and physical design actions such as nature protection, land development, and infrastructure improvements translate to outcomes of global significance. To achieve local action, projects must engage local imaginations as people respond to local and regional plans and designs that are visible and relatable, unlike policies and regulations that are less place-specific. To achieve global-scale change, local actions must lead to globally-significant outcomes. Further, we believe that while aggressively tree-planting to solve climate problems, we must monitor performance to ensure that ALL human needs are met.  We adopt the United Nations Sustainable Development Goals (SDGs) as global metrics for human and environmental sustainability.


IGC was established to address global-scale wicked problems through geodesign, arguing that human actions must be carefully shaped and located to ensure that human and environmental needs are met without exceeding planetary boundaries (Heck et al. 2018; Orland, Steinitz & Fisher 2020). Over 100 IGC design projects have used a common workflow and set of representational conventions to convey otherwise dissimilar projects in a format allowing direct visual comparison between the outcomes of prescribed planning scenarios and timelines (Figures 3a, 3b). 


Figure 3. (a) IGC Workflow, (b) Completed geodesign project in Sao Paulo, Brazil

Each project incorporates an impact assessment using the UNDP SDG framework that relates design changes in systems such as Green infrastructure, Agriculture/Forestry, or Energy infrastructure, to SDGs. Figure 3b shows summary scenario assessments for a project in Sao Paulo, Brazil.

Methodologically, our approach will combine the following:

  1. A review of existing research to reconcile environmental and social metrics and values operating at the global scale with measures of higher granularity and location-specificity operating at local scale.

  2. Analysis at project locations of current and potential local tree-planting implementation relative to other indicators of human and ecosystem well-being, land cover/land use and ecosystem services.

  3. Evaluation of future planning scenarios undertaken by IGC partners involving local governments.

  4. Country-level assessments by IGC partners, in each of nine global eco-regions. Assessments will address land use and land capability based on GIS and remote sensing as well as interviews with governmental and other actors.

  5. A global integration of local- and national-level assessments using advanced interactive mapping based on the Esri Geospatial Cloud platform.


Figure 4: Nine global eco-regions


Bastin, Jean-Francois, Yelena Finegold, Claude Garcia, Danilo Mollicone, Marcelo Rezende, Devin Routh, Constantin M. Zohner, and Thomas W. Crowther. 2019. The global tree restoration potential. Science 365, no. 6448: 76-79.


Crowther, Thomas W., Henry B. Glick, Kristofer R. Covey, Charlie Bettigole, Daniel S. Maynard, Stephen M. Thomas, Jeffrey R. Smith, et al. 2015. Mapping tree density at a global scale. Nature 525, 7568: 201-205.


Heck, V., Hoff, H., Wirsenius, S., Meyer, C., & Kreft, H. (2018). Land use options for staying within the Planetary Boundaries–Synergies and trade-offs between global and local sustainability goals. Global environmental change, 49, 73-84.


Orland, B., Steinitz, C. & Fisher, T. (2020). Improving our global infrastructure. Chapter 1 In, C. Steinitz, B. Orland and T. Fisher, Eds., The International Geodesign Collaboration: Changing Geography by Design.  Redlands: Esri Press.


Steinitz, C. (2012). A framework for geodesign: Changing geography by design.

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