Given the growing interest in the ecosystem services provided by trees, particularly their potential as a carbon sink, the amount of money being spent on tree planting has increased dramatically in the past few years and continues to grow rapidly. This trend is fueled by the implementation of the UN Decade on Ecosystem Restoration, the Bonn Challenge, and the multiple campaigns to plant billions and trillions of trees1 in combination with the boom in investments aimed at improving environmental, social, and governance responsibility. Funders range from billionaires, such as Amazon founder Jeff Bezos, who has pledged US$2 billion to restore forests, to millions of individuals who contribute US$10â$1,000 to tree-planting organizations. Increasingly, both individuals and large corporations look to tree-planting projects to offset their carbon emissions. For instance, Mercado Libre, a Latin American e-commerce company, raised US$400 million in sustainable bonds in 2021 to invest in forest restoration across the region to reduce its carbon footprint, and other companies such as Microsoft, NestlĂŠ, and Shell have followed suit.
These efforts to increase tree cover are largely motivated by good intentions, such as improving human livelihoods, conserving biodiversity, and enhancing water quality and supply.2 Yet most projects set ambitious targets for the number of trees to plant or the area to be restored without following up to evaluate whether the projects were successful in achieving their goals, something that is inconceivable in most business supply chains. For instance, the Ethiopian government garnered a great deal of attention for planting a world-record 350 million trees in a day, but there is no publicly available information on where those trees were planted or whether they survived and grew. When projects are evaluated over time, the evidence suggests that tree-planting projects have frequently failed to achieve the desired outcomes.2,3 For example, costly, large-scale tree-planting programs in India over the past several decades have not increased forest cover or improved peoplesâ livelihoods.3
Although trees can provide many benefits, poorly planned tree planting can have numerous unintended negative consequences, such as reducing water supply when rapidly growing trees transpire large amounts of water in arid regions, destroying biodiverse grasslands and savannas, and increasing social conflicts and income inequity when trees are planted on land without the inclusion of landowners in the decision-making process (Figure 1).1,4 Moreover, if landholders are displaced from their land so that trees can be planted, they might clear forest elsewhere.2 The risk is that tree-planting projects could have net negative effects and even increase forest loss. For example, remote-sensing data suggest that a Mexican government program that pays farmers to plant trees has actually incentivized many farmers to clear existing forest to create open land for tree planting.5
This commentary focuses on arrow 3, the case when private funding supports tree growing on land that is not owned by the funders.
The deluge of funding has led to the explosion of new tree-growing organizations, many of which have minimal past experience. This combined with the common lack of information regarding past project outcomes means that the risks of investing in projects that do not succeed or that do more harm than good have never been so high. In short, funders need guidance on how to select among the myriad tree-growing projects so their money is not wasted on failed projects or, even worse, has the opposite outcome of what they hope to achieve (Figure 1).
Here, we discuss ten key questions that funders should ask of intermediary organizations and that intermediary organizations in turn should use in selecting which local tree-growing projects to support. These questions are based on guidance from several recent papers on how to improve tree-growing efforts,1,7,8 as well as our personal experience as scientists who study forest restoration and advise numerous non-profit and investment groups on tree growing. Critical questions include why the funder wants to grow trees (questions 1 and 2), whether local landowners and communities have been meaningfully engaged in the project and whether the overall benefits outweigh the risks (questions 3â6), how likely the project is to achieve the stated goals over the long term (questions 7 and 8), and the qualifications of and funding allocation among the organizations involved in the project (questions 9 and 10). Although these questions are particularly addressed to private funders and non-landowner funders, most of the questions we discuss are relevant to all funding flows (Figure 2). We use the term tree âgrowingâ rather than tree âplantingâ for two reasons. First, planting trees is not enough; trees need to survive and grow over decades to develop a functional forest that achieves targeted benefits. Second, trees often regenerate naturally without being planted.
Both funders and tree-growing organizations alike often have lofty ambitions of simultaneously sequestering carbon, restoring a biodiverse forest, improving the well-being of local landholders, and more. However, there are tradeoffs among those goals and the most effective strategy for achieving each one.1 For example, most projects plant one or a few species of trees that benefit landholders by producing food, timber, or firewood,9 but those might not be the same species that maximize biodiversity or return on investment in carbon markets. Allowing forests to regenerate naturally without planting trees is often the most cost-effective strategy for recovering biodiversity, yet this typically does not result in the establishment of tree species that are the most economically valuable to landowners. Therefore, it is essential that project funders, intermediary organizations, and local stakeholders ensure that their goals are aligned and that the selected tree-growing strategies and species are consistent with those goals.1
The most cost-effective way to minimize carbon emissions and biodiversity loss from forests and to achieve other desired benefits of trees is to keep existing forest standing and healthy.1,7,10 Deforestation is caused by a complex suite of drivers that operate at global (e.g., demand for agricultural and forest products), regional (e.g., government incentives for land conversion), and local (e.g., firewood harvesting and subsistence agriculture) scales and that vary in importance geographically.11 If pressures to clear forest remain and landholders do not perceive financial or other benefits to maintaining and protecting new tree cover (question 6), the land is likely to be cleared or degraded again, and the investments in tree growing are likely to be partially or completely wasted. Thus, it is critical that implementing groups have addressed the initial cause of forest loss and ensured that protections and/or incentives are in place to minimize the likelihood of future deforestation and degradation.
Although global mapping efforts often suggest that extensive land is available for growing trees,12,13 people live on and earn their income from a large portion of these lands through agricultural and pastoral activities.14 As a result, the single most important factor that consistently determines project success or failure is whether local stakeholders (individuals, communities, and organizations) benefit from the project and are included meaningfully from the planning stage through the project life cycle (goal setting, planning, implementation, maintenance, monitoring, and adaptive management).1,4,7,15 Ideally, projects should be led by local stakeholders and draw on local knowledge in order to provide income for those involved in implementation and maintenance and dramatically increase the likelihood of ongoing project buy-in and success (Figure 1). If landholders depend on income from the current land use (e.g., agriculture and timber), then this income must be replaced either through alternative job opportunities or through payments for ecosystem services throughout the lifetime of the project. Otherwise, landholders are likely to clear trees from either replanted or remnant forest when the initial financial support for tree growing ceases (Figure 1). A large-scale forest corridor restoration project in the Pontal do Paranapanema region of Brazil provides an excellent example of how meaningful stakeholder inclusion can lead to long-term success.16 The project has engaged small farmers from rural settlements, cattle ranches, and sugarcane mills to support local livelihoods and enhance forest connectivity across the landscape.
Given the various, well-documented potential negative consequences of tree growing as discussed previously (Figure 1) and elsewhere,2,4,8 it is crucial that implementing organizations draw on lessons from past project successes and failures and collaborate with stakeholders to evaluate and minimize the potential harmful outcomes for the most vulnerable social groups, ecosystem services, or species of a given region. This information should be shared with intermediary organizations and funders. If the negative biophysical and social effects outweigh the positives, the project should not go forward.
The common tree-planting goals of sequestering carbon and conserving biodiversity require that trees survive and grow for many years, making it critical to determine at the outset who is responsible for paying for and doing maintenance and monitoring (question 8) activities over the long term. Although the âone dollar, one treeâ slogan often used in online advertisements is catchy, costs vary greatly depending on the location and tree-growing strategy used. In nearly all cases, the actual cost is much higher to ensure that trees are maintained over time and that landowners are compensated for lost income, so the trees are not cut within a few years (Figure 1).17,18 We recommend that funders ask what an organizationâs targets are for the number of trees that are alive in 5, 10, or 20 years rather than how many trees they will plant.
As noted previously, information on the success or failure of tree-growing efforts is often lacking. When tree survival and growth are monitored, typically the monitoring lasts for only 1â2 years18 rather than long enough for project managers to determine whether the projectâs goals have been achieved (e.g., a certain amount of carbon sequestered). Other project goals, such as improving water quality or local livelihoods, are rarely monitored.9 Monitoring plans must be closely aligned so they evaluate whether project goals have been achieved over a sufficiently long time period. Monitoring is also important for identifying problems and taking corrective actions to improve project success. The ambitious tree-growing programs planned for the coming years will be implemented in a sequential manner such that the scale of interventions increases dramatically over time, so adaptive management approaches are important for learning from initial mistakes and increasing success from a learning-by-doing process.7
With the global fixation on trees as a way to counteract climate change, the number of new funders, intermediary organizations, and local implementing groups is growing every week. The experience and expertise of these organizations vary greatly. Funders should look at the past track record of the intermediary and implementing organizations and how well they have addressed the prior questions. If the organization is not able to provide this information and data on the outcomes from prior projects, step back. Or start by giving them some pilot funding and assess the results. Lack of transparency and accountability is a recurring problem with current tree-growing initiatives. In deciding where to spend your money, look carefully at their proposal, websites, and annual reports by using the lens proposed by our key questions to draw your own conclusions. In particular, on the basis of monitoring results, how successful has the organization been in achieving their original goals?
Most intermediary organizations are based in the Global North but select and acquire funding for tree-growing projects in the Global South. Although international intermediary organizations play a valuable role in publicizing and connecting local projects with funders and providing project management and reporting expertise, they often retain a disproportionate share of the funding and compromise the financing of those implementing and maintaining the project (Figure 1). Funders should ask for a breakdown of how money will be divided across administrative staff and those directly involved in implementing, maintaining, and monitoring the project to ensure that local stakeholders are sufficiently compensated.
Investments in sustainable development are often influenced by fads, and tree growing is one of the most emblematic âmust-doâ activities. If tree-growing programs are not planned for the long term, there is a high risk of establishing a boom-and-collapse cycle, where a large share of initial investments are wasted on failed projects that do not achieve expected benefits. It is impossible to guarantee success, but we are confident that asking intermediary and implementing organizations to answer the questions discussed above will greatly increase the likelihood of successful outcomes. We urge tree-growing organizations to provide this information in proposals and on their websites to guide funding decisions. Answering these questions will require staff time, but doing so is critical for ensuring the most effective use of future investments in tree growing to realize the potential to contribute to a more livable planet.
13 J.-F. Bastin, Y. Finegold, C. Garcia, D. Mollicone, M. Rezende, D. Routh, C.M. Zohner, T.W. Crowther The global tree restoration potential Science, 365 (2019), pp. 76-79, 10.1126/science.aax0848
14 P. Meyfroidt, A. de Bremond, C.M. Ryan, E. Archer, R. Aspinall, A. Chhabra, G.Camara, E.Corbera, R. DeFries, S. DĂaz, et al. Ten facts about land systems for sustainability Proc. Nat. Acad. Sci. USA, 119 (2022), Article e2109217118, 10.1073/pnas.2109217118
