Advances and shortfalls in applying best practices to global tree-growing efforts

Abstract

As global tree-growing efforts have escalated in the past decade, copious failures and unintended consequences have prompted many reforestation best practices guidelines. The extent to which organizations have integrated these ecological and socioeconomic recommendations, however, remains uncertain. We reviewed websites of 99 intermediary organizations that promote and fund tree-growing projects to determine how well they report following best practices. Nearly half the organizations stated tree or area planting targets, but only 25% had measurable, time-bound objectives. Most organizations discussed the benefits local communities would receive from trees, but only 38% reported measures of these outcomes. Nonprofit organizations with greater prior experience converged more closely on best practices, and their level of scientific expertise was positively associated with clearer project selection standards. Although many tree-growing organizations acknowledge the importance of clear goals, local community involvement, and monitoring, our results raise questions regarding whether long-term benefits are being achieved and emphasize the need for stronger public accountability standards.

INTRODUCTION

Over the past three decades, the number of organizations that plant trees has increased rapidly (Martin et al., 2021) to meet international targets to plant more than a trillion trees. These organizations have lofty goals for sequestering carbon, conserving biodiversity, improving water supply and quality, reducing social inequity, and more. At the same time, planting project failures and negative unintended consequences, both ecological (e.g., destroying diverse grasslands, introducing invasive species, reducing water supply, displacing deforestation into remnant forest) and social (e.g., increasing social inequity, threatening rural livelihoods, exacerbating local conflicts), are widespread (Bond et al., 2019; Coleman et al., 2021; Fleischman et al., 2020; Höhl et al., 2020; Holl & Brancalion, 2020; Kodikara et al., 2017). Mixed outcomes have led to numerous best practices lists to guide the immense enthusiasm and funding for reforestation towards more successful outcomes (e.g., Brancalion & Holl, 2020; Di Sacco et al., 2021; Elias et al., 2022; ITTO, 2022; Sousa-Silva et al., 2023). Nonetheless, the question remains how closely tree-growing organizations follow these guidelines.

The guidelines highlight a few common themes. First, meaningfully engaging local communities throughout the preparation and management phases of tree-growing projects, as well as compensating them for lost income from alternative land uses, is key to long-term success (Adams et al., 2016; Elias et al., 2022; ITTO, 2020; Rana & Miller, 2021). Second, it is critical to consider the underlying direct drivers of deforestation (e.g., agriculture, livestock production, timber and firewood harvesting) to avoid land being recleared following reforestation (Boissière et al., 2021; ITTO, 2020; Le et al., 2014). Third, project planners should evaluate and address potential unintended social and ecological outcomes of reforestation when deciding how and where to grow trees (Di Sacco et al., 2021; Fleischman et al., 2020; Holl & Brancalion, 2022). Finally, the timeframe for managing and monitoring projects needs to be increased dramatically, as many organizations only set targets for the number of trees planted, whereas achieving most desired goals requires that trees survive and grow for multiple decades (Duguma et al., 2020; Holl & Brancalion, 2022).

Here, we ask how well organizations publicly share information about following best practices for tree growing. This information is key for funders to make informed decisions, for local communities to understand how their land and labor investments develop, and to strengthen accountability standards (Holl & Brancalion, 2022; Mansourian & Vallauri, 2023). Our survey expands on work from Martin et al. (2021) and aims to answer the 10 questions Holl and Brancalion (2022) recommend that every tree-growing organization address. We focus on “intermediary organizations” (sensu Holl & Brancalion, 2022) that select and raise funding for many local implementing organizations. We summarize the extent to which intermediary organizations report on how they (1) integrate and provide benefits to local stakeholders throughout the tree-growing process; (2) avoid common pitfalls of reforestation; and (3) make longer term commitments to funding, maintenance, and monitoring. We also assessed the available information on division of funding between intermediary organizations for administration versus project costs on the ground. We use the terms tree growing (Duguma et al., 2020) and reforestation synonymously throughout to refer to increasing tree cover over the long term through natural regeneration, active tree planting, seeding, or other methods.

METHODS

We compiled tree-growing intermediary organizations from Bosshard et al. (2021) and Martin et al. (2021). We supplemented this list by searching Google and online charity platforms (e.g., globalgiving.org, charitynavigator.org) between December 2022 and January 2023 using combinations of the following terms: reforest*, restor*, afforest* AND organization, NGO, project, initiative, company. We restricted our focus to private sector organizations that (1) fund tree-growing or forest landscape restoration projects that are implemented by local organizations and landholders in multiple regions (i.e., at least multiple states/provinces within a country) and (2) have a web presence with information communicating the organization's restoration activities to potential funders (see Extended Methods in the Supporting Information for more details on organization selection). We excluded organizations that are primarily funded by government sources that are less dependent on web pages to share information with potential donors, fundraise for other intermediary organizations, or are exclusively service providers for hire (e.g., planted trees as a business).

We conducted reviews of all organizations’ web pages between January 9, 2023 and March 21, 2023 to answer a mix of categorical and open-ended questions that describe the organizations and their tree-growing practices. Each review consisted of multiple screenings by at least two authors, in which we navigated to all subpages and reports available on the organization's website corresponding to tree-growing standards, such as local community engagement, monitoring, funding, and project longevity; methods and questions are detailed in the Supporting Information (Extended Methods and Table S1). Cumulative review times ranged 50−170 min per organization, depending on the extent of information available. We conducted a final search March 21−25, 2023 for new annual reports to ensure we used the most updated information.

We calculated an index to evaluate the extent of organizations’ adherence and transparency surrounding the 10 questions funders should ask about reforestation (Holl & Brancalion, 2022), hereafter “best practices index.” The index was based on a sum of 21 responses with a total possible value of 22 points derived from presence and extent of information provided by organizations (e.g., no information = 0, vague response = 0.5, information provided = 1; see Table 1 for details). We used multiple regression to test whether certain organizational characteristics (which were not correlated; Table S2), including organization type (nonprofit or for-profit), past experience (prior number of trees or area planted/conserved), and staff scientific expertise, predicted the best practices index. To examine relationships between specific ordinal variables, we used Kendall rank correlation. All data analyses were performed in R 4.3.0 (R Core Team, 2023).

TABLE 1 Description of the information from organization website reviews used to calculate the best practices index.

Question	Value	Criteria description
Goal(s) for tree-growing	1	Identifies at least one goal that tree-growing addresses.
	1	Identifies objectives that are time bound and measurable beyond 1 year.
	1	Specifies criteria used to select and support local projects.
Strategies for tree-growing	1	Specifies a strategy to grow trees.
	1	Discusses whether native versus nonnative trees are planted.
Addresses drivers of deforestation	1	Identifies original drivers of deforestation in project region(s).
	1	Reports measures taken to mitigate destruction/degradation of projects.
Local community engagement	2	Extent to which local stakeholder involvement is discussed: detailed discussion = 2, mention projects locally led = 1, mention vaguely = 0.5
Local benefits	1	Identifies project benefits to local communities/stakeholders.
	1	Measures project benefits to local communities/stakeholders: Yes = 1, Engagement Only,a “Vague” = 0.5
Minimize negative consequences	1	Identifies potential negative consequences of tree growing to people and the environment.
	1	Reports measures taken to mitigate negative consequences.
Maintenance	1	Reports the length of time that projects are maintained beyond initial implementation.
	1	Identifies who is responsible for maintaining project sites.
Monitoring	1	Discusses monitoring protocol.
	1	Reports the length of time that projects are monitored.
	1	Specifies the project parameters that will be measured.
Outcomes of prior projects	1	Reports quantitative data on number of trees or area reforested/protected.
	1	Reports tree survival/mortality or other quantitative data (e.g., CO2 sequestered, tree cover estimates, local biodiversity) from past project monitoring. Yes = 1, Other Summary Statistics,b “Vague” = 0.5
Funding	1	Provides information about the length of time that projects are funded.
	1	Provides information about the percentage of costs that are allocated to intermediary organizations versus tree-growing projects in the field.
Total	22

Note: Each criteria corresponds to one of the 10 questions by which to evaluate tree-growing practices according to Holl and Brancalion (2022).

a

Engagement Only: the website indicated the number of people or communities impacted by a project without specifying the type or extent of impact (e.g., number of community events, number of people affected).

b

Other Summary Statistics: reported numeric figures on variables such as the number of sites planted, nurseries established, and individuals/communities impacted without specifically referencing measures of tree-growing success parameters.

RESULTS Intermediary organization description

The 99 organizations we reviewed are primarily (90%) based in high-income countries (United States, United Kingdom, European Union; Figure S1; Table S3), and most (65%) were founded in the last 25 years (Figure 1a). Ninety percent work in countries other than where they are headquartered, though only 63% of the organizations that work internationally noted having staff in these countries. The majority (69%) are nonprofit organizations (NGOs), and the remainder are for-profit businesses (31%).

FIGURE 1. Basic features of the intermediary organizations reviewed, including (a) decade founded, (b) past tree-growing experience, (c) number of staff, and (d) scientific expertise (bachelors/certificate = at least one staff member with a Bachelor's degree or certification in a relevant scientific field, MS/PhD = at least one staff member with a graduate degree or certification in a relevant scientific field, Scientific advisors = have a scientific advisory board with relevant expertise). No info = no information found on the organizational website.

The organizations span a broad range in the amount of prior experience, number of staff, and extent of scientific expertise noted on their websites (Figure 1b–d). Most organizations mentioned four to six goals of tree growing (Figure S2A), mostly related to improving human well-being, mitigating climate change and sequestering carbon, conserving biodiversity, and providing soil, water, or air ecosystem services (Figure S2B). Most for-profits (58%) disclosed that carbon credit sales are part of their revenue models, whereas comparatively fewer nonprofits (18%) sold carbon credits. Most organizations support projects that primarily plant native and some agricultural trees, and some include natural regeneration and protecting forests among their tree-growing approaches (Figure S3A,B). Many engage in activities beyond reforestation, including rural development, land conservation, environmental education, food security, and cultural preservation.

Adherence to tree-growing standards

The amount of information organizations shared on their web pages about adherence to reforestation best practices varied widely (range 4.0–20.5, median 13.5). Organizations that reported larger numbers of prior trees planted or area reforested and nonprofits had higher best practices index scores (Table 2). In particular, organizations that reported planting at least 100,000 trees or an equivalent area tended to score higher than those with less experience (Figure S4). Greater scientific expertise did not affect reporting on best practices but did correlate with having clearly stated requirements for selecting which implementing organizations to support (34% of organizations, τ_b = 0.25, df = 97, p = 0.004). Common selection criteria focused on measures of poverty or food insecurity in low-income countries, proof of land tenure, minimum planting area, native species used, and compliance with third party carbon credit certification.

TABLE 2 Model estimates for multiple regression of best practices index values (maximum value 22 points), where positive β estimates indicate that a variable increases the extent to which organizations adhere to these standards.

	β	SE	T	p
Intercept	9.60	0.80	11.99	<0.001
Past experience	1.09	0.21	5.22	<0.001
Organization type	−1.75	0.69	−2.55	0.012
Scientific staff	0.45	0.28	1.63	0.106

Note: Organization type compares all for-profit organization models (including social enterprise and B Corps) to nonprofits as a reference level.

Engaging local communities and mitigating conflicts

Most organizations (91%) specified community involvement in at least one phase of project management, most commonly the implementation (e.g., tree planting) phase (Figure 2a). Nearly all organizations (98%) discussed benefits that local communities would receive from tree-growing projects, with the most common being income, education/training, ecosystem services, wellness, and food security (Figure 2b). Despite the focus on benefits to local communities, only 38% reported quantitative measures related to these outcomes. Commonly reported measures included employment and training statistics, survey responses on livelihood improvement, and increased revenue from agroforestry systems. Other organizations (18%) offered limited reporting of “engagement” data (e.g., number of individuals or communities engaged or impacted) that were not quantified further.

FIGURE 2. (a) Percentage of organizations reporting involvement of local communities at different stages of project development and (b) word cloud displaying the relative frequency that aspects of local stakeholder benefits were discussed by organizations.

Most organizations (78%) reported specific drivers of deforestation in their working regions, with agriculture and livestock (63%), logging for timber (47%), and residential/urban development (34%) cited most frequently (Figure S5). Of those that identified threats, 75% discussed specific measures or features of project administration to minimize the risk of project failure. These solutions typically centered around improving livelihoods and reducing the economic incentives to clear regenerating and existing forests. For example, agroforestry projects consistently claim to ensure project longevity by planting utilitarian trees. Other strategies included hiring forest guards, distributing fuel-efficient cooking stoves, and enrolling landowners for payment for ecosystem services programs.

Only 19% of organizations discussed potential negative consequences of reforestation on people and the environment, such as displacing productive land (7 organizations), loss of income (6), reduction of local biodiversity (7), and facilitating the spread of invasive species (7). The few organizations that discussed these factors also presented strategies to avoid adverse outcomes. These included requiring implementing organizations to only use native species or demonstrating measures of human livelihood improvement from trees that are planted (e.g., increased food yield, timber, or income). Others had explicit requirements for local stakeholders to select planting sites and/or develop a regional land-use plan.

Project longevity: Maintenance, monitoring, and funding

Approximately half (49%) of the organizations declared specific growing targets, ranging from 800 trees in a specific location to 1 trillion trees globally. Only 25% of organizations, however, stated measurable time-bound objectives beyond initial planting quantities or area that could be evaluated over time to determine project success. The most frequent objectives included quantity of carbon sequestered, area of land reforested, or number of people with increased food security after a period of 2–30 years.

Attention to land ownership and security of project sites, both key to project longevity, varied widely among organizations. Although 65% discussed the importance of land tenure for achieving results, only 26% of organizations declared a specific requirement for local projects to demonstrate proof of land ownership or legal protection.

Seventy percent of organizations provided clear statements describing monitoring and the data that would be collected to evaluate project success, and 66% reported at least one quantitative result of past projects beyond initial planting totals or growing area. Forty-one percent of organizations reported tree survival rates, which ranged from 9% to 100% in the first year (median 80%; Figure S6). Referencing more scientific expertise correlated positively with whether organizations reported tree survival (τ_b = 0.22, df = 97, p = 0.018). Other commonly proposed or reported ecological parameters included various measures of tree growth, carbon sequestration, and floral and faunal biodiversity.

Forty-six percent of organizations reported cost estimates to grow a single tree or to reforest a given land area. Only a third of organizations—43% of nonprofits and 16% of for-profits—provided clear information about how funds were distributed between administrative costs of the intermediary organization and the cost of implementing reforestation projects. Funding for local project costs ranged from 44% to 92% (median = 80.5%).

Most organizations (61%) did not specify the length of time that projects would be maintained, monitored, and financed, and only a small minority (11%) provided details about continuing both follow-up (maintenance and/or monitoring) and funding beyond the first year (Figure 3). Leaving responsibility for follow-up work to implementing organizations and landholders was the most common approach (30%), although often it was not clear how the ongoing work would be funded (Figure 3). Required commitments beyond 10 years were rare (10%), and only three organizations explained how funding would continue beyond a decade.

FIGURE 3. Extent of commitment to maintenance and/or monitoring work at project sites, including those that leave management responsibilities in the hands of local organizations and people without specifying a timeframe. Funding is either specifically stated to continue in the years following project establishment, referenced indirectly through discussion about supporting implementing groups and landholders via payments, or not discussed.

DISCUSSION

In the wake of several recent critiques of global tree-growing efforts (Fleischman et al., 2020; Höhl et al., 2020; Martin et al., 2021), our study suggests considerable movement of intermediary organizations toward adopting reforestation best practices, based on self-reporting from websites. Many critiques have focused on the lack of local community engagement in tree-growing efforts (e.g., Coleman et al., 2021; Elias et al., 2022; Lobe Ekamby & Mudu, 2022); yet, most organizations highlighted the importance of involving and providing benefits to local communities, albeit often without specifics. Martin et al. (2021) reported that only 18% of organizations mentioned monitoring on their websites. In our study (3 years later), 70% discussed monitoring generally, though most lacked details on timeframes and funding commitments. The next step is to move from general recognition of best practices to developing standardized protocols and accountability to support lasting results (Adams et al., 2016; Donatti et al., 2022; Lamont et al., 2023).

NGOs and those with more past reforestation experience shared more information about following best practices. We suspect this may be because nonprofits generally rely more on public donations as opposed to larger scale private investment or carbon credit revenue, for which accountability can lie with certifying bodies. Transparency of organization purpose, practice, and use of funds through official websites and publicly shared reports is often associated with greater legitimacy and appeal to donors for NGOs (André, 2012; Jordan, 2005; Kolhede & Gomez-Arias, 2022). More “experienced” organizations potentially have had more opportunities to observe and improve local project dynamics and respond to scrutiny from donors and stakeholders. Past experience, however, does not necessarily indicate future success; numerous examples demonstrate that organizations with established infrastructure and funding fail to produce lasting results (e.g., Coleman et al., 2021; Höhl et al., 2020). Notably, of the 23 organizations from our study claiming to have grown over 100 million trees, a substantial portion (26%) neglected to provide clear information about long-term maintenance or funding commitments, and a minority reported values for tree survival at any time postplanting. We expect that additional information could be obtained through direct requests to organization staff; however, these gaps in public accountability should be met with healthy skepticism from would-be contributors. Given the large and growing amount of money being spent on tree growing (Löfqvist et al., 2023), we reiterate previous calls for transparency about practices and outcomes of prior projects to hold both non- and for-profit organizations accountable to donors, investors, themselves, and local collaborators (Lamont et al., 2023; Mansourian & Vallauri, 2023; Martin et al., 2021).

Clearly stated project goals and objectives are key to designing projects and evaluating success (Holl & Brancalion, 2022; Sousa-Silva et al., 2023). Most organizations listed four to six tree-growing goals. Claiming to achieve multiple goals increases attractiveness for potential donors and may reflect varied goals of different projects that intermediary organizations support. Nonetheless, few organizations acknowledge trade-offs between the reforestation approaches to achieve different reforestation goals (Höhl et al., 2020; Holl & Brancalion, 2020; Löfqvist et al., 2022), such as whether to prioritize tree species that maximize carbon sequestration, biodiversity, or food resources. Lack of clear priorities makes it challenging to design projects and monitor whether objectives have been achieved.

Intermediary organizations should move toward establishing clear criteria for selecting local implementing organizations and projects. Two criteria integral to project longevity are secure land tenure and meaningful engagement of local communities throughout the project (Boissière et al., 2021; Le et al., 2014; McLain et al., 2021; Rana & Miller, 2021). Most organizations recognized the importance of securing land tenure in the long term, yet a minority noted restricting their funding to projects requiring this condition. This requirement is challenging to enforce strictly given the varied landholding and property rights in different countries (Vincent et al., 2021) and that many reforestation opportunities are in regions with insecure land rights (Rakotonarivo et al., 2023). Tree-growing efforts also need to be led by and benefit local stakeholders to achieve long-term reforestation (Fleischman et al., 2020; Kassa et al., 2022; Lobe Ekamby & Mudu, 2022). Intermediary organizations almost universally publicly declare how their supported projects benefit communities and on average ∼80% of funding supported implementing reforestation projects. Nonetheless, only a fraction of organizations provides empirical data on community benefits, and many of these only report engagement estimates (e.g., number of people or communities participating) rather than using household surveys to assess whether projects result in improved socioeconomic conditions (Coleman et al., 2021; Ding et al., 2023). Further progress is needed to ensure that project benefits are equitably distributed and inclusive (Löfqvist et al., 2022; Wells et al., 2021).

The long-term viability of global reforestation efforts in producing successful and sustainable outcomes remains a paramount concern given the widespread documentation of secondary forest reclearing globally (Crawford et al., 2022; Schwartz et al., 2020). We and others have found a disconnect between how organizations describe maintenance and monitoring plans versus the financial commitments to match these objectives, which signals a concerning vulnerability to lasting project impacts (Adams et al., 2016; Lamont et al., 2023; Lobe Ekamby & Mudu, 2022; Martin et al., 2021). Over a third of organizations stated that local partner organizations and landholders would manage maintenance and monitoring without clarifying sources of funding, which raises social equity concerns. Additionally, groups failing to engage local stakeholders prior to implementation risk burdening communities with maintaining projects that were not designed consistent with their values or capacity to manage. Specific strategies and innovative funding mechanisms (Katic et al., 2023; Löfqvist et al., 2023) are needed to allow reforestation projects to persist successfully over the scale of decades (Banin et al., 2023; Oakes et al., 2022; Rana & Miller, 2021).

With increasingly ambitious targets from both the global community and individual organizations, the risk rises that project establishment will outpace the ability to identify and secure growing sites where trees will persist. Project failures result in financial waste that could have been spent on other conservation goals and may lead to reduced confidence in tree growing (Höhl et al., 2020; Lobe Ekamby & Mudu, 2022; Rana et al., 2022). We advocate the importance of addressing common pitfalls that have led to previous reforestation failures and the need to follow best practices guidelines to achieve desired goals, particularly as many inexperienced organizations continue to join the reforestation movement. We expect intermediary NGOs will play increasingly larger roles in global reforestation in years ahead, along with other large-monied interests joining these movements (Lamont et al., 2023). Holding the various actors in reforestation movements to a higher standard will require moving beyond narrow focus on tree planting statistics toward increasing collective consciousness among practitioners and funders about practices and standards that are most likely to lead to long-term success.

ACKNOWLEDGMENTS

This research was supported by the MacArthur Foundation Chair at University of California Santa Cruz held by K.D.H. We thank Y. Sheikhvand for assistance with data collection. We appreciate helpful comments on prior versions from P. Brancalion, F. Joyce, S. Mansourian, G. Vasey, and two anonymous reviewers.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are openly available in the Dryad Digital Repository: Schubert, Spencer et al. (2024). Advances and shortfalls in applying best practices to global tree-growing efforts [Dataset]. Dryad. https://doi.org/10.5061/dryad.wdbrv15w4