Restoring indigenous trees can help combat malnutrition in Africa

Abstract

Across African countries and contexts, there is robust evidence of how forests and trees can support people's diets. In particular, indigenous food trees are an important source of micronutrient-rich fruits, leaves, nuts, and seeds. Yet in large-scale landscape restoration projects, these species are often overlooked in favor of exotic, fast-growing tree species—limiting the potential of restoration initiatives to co-address biodiversity loss and malnutrition. With local practitioners in Malawi, we explore challenges to and opportunities for better integration of indigenous food trees in landscape restoration projects. We argue that scientists, policymakers, and restoration practitioners should focus on three primary domains for greater knowledge management and capacity building: (i) tree propagation, (ii) improving seedling survival rates, and (iii) value chain development for tree-based foods. Targeted support for incorporating indigenous food trees in these areas can help promote synergies between human and ecological health in natural resource management agendas.

Introduction

Africa is losing more forest than anywhere else in the world (1)—with immediate and drastic consequences for floral and faunal biodiversity (2). While these ecological impacts are widely recognized, the effects of tree cover loss on people's dietary quality are often overlooked. Indeed, trees can be an important source of nutritious fruits, nuts, seeds, and leafy vegetables (3). There is now solid evidence from different African countries and contexts showing positive links between tree-based landscapes and diets (4–9). This is especially critical for forest-dependent communities—comprising over 250 million people across the continent (10). With 30% of children under five in Africa experiencing stunting (11), an indicator of chronic malnutrition, there is an urgent need to support people's access to nutritious food from forests and trees.

Landscape restoration initiatives have a critical role to play in addressing these challenges. Across Africa, tree planting and natural regeneration have taken root as key strategies to increase tree cover and restore deforested landscapes. In natural forests, regeneration of trees depends on seed dispersal, often with the help of animals that benefit from the presence of these trees (12). Deforestation can disrupt these plant–animal interactions and interfere with processes of natural regeneration, sometimes necessitating direct tree planting to restore landscape functionality. Yet in the interest of achieving these objectives at scale, scientists, policymakers, and restoration practitioners often prioritize a small number of commercially useful, exotic tree species to meet area-based targets (13–15). This narrow, utilitarian focus overlooks the potential of indigenous trees to support both human and environmental health. The Food and Agriculture Organization defines an indigenous or “native” tree species as having evolved in a localized geographic area, and “occurring within its natural range (past or present) and dispersal potential” in the absence of human involvement (16). As such, greater incorporation of indigenous trees in restoration activities can contribute to the conservation of local biodiversity and ecosystem resilience (17, 18). Importantly, indigenous trees can provide nutritious foods that are embedded in local cultures and traditional knowledge systems (19). With public and private institutions pledging well over 1 billion USD in funding for landscape restoration projects across the African continent (20), neglecting indigenous food trees represents a missed opportunity for the restoration community to co-invest in public health and ecological restoration objectives (21).

Here, we examine challenges and opportunities for nutrition-oriented landscape restoration in Malawi, a densely populated country where over 80% of people live in rural areas and depend on natural resources for their livelihoods (22). Pressures on land for supporting a growing population have contributed to widespread tree cover loss: 17% (260 kha) between 2001 and 2024 (23). Moreover, high rates of malnutrition persist in rural communities. For example, 33% of children under five are stunted, and anemia prevalence is 32% in women of reproductive age (11). Recent research in Malawi points to the importance of trees in forests and on farms for people's dietary quality, namely intake of vitamin A, zinc, iron, and folate (24, 25). As such, the country is an optimal case site to examine how landscape restoration practitioners can incorporate a nutrition dimension in their projects.

Our collaboration with restoration practitioners across the country revealed widespread interest in integrating indigenous food trees into landscape restoration initiatives. Yet, local actors voiced a need for greater knowledge management and capacity building across three key domains: (i) tree propagation (i.e., multiplication), (ii) improving seedling survival rates, and (iii) value chain development for tree-based foods. To achieve these aims, we argue that scientists, policymakers, and restoration practitioners need to collaboratively support the strengthening of local knowledge systems on the use, reproduction, and management of indigenous food trees. Such support is key to ensure that restoration projects will promote synergies between human and ecological health—which is vital to catalyze a shift in both paradigm and practice, centering planetary health in natural resource management (26, 27).

The role of indigenous trees in landscape restoration

The launch of the UN Decade on Ecosystem Restoration (2020–2030) has helped spur political pledges such as the African Forest Landscape Restoration Initiative (AFR100), which aims to restore 100 million hectares by 2030 with commitments from 34 countries (28). Yet, the deadlines driving broad-scale tree-planting agendas can fuel a political bias toward planting monocultures of exotic, fast-growing timber species, such as eucalyptus and pine (29, 30). Such simplistic restoration approaches, while generating rapid investment returns, may increase fertilizer and pesticide run-off, increase vulnerability to pests and diseases, deplete groundwater resources, and compromise local biodiversity (31–33). Worse yet, low-diversity plantations are highly vulnerable to wildfires, droughts, and other extreme weather events—a threat exacerbated by climate change (18, 33, 34). Introducing exotic species in large numbers also increases the risk of invasiveness (i.e. a situation in which the introduced species outcompetes local vegetation for vital resources), which can lead to ecosystem disruption and environmental degradation (18). Furthermore, as commonly used plantation trees (e.g. pine and eucalyptus) do not produce edible products, introducing these species in bulk can limit the availability of diverse food sources in restored landscapes. Even smaller-scale agroforestry interventions often prioritize exotic, fast-growing species over longer processes of restoring biodiversity in degraded ecosystems (35). For example, over 60% of AFR100 agroforestry projects focus on nonindigenous species (20), favoring exotic trees that are bred to be highly productive with planting material that is readily available.

Yet, supporting local people's livelihoods and biodiversity restoration does not have to be mutually exclusive (36). Adapted to local climatic conditions, indigenous food trees can help foster greater abundance of local plants and animals (e.g. important pollinators) by creating understory conditions similar to those of natural forests (32). Already deeply embedded in traditional knowledge systems, indigenous food trees can help co-address social and ecological objectives by supporting household diets and providing auxiliary subsistence or income-oriented services, including medicine, animal fodder, and materials for household tools (37). We note that depending on site-specific conditions, exotic (noninvasive) tree species may also deliver nutritional benefits to local communities with minimal ecological trade-offs (33). For example, some exotic food trees have been naturalized over generations—and may now be integrated in local food cultures (e.g. the case of Mangifera indica “mango” in Malawi). In the interest of centering local preferences in tree species selection, such trees should continue to play a role in landscape restoration activities.

Indeed, there is growing evidence that neglecting the social dimensions of restoration can limit a project's ecological outcomes (38). While many large-scale restoration initiatives, including AFR100, are launched by high-level political actors, it is now well established that their success hinges on constructive collaborations between the implementing institutions (i.e., private sector, donors, government, and nongovernmental organizations) and local communities in project areas (39, 40). Rather than a tokenistic approach to community participation, socially just restoration requires shared governance with local institutions (41). Meaningful partnerships in restoration project design and implementation can lead to the incorporation of diverse interests of local actors—which often include social and economic dimensions beyond simply creating carbon stocks (15, 42). In light of their numerous benefits, greater prioritization of indigenous food tree species can help incentivize local communities to take an active role in tree-based landscape restoration, increasing the likelihood of successful achievement of social and ecological objectives (14). To realize such diverse interests and channel funding accordingly, the restoration community must identify how to better support local practitioners in their efforts to restore tree-based landscapes with indigenous species.

The case of Malawi

Malawi has pledged more than 40% of its total land area for restoration under the AFR100—a considerably large proportion compared to other countries (20). Together with local practitioners, we co-developed a survey to assess organizational needs related to nutrition-oriented landscape restoration. We developed this survey in the framework of the European Research Council (ERC) project TREETOOL (parent project FORESTDIET) and received ethical approval from the ERC and the Research Ethics Committee for Science and Health at the University of Copenhagen (hosting institution). Consent forms were read and signed by survey participants to ensure informed, voluntary participation, photo permission, and optional withdrawal at any time in the study prior to data collection. Using snowball sampling, we conducted this survey with representatives from 21 civil society organizations engaged in 39 community-based restoration projects, operating in all 28 districts within Malawi. The survey responses indicated that despite widespread interest from local practitioners in planting and regenerating indigenous food trees, there was a lack of technical resources on the subject. In response, we collaborated with foresters, botanists, and agroecologists in Malawi to co-develop an illustrated tree-planting guide for indigenous edible tree species. The guide draws from local traditional knowledge and features botanical descriptions, a harvest calendar, and step-by-step instructions for planting and management (43). We presented the guide at two regional knowledge-sharing workshops with 40 practitioners from participating organizations. At these workshops, we used the guide as a point of departure for dialogues diving deeper into challenges and opportunities for incorporating indigenous food trees in restoration projects. Activities included a “knowledge champions” exercise, where participants collectively identified domains in which they either had expertise or sought information. Three priority domains emerged in both workshops: propagation, seedling survival, and value chain development. We then facilitated a series of small group discussions around each domain (commonly called a “world café”) to encourage knowledge exchange between experts and attendees. In the concluding plenary sessions, practitioners voiced an overall need for greater support in mobilizing traditional knowledge systems and capacity development across these domains. Here, we discuss the collectively identified challenges and opportunities across the three domains to support greater inclusion of indigenous food trees in restoration activities.

Propagation of indigenous food trees

In Malawi, most restoration projects (87% of surveyed projects) include indigenous tree species—with 67% of all projects including a mix of both indigenous and exotic species (Fig. 1A). The majority of the projects targeting a mix of indigenous and exotic species focus on trees that provide fuelwood (Fig. 1B). Indeed, most of the indigenous tree species cited by organizations do not produce human food, such as Faidherbia albida (white acacia) or Khaya anthotheca (white mahogany). When asked about primary obstacles to integrating a more explicit nutrition focus in their restoration activities, practitioners cited challenges related to the informed selection of indigenous food tree species, procurement of seeds, nursery management, and the preparation of planting sites. For exotic food tree species (e.g., citrus fruits, guava, avocado, and mango) that are more commonly planted, knowledge of these aspects of tree planting and management is—in contrast—well codified and widely accessible. The reason is that such species have received greater government and commercial investment. While popular among local communities in Malawi, indigenous species such as Uapaca kirkiana (wild loquat) are commonly overlooked by commercial breeding programs, despite research supporting their domestication (44). Accordingly, practitioners reported the local forest as the primary source for tree seeds (87% of projects), indicating both a high reliance on wild areas and perhaps underdeveloped tree seed systems for obtaining planting material of sought-after species (45). The limited availability of indigenous tree seeds and seedlings is, however, being increasingly addressed by large-scale restoration initiatives in other regional contexts, such as the Great Green Wall, where practitioners combine community consultations with ecological criteria to select and reproduce indigenous tree species, designing tree-planting projects in line with local preferences (46).

Figure 1.

A) Percentage of restoration projects in Malawi that incorporate either indigenous, exotic, or a mix of indigenous and exotic tree species. B) Proportion of restoration projects that focus on each benefit (multiple answers possible)—disaggregated by project tree species composition. C) Example of how farmers in Malawi typically benefit from planting an exotic pine species (Pinus patula) vs. an indigenous fruit tree species (Parinari curatellifolia). *Based on a survey with 21 tree-planting organizations and their 39 projects covering all 28 districts of Malawi. **Based on workshops with 40 practitioners.

Of the surveyed projects, those including indigenous species target on average five purpose areas, with the most common being food, fuelwood, water retention, timber, and fertilizer (Fig. 1B). In contrast, the projects including exotic species only focus on an average of three purpose areas. An example of a multipurpose indigenous species favored by many projects is Parinari curatellifolia (mbula plum), as it possesses diverse ethno-medicinal and ecological properties beyond the provision of food and timber (19) (Fig. 1C). Mbula plum tree flowers are favored by local pollinators, supporting honey production. The fruits contain high levels of antioxidants and are used to treat various ailments, while the bark and leaf extracts can be used to treat pneumonia, earaches, and cataracts (19, 47). Knowledge of these multiple uses, passed down through generations, embeds these species into local cultures and traditions. Comparatively, popular exotic species, e.g. Pinus patula (Mexican weeping pine), are introduced in the context of their purpose for exploitation—which is often timber. Consequently, workshop participants stressed how such species offer fewer additional benefits to local communities (Fig. 1C). Furthermore, African indigenous fruits, nuts, and seeds have high nutritional value. For example, consuming 100 g of Ximenia americana (sour plum) fruit constitutes twice the recommended daily intake of vitamin C for adults (48). Considering their integration in local food cultures, efforts must be made to further develop and widely disseminate knowledge around indigenous food tree propagation (Fig. 2).

Figure 2.

Key knowledge management and capacity development gaps associated with nutrition-oriented, tree-based restoration projects and example solutions derived from workshops in Malawi. Photo credit: Emilie Vansant. Guide illustrations by Mette Jeppesen.

From tree planting to tree protection

To ensure the long-term success of tree-based landscape restoration efforts, there is an urgent need to broaden project scopes from tree planting to include tree protection—encompassing both planting and naturally regenerating trees. In our survey and workshops, poor seedling survival was widely cited as a challenge in promoting indigenous food tree species, despite 95% of projects surveyed having included it as an area of impact evaluation. Once outplanted, tree seedlings are especially vulnerable to climatic extremes, wildfires, pests, and livestock. Proper weed control to reduce competition for light, soil nutrients, and water has been found to be especially critical for at least several years until tree seedlings are well established (49). For example, a study of agroforestry projects in Rwanda recorded a survival rate of 30–50% over 4 years, which was attributed to poor seedling monitoring and management (50). Moreover, seeds and seedlings that are either poor quality or maladapted to their planting sites may have limited success (51). Indigenous trees often have more restricted environmental niches than commonly introduced exotic species and, therefore, indigenous seedlings may be more vulnerable to irregularities in climate conditions at planting sites (18). Beyond context specificity, encouraging the long-term adaptation of tree communities in a specific site also requires fostering a certain level of intraspecific diversity to ensure the production of viable offspring (17).

An examination of AFR100 reforestation commitments found that half of tree-planting projects were planned to be established in nonforest ecosystems, such as savannahs and grasslands (20). Planting trees in unsuitable environments (e.g. increasing woody cover in grassy ecosystems) not only hinders seedling survival rates but can also lead to ecosystem degradation, including diminishment of critical water resources (34, 52). Promoting open-access decision support tools for indigenous tree planting, such as CIFOR-ICRAF's Global Tree Knowledge Platform (53), is an important preliminary step in ensuring the right trees are planted in the right places. Complementing this information with context-specific, traditional knowledge on well-adapted, indigenous tree species and field techniques will also support seedling survival. For example, our tree-planting guide features locally derived expertise on management techniques, such as mulching regimes for seedlings. This expertise can also be drawn from local communities, universities, and other organizations harboring traditional ecological knowledge—which can provide critical insight on the suitability of species for the biome in focus.

Poor seedling survival rates can also stem from structural issues with an organization's project funding scheme, implementation design, and monitoring and impact evaluation framework. In a review of the websites of 99 intermediary organizations that promote and fund tree-planting projects, less than half (41%) of the organizations monitored and reported tree survival rates, and only 11% stated plans for longer-term maintenance or monitoring beyond the first year (54). In a separate review of data from 174 tree-planting organizations, almost no discussion of seedling monitoring was found in organizational documents and websites—with only 5% of organizations reportedly measuring survival rates or maintaining trees after planting (15). Ambitious targets followed by monetary commitments may be an efficient mechanism to get trees in the ground but will not ensure the long-term sustainability nor ecological integrity of a restoration project. Diversifying funding sources can help ensure that the success of any one tree-planting scheme is not dependent on a single donor or government's priorities (49). Broadening restoration ambitions from tree planting to include tree protection will also require moving beyond short-sighted project planning models via greater investment in tree monitoring and maintenance. There are already some examples in other countries of projects building maintenance programs into tree-planting initiatives through mobilizing the education system as a governance tool to instill the youth with a culture of tree care (55). A strong focus on tree monitoring is especially important for indigenous food trees, which are often slow to produce harvestable products, likely delaying any impacts on dietary quality for a few years after planting (56).

Beyond planting trees, encouraging assisted natural regeneration of established indigenous food tree species is also a promising complementary strategy to both protect and restore local biodiversity. This form of in situ conservation helps ensure the preservation of habitats in which indigenous food tree species naturally occur. Here, genetic resources are maintained in either uncultivated landscapes or as crop cultivars in traditional agricultural systems (e.g., agroforestry)(57). Natural regeneration of trees in a variety of environments helps preserve genetic diversity within the species, which in turn improves seed quality for future generations. Furthermore, regenerating indigenous food trees in their natural environments—in lieu of introducing exotic species—can help restore the ecological integrity (pre-disturbance composition, structure, and function) of tree-based landscapes (14). Even if these trees are regenerated as part of managed agroforestry systems, the incorporation of indigenous species can help sustain biodiversity across fragmented forest-agriculture landscapes (58). Protecting and actively nurturing existing indigenous trees can lead to more resilient seedlings than those planted and raised in tree nurseries (59). This may be particularly relevant for indigenous food trees, which have not traditionally been the target of scientific programs to develop robust rootstocks tolerant to biotic stresses, such as fungal infections (57). Assisted natural regeneration is therefore a viable, cost-effective restoration strategy to (i) ensure the tree is ecologically compatible with the biophysical conditions of the target area and (ii) bypass the challenges associated with tree seed propagation and early-stage seedling survival.

Supporting value chain development of tree-based foods

Value chain development of tree-based foods and food products (e.g., fruits, nuts, seeds, and leafy vegetables) can help create economic incentives for planting and protecting indigenous food trees, improving the long-term viability of nutrition-oriented restoration. Using markets to leverage investment in landscape restoration (i.e., co-prioritizing economic and ecologically valuable tree species in planting designs) has emerged as a potential mechanism for providing material benefits to local communities living in restoration areas (60). In our workshops, participants identified “value addition” as an important topic area for knowledge exchange and capacity building. This is largely because the restoration experts working in Malawian communities have strong backgrounds in ecology and forestry. They were keen to advance their skills to extend the nutritional benefits of tree-based foods beyond the producer and into the market system, voicing a need for training in business management, including marketing, finance, and digital literacy. About 87% of surveyed restoration projects involve close collaboration with local village development committees, which makes restoration practitioners well-positioned to economically empower the communities in which they work. Yet, such efforts must also be accompanied by a broader reorientation of political support (e.g. subsidies) for tree-based value chains, including the standardization of agro-techniques for quality production, storage, processing, and distribution.

A successful example has been the surge in the commercialization of Adansonia digitata (baobab) products in domestic markets across Africa, which can create income opportunities for local communities (61). Export markets for baobab have also grown following the acceptance of the fruit pulp as a marketable “novel food” in the European Union and the United States in 2008 (62). In Malawi, the baobab fruit pulp can be found in ice-lollies, juices, powders, jams, and sweets—while seeds can be roasted and ground into powder (63). Processing raw fruits into more shelf-stable products allows for year-round access to nutritious fruits. While baobab is renowned for its high vitamin C content, variable storage duration and conditions have been found to affect the nutrient content of baobab products (64). As such, keeping up with growing domestic and international demand for baobab will require further development and standardization of quality processing and storage infrastructure. To prolong shelf life for such perishable foods, investments and training are also needed in the use of natural preservatives—as well as proper packaging. Here, local universities can also play a role in training extension workers through food science programs. Setting up networks or cooperatives to share equipment (and costs) will also be key in increasing the profitability of tree-based foods. In addition to processing facilities, indigenous fruits that are less known outside local contexts, such as Vangueria infausta (African medlar), might need consumption-oriented interventions (e.g., education on their nutritional value) to be successfully mainstreamed into global markets (65).

Outlook

At a time when the outlook for concurrently addressing the interlinked global crises of biodiversity loss and malnutrition often seems dire, we here explore strategies for restoration practitioners to tackle these crises in tandem. Our collaboration with Malawian civil society organizations revealed a strong, widespread interest in planting and restoring indigenous food trees. Integration of these trees in landscape restoration projects can leverage synergies between human and ecological health, helping safeguard local biodiversity while making nutritious, tree-based foods accessible to households through monetary and nonmonetary means. This is especially crucial given recent surges in global food prices, which have made a healthy diet unaffordable for 92% of the population in Malawi (11). Yet, for practitioners working on the ground, greater incorporation of indigenous food trees in restoration projects requires further knowledge management and capacity building concerning species propagation, seedling survival, and value chain development for tree-based foods.

On a broad scale, tackling these challenges will also require greater integration across siloed policy domains, namely ecological restoration and public health agendas. Such efforts must also be coupled with a realignment of policy and funding mechanisms away from short-term tree-planting area targets. The current over-reliance on exotic, fast-growing species to meet restoration goals undermines biodiversity restoration and climate change mitigation efforts (31)—with ample evidence that plantations store less carbon and harbor less biodiversity than diverse, native forest ecosystems (32, 66). Recent research has argued that top-down tree-planting initiatives are often not tailored to local needs and contexts and are therefore unlikely to benefit local people, whereas projects that have coupled social-ecological objectives provide stronger incentives for longer-term community management (30, 49). Our study shows that restoration practitioners working with Malawian communities see indigenous food trees as a way to fulfill ecological restoration objectives while supporting people's dietary quality. Knowledge and capacity building for appropriate food tree species selection and management to this effect aligns with the United Nation's recent adoption of dietary quality as a Sustainable Development Goal indicator. This new indicator is a major step forward in recognizing how better diets are key to addressing many health, development, and sustainability challenges. Most importantly, it marks an unprecedented opportunity to mobilize landscape restoration funds and expertise to help combat malnutrition in Africa.

Funding

E.V. and L.V.R. were supported by the European Research Council under the European Union Horizon 2020 research and innovation program (grant agreement no. 101138338, TREETOOL and grant agreement no. 853222, FORESTDIET). The work was also supported by the Danish National Research Foundation, Center for Remote Sensing and Deep Learning of Global Tree Resources (TreeSense), DNRF192—and it contributes to the Global Land Programme (https://glp.earth).

Competing Interest

The authors declare no competing interests.

Author Contributions

Emilie Vansant (Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Visualization, Writing—original draft, Writing—review & editing), Bowy den Braber (Data curation, Formal analysis, Methodology, Writing—original draft, Writing—review & editing), Charlotte Hall (Writing—original draft, Writing—review & editing), Judith Kamoto (Conceptualization, Investigation, Writing—review & editing), Esther Lupafya (Investigation, Writing—review & editing), Stepha Mcmullin (Writing—review & editing), Sain Muskambo (Investigation, Writing—review & editing), Richard Swirah (Investigation, Writing—review & editing), Lovemore Mkunkha (Investigation, Writing—review & editing), and Laura Vang Rasmussen (Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Supervision, Writing—original draft, Writing—review & editing)