Ethics statement

Research clearance was obtained from the LSHTM University Ethics Committee (Reference 26323). Research permits and clearance were issued by the Tanzanian Commission for Science and Technology (COSTECH), Permit No 2021-638-NA-2021. The study was conducted according to the guidelines of the Declaration of Helsinki. All participants provided written informed consent before participation, and the study adhered to all ethical regulations.

Study design

We undertook in-depth group discussions to explore the health and well-being impacts of landscape regeneration. The data was collected via 90-minute long audio-recorded focus group discussions led by the study team that comprised of an epidemiologist, a clinician, and monitoring and evaluation (M&E) experts. Both the clinician and M&E experts work with the implementing organisations [19, 20] and are well known in the community.

The group discussions were conducted in four rural villages (Village 1–4 in the Results section) around the Mpwapwa district of Dodoma region. The area is semi-arid characterised by warm to hot temperatures all year round and annual precipitation of around 650mm [21]. S1 Fig summarises Dodoma’s climatology and seasonal cycle for mean, maximum and minimum surface temperature and precipitation for the latest climatology, 1991–2022 [21]. The majority of households rely on subsistence farming for income. Rain-fed crop production and livestock rearing are vital economic activities, but these are characterised by low productivity due to the harsh climatic conditions [22]. Compared to other areas in Tanzania, Mpwapwa district also has higher maternal and infant mortality rates [23] and lower levels of literacy [23, 24]. At the time of the study, FMNR had been operational for 36 months in villages 2 and 3, and for 18 months in villages 1 and 4.

A semi-structured discussion guide was used to draw out the participants’ experience of practising FMNR, perceived short and long-term impact (positive and negative) on health and well-being, barriers and opportunities of implementation as well opinions on how to scale up the intervention across other settings. In order to capture the diversity of experience, participants were purposively sampled to ensure an equal distribution of men and women, income levels and occupation groups. The recruitment was conducted by word of mouth in November 2021 and was done by local program coordinators who worked closely with village leaders to identify 6–8 participants per village. Participants were provided with details on the scope and purpose of the study, and written informed consent to participate and record the discussions was sought during the recruitment. The discussions were conducted in Swahili and the recordings were transcribed and translated into English. More detail on the study design is provided in the S1 Text.

Analysis

The transcripts were coded on NVIVO software to identify the emerging dominant themes, which were thereafter categorised into four ecosystem services defined by the Millenium Ecosystem Assessment (MEA) framework [4]; this groups ecosystem services with known benefits to human well-being as; provisioning, regulating, cultural and supporting services (see S1 Text for a full definition).

We thereafter used the ecosystem services cascade model [25] to conceptualise how the respondents defined pathways from ecosystem restoration to health outcomes. The cascade model is considered an improvement to the MEA framework, the latter has been criticised for defining ‘ecosystem benefits/ends’ and ‘ecosystem services/means’ interchangeably, thereby, failing to distinguish the differences between ‘benefits’ accrued and the ‘mechanisms’ that give rise to given services [25, 26]. Services can be defined as the aspects of ecosystems utilized (actively or passively) to produce human well-being benefits; services are therefore ecological in nature and what are traditionally defined as cultural services such as recreation are simply benefits [26]. Another criticism of the MEA framework is that it omits intermediary components along the pathway to well-being, whereas the cascade model assigns these components as ecosystem ‘services’ and ‘functions’ [25], although their distinctiveness has been debated [25].

Ecosystem services, functions and benefits

In this study, we have used ‘functions’ to indicate the capability of the ecosystem to do something that is potentially useful to people, for example, woodlands have the capacity (function) to slow the passage of surface water and modify the intensity of flooding—flood control being the ‘service’ in this scenario [25]. Whether a ‘function’ leads to a given ‘service’ is context-dependent and is determined by how beneficial the ‘service’ is perceived [25]. In this study, a service was considered to generate ‘benefits’ or ‘disbenefits’ if it contributed to self-perceived outcomes related to human well-being.

Understanding what constitutes ecosystem functions, services and benefits requires contextual understanding of societal values, as well as knowledge of the structure and dynamics of ecological systems [25]. The cascade model can adequately handle the multi-dimensional and context dependency of the underlying value and impacts [27], for example, a given ecosystem may generate provisioning services in one community and regulating services in another; provisioning-regulating services tension could arise if consumption exceeds the levels needed to regulate ecosystem processes. This level of detail is an important step towards informing decision making, detailed mapping of causal pathways can enable the definition of credible metrics and end-points that facilitate the evaluation of landscape management and policy interventions [25].

The Results section presents the emerging themes and outcomes in various ways, firstly, as a word cloud to show the frequency of occurrence of the most common 100 words, this highlights the most important themes from the respondents’ perspectives. Secondly, the emerging themes and outcomes are mapped against four broad ecosystem services as per the MEA framework, this is to assess how local knowledge matches the existing literature, and the strength of the evidence i.e. how frequently the themes were discussed across the sites. Lastly, the cascade model is applied across four pathways to demonstrate how intermediary ecosystem functions and services translate to measurable impact on health and well-being. The pathways are supported by verbatim quotes from the group discussions to add depth in illustrating the lived experience. Similar emerging concepts across the different study sites are also reported to validate the findings. During the translation, some editing was required to remove redundant words and to capture the key points whilst retaining meaning and context.

Pathways from regeneration to health outcomes

Emerging pathways linking FMNR, ecosystem and health outcomes are summarised in Fig 2, the arrows show the direction of flow from regeneration to health outcomes via intermediary components. The line thickness is a qualitative assessment of how frequently the pathway emerged from the group discussions; the thickest lines suggest emergence across all four study sites. Although provisioning services in relation to food security were frequently reported across all sites, regulating services were associated with the greatest number of health outcomes that included respiratory, water-borne and eye diseases, chronic back pain, dehydration, sanitation and mental health. Fig 2 shows complex interactions in how ecosystem services work to drive human health. This complexity renders the MEA framework inadequate for quantifying impact and for informing decision making on ‘where to intervene’ to deliver desired effects.

In Fig 3A–3D, we show how the cascade model can help determine causal pathways characterised by intermediary components and measurable health outcomes. Four pathways emerged from our content analysis of the group discussions (Fig 3A–3D), these do not describe all the possible pathways, but rather summarise dominant routes through which respondents perceived FMNR’s impact on their health and well-being. Inevitably, there are overlaps in the intermediary functions and services shown in each pathway, but the end health-related outcomes are distinct. The pathway model enables the identification of end outcomes and key mediating factors which can inform the evaluation of impact by guiding decisions on ‘what to measure’ and ‘where to intervene’.

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Fig 3.

(A-D)–Use of the cascade model to show causal pathways from ecosystem regeneration to health outcomes, highlighting intermediary components and the final health outcomes.

https://doi.org/10.1371/journal.pclm.0000206.g003

Pathway (A) is the simplest and shows a direct impact from ecosystem changes to health without intermediary factors. Pathway (B) suggests a complex pathway with one clear intermediary ecosystem service to health. Pathway (C) is more complex and involves multiple intermediary ecosystem services and functions to achieve health and pathway (D) is marked by socioeconomic factors that act to mediate health outcomes.

Summary of key findings

Our study reports findings of in-depth group discussions with local participants who are actively restoring degraded landscapes in Central Tanzania using FMNR. The participants reported how the restoration has reversed decades of degradation, whilst delivering multiple health and well-being co-benefits in relation to food and nutritional security, improved respiratory health, access to clean water, poverty reduction, gender equality, heat adaptation and many more. These benefits were perceived across all the study sites, regardless of the length of implementation which ranged from 18–36 months.

Using the MEA categorisation of ecosystem services, we found provisioning services in relation to food security were more frequently reported across the study sites, but regulating services were associated with a greater number of health outcomes (Fig 2). We demonstrate how the application of the cascade model can be mainstreamed in health studies; despite the perceived impact of many nature-based solutions such as FMNR, there is limited empirical evidence quantifying the health co-benefits of these solutions. Our study makes an important contribution towards conceptualising some of the ways that the restoration of natural habitats contributes to human health outcomes. We demonstrate how a pathway approach within the cascade model can map out causal mechanisms between ecosystem structure, functions, services and well-being. Four pathways emerged from the group discussions, ranging from direct pathways between natural regeneration to health, to pathways where health outcomes are mediated by complex changes in ecological or socio-economic factors (Fig 3). This pathway approach can help identify the exact metrics for use in quantifying impact and should be a fundamental process in designing rigorous impact and process evaluations of nature-based solutions.

Experiencing health and socio-economic benefits was seen as a key driver for conservation as it boosted FMNR uptake and sustainability. This exemplifies nature-based solutions’ ability to unite health and ecological objectives which have traditionally been implemented in isolation (at least until the recent emergence of Planetary and One Health paradigms [29]). The cascade model supports this unification in several ways; firstly, quantifying changes in the ecosystem alongside health and well-being outcomes can help with measuring attribution. Secondly, characterising socio-economic mediation (Fig 3D) is important for public health which places great interest in understanding variations in exposures and outcomes by population vulnerability.

Contextualising our findings in the existing literature

The exploitation of natural ecosystems has made positive contributions to human well-being and economic development but has resulted in the rapid degradation of many ecosystem services [4, 30]. This deterioration is a principal factor in exacerbating poverty in marginalised groups [4] many of whom reside in drylands. Reversing it using nature-based solutions such as FMNR can offer effective climate change solutions [3] and help meet Sustainable Development Goals.

Widespread and successful solutions require a collective change in priorities and practices, shared positive experiences and enabling contextual factors [31]. Adoption of FMNR is no different, the successful implementation of the practice can be credited to the successful training of local farmers and to a sincere desire by communities to combat desertification through landscape restoration. However, the widespread success of the FMNR and its large scale implementation is mostly attributed to the positive feedback loops from restoration to experiencing benefits (including health and socio-economic benefits) which are often passed on by word of mouth. This indicates the need for joint policy formulation between environmental and health actors and is particularly important during the UN Decade on Ecosystem Restoration 2021–2030 which aims to significantly scale up global protection and restoration of ecosystems, and support integrated approaches that engage all stakeholders, and in particular local communities [7].

Engaging local communities is profoundly valuable, our findings confirm how tapping into the vast reservoir of indigenous knowledge can set research directions and support the successful implementation of nature-based solutions [32, 33]. In this study, some of this indigenous knowledge included respondents’ astute accounts of linking ecosystem functions and services to human health, identification of the functional use of various tree species, and great insights of plant biodiversity including an understanding of the role of biodiversity in maintaining fundamental ecosystem functioning.

Strengths and limitations

Focus groups can draw out rich perspectives in a way that is not possible with quantitative methods, they also generate new hypotheses to formulate further research. Nevertheless, limitations in reporting the subjective experience of participants include the likelihood of over-attributing benefits to project activities where respondents may be concerned about damaging relationships with implementing NGOs [10]. Another limitation is recall bias, where respondents fail to accurately remember experiences before the intervention. We addressed these limitations by conducting group discussions across four villages that differed by ‘time since implementation’ and ‘geographical proximity’, we also varied the facilitators by village. Reassuringly, we found consistency in the dominant themes across all the sites, which increased the validity of the findings.

Several outcomes reported during the group discussions are difficult to verify, the surest way of demonstrating impact is to triangulate these accounts with robust quantitative studies. Future studies should also examine the trade-offs associated with landscape regeneration. Although no trade-offs emerged during the group discussions, tree intercropping has previously been shown to reduce crop yields but this is dependent on crop type [17]. Increased vegetation can also allow pests, pathogens and wildlife to accumulate over time, which may increase vector borne diseases, pests attack on crops and can lead to human-wildlife conflict [34]. Some ecosystem-based mitigation solutions have also been criticized for compromising the cultural and ecological rights of indigenous communities [35]. Our study did not report these disbenefits, presumably because FMNR focuses on improving livelihood and increasing climate resilience, rather than mitigation. Also, farmers implementing FMNR are trained on the optimal number of trees per farm to avoid compromising crop yields, furthermore, the implementation is at an early phase so the landscape may not yet support the proliferation of pathogens and wildlife.