Systematic Literature Review: Tree-based farming systems can be a win-win for people and nature

Fruit and timber trees scattered within maize fields in Mulanje District, Malawi (photo credit: Emilie Vansant)

A new paper was published in People & Nature by Emilie Vansant in collaboration with a team of scientists at CIFOR-ICRAF. The study reviews literature linking tree-based farming systems and dietary quality in low- and middle-income countries (LMICs). The synthesis of 36 studies finds:

  1. Maintaining trees in and around farmland – and using these trees for both the direct provision of foods and as a source of income – can serve as a key strategy for households to diversify food consumption and improve dietary quality.
  2. How much a tree-based farming system can influence diets is dependent on policies and institutions at the national scale, bioclimatic and geographical factors at the landscape scale, as well as socioeconomic factors at both the landscape and household levels.
  3. Indigenous populations practicing traditional forms of tree-based farming (which are often diverse systems integrated with wild landscapes) seem to maintain high levels of dietary quality through sourcing food from both wild and cultivated areas

The existing evidence, though limited, points at important knowledge gaps – namely the lack of a typology of tree-based farming systems to facilitate objective comparisons across cultural and geographical contexts. Additionally, there is a paucity of research that explicitly examines the role of non-forest trees in influencing dietary quality. By recognizing the potential of trees to contribute to positive nutritional outcomes in rural communities, this study supports the development of nutritionally-sensitive landscapes in LMICs.

Promotion of the article in CIFOR’s Forest News blog:

Read the full article here.

New study published in PNAS – “deforestation reduces fruit and vegetable consumption in rural Tanzania”

Using a novel modelling technique which combined two-way fixed effects modelling with covariate balancing generalised propensity score (CBGPS) weighting analyses, we were able to isolate deforestation as a causal factor in the decline in household dietary quality over the study period. Specifically, for the average household who experienced a loss of 171 hectares of forest, fruit and vegetable intake decreased by 14 grams per person per day. Given the very low intake of fruit and vegetables in these communities (130 grams per person per day on average, relative to the recommended intake of 400 grams per day), this represented a substantial proportion (11%) of daily intake. Exploration into the potential causal mechanisms of this reduction pointed towards the ‘direct consumption pathway’, indicating that deforestation reduced people’s ability to directly source wild fruits and vegetables from the forest. Given the high vitamin A content of these types of foods, deforestation was also responsible for a reduction in micronutrient adequacy of people’s diets. The results of this study have important implications for policy makers. Strategies to achieve food security very rarely attend to the role of forests, and often promote agricultural intensification and expansion which often comes at the expense of forest landscapes. This study, showing that deforestation caused a decline in dietary quality, highlights the need to better understand the importance of forests for nutrition in certain settings. Indeed, conserving forests potentially offer win-wins in terms of meeting both nutrition goals as well as conservation and environmental goals.  

This new study, published in PNAS, is the first of its kind to establish a causal link between deforestation and people’s dietary quality. While many studies in recent years have found positive associations between living in/near forests and people’s diets in low- and middle-income countries, none to date have established a causal relationship. We used food consumption data from the World Bank’s Living Standards Measurement Study (LSMS) which was collected as part of a panel study from 2008 to 2013 across Tanzania. We examined 1256 rural households that were part of the panel study and used the food consumption data to assess their dietary diversity, dietary adequacy (in terms of calorie and nutrient intakes), and consumption of nutritionally important food groups (i.e. fruits and vegetables). Over the five-year study period, there was a general decline in dietary quality across the sample households. We used the Hansen et al. (2013) tree cover dataset to calculate the extent of forest loss over the study period, measuring forest loss in a ten kilometre radius around clusters of households. The average household experienced a loss of 171 hectares of forest in the surrounding area over the five years.

https://www.pnas.org/doi/10.1073/pnas.2112063119

A global shift towards more plant-based diets is recommended, but is a uniform approach the best solution for countries with different nutritional and socio-economic challenges?


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Our new commentary in One Earth argues that a “one-size fits all” approach to achieving a global shift towards more plant-based diets is unlikely to be successful given the different nutritional and livelihood challenges facing different world regions

https://authors.elsevier.com/a/1dmB59C%7EItuXlO

Paper on Mega-trends affecting social and environmental dynamics in forest landscapes is out now in Nature Plants

The paper describes five mega-trends affecting forests and forest communities. These trends are poorly understood, but likely to have major consequences for forests and forest livelihoods over the coming decade. The five trends are: 1) Forest mega-disturbances, 2) Changing rural demographics, 3) The rise of the middle-class in low-and middle-income countries, 4) Increased availability, access and use of digital technologies, and 5) Large-scale infrastructure development.

The GFEP report on forests and poverty is published


I am happy to have contributed to this global assessment led by Daniel Miller. Some of the key messages from the report:

1) Forests and trees support human wellbeing and contribute to global efforts to end poverty,

2) Benefits from forests and trees to human wellbeing are unevenly distributed, 

3) Inadequate land use policies and programmes may lead to excessive costs being borne by the poor

Partnership with ICRAF-CIFOR and the Nutri-Scapes Platform

Emilie Vansant, a PhD Fellow on the FORESTDIET project, was recently awarded a small grant to contribute to the recently-established Nutri-Scapes Transformative Partnership platform, a joint initiative by the Center for International Forestry Research (CIFOR) and World Agroforestry (ICRAF). The platform aims to foster the development of nutrition-centered landscapes that can simultaneously support food security, livelihoods and conserve biodiversity.

In line with Nutri-Scapes’ objectives, Emilie is examining existing empirical research on the linkages between different classifications of tree-based agricultural systems and dietary quality in low- and middle-income countries (LMICs). Her planned synthesis will add to existing knowledge on forest-diet linkages and agrobiodiversity-diet linkages by focusing on agricultural systems that utilize single trees, tree crops, and/or forest cover. Classifying farming systems by tree-cover amount, configuration, and level of integration could lend valuable insight into how tree-based farming can provide direct and indirect benefits to the diets of small-holder farmers. Using the relationships between forests and diets as a point of departure, her narrow scope will permit a thorough examination of these complex mechanistic pathways in an agricultural context and allow for comparison across a gradient from single trees towards dense, forest-based farming systems.

Farming with trees in Sarawak, Malaysia (personal photo, 2018)

“Food quality could be more problematic than food quantity for sub-Saharan countries over the coming decades”

A summary of my PhD findings, by Charlotte Hall

Providing the global population with sufficient and nutritious food, while also trying to minimise and reverse damage to the natural environment, is a major societal challenge. Nowhere is this challenge greater than in sub-Saharan Africa (SSA) where one in four people are currently undernourished, and micronutrient deficiencies are widespread. The results of my PhD findings suggest that food supply quality (in terms of micronutrient provision) could be more problematic over the coming decades than food supply quantity (in terms of dietary energy provision) in SSA, using Malawi as a case study. Using a novel modelling framework (FEEDME), supplies of energy, protein, iron, zinc and vitamin A were assessed under a range of future climatic and socio-economic scenarios. In all future scenarios, supplies of energy and protein were adequate, whereas supplies of the three micronutrients were inadequate to meet population-level requirements (with the exception of zinc in a ‘best-case’ future scenario) (see Figure 1). These results are novel as the majority of studies to date have focused on impacts on yields of staple crops and the resulting impact on undernourishment prevalence. The suggestion that nutrient supply may be more problematic in the future than energy supply highlights the need to move beyond the traditional focus on the production of staple crops towards a more holistic view of nutrition security whereby dietary diversity and consumption of micronutrient-dense foods are promoted. Indeed, until very recently, Malawian households were considered to be food secure if they had adequate access to maize with little to no emphasis on dietary diversity. This situation is reflected in (and exacerbated by) national development agendas whereby food security is a key priority for agricultural policies, but nutritional issues (such as stunting and wasting) are considered a health issue. This lack of nutritional consideration within agricultural systems can be considered one of the main causes of food insecurity and malnutrition in today’s society. It is essential that agricultural and nutrition sectors work together in order to form food security strategies that tackle not only undernourishment, but micronutrient deficiencies and their associated health consequences.

In an attempt to explore solutions and adaptation options for Malawi, my PhD research also examined the linkages between land use and dietary quality. The results showed a positive relationship between households located in more forested areas and vitamin A adequacy. Indeed, households who reported consuming wild foods had a 54% higher intake of vitamin A than households who did not consume these foods (https://link.springer.com/article/10.1007/s12571-019-00923-0). These results are supportive of a wider literature which shows forests can have a multitude of benefits for human health. The implications of these results are strongly linked to the earlier findings surrounding dietary quality, as the focus on increasing yields of staple crops via agricultural expansion has often come at the expense of natural landscapes such as forests. Given the growing body of research which shows the importance of forests for nutrition in many low- and middle- income countries, careful consideration must be given to the types of food production systems we adopt in the future. Forest conservation and restoration is likely to not only be critical for ensuring nutrition security for some of the world’s poorest people, but also for tackling climate change and biodiversity loss, which are all key outcomes of the global Sustainable Development Goals.

Figure 1. Micronutrient supply in all future scenarios was inadequate to meet population-level requirements, except for zinc in a “best-case” scenario (SSP1/RCP 4.5).