Deforestation reduces fruit and vegetable consumption in rural Tanzania

Strategies to improve food and nutrition security continue to promote increasing food via agricultural intensification. Little (if any) consideration is given to the role of natural landscapes such as forests in meeting nutrition goals, despite a growing body of literature that shows that having access to these landscapes can improve people’s diets, particularly in rural areas of low- and middle-income countries. In this study, we tested whether deforestation over a 5-y period (2008–2013) affected people’s dietary quality in rural Tanzania using a modeling approach that combined two-way fixed-effects regression analysis with covariate balancing generalized propensity score (CBGPS) weighting which allowed for causal inferences to be made. We found that, over the 5 y, deforestation caused a reduction in household fruit and vegetable consumption and thus vitamin A adequacy of diets. The average household member experienced a reduction in fruit and vegetable consumption of 14 g⋅d⁻¹, which represented a substantial proportion (11%) of average daily intake. Conversely, we found that forest fragmentation over the survey period led to an increase in consumption of these foods and dietary vitamin A adequacy. This study finds a causal link between deforestation and people’s dietary quality, and the results have important implications for policy makers given that forests are largely overlooked in strategies to improve nutrition, but offer potential “win–wins” in terms of meeting nutrition goals as well as conservation and environmental goals.

The challenge of achieving food and nutrition security for the worlds’ growing population while also minimizing and reversing damage to the natural environment is unprecedented. The dominant narrative on how to achieve food and nutrition security continues to be centered on intensifying agricultural production to produce more food (1–3). While agricultural intensification is undoubtedly a key reason we have kept pace with food demands and ended hunger for millions of people over the past decades, it has led to a preoccupation with dietary energy (calories), and thus the production of staple grains which provide the majority of calories globally (4, 5). The focus on staple foods has resulted in dietary quality and diversity being overlooked, despite the fact that far more people suffer from micronutrient deficiency than undernourishment (6–8). Likewise, agricultural intensification is a leading driver of environmental degradation (9–11). There has been much research in recent years examining the impact of different diets on land use (12–15), but less attention has been given to the reverse of this relationship: How do landscapes affect diets? A growing body of literature has examined this relationship with a focus on the linkages between forests and diets in low- and middle-income countries. This relatively new field of research has important implications for strategies to achieve food and nutrition security worldwide, particularly for rural areas in low- and middle-income countries where there are strong connections between livelihoods and landscapes, and undernourishment is most prevalent.Forests provide critical ecosystem services that benefit human populations in several ways, such as the provision of food and fiber, and climate and water regulation (16), with an estimated 1.5 billion forest-proximate people worldwide (i.e., living within 5 km of a forest) (17). Forests can improve people’s diets via four key pathways (18, 19). The most direct way is via the provision of wild forest foods, which most often include fruits, vegetables, mushrooms, and animal products (i.e., bushmeat and insects), all of which tend to be high in essential micronutrients (20–22). The second pathway is via income generation from the sale of forest foods and other nontimber forest products (NTFPs), which can improve livelihoods and facilitate the purchase of nutritious foods from markets (23, 24). The third pathway is via the flow of ecosystem services from forests into surrounding agricultural landscapes (e.g., forests can contribute to soil formation and nutrient cycling, and increase pollination) which can increase and/or diversify production (25). The final pathway is the provision of fuelwood for cooking, which is a key (but often overlooked) pathway that can improve nutrition by facilitating the preparation of a range of foods, particularly those with long cooking times (26, 27).The majority of studies have found a positive relationship between living near (having access to) forests and several measures of diet, nutrition, and food security outcomes. Most studies use metrics of diet quality such as dietary diversity scores or consumption of certain nutritious food groups. Very few studies have examined more detailed measures of dietary quality such as energy and nutrient intakes (28–30), and only one study has examined these in relation to forest cover using multivariate regression (31). Moreover, the majority of studies examine the relationship between forests and diet quality at a single point in time. Two studies have examined the relationship between diets and previous forest loss (32, 33), but no studies, to date, have used longitudinal data to understand concurrent changes in forests and diets over time. In this sense, most studies have only been able to identify associations between forests and diets as opposed to causal relationships. Furthermore, only one study, to date, has examined how the spatial arrangement of forests (as opposed to just forest amount) can affect people’s diets (34), finding that forest configuration may be as important as forest amount for dietary quality.This study aimed to advance the current knowledge on the forest–diet relationship in three main ways:

• 1)By using panel data and a rigorous estimation method which combines covariate balancing generalized propensity score (CBGPS) weighting with two-way fixed-effects regression, we were able to test the causal impact of forest changes on diets, which no studies, to our knowledge, have done. We were also able to explore the causal mechanisms by which forest cover change is hypothesized to affect people’s diets (the direct consumption pathway, the income pathway, and the ecosystem services pathway).
• 2)Most existing studies rely on measures such as dietary diversity scores and consumption of nutritious food groups as proxies for overall diet quality. In addition to these, we also quantified household energy and nutrient adequacy levels in order to gain a better understanding of how forests can affect people’s diets.
• 3)We considered not just forest amount but also the spatial arrangement of forests in relation to diet quality, which only one study has done, to date (34). Thus, this study aimed to extend this research to examine whether changes in forest configuration [in terms of fragmentation (35)] were related to people’s dietary quality.