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A study reveals a causal link between deforestation and the reduction in the quality of people’s diets

Current policies aimed at ensuring food security emphasize the importance of agricultural land, but forests also play an essential role. Forested areas can help communities that rely on wild foods diversify their diets and meet their nutritional needs, say researchers who have found direct links between deforestation and reduced fruit and vegetable consumption in rural areas from Tanzania.

In recent years, an increasing number of studies have shown strong positive links between forests and food security in low- and middle-income countries. Our study is the first of its kind to find a causal relationship between deforestation and a reduction in the quality of people’s diets.”


Charlotte Hall, postdoctoral fellow, University of Copenhagen, Denmark, and lead author of the article

The researchers studied the food consumption of 1,256 rural households in Tanzania over a period of five years. The data, provided by the World Bank, was georeferenced and randomly moved up to 3.11 miles for privacy, giving researchers a rough measure of household proximity to forest areas. The team used satellite images and geospatial datasets to measure forest cover over the study period.

Powell has spent his career working alongside and alongside people thinking about how agricultural systems can support food quality and food security. She noted that previous studies have attempted to generate numbers in terms of the impact of crop diversity or an agricultural intervention on diet.

“The magnitude of the impact we see from agriculture on diet is less than what we see in this study,” Powell said. “So this research should really push people to think beyond the field when trying to help rural communities improve food security in places where wild foods matter.”

The majority of policies aimed at improving food security in low- and middle-income countries tend to promote increased agricultural production, especially staple crop production, which often comes at the expense of forests, Hall said. The results of this study indicate an alternative approach to improving food security in these countries.

“While increased agricultural production will undoubtedly be important to meet the food needs of a growing population, policymakers should pay more attention to the role of forests,” Hall said. “This is particularly important given that micronutrient deficiencies affect many more people than undernutrition, and our study has shown that deforestation directly reduces people’s ability to source important nutrient-rich fruits and vegetables such as than vitamin A. Ultimately, we advocate the preservation of forests, which can provide benefits for all in terms of meeting nutritional and environmental goals.”

Laura Vang Rasmussen and Rasmus Skov Olesen, University of Copenhagen; Cecilie Dyngeland, Inland Norway University of Applied Sciences; and Suhyun Jung of West Virginia University also contributed to the study. The European Research Council funded this research.

Wild food is central to the diets of rural people in Tanzania, and the country has seen significant environmental change and deforestation over the past two decades, said Bronwen Powell, assistant professor of geography, African studies and science. anthropology at Penn State and co-author of the study. . Powell has conducted nutritional research in Tanzania for more than a decade, and his doctoral work helped lay the foundation for the current study.

“The results of the study are surprising,” Powell said. “We have this very clear signal in the fruit and vegetable consumption data. Additionally, we fully understand that fruit and vegetable consumption is associated with health outcomes. Low consumption of these foods is one of the leading causes of death in the world. It’s up there with risk factors like alcohol consumption and unprotected sex. If we can establish a link between deforestation and the consumption of fruits and vegetables, it is very worrying.

The team found the biggest drop in daily consumption of leafy green vegetables, mangoes and other fruits -; most often fodder products from the forest or grown on trees. These foods are rich in vitamin A, an essential micronutrient.

“We focused on three key micronutrients in our study — iron, zinc and vitamin A — because these are the nutrients most often deficient in low- and middle-income countries,” Hall said. “We did not find a link between forest loss and iron or zinc, but we found a strong link between forest loss and vitamin A.”

The researchers found that household vitamin A adequacy declined over the study period due to deforestation. Vitamin A deficiency has serious health consequences and can lead to blindness, weakened immune function and respiratory tract infections, Powell said.

Wild food is central to the diets of rural people in Tanzania, and the country has seen significant environmental change and deforestation over the past two decades, said Bronwen Powell, assistant professor of geography, African studies and science. anthropology at Penn State and co-author of the study. . Powell has conducted nutritional research in Tanzania for more than a decade, and his doctoral work helped lay the foundation for the current study.

“The results of the study are surprising,” Powell said. “We have this very clear signal in the fruit and vegetable consumption data. Additionally, we fully understand that fruit and vegetable consumption is associated with health outcomes. Low consumption of these foods is one of the leading causes of death in the world. It’s up there with risk factors like alcohol consumption and unprotected sex. If we can establish a link between deforestation and the consumption of fruits and vegetables, it is very worrying.

The team found the biggest drop in daily consumption of leafy green vegetables, mangoes and other fruits -; most often fodder products from the forest or grown on trees. These foods are rich in vitamin A, an essential micronutrient.

“We focused on three key micronutrients in our study — iron, zinc and vitamin A — because these are the nutrients most often deficient in low- and middle-income countries,” Hall said. “We did not find a link between forest loss and iron or zinc, but we found a strong link between forest loss and vitamin A.”

The researchers found that household vitamin A adequacy declined over the study period due to deforestation. Vitamin A deficiency has serious health consequences and can lead to blindness, weakened immune function and respiratory tract infections, Powell said.

Scientists found that as forest cover decreased, reported fruit and vegetable consumption also decreased. Forest cover declined on average by about 423 acres over the five-year period. Fruit and vegetable consumption decreased by 14 grams, or half an ounce, per person per day, representing an 11% reduction in the amount consumed daily. The researchers published their findings in the Proceedings of the National Academy of Sciences.

Source:

Journal reference:

Room, CM, et al. (2022) Deforestation reduces fruit and vegetable consumption in rural Tanzania. PNAS. doi.org/10.1073/pnas.2112063119.