Forests moderate the effectiveness of water treatment at reducing childhood diarrhea

Abstract

Environmental degradation has been associated with increased burden of diseases such as malaria, diarrhea, and malnutrition. As a result, some have argued that continuing ecosystem change could undermine successes in global health investments. Here we conduct an empirical study to investigate this concern. Child deaths due to diarrhea have more than halved since the year 2000, partly due to increased access to improved water, sanitation and hygiene (WASH). We examine how the effectiveness of a water quality treatment may vary as a function of upstream watershed condition. We use data on occurrence of diarrhea and point-of-use water treatment methods from the Demographic and Health Surveys for Haiti and Honduras. We integrate these data with a variable that reflects the influence of upstream tree cover on surface water quality. Point-of-use chlorination is significantly associated with 3.4 percentage points reduction in prevalence of diarrheal disease on average. However, we only detect a significant reduction in diarrheal prevalence when upstream watersheds are moderately forested. At low upstream tree coverage, point-of-use water chlorination does not have significant effects, suggesting that forest clearing could undermine its effectiveness at reducing childhood diarrhea. Our results suggest that forested watersheds may reduce water-borne sediments and contaminants, and thus improve raw water quality in ways that moderate the effectiveness of water quality treatment. Watershed protection should be considered in WASH investments, as deforested watersheds could undermine their effectiveness, particularly in parts of low-income countries where access to improved WASH services is challenging.

Toward SDGs: Forest, Market and Human Wellbeing Nexus in Indian Western Himalayas

“…The frequency of health conditions such as body aches and backache arising from extreme labor (in resources collection) was found higher for the households located away from the forest (Table 1). Because forests are known to contribute to water filtration and purification (Piaggio and Siikamäki, 2021;Rasolofoson et al, 2021), the present study reported a lower frequency of water-borne diseases in households located close to forests, as they were using natural water sources originating from the forests (Table 1). Alike the rest of the Himalayan agricultural system in the Upper Ganga River Basin, agricultural practices in the NDBR area are also connected with the forest resources (Saxena et al, 2005).…”

Access to Human Health Benefits of Forests in Rural Low and Middle-Income Countries: A Literature Review and Conceptual Framework

“…Such a shift in time and energy allocation by women, who are also the primary household caregivers, takes their time and energy away from food preparation, more careful child feeding behaviors, income generation, and health care, and thus can impact the health of household members [39]. As an example for infectious diseases, Rasolofoson et al [40] suggest that good upstream forest conditions can render chlorination more effective at reducing diarrhea prevalence in Haiti and Honduras. They indicated that when forests in upstream areas of watersheds are degraded, the quality of downstream raw water can become poor, which limits the effectiveness of chlorination in dealing with diarrhea [40].…”

“…As an example for infectious diseases, Rasolofoson et al [40] suggest that good upstream forest conditions can render chlorination more effective at reducing diarrhea prevalence in Haiti and Honduras. They indicated that when forests in upstream areas of watersheds are degraded, the quality of downstream raw water can become poor, which limits the effectiveness of chlorination in dealing with diarrhea [40]. Preservation of forests through the establishment of protected areas in upstream watersheds was associated with a reduced downstream prevalence of diarrhea on the island of Flores in Indonesia [41].…”

“…Additional infrastructure is, however, needed at point-of-use or source (e.g., point-of-use chlorination, water treatment plants) to enhance the benefits of water filtration by forested watersheds in providing clean drinking water and preventing waterborne disease. For example, chlorination was still needed to reduce the prevalence of diarrhea in Haiti and Honduras, but the presence of upstream forests could increase its effectiveness [40].…”

“…Forests can affect health outcomes through the provision of ecosystem services of direct relevance to human health (e.g., nutritious forest food [42], medicinal plants [32], and water purification [40]) (Figure 2). Forest ecosystem services that are not directly Forests can affect health outcomes through the provision of ecosystem services of direct relevance to human health (e.g., nutritious forest food [42], medicinal plants [32], and water purification [40]) (Figure 2). Forest ecosystem services that are not directly relevant to human health can also be transformed to impact health outcomes (Figure 2).…”