Climate change, food security, and diarrhoea prevalence nexus in Tanzania

The study addresses the intertwined challenges of climate change, food security, and public health, particularly diarrhoea prevalence, in Tanzania. A projected global population increase by 2080, with significant contributions from countries like Tanzania, intensifies the demand for food and healthcare. Climate change significantly impacts agriculture and health, disrupting food production and reducing immunity, leading to increased susceptibility to diseases like diarrhoea. Diarrhoea remains a major public health concern globally and in Tanzania, contributing significantly to mortality, especially among children. Climate change exacerbates the spread of diarrhoea, particularly in Sub-Saharan Africa. Existing research largely focuses on adaptation and resilience, leaving a knowledge gap regarding the direct impacts of climate change on health and food security in Tanzania. This study aims to fill this gap by examining the complex relationships between climate change, food security, and diarrhoea prevalence, providing crucial insights for policymaking and intervention strategies.

Existing literature highlights climate change's detrimental effects on global development, particularly through its impacts on agriculture and food security. Rising temperatures and altered precipitation patterns reduce crop yields, increase pest proliferation, and threaten food security. The increased frequency of extreme weather events further exacerbates these issues, leading to economic losses and land degradation. Climate change also contributes to the spread of diseases, including diarrhoea, through environmental deterioration. Studies consistently link increases in temperature and changes in precipitation to higher diarrheal disease prevalence, particularly affecting vulnerable populations such as children and older adults. The impact of climate change on diarrhoea is complex, but empirical evidence shows a positive correlation between temperature and diarrhoea rates and a negative correlation between water availability and diarrhoea rates. Projections indicate reduced crop production and increased malnutrition in Sub-Saharan Africa due to climate change, with the most significant impact observed among impoverished populations. The need for robust empirical data to understand climate change's impacts and mechanistic systems-based approaches to study its effects on diarrheal diseases is evident in the literature. While existing studies on Tanzania touch on the effects of climate change on food security and health, there remains a gap in understanding the direct impacts, especially concerning the complex interplay between these factors. This study seeks to address this knowledge gap and provide evidence for policy recommendations.

This study leverages three rounds of Tanzania's National Agriculture Sample Census data (2002/03, 2007/08, and 2019/20) focusing on a sample of 32,560 smallholder farmers. The data include socio-demographic characteristics, climate change indicators, food security measures (using FAO components), and diarrhoea prevalence (measured by the presence of diarrhoea in the household within twelve months). Climate change was assessed based on variations in annual precipitation, categorized as above or below a threshold. Diarrhoea and food security were also categorized as present/absent and secured/insecure respectively. To analyse the effects of climate change on diarrhoea prevalence, an Instrumental Variable (IV) Probit model was employed, using average temperature anomalies as an instrumental variable to address endogeneity. The Control Function Approach was used to analyze the effects of climate change on food security, again using temperature anomalies and mitigating heterogeneity through predicted residuals from auxiliary regression. Average temperature anomalies were calculated using historical temperature data. The study also examined the coverage of climate change, food security, and diarrhoea prevalence across household socioeconomic characteristics.

Descriptive statistics reveal that 56.41% of households are rural, with a slightly higher percentage of female heads of households. Access to extension services and membership in agriculture societies are low, and farmers express dissatisfaction with government support. Figure 3 shows a positive correlation between education levels and the perception of climate change's impact on health. Table 4 shows trends in climate change, food security, and diarrhoea prevalence across different socioeconomic groups (religious affiliation, education, residence, employment sector, economic status) from 2002/03 to 2019/20. Generally, increases in climate change prevalence were associated with decreases in food security and increases in diarrhoea prevalence across most groups. Rural residents showed particularly strong negative trends in food security and positive trends in climate change and diarrhoea prevalence. Poor individuals faced the most significant declines in food security, along with increases in climate change and diarrhoea prevalence. Figure 4 and Figure 5 show the relationship between average temperature and precipitation with diarrhoea prevalence and food insecurity. Table 5 shows the results of the Instrumental Variable Probit model on diarrhoea prevalence. Older age, male sex, lower household income, lower education, lack of access to financial services, no government support, poor sanitation, and rural residence are significantly associated with higher diarrhoea prevalence. Climate change significantly increases the prevalence of diarrhoea (0.214602, p<0.01). Table 6 presents the results of the Control Function Approach model for food security. Increasing age, lack of fertilizer use, male sex, lower household income, lower education, lack of employment, lack of access to extension services, and non-membership in agriculture societies are associated with lower food security. Rural residence is also associated with lower food security. Climate change significantly reduces food security (-0.331142, p<0.01).

The findings strongly support the hypothesis that climate change significantly impacts both food security and diarrhoea prevalence in Tanzania. The negative relationship between climate change and food security is consistent with the literature's emphasis on climate change's adverse effects on agricultural productivity. The positive relationship between climate change and diarrhoea prevalence highlights the increased risk of waterborne diseases associated with altered weather patterns. The study's findings underscore the vulnerability of specific populations, particularly older individuals, those in rural areas, those with lower socioeconomic status, and those without access to essential services like education, financial services, and extension services. The results highlight the interconnected nature of climate change impacts, with food insecurity potentially exacerbating the vulnerability to disease outbreaks. This calls for comprehensive, multi-sectoral interventions. The choice of instrumental variables and the use of advanced statistical methods like IV Probit and Control Function Approach enhance the robustness and reliability of the findings, addressing endogeneity concerns.

This study demonstrates the significant negative impact of climate change on food security and the significant positive impact on diarrhoea prevalence in Tanzania. The vulnerability of various population segments is highlighted, particularly those lacking access to resources and services. The study underscores the need for policy interventions targeting sustainable agriculture, improved sanitation, public health initiatives, and community empowerment to mitigate the effects of climate change on food security and health. Future research could explore specific adaptation strategies, delve deeper into the regional variations of these impacts, and investigate the long-term implications of these complex interactions.

The study relies on cross-sectional data, limiting the ability to establish definitive causal relationships over time. The self-reported nature of some variables, such as diarrhoea prevalence, may introduce some measurement error. The focus on smallholder farmers may limit the generalizability of the findings to other farming systems. The accuracy of historical temperature data used in the calculation of temperature anomalies could affect the findings, and further refinement of the instrument used could potentially enhance the results. The use of a single instrument may lead to challenges related to potential issues of weak identification. Future research utilizing panel data and/or more sophisticated methods could address these issues to further refine the findings.