Human health alters the sustainability of fishing practices in East Africa

Abstract

Understanding feedbacks between human and environmental health is critical for the millions who cope with recurrent illness and rely directly on natural resources for sustenance. Although studies have examined how environmental degradation exacerbates infectious disease, the effects of human health on our use of the environment remains unexplored. Human illness is often tacitly assumed to reduce human impacts on the environment. By this logic, ill people reduce the time and effort that they put into extractive livelihoods and, thereby, their impact on natural resources. We followed 303 households living on Lake Victoria, Kenya over four time points to examine how illness influenced fishing. Using fixed effect conditional logit models to control for individual-level and time-invariant factors, we analyzed the effect of illness on fishing effort and methods. Illness among individuals who listed fishing as their primary occupation affected their participation in fishing. However, among active fishers, we found limited evidence that illness reduced fishing effort. Instead, ill fishers shifted their fishing methods. When ill, fishers were more likely to use methods that were illegal, destructive, and concentrated in inshore areas but required less travel and energy. Ill fishers were also less likely to fish using legal methods that are physically demanding, require travel to deep waters, and are considered more sustainable. By altering the physical capacity and outlook of fishers, human illness shifted their effort, their engagement with natural resources, and the sustainability of their actions. These findings show a previously unexplored pathway through which poor human health may negatively impact the environment.

Keywords: Lake Victoria; environmental change; fishing livelihoods; health and environment; social-ecological systems.

Fig. 1.

(Right) Traditional and (Left) alternative pathways linking human and environmental health in fishing communities. In the face of illness, households may alter their pressure on environmental resources to increase their reliance on destructive practices or curtail their harvest effort. These feedbacks portend sharply different environmental consequences of human illness, even as outcomes for households remain similar.

Fig. S1.

Histograms comparing the (A) physical health and (B) mental health scores of individuals who are not currently fishing and are currently fishing. We observe a more skewed distribution of physical than mental health with a relatively long tail, indicating poorer health, particularly among those not currently fishing. Model results of participation in fishing are provided in Table S4.

Fig. 2.

For men (n = 253) facing markedly different levels of illness, we observe that (A) fishing participation is widespread; individuals not fishing are largely employed in other sectors, whereas a smaller number of fishers who experience poor health are not fishing. (B) Fishing effort, measured as hours fishing, is relatively stable across experiences of (i) physical health and (ii) mental health. Individual experience of poorer health (moving to the right on each graph) is assessed in multivariate panel regression models. Models show that mental and physical health did not affect participation in fishing, hours fished, nights spent away from home, or income earned per hour and had a modest effect on hours traveled (Tables S4 and S5).

Fig. 3.

ORs of (A) fishing method legality and (B) fishing with a particular method. ORs for poorer physical health (A, B) and poorer mental health (A) and 95% confidence intervals (vertical lines) are derived from full conditional fixed effect logit models (Tables S6 and S7) among individuals who report participation in fishing in the preceding 3 mo. In the Lake Victoria fishery, five fishing methods predominate. Three methods—long line, gillnet, and small seine for dagaa—are legal offshore methods (green) and subject to regulations designed to provide for fishery sustainability, including mesh dimensions, hook sizes, and movement patterns. Two methods—beach seine and monofilament—are focused on inshore regions (red), and although outlawed by fishery regulations because they are environmentally destructive, they remain widely practiced (51). Odds are for 1 SD poorer (A, Left) physical health and (A, Right) mental health as well as (B) physical health comparing across individuals who sometimes participated in fishing methods. Models include a full set of time-variant covariates (physical health, mental health, income, fishery role, and time point). Where the 95% confidence intervals cross one, the association is not statistically significant. *P < 0.05, **P < 0.01.