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Downing, A.S., van Nes, E.H., Balirwa, J.S. and Beuving, J.J., 2014. Coupled human and natural system dynamics as key to the sustainability of Lake Victoria’s ecosystem services. |
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East Africa’s Lake Victoria provides resources and services to millions of people on the lake’s shores and abroad. In
particular, the lake’s fisheries are an important source of protein, employment, and international economic connections for the whole
region. Nonetheless, stock dynamics are poorly understood and currently unpredictable. Furthermore, fishery dynamics are intricately
connected to other supporting services of the lake as well as to lakeshore societies and economies. Much research has been carried out
piecemeal on different aspects of Lake Victoria’s system; e.g., societies, biodiversity, fisheries, and eutrophication. However, to
disentangle drivers and dynamics of change in this complex system, we need to put these pieces together and analyze the system as a
whole. We did so by first building a qualitative model of the lake’s social-ecological system. We then investigated the model system
through a qualitative loop analysis, and finally examined effects of changes on the system state and structure. The model and its
contextual analysis allowed us to investigate system-wide chain reactions resulting from disturbances. Importantly, we built a tool that
can be used to analyze the cascading effects of management options and establish the requirements for their success. We found that
high connectedness of the system at the exploitation level, through fisheries having multiple target stocks, can increase the stocks’
vulnerability to exploitation but reduce society’s vulnerability to variability in individual stocks. We describe how there are multiple
pathways to any change in the system, which makes it difficult to identify the root cause of changes but also broadens the management
toolkit. Also, we illustrate how nutrient enrichment is not a self-regulating process, and that explicit management is necessary to halt
or reverse eutrophication. This model is simple and usable to assess system-wide effects of management policies, and can serve as a
paving stone for future quantitative analyses of system dynamics at local scales. |
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