Coupled human and natural system dynamics as key to the sustainability of Lake Victoria’s ecosystem services

Andrea S. Downing, Stockholm Resilience Centre, Stockholm University, Sweden; Aquatic Ecology and Water Quality Management group, Wageningen University, Netherlands; Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
Egbert H. van Nes, Aquatic Ecology and Water Quality Management group, Wageningen University, Netherlands
John S. Balirwa, National Fisheries Resources Research Institute (NaFIRRI), Jinja, Uganda
Joost Beuving, Department of Cultural Anthropology and Development Studies, Faculty of Social Sciences, Radboud University, Nijmegen, Netherlands
P.O.J. Bwathondi, University of Dar es Salaam, College of Natural and Applied Sciences, Department of Aquatic Sciences and Fisheries, Dar es Salaam, Tanzania
Lauren J. Chapman, Department of Biology, McGill University, Montreal, Canada
Ilse J. M. Cornelissen, Aquaculture & Fisheries Group, Wageningen University, Netherlands; Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
Iain G. Cowx, Hull International Fisheries Institute, University of Hull, United Kingdom
Kees P. C. Goudswaard, Institute for Marine Resource and Ecosystem Studies (IMARES), Wageningen University, Yerseke, Netherlands
Robert E. Hecky, Biology Department and Large Lakes Observatory, University of Minnesota-Duluth, USA
Jan H. Janse, Netherlands Environmental Assessment Agency (PBL), Bilthoven, Netherlands; Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
Annette B. G. Janssen, Aquatic Ecology and Water Quality Management group, Wageningen University, Netherlands; Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
Les Kaufman, Boston University Marine Program, Biology Department, Boston University, USA
Mary A. Kishe-Machumu, Tanzania Fisheries Research Institute (TAFIRI), Dar es Salaam, Tanzania
Jeppe Kolding, Department of Biology, University of Bergen, Norway
Willem Ligtvoet, Netherlands Environmental Assessment Agency (PBL), The Hague, Netherlands
Dismas Mbabazi, National Fisheries Resources Research Institute (NaFIRRI), Jinja, Uganda
Modesta Medard, Department of Sociology of Development and Change. Social Science Group, Wageningen University, Netherlands
Oliva C. Mkumbo, Lake Victoria Fisheries Organisation, Jinja, Uganda
Enock Mlaponi, Tanzania Fisheries Research Institute (TAFIRI), Mwanza, Tanzania
Antony T. Munyaho, National Fisheries Resources Research Institute (NaFIRRI), Jinja, Uganda
Leopold A. J. Nagelkerke, Aquaculture & Fisheries Group, Wageningen University, Netherlands
Richard Ogutu-Ohwayo, National Fisheries Resources Research Institute (NaFIRRI), Jinja, Uganda
William O. Ojwang, Kenya Marine and Fisheries Research Institute (KMFRI), Kisumu, Kenya
Happy K. Peter, Aquaculture & Fisheries Group, Wageningen University, Netherlands
Daniel E. Schindler, Aquatic & Fishery Sciences/Department of Biology, University of Washington, USA
Ole Seehausen, Eawag, Kastanienbaum, Switzerland
Diana Sharpe, Smithsonian Tropical Research Institute, Panama City, Panama; Department of Biology, McGill University, Montreal, Canada
Greg M. Silsbe, Royal Netherlands Institute for Sea Research, Yerseke, Netherlands
Lewis Sitoki, The Technical University of Kenya, Nairobi, Kenya
Rhoda Tumwebaze, National Fisheries Resources Research Institute (NaFIRRI), Jinja, Uganda
Denis Tweddle, South African Institute for Aquatic Biodiversity, Grahamstown, South Africa
Karen E. van de Wolfshaar, Institute for Marine Resource and Ecosystem Studies (IMARES), Wageningen University, Ijmuiden, Netherlands
Han van Dijk, Department of Sociology of Development and Change. Social Science Group, Wageningen University, Netherlands
Ellen van Donk, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
Jacco C. van Rijssel, Institute of Biology, University of Leiden, Netherlands; Naturalis Biodiversity Center, Leiden, Netherlands; Eawag, Kastanienbaum, Switzerland
Paul A. M. van Zwieten, Aquaculture & Fisheries Group, Wageningen University, Netherlands
Jan Wanink, Institute of Biology, University of Leiden, Netherlands; Koeman en Bijkerk bv, Ecological Research and Consultancy, Haren, Netherlands
F. Witte, Institute of Biology, University of Leiden, Netherlands; Naturalis Biodiversity Center, Leiden, Netherlands
Wolf M. Mooij, Aquatic Ecology and Water Quality Management group, Wageningen University, Netherlands; Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands

DOI: http://dx.doi.org/10.5751/ES-06965-190431

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Abstract

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.

Key words

eutrophication; feedbacks; fisheries; Lake Victoria; model; multidisciplinary, social-ecological system; sustainability

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