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

Abstract

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.

Challenges in Using Hydrology and Water Quality Models for Assessing Freshwater Ecosystem Services: A Review

“…In the literature on freshwater ecosystem services modelling, many studies have focused on fish populations: for example Boughton and Pike [52] studied the impacts of altered storm patterns on fish migration windows, Bouska, et al [53] studied the impact of environmental changes on fish species distributions, Downing, et al [54] focused on the effect of lake management on the stock of fish, Nelson, et al [55] studied the impact of sediments, water flows and temperature on fish assemblages, and van Poorten, et al [56] studied the effects of stocking management on the fish population. However, the fish dynamics depend mainly on the availability of food.…”

“…They can also be deterministic models where the links are characteristics by empirical equations from the literature [55,56]. More qualitative approaches can also be used, such as feedback diagrams where only the positive or negative character of the relationships between variables is expressed [54].…”

Vulnerability of tropical forest ecosystems and forest dependent communities to droughts

“…Many studies have focused on measuring the vulnerability of coupled human and natural systems to climate change (e.g., IPCC 2012) by integrating information from the social and natural sciences (e.g., Chuvieco et al 2014; Downing et al 2014; Mumby et al 2014). Despite the multitude of research, it has been challenging to equate social and ecological resilience with vulnerability to climate change.…”

“…Further, one cannot focus on a single part of the coupled socio-ecological system (Maxwell 2014;Silva 2014) and expect to understand the mechanistic links between them. Even when research has effectively linked the complexity of socio-economic interactions with resources, they have been less able to validate what variables should be managed to reduce the impacts on both people and the environment (e.g., Downing et al 2014;Görg et al 2014; but see Scullion et al 2014). …”

Intergroup cooperation prevents resource exhaustion but undermines intra-group cooperation in the common-pool resource experiment

“…There are concerns that climate change will escalate the scarcity of renewable resources. Much has been written about the impact of climate change on resource conflicts (Ember and Ember 1992, Mwiturubani 2010, Downing et al 2014Harari and La Ferrara 2014, unpublished manuscript). Intergroup competition has also achieved a lot of attention in the theoretical and experimental literature (e.g., Bornstein 2003, Tan and Bolle 2007, Abbink et al 2010.…”