UBC Theses and Dissertations

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UBC Theses and Dissertations

Sea otters, kelp forests, and ecosystem services : modelling habitats, uncertainties, and trade-offs Gregr, Edward James


Resource management is increasingly about the equitable distribution of benefits amongst a diversity of beneficiaries while ensuring the persistence of desirable social and ecological systems. Largely because of the complexity of social-ecological systems, models intended to support integrated resource management continue to suffer from poor treatment of uncertainty, and the challenges of defining appropriate model scope and benefit representation. I explored these challenges through the process of combining field data with population, habitat, and service models to build an integrated model of coastal ecosystem services on the West coast of Vancouver Island, British Columbia, Canada. I examined the tradeoffs between sea otter and invertebrate dominated systems under 3 spatial sea otter management plans. The model predicts that an otter-dominated system will produce, in aggregate, between 30 and 90 M$ / year more than one dominated by invertebrates. Disaggregation by benefits and by location provides insight into trade-offs and equity. For example, the value of increased finfish production from enhanced primary productivity is predicted to be almost double the losses incurred by the invertebrate fishery; while increased detail on the distribution of benefits supports the definition of novel, more equitable and legitimate indicators, allowing management alternatives to be more salient. Development of the model led to advances in the applied and theoretical aspects of integrated model development. Chapter 2 confirms that uncertainties and design assumptions are mostly ignored in the popular modelling literature, and includes a conceptual model to support more consistent model design decisions. In Chapter 3 I characterised key aspects of kelp ecology in Pacific Canadian waters, and showed how the trade-off between precision and accuracy depends on whether one is pursuing knowledge or application. Chapters 4 and 5 tell the story of the integrated model, respectively focusing on ecosystem service production, and the distribution of benefits. My results show how spatial resolution is key to identifying indicators of social and ecological value. All told, my dissertation offers applied, theoretical, and methodological advances in the use of ecosystem models for integrated management. Extending the model to include stakeholder objectives would complete the data-to-decision model, allowing formal decision analysis.

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