ABSTRACT. The complexity of social-ecological systems is well recognized (Berkes et al. 2003, Norberg andCumming 2008). However, in the study of such systems, it is often the uncertainty that results from nonlinear interactions that forms the focus of discussion. Here, the normative implications of complexity for our knowledge of such systems are emphasised, by drawing largely on the work of Cilliers (1998Cilliers ( , 2005a, who introduced the term "critical complexity." This perspective on complexity is distinct in bringing the value-based choices that frame our knowledge generation strategies to the fore. It is from this view that we investigate the implications of complexity for social-ecological systems research. Based on these implications, we propose a set of five key questions to guide the incorporation of insights from critical complexity into such research. We end with a brief application of the questions proposed to the National Freshwater Ecosystem Priority Areas (NFEPA) project in South Africa, to illustrate their potential use in the context of resource management.

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Non-technical summary There are significant challenges to retaining indigenous biodiversity and ecological infrastructure in African cities. These include a lack of formal protection and status for remnant ecologically functional patches rendering them open to ad hoc human settlement, which is in part linked to weak governance and management emerging from complex histories, and competing crisis-ridden demands. Persistent gaps in knowledge and practice mean that the social, economic, development and well-being benefits of ecological infrastructure are not understood or demonstrated. Addressing these challenges requires the adoption of multiple top-down government interventions and bottom-up community and neighbourhood actions. The development of detailed case studies that engage with knowledge generation and sharing at multiple scales through co-learning practices will also help create a much-needed deeper understanding of development options within this context.

If environmental assessment is to more effectively assist in the move towards sustainability goals, deeper consideration of substantive, value-based questions associated with this field is required. Such questions relate, for example, to the way in which we conceive of and value the environment, the various stakeholder perceptions of development and the types of knowledge most appropriate to the environmental assessment endeavour. These issues are explored in this paper, which is based on the Applied Integrative Sustainability Guide (2010) produced by the Council for Scientific and Industrial Research (CSIR) in South Africa. In so doing, the authors draw on the work of leading thinkers in the fields of complexity theory, environmental ethics, development economics and planning.

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