The water-energy-food nexus in the anthropocene: moving from ‘nexus thinking’ to ‘nexus action’ Gareth B Simpson 1 ,3 and Graham PW Jewitt 2 ,3 The Water-Energy-Food (WEF) nexus has emerged as a multi- centric lens for assessing integrated resources management and sustainable development in the past decade. This paper initially reviews the current status of this approach, which has received some critique for being largely conceptual. The call to operationalise the nexus is heralded in many recent publications and a common theme is that ‘nexus thinking’ must evolve into ‘nexus doing’. To this end, this paper seeks to present opportunities to enable and achieve ‘nexus doing’ through a synthesis of approaches proposed in both contemporary academic journal articles and grey literature. Our synthesis shows that there is a good basis to move forward to implementation and that in places, this has actually started. Nexus policies are being enabled at different spatial extents from regional and national scales to a city level, and appropriate mechanisms and decision support tools to achieve integrated nexus planning are evolving. However, there is no single method that fits all situations; rather the approach must be tailored for each unique situation. Addresses 1 Jones & Wagener (Pty) Ltd, Centurion, South Africa 2 IHE Delft Institute for Water Education, Delft, Netherlands 3 Centre for Water Resources Research, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Pietermaritzburg, South Africa Corresponding author: Simpson, Gareth B (simpson@jaws.co.za) Current Opinion in Environmental Sustainability 2019, 40:117–123 This review comes from a themed issue on System dynamics and sustainability Edited by Hester Biemans, Maryna Strokal and Pieter van Oel Received: 20 February 2019; Accepted: 18 October 2019 https://doi.org/10.1016/j.cosust.2019.10.007 1877-3435/ã 2019 Elsevier B.V. All rights reserved. Introduction As a result of humanity’s pervasive impact upon Earth, it was proposed at the beginning of the twenty-first century that a new geological epoch, the Anthropocene, be declared [1]. The consequences of people’s activity have resulted from the exponential growth in the world’s population since the industrial revolution, together with the associated demand for all manner of resources [2]. Numerous approaches have been adopted to manage the supply and demand of these resources, with various nexus configurations being promoted in the last decade. One approach, termed the Water-Energy-Food (WEF) nexus, has gained appreciable attention as a potential lens to contribute to the achievement of sustainable develop- ment and integrated resource management [3]. Research interest in the WEF nexus has been so substantial that it has almost increased exponentially since 2009 [4]. Regarding the linkages within the WEF nexus, global estimates of the proportions that each resource sector supplies or obtains from the adjacent sector are presented schematically in Figure 1. The connections in this dia- gram demonstrate the profound interdependencies within the WEF nexus. Projections indicate that the demand for resources will continue to grow in the coming decades unless there is a significant departure from ‘business as usual’ [5]. The values in this schematic indicate that food produc- tion is decidedly dependent upon both water availability and energy generation, with the agricultural sector requir- ing 71% of the former and 30% of the latter. The propor- tion of food waste generated worldwide is significant in itself. But it also represents the loss of crucial resources used in food production, such as water, energy, and land [9]. In developing countries, most of the food loss occurs in-field and at the post-harvesting stages, while in devel- oped nations the majority of the waste occurs at the retail, food-service and household level [14]. Further, this sche- matic shows that approximately 86% of the available freshwater is utilised within the energy and food sectors (although some of this water may be reused). Both food and energy security are at risk in regions where climate change is predicted to result in a reduction of mean annual rainfall levels, for example, southern Africa [15]. There are several robust motivations for investigating and applying the WEF nexus. The first is the global security of resources, with the World Economic Forum [16] listing extreme weather events, natural disasters, the failure of climate-change mitigation and adaptation, and water crises as four of the top risks in their Global Risks Report 2018. Regarding agriculture, they explain that the preva- lence of monoculture farming increases vulnerability to a collapse in the food system [16]. In this regard, they note Available online at www.sciencedirect.com ScienceDirect www.sciencedirect.com Current Opinion in Environmental Sustainability 2019, 40:117–123