Making eco logic and models work Making eco Making eco logic and models work An integrative approach to lake ecosystem modelling Jan Jurjen Kuiper Jan Jurjen Kuiper Making eco logic and models work An integrative approach to lake ecosystem modelling Jan Jurjen Kuiper Thesis Committee Promotor Prof. Dr W.M. Mooij Professor of Aquatic Foodweb Ecology Wageningen University Co-promotors Dr J.H. Janse Senior researcher PBL Netherland Environmental Assessment Agency, Bilthoven Dr J.J.M. de Klein Assistant professor, Aquatic Ecology and Water Quality Management Group Wageningen University Other members Prof Dr C. Kroeze, Wageningen University Prof. Ir N.D. van Egmond, Utrecht University Dr S. Hilt, IGB, Berlin, Germany Prof Dr J.T.A. Verhoeven, Utrecht University This research was conducted under the auspices of the C.T. de Wit Graduate School for Production Ecology and Resource Conservation (PE&RC). Making eco logic and models work An integrative approach to lake ecosystem modelling Jan Jurjen Kuiper Thesis submitted in fulfilment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus Prof. Dr A.P.J. Mol, in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Friday 18 November 2016 at 1.30 p.m. in the Aula. Jan Jurjen Kuiper Making eco logic and models work. An integrative approach to lake ecosystem modelling, 192 pages. PhD thesis, Wageningen University, Wageningen, NL (2016) With references, with summaries in English and Dutch ISBN 978-94-6257-944-6 DOI 10.18174/391208 Contents Chapter 1 General introduction 7 Chapter 2 Serving many at once: How a database approach can create 23 unity in dynamical ecosystem modelling Chapter 3 The weak link between ecosystem models and real 41 ecosystems: Reflections on the consequences for model calibration and improvement Chapter 4 Food-web stability signals critical transitions in temperate 57 shallow lakes Chapter 5 Sampled equilibrium solutions and the predictability of 83 ecosystem stability along a gradient of environmental stress Chapter 6 Mowing submerged macrophytes in shallow lakes with 103 alternative stable states: Battling the good guys? Chapter 7 General discussion 127 Chapter 8 Synopsis of a collaborative research project on PCLake & 141 PCDitch Reference list 153 Summary 173 Samenvatting (Dutch summary) 177 Dankwoord (Acknowledgements) 183 About the author 187 List of publications 189 PE&RC Training and Education Statement 191 Chapter 1 General introduction 7 8 1.1 A personal note “There are these moments in life that change the way you look at the world. About one decade ago I had such a moment when I was hiking along a beach in the heart of Corcovado national park in Costa Rica. This peninsula is renowned for being among the places on earth with the highest biodiversity and I found myself happy to work there as a volunteer. I have always been intrigued by nature - as a kid you could often find me sitting on my knees observing pond life - yet the natural beauty I encountered during that walk was purely amazing. But what struck me most was witnessing the piles of human waste that had been washed up on the shore, especially since I was in the absolute middle of no-where (the nearest town was 50 km away, and it took me a 2 hour 4WD ride through the jungle, 30 minutes by boat and a 3 hour hike to get where I was). Shampoo bottles, lighters, flip-flops and drinking bottles were everywhere, and some of them I found deep inside the rainforest. It was then when I fully realised that humans are dominating this planet, affecting even the most remote places.” 1.2 The main challenge of our time If humanity continues to use more of the natural systems than what these systems can provide for, resulting changes in our physical environment will remain to pose large risks on many societies (Meadows et al., 1972; Rockström et al., 2009). For example, by extracting fossilized carbon from the earth’s crust at a rate much higher than the rate at which the biosphere can sequestrate carbon, we allow the atmospheric CO2 concentration to rise and the global climate to change (Schneider, 1989). Already we are subjected to increasing temperatures and more frequent extreme weather events (Blunden and Arndt, 2016; IPCC, 2013; Van den Hurk et al., 2014). Indeed, it has recently been postulated that climate change related droughts were a major impetus for the civil war in Syria which is currently lacerating the Middle East (Kelley et al., 2015). Ultimately, the rise of CO2 in the atmosphere may lead to so called Large-Scale Discontinuities, such as substantial reduction of the North Atlantic Meridional Overturning Circulation or the complete deglaciation of the Greenland and West Antarctic ice sheets, which are conceivably the biggest cause for climate concern (Lenton et al., 2008; Smith et al., 2009). Other planetary boundaries that we probably have exceeded already include the loss of biodiversity and disruption of the Nitrogen and Phosphorus cycles (Rockström et al., 2009; Steffen et al., 2015). More than forty years ago it was predicted that growth of the human ecological footprint was unlikely to be stopped until after the sustainable limits had been exceeded due to delays in global decision making (Meadows et al., 1972; Randers, 2012). Indeed, only recently world leaders have started to recognize lowering the human ecological footprint as being one of the most critical challenges of our time. For example, in December 2015 - the warmest year ever recorded - 195 countries adopted a new climate agreement (the ‘Paris Agreement’), committing themselves to stop global warming below 2 ⁰C (UNFCCC, 2015). Moreover, the leader of the Catholic Church, Pope Francis, presented an encyclical completely devoted to ecology and environmentalism, which he - for the first time in history - addressed to every person on the planet, followers and non-followers 9 alike (Pope Francis, 2015). How societies can and should reform to circumvent the detrimental consequences of anthropogenically induced global environmental change is still largely an open question however (Hatfield-Dodds et al., 2015). 1.3 Responsibilities of environmental research Global sustainability problems are sometimes referred to as ‘messy’ or ‘wicked’ because they are multidimensional, value-laden and originate in complex adaptive systems with numerous interactions and interdependencies at different scales (Verweij et al., 2006). In fact, they cannot be seen as single problems as they result from a combination of multiple interacting problems (Meadows et al., 1972). Because science is all about making the world more intelligible, there is an apparent role for scientists in supporting human societies to resolve these complex issues. However, the traditional way of knowledge production, which is curiosity driven, taking place within academic institutions and societies, and structured by scientific disciplines, appears to be insufficient, as sustainability problems typically fail to respond to non-integrative monodisciplinary approaches (Jones et al., 2010). In fact, what is called for is a post-modern science that is able to support decision makers in times when interests are conflicting, uncertainty is high and decisions are urgent (Funtowicz and Ravetz, 1993; Hessels and van Lente, 2008). In democracies, decision makers typically respond to constituencies which push their short-term profit interests, thereby imposing a great responsibility on scientists to elucidate and represent the long term interests (Safina, 1999). Indeed, we see that the science system is changing, whereby knowledge is increasingly being produced in the context of its application and by pan-disciplinary research teams (Hessels and van Lente, 2008). Along this path we see that science is becoming more predictive. Enabling decision makers and ecosystem managers to foresee the consequences, costs and benefits of future policies and management actions is probably decisive in designing successful routes towards sustainability. The most common way of predicting is by projecting our current understanding into the future using mechanistic models (Pace, 2001). 1.4 Models for understanding and prediction In daily life humans are constantly turning experiences into judgements, assumptions and guesses in order to respond swiftly to novel circumstances, and generally these generalizations tend to be accurate (Gigerenzer and Brighton, 2009). In science, experience- based generalizations are referred to as ‘hypotheses’, and in the pursuit of truth we aim to falsify such generalizations by means of carefully designed experiments. Yet, certain issues are so complex that we cannot grasp them by performing (thought) experiments only, for example when we want to understand or predict the dynamics of complex dynamic ecosystems that are perturbed by human actions. In those cases mechanistic modelling may provide a solution, helping to gain experience with complex or counterintuitive phenomena, and turning experiences into predictions of future conditions. Models provide a logical structure that enables synthesizing various types of knowledge and data into an integrated 10 view of the system it portrays. By manipulating the model we can identify the most important processes and components, and learn about the relationships between processes and model outputs (Carpenter, 2003). This is particularly useful when we have some understanding of the structure and dynamics of a system but only little data. Yet, when there is empirical data to confront the model with, we may be able to confirm that the essential mechanisms needed to reproduce observed system dynamics are indeed accounted for. If that is the case and there is enough confidence, we may continue with making quantitative predictions about how a system reacts when it is perturbed under given scenarios. 1.5 Shallow lakes Small and shallow lakes are the most abundant of the ~117 million lakes in the world >0.2 ha (Verpoorter et al., 2014), and provide crucial ecosystem services for human wellbeing (Millennium Ecosystem Assessment, 2005).