Open Access

This paper-based dissertation deals with the concepts of economic heterogeneity and environmental uncertainty from different perspectives, and at multiple levels of abstraction. At its core sits the observation that heterogeneity and uncertainty are deeply entangled, for there would be no uncertainty without heterogeneity of options to act regarding multiple future states of the world. At the same time, heterogeneity - in the form of diversification - has been suggested as a way to reduce uncertainty in portfolio theory (Markowitz 1952). The dissertation evolves around two research foci: (1) methodological implications of heterogeneity of scientific theories in the face of empirical data (Paper 1), and (2) two different forms of uncertainty are considered, environmental risk (Paper 2) and Knightian uncertainty (Paper 3). Paper 1 develops a new framework for model selection for the special case of fitting size distribution models to empirical data. It combines Bayesian and frequentist statistical approaches with the criterion of model microfoundation, which is to select, all other things considered being equal, the model that comes with a suitable micromodel, that explains, from the perspective of the individual constituent, the genesis of the overall size distribution. The approach is subsequently illustrated with size distribution data on commercial cattle farms in Namibia. We find that the double-Pareto lognormal distribution fits the data best. Our approach might have the potential to reconcile one of the oldest debates in current economics, i.e. the one about the best model to describe and explain the distribution of economic key variables such as income, wealth and city sizes in a country. The second paper revisits the Namibian commercial cattle farm data and uses it to put some theories from the agricultural economics literature regarding farm management under environmental risk to an empirical test. We focus on the relations between inter-annual variability in rainfall (environmental risk), risk preferences, farm size and stocking rate. We demonstrate that the Pareto distribution - which separates the distribution into two parts - is a statistically plausible description of the empirical farm size distribution when ´farm size´ is operationalized by herd size, but not by rangeland area. A statistical group comparison based on the two parts of the Pareto distribution shows that large farms are on average exposed to significantly lower environmental risk. Regarding risk preferences, we do not find any significant differences in mean risk attitude between the two branches. Our analysis confirms the central role of the stocking rate as farm management parameter, and shows that environmental risk and the farmer´s gender are key variables in explaining stocking rates in our data. Paper 3 develops a non-expected-utility approach to decision making under Knightian uncertainty which circumvents some of the conceptual problems of existing approaches. We understand Knightian uncertainty as income lotteries with known payoffs but unknown probabilities in each outcome. Based on seven axioms, we show that there uniquely (up to linear-affine transformations) exists an additive and extensive function from the set of Knightian lotteries to the real numbers that represents uncertainty preferences on the subset of lotteries with fixed positive sum of payoffs over all possible states of the world. We define the concept of uncertainty aversion such that it allows for interpersonal comparison of uncertainty attitudes. Furthermore, we propose Renyi´s (1961) generalized entropy as a one-parameter preference function, where the parameter measures the degree of uncertainty aversion. We illustrate it with a simple decision problem and compare it to other decision rules under uncertainty (maximin, maximax, Laplacian expected utility, minimum regret, Hurwicz).

The principle of sustainability contains two objectives of justice regarding the conservation and use of ecosystems and their services: (1) global justice between different people of the present generation ("intragenerational justice"); (2) justice between people of different generations ("intergenerational justice"). International sustainability policy attaches equal normative importance to both objectives of justice. Accordingly, environmental philosophers ethically justify that people living today and people living in the future have equal rights to certain basic goods, including ecosystems and their services (e.g. Feinberg 1981, Visser’t Hooft 2007). Whereas ideal theories of sustainability and justice do not recognize interdependencies between intragenerational and intergenerational justice, conflicts in attaining the justices possibly arise in policy implementation. Identifying and preventing such conflicts is fundamental to devise an ethically legitimate, politically consistent and actually effective sustainability policy. This dissertation systematically investigates conflicts between intragenerational and intergenerational justice in the use of ecosystem services. Human wellbeing depends on the services provided by ecosystems. Yet, humans substantially degrade world’s ecosystems, and therewith cause the loss of important ecosystem services (MEA 2005: 26ff.). The idea of sustainability demands to use ecosystem services in accordance with the two objectives of intragenerational justice and intergenerational justice. Reality, however, is far from attaining these objectives: Both today’s global poor and future persons are, resp. will be, disproportionately affected by the loss of vital ecosystem services (MEA 2005: 62, 85). Especially severe affected are the rural poor who directly depend on local ecosystem services for food, income and health. The political discourse on the relationship between the objectives of intra- and intergenerational justice in the use of ecosystem services (‘justice-relationship’) is blurred. Further, the political discourse lacks a common understanding of justice in ecosystem-use and a systematic reflection on the actual ‘justice-relationship’, such as on the factors that cause conflicts between the two justices. In this dissertation, I investigate the ‘justice-relationship’ along three central questions: • What conception(s) of justice can adequately address the distribution of access rights to ecosystem services? • How must sustainability policy be designed to enhance both intragenerational and intergenerational justice in the use of ecosystem services? • (How) Can economics be helpful for characterizing and assessing trade-offs between the two justices? I approach these questions both generally and by the example of a case study, the MASIPAG farmer network in the Philippines. Methodologically, I combine a normative and a positive analysis of the relationship between intra- and intergenerational justice in the use of ecosystem services: The normative analysis serves the explication, justification and reflection of the norms underlying the ‘justice-relationship’; the positive analysis serves the description of the ‘justice-relationship’ in the sustainability discourse and in practical contexts, as well as the provision of explanations on the determinants of the ‘justice-relationship’. As methodological approach, I apply the “comprehensive multi-level approach” as developed by Baumgärtner et al. (2008) – investigating the ‘justice-relationship’ simultaneously on the three levels of (i) concept, (ii) model and (iii) case study.

The Ili Delta in Kazakhstan is an important ecosystem that offers crucial wetland habitats for several bird species. However, the Ili River, the Ili Delta and the Balkhash Lake are suffering from water shortage due to climate change and human activities. The desertification of the Aral Sea, an obvious point of comparison to the Balkhash region, also involved the degradation of wetland habitats and the related loss of many bird species relying on these habitats. Therefore, water shortage at the Ili Delta may also be the reason for the loss of wetland habitats and bird species. In this study, bird species numbers, species abundances as well as bird diversity at different habitats in the Ili Delta were examined. There are many habitat types provided by the Ili Delta, for example reed bed vegetation, Tugay forest, bare soil floodplains along rivers and steppe. The results of this study showed that the central delta region with habitats of submerged reed vegetation showed the highest number of bird species and the greatest diversity. Threatened bird species at the Ili Delta were also observed only in these wetland habitats. Steppe habitats showed the lowest numbers of bird species and the lowest bird diversity. In general, all habitats at the Ili Delta are important for the ecosystem and essential for the bird species that depend on them for their survival. With expansion of arid steppe habitats due to water shortage, however, previous wetland habitats may be lost. Moreover, bird species that depend on these wetland habitats may also be lost. Therefore, protective measures for the Balkhash region in general and the wetland habitats at the Ili Delta and its distinct avifauna in particular are urgently needed.