Personal norms of sustainability and their impact on management – The case of rangeland management in semi-arid regions

We empirically study personal norms of sustainability, conceptualized according to the normactivation theory and operationalized under the notion of strong ecological-economic sustainability, for commercial cattle farmers in semi-arid rangelands of Namibia, a system that is subject to extensive degradation. We characterize farmers’ personal norms, study their determinants, and analyze their impact on actual management based on the dual-preferences model. We find personal norms of sustainability that are heterogeneous across farmers, but vary little with socio-demographic or environmental characteristics. We find no evidence for a significant impact of personal norms on actual management behavior, which may be due to farmers not feeling capable for averting adverse long-term consequences of their management. This may contribute to the observed degradation of rangelands in Namibia.commercial cattle farming, Namibia, norm-activation theory, personal norms, dual-preferences model, semi-arid rangelands, sustainability

Complementarity, impatience, and the resilience of natural-resource-dependent economies

We study how human preferences aect the resilience of economies that depend on more than one type of natural resources. In particular, we analyze whether the degree of substitutability of natural resources in consumer needs may give rise to multiple steady states and path dependence even when resources are managed optimally. This is a major shift in the interpretation and analysis of resilience, from viewing (limited) resilience as an objective property of the economy-environment system to acknowledging its partially subjective, preference-based character. We nd that society tends to be less willing to buer exogenous shocks if resource goods are complements in consumption than if they are substitutes. Hence, the stronger the complementarity between the various types of resource goods, the less resilient the economy is.Resilience; substitutes and complements; discounting; multiple steady states; natural resources; path dependence; regime shifts; tipping points

Risk preferences under heterogeneous environmental risk

We study risk preferences and their determinants for commercial cattle farmers in Namibia who are subject to high and heterogeneous precipitation risk, using data from questionnaire and field experiments, simulated data for on-farm precipitation risk and data on famers’ previous place of residence. We find that the relationship between risk preferences and precipitation risk is contingent on early-life experience with this risk. We also find that adult farmers self-select themselves onto farms according to their risk preferences. Results are not confounded by background risks or liquidity constraint.risk preferences, environmental risk, experimental elicitation, endogenous preferences, self-selection, field experiment

ENERGY ACQUISITION AND ALLOCATION IN PLANTS AND INSECTS: A HYPOTHESIS FOR THE POSSIBLE ROLE OF HORMONES IN INSECT FEEDING PATTERNS

A distributed delay age structure model is presented for plants and insects that describes the dynamics of per capita energy (dry matter) acquisition and allocation patterns, and the within-organism subunit (e.g. leaves, fruit, ova) number dynamics that occur during growth, reproduction, and development. Four species of plants (common bean, cassava, cotton, and tomato) and two species of insects (pea aphid and a ladybird beetle) are modeled. A common acquisition (i.e. functional response) submodel is used to estimate the daily photosynthetic rates in plants and consumption rates in pea aphid and the ladybird beetle. The focus of this work is to capture the essence of the common attributes between trophic levels across this wide range of taxa. The models are compared with field or laboratory data. A hypothesis is proposed for the observed patterns of reproduction in pea aphid and in a ladybird beetl