How market structure drives commodity prices

We introduce an agent-based model, in which agents set their prices to maximize profit. At steady state the market self-organizes into three groups: excess producers, consumers and balanced agents, with prices determined by their own resource level and a couple of macroscopic parameters that emerge naturally from the analysis, akin to mean-field parameters in statistical mechanics. When resources are scarce prices rise sharply below a turning point that marks the disappearance of excess producers. To compare the model with real empirical data, we study the relationship between commodity prices and stock-to-use ratios in a range of commodities such as agricultural products and metals. By introducing an elasticity parameter to mitigate noise and long-term changes in commodities data, we confirm the trend of rising prices, provide evidence for turning points, and indicate yield points for less essential commodities

It is getting hotter in here: determining and projecting the impacts of global environmental change on drylands Introduction

Drylands occupy large portions of the Earth, and are a key terrestrial biome from the socio-ecological point of view. In spite of their extent and importance, the impacts of global environmental change on them remain poorly understood. In this introduction, we review some of the main expected impacts of global change in drylands, quantify research efforts on the topic, and highlight how the articles included in this theme issue contribute to fill current gaps in our knowledge. Our literature analyses identify key under-studied areas that need more research (e.g. countries such as Mauritania, Mali, Burkina Faso, Chad and Somalia, and deserts such as the Thar, Kavir and Taklamakan), and indicate that most global change research carried out to date in drylands has been done on a unidisciplinary basis. The contributions included here use a wide array of organisms (from micro-organisms to humans), spatial scales (from local to global) and topics (from plant demography to poverty alleviation) to examine key issues to the socio-ecological impacts of global change in drylands. These papers highlight the complexities and difficulties associated with the prediction of such impacts. They also identify the increased use of long-term experiments and multidisciplinary approaches as priority areas for future dryland research. Major advances in our ability to predict and understand global change impacts on drylands can be achieved by explicitly considering how the responses of individuals, populations and communities will in turn affect ecosystem services. Future research should explore linkages between these responses and their effects on water and climate, as well as the provisioning of services for human development and well-being

The demise of a new conservation and development policy? Exploring the tensions of the Yasuní ITT initiative

The Yasuní ITT is known as a government-led proposal to ban oil exploration and extraction activities within an Ecuadorian National Park and to obtain financial resources from the international community to compensate (partially) forgone oil revenues. The initiative brought into focus and tried to solve a classic dilemma: conventional policy options would imply either that Ecuador forgoes large revenues, or that the world loses a natural and cultural patrimony irreversibly. The ground-breaking significance of the initiative is reflected by the attention and endorsements received at the national and international level. However, attention and endorsements have been accompanied by a difficult process of implementation and eventually the (temporary?) termination-in mid-2013-of the initiative. In this paper we analyze the numerous tensions that have characterized the development of the proposal and can help explain the imbroglio. The aim of this paper is to highlight and contextualize these tensions that reside in specific features of the socio-political configuration of the state-society relationship in Ecuador and the position of the country in the international arena, in the very novelty of the initiative and the misfit with the existing global environmental policy frameworks. We argue that the demise of the initiative depends to a large extent on the inability of policy makers to identify and resolve these tensions