Ponencias Invitadas.-Desertification: the broader context

Abstract

ABSTRACT After over twenty years of research, there is still not complete consensus on even how to define desertification. This is reflected in the changing emphasis of UNCCD and EU programmes. The focus on physical processes in the 1990s has changed, first to an emphasis on the impacts of desertification and global change, and more recently towards sustainability rather than degradation as the core of most research effort, although much is still concerned with scenarios of possible future change. Different research tools are able to survey different windows on changing degradation status. Remote sensing methods, for example, provide an excellent window on the recent past, but little forecasting potential beyond projecting linear trends. Dynamic models add some understanding of the interaction of different components, and are increasingly engaging with socio-economic as well as strictly bio-physical processes, but are still limited by the intervention of the unexpected – the boom in biofuel demand, the credit crunch etc – that severely limit their forecasting horizons. This survey examines some of the over-arching relationships that must always constrain the relationships between population, food, land, water and energy, constraining the overall sustainability of global systems in a way that can only temporarily be ignored through irreversible mining of resources and exploitation of one region at the expense of another. The land sets constraints on food production that can partially be overcome through technological development, linked as both cause and effect to population growth, and may also be reduced by degradation. Less developed countries generally have a larger proportions of rural population and higher rates of rural-urban migration, but higher overall rates of population increase still lead to increasing rural populations (in contrast to more developed economies with falling rural numbers), adding to pressure on land resources and, almost inevitably, to degradation. This example demonstrates how broader social and economic forces lie at the root of much desertification, so that alleviation measures should not be confined to the directly affected area, but linked to national policies and development.