Extract

In recent years, much of the discussion on finite global resources has focused on the depletion of non-renewable resources, such as petroleum or rare-earth metals. However, it is increasingly evident that renewable resources, and the ecosystem services that they provide, are also at great or even greater risk (MEA, 2005; UNDP, 2011; WRI, 2011; UNEP, 2012; Lee et al., 2012). Economies the world over depend on the biosphere for a steady supply of the basic requirements for life – food, energy, fibre, waste sinks, and other life-support services. Any decline of these services is particularly risky at a time of growing ecological overshoot because it accelerates the rate at which natural assets are liquidated (Wackernagel et al., 2002). Out of this concern, the sustainability proposition emerges. Sustainability is a simple idea. Its ecological bottom-line principle is based on the recognition that when resources are consumed faster than they are renewed, or wastes are emitted faster than they are absorbed, resources are eventually exhausted and wastes accumulate in the biosphere(such as the current accumulation of greenhouse gases in the atmosphere).