Anthropocene Futures and Water Security
Abstract. A central claim about the Anthropocene is that this new epoch, in which people have become the primary geological force, raises profound questions about the sustainability of human development (Crutzen 2002). Human populations have grown dramatically, especially over the past two centuries; these people have grown on average wealthier, drawing on massively greater natural resources and environmental services, including water (Steffen et al. 2011).
A number of ‘planetary boundaries' have been defined (Röckstrom et al. 2009), which point to the most urgent dimensions of the global sustainability problems that flow from the scale and scope of human appropriations and interventions in biophysical Earth Systems. These include by now familiar changes and impacts associated with climate change, ozone depletion, biodiversity loss and land-use change, as well as global freshwater use. Röckstrom et al. (2009) suggest using consumptive water run-off (or blue water use) as a proxy for global freshwater use. Assuming an upper limit of ~12 500–15 000 km3 year−1 of accessible blue water resources, they suggest that consumptive uses above a threshold of 4000–6000 km3 year-1 would represent a significant risk to ecosystems, moisture feedbacks and freshwater/ocean mixing. Given that consumptive use is now at about 2600 km3 year−1 the authors conclude that there appears to be some room for manoeuvre, although there continues to be a trend of rapidly growing consumptive water use at the global scale.
In addition, a number of other problems associated with access to resources have been pointed to: peak oil; peak phosphorus; and the resilience of ecosystem services (Steffen 2011). Beyond this, there is the growing awareness of "systemic risks" to global economic, financial and political systems linked to the degradation, failure or transformation of key biophysical and ecological systems. Perhaps one of the most striking claims is that an epoch of relative stability in these systems (the Holocene) has been replaced by a new period of rapid change, instability and continuing transience, with growing risks of thresholds and tipping points (Lenton et al. 2008).