In a landmark study published a decade ago, the International Water Management Institute (IWMI) suggested that under likely scenarios the world's freshwater supplies should be adequate to meet future demands from agriculture, industry and other sectors. (1) A lot has happened since then that makes it difficult today to frame this essentially accurate conclusion in such optimistic terms. It is clear now that, without significant improvement in water management, we can no longer assure sustainable development in the face of climate change and related pressures.
Water crises are, in fact, the single most worrying global issue on the minds of leaders surveyed recently by the World Economic Forum. (2) Moreover, of the top five concerns cited, four centre on or are directly linked to water, including the "failure of climate change mitigation and adaptation," which occupied second place. (3) Within the last few years, it has become a truism of work on adaptation that climate change impacts will weigh on societies, economies and the environment primarily through water.
What combination of factors accounts for such a pronounced shift in perspective over the course of just 10 years? A central issue is the rising concern about growing water scarcity relative to demand, driven by rapid population growth, urbanization and economic development. Climate change will compound the scarcity challenge, because higher temperatures will boost rates of evaporation from both soils and water surfaces, increase crop water requirements and raise demand for cooling water necessary to generate the energy that consumers will demand in response to higher temperatures.
The outlook is especially ominous for the world's vast dry areas, which may be considered the front lines of climate change adaptation. Streamflow declines of more than 50 per cent are "confidently predicted" for these areas, as a result of lower rainfall. (4) This will also reduce infiltration of water into aquifers, threatening communities that are highly dependent on groundwater, which is inherently difficult to monitor and manage.
Of particular concern are many poor, agrarian communities in arid regions of sub-Saharan Africa and South Asia, where high rates of rural poverty and low levels of adaptive capacity leave people highly vulnerable to the effects of reduced water availability. Similarly, in many fragile regions of the Middle East and North Africa, climate change is predicted to significantly worsen water scarcity, which could act as a stressor compounding the risks of conflict and migration. (5)
THE DUAL CHALLENGE OF WATER SECURITY
Heightened concern about water scarcity oversimplifies the challenge, however. Climate change will give rise not only to reduced water availability in many places but also to increasingly variable and unpredictable water supplies. More frequent and severe...