The 21st Century climate challenge

prominently in low human development traps,eroding the ecological resources on whichthe poor depend, and restricting options foremployment and production.Water is a source of life and livelihoods. Aswe showed in the Human Development Report2006, it is vital to the health and well-beingof households and an essential input intoagriculture and other productive activities.Secure and sustainable access to water—watersecurity in its broadest sense—is a conditionfor human development.Climate change will be superimposed onwider pressures on water systems. Many riverbasins and other water sources are alreadybeing unsustainably ‘mined’. Today, around1.4 billion people live in ‘closed’ river basinswhere water use exceeds discharge levels,creating severe ecological damage. Symptoms ofwater stress include the collapse of river systemsin northern China, rapidly falling groundwaterlevels in South Asia and the Middle East, andmounting conflicts over access to water.Dangerous climate change will intensifymany of these symptoms. Over the course ofthe 21 st Century, it could transform the flows ofwater that sustain ecological systems, irrigatedagriculture and supplies of household water. Ina world that is already facing mounting pressureon water resources, climate change could addaround 1.8 billion people to the populationliving in a water-scarce environment—definedin terms of a threshold of 1000 cubic metres percapita per annum—by 2080. 68Scenarios for the Middle East, already theworld’s most water-stressed region, point inthe direction of increasing pressure. Nine outof fourteen countries in the region already haveaverage per capita water availability below thewater scarcity threshold. Decreased precipitationis projected for Egypt, Israel, Jordan, Lebanonand Palestine. Meanwhile, rising temperaturesand changes in runoff patterns will influencethe flow of rivers upon which countries inthe region depend. The following are amongthe findings to emerge from national climatemodelling exercises:• In Lebanon, a 1.2°C increase in temperatureis projected to decrease water availabilityby 15 percent because of changed runoffpatterns and evaporation. 69• In North Africa even modest temperatureincreases could dramatically change wateravailability. For example, a 1°C increasecould reduce water runoff in Morocco’sOuergha watershed by 10 percent by2020. If the same results hold for otherwatersheds, the result would be equivalentto losing the water contained by one largedam each year. 70• Projections for Syria point to even deeperreductions: a 50 percent decline in renewablewater availability by 2025 (based on1997 levels). 71Climate change scenarios for water in theMiddle East cannot be viewed in isolation.Rapid population growth, industrial development,urbanization and the need for irrigationwater to feed a growing population are alreadyplacing immense pressure on water resources.The incremental effects of climate changewill add to that pressure within countries,potentially giving rise to tensions over waterflowing between countries. Access to the watersof the River Jordan, cross-border aquifers, andthe River Nile could become flashpoints forpolitical tensions in the absence of strengthenedwater-management systems.Glaciers in retreatGlacial melting poses threats to more than40 percent of the world’s population. 72The precise timing and magnitude of thesethreats remains uncertain. However, theyare not a distant prospect. Glaciers are alreadymelting at an accelerating rate. That trendis unlikely to be reversed over the next twoto three decades, even with urgent mitigation.Climate change scenarios point to increasedflows in the short term, followed by long termdrying.The thousands of glaciers located acrossthe 2,400 kilometres of the Himalayan rangeare at the epicentre of an emerging crisis. Theseglaciers form vast water banks. They store waterand snow in the form of ice, building up storesduring the winter and releasing them during thesummer. The flow sustains river systems that areClimate change will besuperimposed on widerpressures on water systems.Many river basins and otherwater sources are alreadybeing unsustainably ‘mined’2Climate shocks: risk and vulnerability in an unequal worldHUMAN DEVELOPMENT REPORT 2007/2008 95