GEF

Unit 1  |  Why Water Matters 19 and also contributed to the building of dense cities, economic growth, political organization, and empires. Centralized power and organization also made these exten- sive settlements vulnerable to disruptions in the water supply. Droughts, water scarcity , and over-extended water infra- structure have dealt a crippling blow to countless communities and civilizations throughout history. The Sumerians hastened their own demise by deforesting the hillsides surrounding their cities. Cutting down the trees greatly increased erosion and washed away fertile topsoil that had provided nutrients for their crops. Repeated flooding and drying of irrigated soil increased the salt content, a process called salinization . This steady increase in soil salts eventually made growing wheat impossible, and sharply decreased yields of barley. Water scarcity has been a critical issue for centuries. In a pattern repeated by agricultural civilizations around the world, rising population levels in Mesopotamia combined with decreased crop yields led to conflicts over water resources, even leading to the first recorded war over water. Weakened by internal strife, Sumerian culture collapsed from a combination of agriculture failure and military invasions from other regions. WATER SCARCITY Having less than 1,000 cubic meters of water available per person per year. DEFORESTING The action of cutting down trees to create clear land. EROSION The process by which soil or rock is removed by water or wind. SALINIZATION A buildup of minerals and salts in the soil that renders it sterile.