"Environmental security" has three different meanings. First, it can be used to explain conflict. Resources can be causes, tools, or targets of warfare. Disputes over water can cause conflict between nations. Upstream states can use water as a tool of warfare by manipulating shared river basins to inflict pain on other riparian states. The infrastructure of water supplies -- dams, irrigation systems, desalination plants and reservoirs -- can be the targets of attack in times of war. Food scarcity and famine can generate domestic instability and breakdown of law and order, or provoke mass migration of people to other countries and an increase in cross-border tensions.

Water is indispensable and irreplaceable. Over the next quarter century, half the world's people will face problems finding enough freshwater for farming and drinking. Asia's water stocks are already among the most polluted in the world, and water tables are falling 1 to 3 meters annually in parts of China and India. As water tables and stocks of arable land fall, disputes over them could multiply, intensify and generate instability and violence.

A wealth of resources can increase the probability and durability of violent conflict as groups seek enrichment through wars and illicit means (such as trafficking in guns, drugs and diamonds). Competing claims to exclusive economic zones and the right to exploit their fisheries could provoke tensions and conflict among Northeast Asian countries.