Changes in temperature, evaporation and precipitation can create the conditions for floods, droughts and desertification. And as expected, we have already seen a significant increase in all three in various parts of the world in recent years. In the last half century there has been a six-fold increase in the number of major floods in Asia—the most seriously affected continent (and within Asia, especially China). At the same time, Africa has suffered the most severely from the opposite problem—droughts. Normally, the earth stores CO2, which fertilizes the soil. Drought conditions cause the microbes in the soil to rapidly decompose organic matter so that this stored CO2 is then emitted into the atmosphere, creating even more problems. Prolonged droughts have also led to desertification. More than 2 billion people live in areas that are characterized as drylands, found especially in Africa and Asia. These cover over 40% of the earth's land surface, and vast areas of these drylands are becoming deserts.