Unsustainable agriculture and inefficient urban water use causes or contributes to erosion, floods, fires, desertification, water and crop loss. 35 states pump their underground water faster than it refills. This can cause sink holes that destroy aquifers and even swallow cars and houses. More than 1.7 billion people worldwide don't have an adequate supply of safe drinking water. Lake Mead—the largest reservoir in the United States that provides water for 40 million people—sits at only a 35% capacity, the lowest level since it was being filled in 1935. 75% of Earth's land area is already degraded, 1.61 million square miles are degraded annually, and by 2050 90% will be in this condition. Women and girls globally spend 200 million hours every day just collecting water. Drought impacts 40% of the world’s population, 700 million people. Climate change, population growth, and higher temperatures threaten to increasingly make this and other problems much worse.