Rises in the costs of living make poor people less able to afford items. Poor people spend a greater portion of their budgets on food than wealthy people. As a result, poor households and those near the poverty threshold can be particularly vulnerable to increases in food prices. For example, in late 2007 increases in the price of grains led to food riots in some countries. The World Bank warned that 100 million people were at risk of sinking deeper into poverty. Threats to the supply of food may also be caused by drought and the water crisis. Intensive farming often leads to a vicious cycle of exhaustion of soil fertility and decline of agricultural yields. Approximately 40% of the world's agricultural land is seriously degraded. In Africa, if current trends of soil degradation continue, the continent might be able to feed just 25% of its population by 2025, according to United Nations University's Ghana-based Institute for Natural Resources in Africa. Every year nearly 11 million children living in poverty die before their fifth birthday. 1.02 billion people go to bed hungry every night.