The United Nations warned that a "silent tsunami" caused by expensive food is putting 100 million people at risk. Aid groups are concerned that limiting exports will only exacerbate the problem. Prime Minister Gordon Brown stated that Britain will push for changes to EU biofuels targets if it is proven that growing crops for fuel is contributing to the increase in food prices. The World Food Programme expressed alarm at the growing hunger crisis, with their director Josette Sheeran highlighting the rapid rise in the number of people facing hunger. Riots in impoverished Asian and African nations have erupted due to the sharp spike in food prices, which can be attributed to various factors such as higher fuel costs, adverse weather conditions, increased demand due to rising incomes, and the use of land for biofuel production. The price of rice from Thailand, the leading exporter in the world, has more than doubled this year. Countries such as Indonesia, Kazakhstan, Egypt, and Cambodia have restricted food exports to ensure adequate supplies. According to Sheeran, artificial shortages have worsened the situation as the world has been consuming more than it produces for the past three years, leading to a depletion of stocks. The rising prices have caused a shortage of funds for the World Food Programme to purchase food for its programs, resulting in cutbacks to school feeding plans in Tajikistan, Kenya, and Cambodia. The WFP had estimated it would need $2.9 billion in 2008 to meet its needs, but now anticipates having to increase that amount by 25% due to the spike in prices of staples such as wheat, maize, and rice. The end of an era was marked by Britain's pledge of $900 million to assist the WFP in addressing immediate issues, with Brown expressing concerns about using crops for fuel production. He mentioned the possibility of revising the UK's approach and advocating for changes in EU biofuels targets. Meanwhile, Japan's Agriculture Minister called for the establishment of clear rules by the WTO regarding food export restrictions imposed by producer countries. The Asian Development Bank's managing director general also emphasized that the era of inexpensive food was coming to an end, urging Asian governments to avoid market distortions through export restrictions and instead use fiscal measures to help the less fortunate. U.N. Secretary-General Ban Ki-moon has warned that rising food prices could undo efforts to reduce poverty. Former Secretary-General Kofi Annan also emphasized that climate change is worsening the global food crisis, putting many poor countries at risk of severe hunger crises. He stressed that the poorest populations are suffering the most from climate change, despite contributing the least to it, and called for those responsible for polluting the environment to take responsibility. Annan highlighted that climate change poses a comprehensive threat to health, security, political stability, and social unity.