The global rush to switch from oil to energy derived from plants will drive deforestation, push small farmers off the land and lead to serious food shortages and increased poverty unless carefully managed, says the most comprehensive survey yet completed of energy crops. The United Nations report, compiled by all 30 of the world organisation's agencies, points to crops like palm oil, maize, sugar cane, soya and jatropha. Rich countries want to see these extensively grown for fuel as a way to reduce their own climate changing emissions. Their production could help stabilise the price of oil, open up new markets and lead to higher commodity prices for the poor.