 A rapidly growing population, climate change and degradation of land and water resources are likely to make the world more vulnerable to food insecurity and challenge the task of feeding its people by 2050, the United Nations' food agency said. The world would have to boost cereals output by 1 billion tons and produce 200 million extra tons of livestock products a year by 2050 to feed a population projected at 9 billion people, up from 7 billion now, according to UN estimates. Intensive farming of the past decades has helped to feed millions of hungry people but it has often led to degradation of land and water systems on which food production depends, the U.N. Food and Agriculture Organization (FAO) said on Monday. "These systems at risk may simply not be able to contribute as expected in meeting human demands by 2050. The consequences in terms of hunger and poverty are unacceptable. Remedial action needs to be taken now," FAO Director-General Jacques Diouf said. A quarter of the earth's land is highly degraded, another 8 percent is moderately degraded, while 36 percent is stable or slightly degraded and 10 percent ranked as improving, the FAO said in its report - State of the World's Land and Water Resources for Food and Agriculture. Water scarcity is growing as salinisation and pollution of groundwater, as well as degradation of water bodies and water-related ecosystems, rise, the report said. In many large rivers, only 5 percent of former water volumes remain in-stream and some rivers such as China's Huang He (Yellow River) no longer reach the sea year-round. Large lakes and inland seas have shrunk and half the wetlands of Europe and North America no longer exist, the Rome-based FAO said. With the increasing competition for land and water for food and feed in agriculture as well as industry and urban development uses, the challenge of providing sufficient food for everyone has never been greater, it said. Almost 1 billion people are now undernourished, with 578 million people in Asia and 239 million in sub-Saharan Africa, the FAO said. In developing countries, even if agricultural output doubled by 2050 as expected to feed the world, one person in 20 would still risk being undernourished, an equivalent to 370 million hungry people, most of whom would be in Africa and Asia, it said. STEPS TO TAKE Future agricultural production would have to rise faster than population growth for nutrition to improve and for food insecurity and hunger to recede, the FAO said. That would have to occur largely on existing farming land with improvements coming from sustainable intensification that uses land and water efficiently without harming them, it said. There have been warning signs of a slowdown of agricultural output growth rates in many areas to only half of what they were during the green revolution, it said, referring to a period in the 1960s and 1970s when farm yields got a boost through intensive practices and new seed varieties. Innovative farming practices such as conservation agriculture, agro-forestry, integrated crop-livestock systems and integrated irrigation-aquaculture systems can help boost food production while limiting impacts on ecosystems, it said. Most irrigation systems across the world perform below their capacity, so improving the efficiency of water use by farmers with improved management of resources and modern technology would be crucial, the FAO said. Gross investment needs between 2007 and 2050 for irrigation development and management are estimated at almost $1 trillion, while land protection and development, soil conservation and flood control would require around $160 billion in the same period, the report said.