ROME (AFP) - World food production must increase by 70 per cent by 2050, to nourish a human population then likely to be 9.1 billion, the UN Food and Agriculture Organisation forecast Wednesday. FAO is cautiously optimistic about the worlds potential to feed itself by 2050, said FAO Assistant Director-General Hafez Ghanem. However, he stressed that feeding everyone in the world by then will not be automatic and several significant challenges have to be met. The agency is preparing for a high-level expert forum in Rome on October 12-13 on How to Feed the World in 2050 and plans to gather 300 specialists from academic, non-governmental and private sector institutions. This forum will pave the way for a World Summit on Food Security in Rome on November 16-18. The world population is expected to grow from 6.8b today to 9.1b in 2050, according to the latest UN forecast. Nearly all of the population growth will occur in developing countries. Sub-Saharan Africas population is expected to grow the fastest (up 108pc, 910m people), and East and South East Asias the slowest (up 11pc, 228m). Around 70pc of the world population will live in cities or urban areas by 2050, up from 49pc today, the document said. The demand for food is expected to grow as a result of rising incomes as well as population growth, the discussion paper added. Cereal production will have to increase by almost a billion tonnes from 2.1b today and meat production will have to grow by more than 200m tonnes to reach a total of 470m tonnes in 2050. The FAO estimated that the production of biofuels could also increase the demand for agricultural commodities, depending on energy prices and government policies. More land will be needed for crops despite the fact that 90pc of the growth in crop production is projected to come from higher yields and increased cropping intensity. The FAO estimated that arable land will have to expand by around 120m hectares in developing countries, mainly in Africa and Latin America, while arable land in use in developed countries is expected to decline by some 50m hectares, although this could be changed by the demand for biofuels. Globally, there is still enough land to feed the future world population, but much of the potential land is suitable for growing only a few crops, and the FAO warned of other difficulties, such as chemical and physical constraints, endemic diseases and a lack of infrastructure. Overcoming such problems will require significant investments, the FAO said, adding that some countries in the Near East, north Africa and South Asia have already reached or are about to reach the limits of land available. The FAO expects water withdrawals for irrigated agriculture to grow by almost 11 percent by 2050. The world has enough fresh water resources, but they are very unevenly distributed and water scarcity will reach alarming levels in an increasing number of countries or regions within countries, particularly in the Near East/North Africa and South Asia.