Farmers need to increase global food production by some 70% in the coming decades to feed an additional 2.3 billion people by 2050, warned a paper published by the United Nations food agency today, which calls for urgent investment in agriculture.

With the world population expected to balloon by one-third to 9.1 billion people, the Food and Agriculture Organization (FAO) underscored the importance of using scarce natural resources more efficiently and investing in agriculture to combat a deepening hunger and poverty crisis.

"FAO is cautiously optimistic about the world's potential to feed itself by 2050," said the Rome-based agency's Assistant Director-General Hafez Ghanem, spotlighting several significant challenges to achieving the goal.

Global projections show that in addition to large-scale investments in agriculture, further significant outlays will be needed to improve access to food to avoid some 370 million people - 5 per cent of the global population - remaining malnourished in 40 years from now.

FAO highlighted the challenge of the expanding global population, with sub-Saharan Africa expected to grow by 108 per cent, or 910 million people, by 2050.

"Nearly all of the population growth will occur in developing countries. Sub-Saharan Africa's population is expected to grow the fastest (up 108 percent, 910 million people), and East and South East Asia's the slowest (up 11 percent, 228 million).

"Around 70 percent of the world population will live in cities or urban areas by 2050, up from 49 percent today," the document said.