With nearly one billion people still suffering from food shortages around the globe, the world must take a united stand against hunger, the United Nations said here Friday, marking World Food Day.

The number of the world's hungry has dipped slightly from its record high last year, but "we are continually reminded that the world's food systems are not working in ways that ensure food security for the most vulnerable members of our societies," UN Secretary-General Ban Ki-moon said in his message on the Day, which falls on Saturday.

World Food Day is celebrated every year around the world on Oct. 16 in honor of the date of the founding of the Food and Agricultural Organization (FAO) in 1945.

The Millennium Development Goal (MDG) of halving the proportion of hungry people in the world is a pillar for achieving all eight of the globally-agreed targets with a 2015 deadline, Ban said.

"When people are hungry, they cannot break the crippling chains of poverty, and are vulnerable to infectious diseases," the secretary-general said. "When children are hungry, they cannot grow, learn and develop."

This year alone, Ban said, millions have been pushed into hunger by the earthquake in Haiti, the drought in the Sahel and floods in Pakistan, while the twin food and financial crises continue to affect the world's most vulnerable.

He highlighted the need for global cooperation -- bringing together governments, intergovernmental organizations, regional and sub-regional bodies, business and civil society groups -- to combat hunger.

"Increasingly, their approach is comprehensive," Ban said, covering all aspects of food security, ranging from small farms to feeding schoolchildren.

He urged everyone to press ahead with this approach to build on progress made in reducing the number of hungry people in the world. "Let us unite against hunger and ensure food and nutrition security for all," he said.

The UN food agency's 1billionhungry.org campaign, which aims to encourage governments to make eliminating hunger their top priority, has surpassed 1 million signatures.

A celebration was held to commemorate the Day in Rome, where the FAO is seated, on Friday, with the FAO appointing four new Goodwill Ambassadors -- Italian actor Raoul Bova, Canadian singer Cline Dion, Filipino singer Lea Salonga and United States actress Susan Sarandon -- to raise awareness of the global fight against hunger.

By taking on the role, they commit themselves to addressing the universal humanitarian goals underpinning the agency's mission to build a food-secure world.

Also taking part in the ceremony were the heads of the FAO, the UN World Food Program (WFP) and the International Fund for Agricultural Development (IFAD).

Kanayo F. Nwanze, the president of IFAD, urged world leaders to boost investments in agriculture and in enhancing farm productivity.

It is estimated that half of the world's poor are smallholder agriculturalists, with more than two billion men and women in Africa, Asia and Latin America depending on smallholder farms.

"Smallholder farmers can feed the world, but they cannot do it alone," he told reporters. "Greater long-term investment in agriculture is needed, creating conditions to bring rural people out of subsistence and into the marketplace."

Nwanze underlined the crucial role of agriculture in fighting poverty.

"Agriculture is the key to food security and a fundamental engine of economic growth and wealth generation," he said.

For its part, the UN World Food Program (WFP) hailed the bold leadership of governments in finding lasting solutions to hunger and malnutrition.

"When we act together, we have the power to bring about real change in the lives of millions of people who would otherwise struggle to feed their families," said the agency's deputy executive director for hunger solutions, Sheila Sislu.

She pointed to the example of Cape Verde, whose government took full ownership of the national school meals programmes last month after more than three decades of cooperation with WFP.

Meanwhile, Olivier De Schutter, the UN special rapporteur on the right to food, said on Friday that there is little to rejoice about on World Food Day, calling for a shift to low-carbon agriculture to ensure there is enough food for all, especially in the face of climate change.

There are nearly one billion hungry people in the world, "but the worst may still be ahead, since current agricultural developments are also threatening the ability for our children's children to feed themselves," he said.

Current farming methods focus on the provision of chemical fertilizers and a greater mechanization of production. "Such efforts are far distant from the professed commitment to fight climate change and to support small-scale, family agriculture," he said.

The current approach, De Schutter stressed, is a "recipe for disaster," calling for reliance on agro-forestry, better water harvesting techniques and other low-carbon methods to ensure that farming plays a large role in mitigating climate change's effects instead of exacerbating them.