Soaring commodities prices once again haunt the world economy. The global recovery has seen prices surge. Many commodities are near or above their 2008 peaks. Maize is an astounding $290 per tonne, and oil is back above $100 a barrel. Soaring food and energy prices now pose severe economic, political, and social risks in developing countries.

Finance ministers from the Group of 20 leading economies meet in Paris today to discuss the food crisis against a backdrop of rising hunger and political instability in food-scarce countries in Africa, the Middle East and beyond. President Nicolas Sarkozy has put food security among the top objectives of France's G20 leadership, but the G20 has yet to adopt a convincing line of attack.

Global food supplies are being stretched by increased growth. China's economy is roughly 20 times larger than at the start of market reforms in 1978; India's roughly four times larger than in 1991, when its reforms began. The world's resource demands are soaring and will soon outstrip capacity without a shift to sustainable technologies and decisive action to stabilise population. Human-induced climate change is making things worse: heatwaves in Russia and Ukraine this summer sharply cut grain production and exports, while northern China is facing a potentially massive 2011 drought, which could severely aggravate the global grain shortfalls.

The first and easiest step to counter these problems would be to end the US Federal Reserve's policy of quantitative easing. This might seem peripheral, but the Fed is pouring oil on the commodity fire, ignoring commodity and asset price signals, and risking another boom-bust cycle.

More fundamentally, the G20 must promote increased food production, especially in the poor and food-deficit regions. Africa should be top of the list. Much of the continent is on the edge of extreme hunger, but it also happens to be amenable to a significant rise in food production. The yield of 1.1 tons per hectare in tropical Africa is less than a third of the yields achieved in Asia or Latin America. Part of this "yield gap" is made up by about 25m tons of cereal imports. The rest of the gap, alas, is felt in chronic hunger.

Leading agronomists have been saying for years that tropical Africa can produce vastly more food; enough to end food insecurity and import dependence. The agronomic path to doubling cereal production is also clear: modest government help to smallholders would provide improved seeds, fertiliser and small-scale water management. Farmers could double, even quadruple, food production. African governments have prepared plans to do this and won promises of support from the group of eight leading economies at the 2009 L'Aquila summit.

The real remaining barrier is financing: impoverished smallholders lack creditworthiness to get market loans. Simple government programmes, for example, vouchers to provide farmers with subsidies, could enable a boom in production. Malawi, for instance, quickly doubled its national food production using such an approach. Others are desperate to do the same, and are appealing for the promised G8 help.

At their meeting, the G20 finance ministers can still choose to strike a blow for food price stabilisation and poverty alleviation if they follow up on the L'Aquila promises. They pledged $22bn, over three years, including a special fund at the World Bank, called the Global Agriculture and Food Security Program, to administer much of the money. That fund has received a pitiful $350m.

It seems likely the G8 promise was a mirage. President Barack Obama will struggle to deliver a single dollar through the recklessly insular Republican-dominated House of Representatives. France, the G20 leader, has cut back on its own aid promises. Italy, host to the L'Aquila summit, is in a vertiginous political crisis. But there is hope. China, in particular, has reason to lead. It has nearly $3,000bn of foreign reserves, a huge current account surplus and the growing likelihood of having to increase food imports. The Middle East, too, has a vital stake in bolstering Africa's capacity to feed itself. So while Paris will host today's meeting, eyes will be looking eastward in hope of bold leadership. For the sake of the world's poorest people, let us hope they find it.

The writer is director of the Earth Institute at Columbia University