Food riots are erupting all over the world. To prevent them and to help people afford the most basic of goods, we need to understand the causes of skyrocketing food prices and correct the policies that have fueled them.

World food prices rose by 39 percent in the last year. Rice alone rose to a 19-year high in March — an increase of 50 percent in two weeks alone — while the real price of wheat has hit a 28-year high.

As a result, food riots erupted in Egypt, Guinea, Haiti, Indonesia, Mauritania, Mexico, Senegal, Uzbekistan and Yemen. For the 3 billion people in the world who subsist on $2 a day or less, the leap in food prices is a killer. They spend a majority of their income on food, and when the price goes up, they can't afford to feed themselves or their families.

Analysts have pointed to some obvious causes, such as increased demand from China and India, whose economies are booming. In the last 30 years, developing countries that used to be self-sufficient in food have turned into large food importers.

Rising fuel and fertilizer costs, increased use of biofuels and climate change have all played a part.

But less obvious causes have also had a profound effect on food prices.

Over the past few decades, the United States, the World Bank and the International Monetary Fund have used their leverage to impose devastating policies on developing countries. By requiring countries to open up their agriculture market to giant multinational companies and by persuading them to specialize in exportable cash crops such as coffee, cocoa, cotton and even flowers, Washington, the IMF and the World Bank created a downward spiral.

They made matters worse by demanding the dismantling of marketing boards that kept commodities in a rolling stock to be released in event of a bad harvest. These boards shielded both producers and consumers against sharp rises or drops in prices. But the shield is no longer there.

Here's what we must do to prevent an epidemic of starvation from breaking out.

First, it is essential to have safety nets and public distribution systems put in place. Donor countries should provide more aid immediately to support government efforts in poor countries and respond to appeals from U.N. agencies, which are desperately seeking $500 million by May 1.

Second, we should help affected countries develop their agricultural sectors to feed more of their own people and decrease their dependence on food imports.

We should promote production and consumption of local crops raised by small, sustainable farms instead of growing cash crops for Western markets.

And we should support a country's effort to manage stocks and pricing so as to limit the volatility of food prices.

To embrace these crucial policies, however, we need to stop worshipping the golden calf of the so-called free market and embrace, instead, the principle of food sovereignty. Every country and every people have a right to food that is affordable. When the market deprives them of this, it is the market that has to give.