Underinvestment and market failures have trapped many countries in a vicious cycle of low productivity and exposure to price hikes, says Olivier de Schutter, the UN special rapporteur on the right to food

How can we feed the world and still save the planet?

Food has become subject to one of the sharpest global debates, with rising anxiety about how the world's growing population is going to feed itself. Increasingly, Olivier de Schutter, the UN special rapporteur on the right to food, is establishing himself as one of its key protagonists with an unapologetically radical agenda.

In London this week to give evidence to a UK parliamentary working group on food and agriculture, he explained the challenge he is putting to the donors and the international community.

Chronic underinvestment in agriculture over the last 20 years combined with trade liberalisation has trapped many developing countries in a vicious cycle of low agricultural productivity and dependence on cheap food imports, he argues. The one exacerbates the other as local farmers struggle, and fail, to get a decent price for their produce in competition with imports, which have often benefited from government subsidies.

Local farming goes into steep decline leading to migration to the cities. This is a serious market failure.

Faced with large hungry (and often jobless) urban populations, government policy is driven by the need to keep food cheap at all costs or risk political instability, such as the rioting seen recently in countries such as Algeria.

"In the short term, lower import tariffs to let in food ensure urban populations are fed, but in the long term it is a disaster because local farmers can't compete," says de Schutter, adding that cheap food imports make the country extremely vulnerable to price hikes in the global markets – such as those we are now seeing.

"Since the early 1990s, the food bills of developing countries have increased by five- or six-fold," says de Schutter. "This addiction to cheap food leads to balance-of-payments problems and then political instability. It deprives countries of their abilities to feed themselves."

This situation has skewed the politics of countless countries where the priority has been to maintain calm in urban areas while squeezing any value they can from farmers. Farmers are marginalised politically and become increasingly poor, further accelerating the migration to cities.

Donors are finally recognising the need to invest in agriculture, but the danger is that they put money into monoculture cash crops for export, a strategy that that has no impact on improving food security for the poorest, argues de Schutter.

Another major mistake being made by donors, he adds, is to offer inputs to farmers such as subsidised fertiliser. This works in the short term but is not sustainable in the longer term because the price of fertilisers are linked to the rising price of oil, and the urgent task is to decouple agriculture from oil.

The environmental challenge is huge. "A third of all greenhouse emissions come from agriculture, so we need to focus our efforts on an agriculture which does not degrade the soil and which increases carbon capture," he explains, adding that he will be presenting a paper on agroecology to the UN Human Rights Council in March.

He wants donors to move away from the model of subsisidised fertilisers and seeds – which he calls "private goods", to supporting "public goods" such as better infrastructure, strengthening local markets, ensuring access to credit and building storage capabilities. Much of this needs farmers to organise themselves to really bring benefits to rural areas.

"Farmers' co-operatives emerged from the bottom-up in the 90s, and they now need to move up the value chain into processing and packaging. Farmers can get a better price if they organise together. And if they are organised, then governments have to engage with them. Farmers need a greater voice in the political process otherwise they don't get consulted and are cheated," he says.

But he acknowledges that this is not always a popular message. In many countries governments are wary of a strong, well-organised farmers' co-operative movement that could threaten their strategy to feed urban populations.

The challenge is huge because in the last 25 years state agricultural extension services have been dismantled, largely at the behest of structural adjustment programmes, and farmers have been left to fend for themselves. To increase productivity and introduce agroecology techniques in places such as sub Saharan Africa requires institutions that can disseminate knowledge into remote rural areas. This is no easy task.

Finally, de Schutter has one other urgent recommendation. The G20 in May will be considering measures to manage food-price volatility and he believes that food reserves are an essential tool.

"My view is that food reserves could be used to support the income of farmers, buying at a good price and then make food affordable during times of rising prices. If a food reserve is well managed and transparent, it could limit volatility and secure incomes," he says.

He points out that China now has huge food reserves in wheat, maize and rice that can shield the population from price spikes. There are ongoing negotiations to arrange regional collaboration across south-east Asia and to mutualise national food reserves. Similar discussions took place last December in West Africa. The G20 must put greater impetus behind such regional co-operation.