Save the Children is to be applauded for reminding us all of one of the most extraordinary and humiliating aspects of living in the modern world: child hunger. Drawing a parallel with the fight to abolish slavery, the Ghanaian philosopher Kwame Anthony Appiah recently asked what future generations will condemn us for. One sure candidate is the needless human carnage wrought by hunger. Some 850 million people (one in eight of the world's population) go to bed hungry every night. Many of them are children, for whom early hunger leaves a lifelong legacy of cognitive and physical impairment. The human and economic waste is horrifying.

Such hunger is not due to a shortage of food – globally there is enough to go round and if (a big if) we make the right decisions now, we can continue to feed the world despite population growth and climate change. By some estimates, stopping the waste of food after harvest due to poor storage or transport infrastructure, and then in our own kitchens, could free up half of all food grown. The number of overweight and obese people in the world, suffering their own health problems, including a sharp rise in heart disease and diabetes, is roughly equal to the number of hungry people. That highlights one of the underlying causes of hunger – extreme levels of inequality, both within and between countries.

Ending hunger is entirely feasible (indeed, once achieved, the only question will be why it took us so long). It requires action at several different levels. At a national level, progressive governments in Brazil and Ghana have shown how to cut hunger sharply, through cash transfers to poor people, raising the minimum wage and investing in smallholder farmers (especially women), who both produce food, and are some of the poorest and hungriest people in the Alice in Wonderland world of a brutally unfair farming system.

That focus on national decisions and national politics highlights how fast the world is changing. In many cases, aid is no longer the main story – countries like India, growing at 8% a year and with a mushrooming middle class, need to take responsibility for their hungry masses, introducing proper taxation and effective social services to end hunger and malnutrition. Oxfam is working with people's organisations within the country to bring that about. Elsewhere, though, international food aid remains essential, but should be improved, for example by ending the waste and delay of transporting food thousands of miles from donor countries and giving cash instead.

Beyond supporting aid for food and agricultural investment, what else can we in the well-fed countries do? Start by putting our own house in order. The rich countries are part of both the solution and the problem. Europe and America's push to reduce their dependence on imported oil and gas has led them to introduce targets and subsidies for biofuels, but these compete directly with food production, forcing up prices for poor people. Rich country greenhouse gas emissions are driving climate change at a pace that outstrips even the most pessimistic projections of the climate modellers, and there are few signs of governments agreeing (still less achieving) the kinds of reductions needed to avoid catastrophic temperature rises that will particularly harm tropical agriculture. We urgently need an international effort to find a way to feed the planet's growing population without destroying its ecosystems, yet current investments are feeble.

Hunger is both a cause and a symptom of poverty. Damaged bodies and brains are a moral scandal and a tragic waste of economic potential. That hunger exists at all shows the urgency of redistributing income and assets to achieve a fairer world. Providing the additional calories needed by the 13% of the world's population facing hunger would require just 1% of the current global food supply. That that redistribution has not already taken place is truly something to be ashamed of.

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