South Sudan’s and Yemen’s are the most clearly avoidable famines. But Nigeria’s comes close. There, a famine may already have happened late last year—nobody is sure, because it was too difficult to gather data. Over the past two years, as the Nigerian army has clawed back towns in the north-east of the country from Boko Haram, an Islamist group, starving people have poured in from nearby villages. The population of Maiduguri, the capital of Borno State, has doubled as almost 800,000 hungry displaced people have moved into makeshift shelters there. Perhaps as many remain in areas that aid workers cannot reach. Part of the reason is that the Nigerian army does not allow them in. But most aid agencies are reluctant to deliver food in areas held by murderous jihadists anyway. “You don’t really have someone to negotiate access with,” says Peter Lundberg, the UN’s deputy humanitarian co-ordinator in Nigeria. Still, in the areas that the army has secured, malnutrition has fallen sharply.

Only in Somalia, which in 2011 was the last country to suffer an officially declared famine, does the risk of starvation derive in large part from weather. A drought afflicting much of east Africa has wrecked crops and killed animals. “I am 73, but I have a very sound memory and what I am saying is true: this is the worst,” says Mohamed Yahir, a farmer in the south-western city of Baidoa, whose past three harvests have failed and whose livestock has all died.

This year’s Somali famine may be easier to tackle than the one in 2011, when al-Shabab, a vicious Islamist militia, held a much larger part of the country. Now, aid is at least trickling in. But a hangover from the former troubles remains. Without much of a state, and men with guns everywhere, much of the Somali hinterland is still too dangerous and expensive for aid to get to where it is needed.

A challenge to the world

What does the return of famine mean for international organisations such as the UN and for Western countries, which provide most of the finance for emergency aid? The UN’s humanitarian co-ordinator, Stephen O’Brien, has said that this year is “the largest humanitarian crisis” since 1945. Not so: China’s famine during the Great Leap Forward of 1958-62 caused between 20m and 55m deaths. The situations in Yemen and South Sudan are not yet as shocking as the Ethiopian famine of 1984, when hundreds of thousands of people starved even as the country’s military regime taxed aid and spent the proceeds on a grand celebration of the success of Marxism.

Still, today’s famines are real and severe. Sadly, in all four countries, the global response has been inadequate. Western governments and aid agencies have invested large amounts of money and energy in providing assistance, but they have done little to address the political problems that cause starvation. In South Sudan and Yemen they acquiesce to the obstacles that governments place on distributing aid.

Though there are 17,000 peacekeepers in South Sudan, with a Chapter 7 mandate (which authorises the use of force to protect civilians), the UN is loth to criticise the government that hosts its mission. Yet the government is responsible for most of the violence, and the consequent displacement and starvation. “They want these people dead,” notes a UN official who would never say so publicly. In December the head of the Norwegian Refugee Council was expelled. Both the UN and other Western governments seem to have decided that it is better to shut up than to be kicked out and lose access to the people they are trying to help.

The situation in Yemen is more squalid. There, the weapons used to bomb Houthi rebels are mostly supplied by Britain and America; America has given logistics and intelligence support to Saudi Arabia’s war effort for two years. Yet diplomats tiptoe round criticism of the Saudi-led coalition. They insist that they are pushing for more aid to be allowed in, but shy away from sanctions that might force leaders to comply. One UN official describes a “conspiracy of silence” about Yemen.

That is partly true of Nigeria, too. The release of some of the girls kidnapped by Boko Haram shows that it is possible to negotiate with the jihadists. Yet there is “no conversation” about aid crossing front lines, according to one aid worker. The Nigerian government’s rules about where aid agencies can go are simply accepted, even though starvation has been a weapon of choice for defeating insurgencies in Nigeria since the war over Biafran secession in the 1960s.

According to Alex de Waal of Tufts University, formally declaring a famine is a “political act” that is intended to produce action. “This will be a test case for whether it works,” he writes. In 2011, when Somalia was last hit by drought, the declaration of famine forced America to change the rules that were stopping aid agencies from supplying food to territory held by al-Shabab.

Yet few want to intervene. In 1992 George Bush senior sent American troops to Somalia to force the local warlords to let aid in. Bill Clinton pulled the troops out after some of them were killed, and since then military intervention to end famine has gone out of fashion. In South Sudan, a country created by American political pressure, even introducing an arms embargo or sanctions against president Salva Kiir has proved impossible. Similarly, Britain and America show no sign of wanting to force Saudi Arabia or its allies to curtail their war in Yemen. But there is no alternative plan, either. And so famine, which should have been abolished throughout the world by now, is coming back.