It seems almost beyond belief that more than 200 girls can be kidnapped from a school in northern Nigeria, held by the terrorist group Boko Haram, and threatened on a video – shown worldwide – with being sold into slavery by their captors.

The disbelief is compounded by today's news that, overnight, eight more girls have been kidnapped by suspected Boko Haram gunmen in north-east Nigeria. This tragedy touches the hearts of everyone, evoking a feeling of revulsion not only at the danger and loss of freedom itself, but at the assumption that for young girls their destination must be forced marriage and servitude, not education.

There is rightly anger that so little has been done by the Nigerian government to find the girls, and that those who have demonstrated in huge numbers against President Goodluck Jonathan have themselves been accused of causing trouble or even temporarily arrested.

But we should be wary of the narrative now emerging. This follows a wearily familiar pattern, one we have already seen in south Asia and the Middle East, but that is increasingly being applied to Africa as well.

It is the refrain that something must be done and that "we" – the enlightened west – must be the people to do it. As the US senator Amy Klobuchar put it: "This is one of those times when our action or inaction will be felt not just by those schoolgirls being held captive and their families waiting in agony, but by victims and perpetrators of trafficking around the world. Now is the time to act."

The call has been for western intervention to help find the girls, and to help "stabilise" Nigeria in the aftermath of their kidnap. The British government has offered "practical help".

Yet western intervention has time and again failed to deal with particular problems and – worse – has led to more deaths, displacements and atrocities than were originally faced. All too often it has been justified with reference to women's rights, claiming that enlightened military forces can create an atmosphere where women are free from violence and abuse. The evidence is that the opposite is the case.

Women's rights were a major justification for the Afghanistan war, launched in 2001, when Cherie Blair and Laura Bush supported their husbands' war as a means of liberating Afghan women. Today, with millions displaced and tens of thousands dead, Afghanistan remains one of the worst countries on earth for women to live, with forced marriage, child marriage, rape and other atrocities still occurring widely.

And western intervention is already firmly embedded in Africa. It does not have the same profile as in Afghanistan or Iraq, because past wars have made it harder to put boots on the ground. But Barack Obama has his military forces engaged in West Africa through their Predator drone base in Niger, which borders northern Nigeria. It also borders Mali, the scene of recent French and British interventions, and Libya, object of a disastrous western bombing campaign in 2011 that has left that country in a state of civil war and collapse.

US drones also operate in Djibouti, Ethiopia and just across the Red Sea in Yemen. The west has been engaged in proxy wars in Somalia in recent years.

If Islamism is now a threat to western interests in growing parts of Africa, it is one that they have played a large part in creating.

But there is another war going on in Africa: economic war. A continent so rich in natural resources sees many of its citizens live in terrible conditions. In President Jonathan's Nigeria, economic growth has not trickled down to the poor. Healthcare and education are beyond the reach of many.

There is widespread corruption, yet weapons and armies are paid to protect the wealthy and the foreign companies, such as Shell, that want to access the country's resources, especially oil. This corruption and inequality is not separate from the role of the west, but an integral part of a system that is prepared to go to war over resources such as oil and gas, but will not go to war on poverty or to provide education for all.

It is this background that informs the terrible plight of the kidnapped girls in Nigeria. It will not be improved by more western weapons and armies on the ground or in the air.