The Sahel is the borderland of 3 million square kilometres between the Sahara Desert and the African savannah and forest lands further south. Much of this huge area is inhospitable. Insurgencies are common, as are migration and smuggling, jobs being as rare here as effective government interventionstate power extends only fitfully, and the region resists attempts to subdue militants, people-traffickers, nomadic herders or anyone excluded from power.

The Western Sahel's fragile states face growing popular discontent, complicated by both climate change and military intervention by France and other powers. Mali is the epicentre of the Sahel crisis: Morten Bs charts the history of Mali and its fragile neighbours, identifying their current frailty as unsettled states, without legitimate social contracts or political consensus. This in turn has generated competing identities and economic interests, which spill over into resource conflicts over grazing, water, mineral reserves or smuggling routes. Such local contests have been manipulated by elites intent on their own preservation, and appropriated by jihadi insurgents eager to integrate into local communities.

What will happen if all the ingredients of this perfect storm coalesce? What are the ramifications for the Sahel, its neighbours, Europe and the wider world?