Rows of women sit low to the ground in the central Nigerian town of Bida, holding sticks that rise and fall in a steady rhythm.

The air is filled with the dull thud of wood against shell - the dark sun-dried, brown exterior of the shea fruit giving way to reveal the hard nut inside.

The produce, harvested in the wild after falling from the trees, is being readied for the middlemen to collect and then supply factories.

These are the early stages of a process that ends with shea butter on the counters of cosmetics shops across the world - as well as in other products such as chocolate.

Women in Nigeria - which accounts for nearly 40% of the world's shea crop - are at the heart of the industry, but their livelihoods have been threatened by a dramatic recent change in government policy.

In late August, in the midst of the harvest season, the authorities announced a six-month ban on the export of the raw nut.

The intention was to boost local production of the finished butter - as opposed to the nuts - and so increase the amount of the profit which stays in Nigeria. But the sudden shift has led to a fall in demand for the shea nut as there is not enough local capacity to process all of the country's harvest.

The reduction in demand has led to a collapse in the price of shea nuts, which in turn has meant that the income from their work is no longer enough for the women to live on.

In Niger state alone, where Bida is located, hundreds of thousands of women are believed to depend on some part of the shea production chain.

Hajaratu Isah, 40, who has been preparing the fruit all her adult life, tells the BBC that the government's new policy has left her, her family and other women in the community struggling to survive.

Ms Isah lives with 11 other people, including her six children, and has a recurring eye condition, conjunctivitis, that flares up when the weather changes and requires regular medication.

"We are feeling hopeless. We cannot eat, we do not have money, and our children can no longer go to school," she says.

Before the export ban, she earned up to 5,000 naira ($3.30; £2.45) a day, enough to cover school fees, which she paid........

© BBC