The Mexican women who defied drug-dealers, fly-tippers and chauvinists to build a thriving business

Graciela ‘Chela’ Olachea, one of Las Guardianas. None of the women were well educated but they knew they risked losing everything unless they protected the environment Photograph: Benjamin Soto/The Guardian

Ahead of the small boat, as it bobs on the waters near La Paz in the Mexican state of Baja California Sur, is a long line of old plastic bottles strung together on top of the waves. Underneath them are as many as 100,000 oysters, waiting to be sold to the upmarket hotels down the coast.

Cheli Mendez, who oversees the project, pulls a shell up from below, cuts it open with a knife, and gives me the contents to try: a plump, tasty oyster. Mendez is one of a group known as Guardianas del Conchalito, or guardians of the shells, and theirs is the first oyster-growing business in the region run entirely by women, she says.