The leaves on the tea bushes in the plantations of the Kenyan region of ­Kericho are a sickly shade of green. In the small town of Narok, the river has become toe-deep, a giant puddle that residents use as a communal car wash. Sun-beaten rhinoceroses loaf across Nakuru national park, their ribs jutting out from thinning bodies.

All three – cash crops, ­rivers and wildlife– are crucial to Kenya’s long-term viability. But they are being starved of moisture because of the degradation of the Mau forest that serves as the drainage basin at the country’s ecological heart.