At low tide, the white sands of Mombasa’s northern beaches stretch nearly half a mile out to sea. The shore is framed by palm trees, run-down hotel buildings, and wooden stalls selling fried cassava chips and cold Coca-Cola; in the distance, the vivid blue of the Indian Ocean is painted with the faded...

“Take care for the tree,” a boy calls out calmly as a gnarled branch whooshes inches from my head.

Good thing he gave me time to duck, I say to myself, readjusting my position on top of the truck so the next tree doesn’t cut it so close. In the ink black of this midnight desert, the waning...