Among African animals, the black rhino is one of those most threatened with extinction. The primary reason is poaching: A black rhino’s two horns go for as much as $50,000 on the black market for use as Arab dagger handles or Oriental medicines.

(Text adapted from "A Personal Vision of Vanishing Wildlife," April 1990, National Geographic magazine)

(Photograph shot on assignment for, but not published in, "A Place for Parks in the New South Africa," July 1996, National Geographic magazine)