Welcome to the Sixth Mass Extinction

Aging and solitary, a rhino named Sudan became a minor celebrity in 2015 for a sobering reason: He is the last remaining male northern white rhinoceros. Since he’s too old to reproduce, and his female counterparts are unable to give birth, the survival of his species hinges on human intervention: fertilizing eggs with frozen sperm and implanting the embryo in a young southern white rhino. But the odds of success are low, and Sudan likely won’t live to see the outcome. — Alyssa Favreau | Jan Stejskal/Ol Pejeta Conservancy