18,000 portraits in 20 years: The man racing to photograph life on Earth

Joel Sartore photographs like he's running out of time. Twenty years into his monumental project, the National Geographic Photo Ark, he's taken portraits of over 18,000 species around the world. At least one of those species has since become extinct – but he holds out hope that his photography can help save others, as part of the Rolex Perpetual Planet Initiative. #calltoearth #perpetualplanet