Experts estimate that half of our planet's species will become extinct by the year 2100. National Geographic photographer Joel Sartore is trying to change those projections. He aims to inspire people to care more about the animals we share Earth with through stunning photography. To date, Sartore has photographed more than 5,000 species in zoos and preserves around the world. His goal is to complete portraits of the world's 12,000 captive species and to compile them in his Photo Ark project-before they disappear.