We have entered into the sixth great extinction of the earth’s species, according to many biologists. The previous five were caused by natural events—meteorite impacts and global temperature change—but this latest is decidedly human-generated, primarily through habitat destruction. Around 20 percent of all species on the planet are now threatened with extinction. In this collection (with descriptions by conservationist Jonathan Baillie), photographer Tim Flach captures the personality and character of some of the earth’s most threatened denizens. He looks into the eyes of Philippine eagle; captures a curled-up pangolin—the most heavily trafficked mammal in the world; and immortalizes a forest full of glowing fireflies. Each image is a reminder of all we could lose if we don’t stand up for these creatures. –Andrea Gawrylewski