The last passenger pigeon died in the Cincinnati Zoo one hundred years ago today. A species that once numbered in the billions, spectacularly darkening the sky as huge flocks flew overhead, was hunted to extinction in a mere half century. For the lure of a cheap meal, the death sentence was announced and the trigger pulled, heedless of the costs to nature’s diversity and to posterity. We who live in that impoverished future would do well to pause in memoriam to Martha (for that last bird had a name) and remember that the killing fields go on. Indeed, bullets of destruction far more ubiquitous and subtle than once faced by her kind—the multitude of human impacts on the natural world— now target millions of other species. A fitting remembrance would be a redoubling of efforts to slow and reverse the sixth great extinction, the only one caused by a fellow species.