Today an estimated 13 percent of birds are threatened, according to the International Union for Conservation of Nature. So are 25 percent of mammals and 41 percent of amphibians, in large part because of human activity. Hydropower and road construction imperil China's giant pandas. The northern bald ibis, once abundant in the Middle East, has been driven almost to extinction by hunting, habitat loss, and the difficulties of doing conservation work in war-torn Syria. Hunting and the destruction of wetlands for agriculture drove the population of North America's tallest bird, the whooping crane, into the teens before stringent protections along the birds' migratory route and wintering grounds helped the wild flock build back to a few hundred. Little brown bats are dying off in the United States and Canada from a fungus that might have been imported from Europe by travelers. Of some 300 species of freshwater mussels in North America, fully 70 percent are extinct, imperiled, or vulnerable, thanks to the impacts of water pollution from logging, dams, farm runoff, and shoreline development.