Half of the world’s turtle species are in danger of extinction, according to scientists gathered at a conference in Nevada. The main cause of the crisis is human consumption of the critters, for both food and traditional medicine. The Chinese in particular seem to have an insatiable appetite for turtles, and scientists believe that several Chinese species identified in the last two decades may already be extinct. China imports large numbers of turtles from Bangladesh, Indonesia, and Vietnam. More than 7 million turtles are exported annually from the U.S., where many freshwater species have little or no protection.