American freshwater turtles are being harvested at an unsustainable rate to feed the voracious appetite for turtle meat in Asia, warns the Center for Biological Diversity in Tucson, Arizona.

Earlier this month, the organization petitioned eight U.S. states (Arkansas , Iowa, Kentucky, Louisiana, Missouri, Ohio, South Carolina, and Tennessee) to ban turtle hunting in all public and private waters. Meanwhile, Florida's Fish and Wildlife Conservation Commission has proposed its own ban, and will present a draft of the rules at a Commission meeting next month. The Commission recently estimated that 3,000 pounds of softshell turtles are flown out of Tampa International Airport every week, enroute to food markets in Asia.

According to data collected by the CBD, turtle harvesting has increased dramatically over the past decade. Harvesters in Iowa, for example, collected 235,000 pounds of turtles in 2007, up more than 800 percent from the 29,000 pounds collected in 1987. In Arkansas, nearly 600,000 turtles were collected between 2004 and 2006.

While some freshwater species are endangered in the U.S., protection is difficult since many species look similar to untrained eyes. Alligator snapping turtles (Macrochelys temmickii), which are protected by state law in Iowa and Illinois, look almost exactly like common snapping turtles (Chelydra serpentina), which are not endangered.

So why is turtle collection from the wild such a problem? "Because freshwater turtles are long lived (some may reach 150 years of age), breed late in life, and have low reproductive and survival rates, they are highly vulnerable to overharvest," the CBD said in a statement.

Would banning the wild-turtle trade help? Supporters of such a move point to Texas as an example. The state outlawed most turtle harvesting two years ago, and as a result saw Asian exports through Dallas/Fort Worth International Airport drop from 122,610 turtles in 2004 to just 8,882 in 2007, according to U.S. Fish & Wildlife Service numbers cited by the Dallas Morning News. Commercial harvesting of three turtle species from private waters is still allowed under Texas law.

Images: Turtle soup and Alligator snapping turtle (Macrochelys temmickii), both via Wikipedia