Maryland’s Poplar Island is home to a program to foster the population growth of terrapin turtles in the Chesapeake Bay. The trade in freshwater tortoises and turtles, including Maryland’s famous terrapin, was curtailed by an international wildlife summit. (Sarah L. Voisin/THE WASHINGTON POST)

The United States, in a conservation victory Friday, won the approval of an international wildlife summit for stronger protections for endangered freshwater tortoises and turtles, including Maryland’s iconic diamondback terrapin.

Working with China and Vietnam, a U.S. delegation that included Fish and Wildlife Director Daniel M. Ashe persuaded international wildlife officials to protect 47 species of tortoises and turtles in Asia and the United States by banning the commercial trade of some and placing quotas on the sale of others.

More than half the world’s freshwater tortoises and turtles face extinction, yet they are hunted for food, pets and trinkets made from their shells, mostly in Asia. Turtles are also killed by urban sprawl, boat strikes and crab traps, particularly in Texas, Maryland and other Gulf and Mid-Atlantic states. Crab bait also lures turtles.

The adoption of one of the Obama administration’s top priorities at the wildlife summit in Bangkok — the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) — came on the heels of the defeat of a proposal to increase protections for polar bears.

Working with China and Vietnam was “the big difference” in outcomes, Ashe said. “CITES parties always look for agreement.” On the polar bear, he said, “We did not have that.”

While the United States and China engage in so-called panda diplomacy, with the Chinese loaning the cherished bear to U.S. zoos, they are at odds over harvesting sharks for fins used to make soup and allowing too much illegal elephant ivory to enter the country for display in homes and businesses as ornately carved sculpture.

The problems of freshwater turtles intensified when they became the focus of hunters and collectors after CITES banned the commercial trade of several other types of turtles, including marine turtles.

Bryan Arroyo, head of the U.S. delegation at CITES, called the outlook for Asian turtles grim. Officials in Bangkok adopted a proposal from Vietnam and the United States to transfer big-headed Asian turtles from a protection category that allows commercial trade under a quota to one that bans it.

Another turtle species, the Roti Island snake-neck turtle, was kept in the category that allows commercial trade under a quota, but the quota for the export of such turtles caught in the wild was lowered to zero.

The new protections for Asian turtles all but ensure that traders will now target freshwater turtles in the United States.

To head that off, the United States proposed to list three native species: the spotted turtle, Blanding’s turtles and the diamondback terrapin, the University of Maryland’s mascot. CITES puts the three species in the category that allows commercial trade, but with a strict limit to protect them from being over-harvested.

U.S. trade data show that 26,342 diamondback terrapins were exported between 1999 and 2010, mostly to Asia. Twenty-seven percent of them were taken from the wild. The others were bred or farmed.

Exports of diamondbacks from the United States increased from below 1,000 per year in 1999 to 3,000 per year by 2010.

Other U.S. priorities at CITES include stronger protections for elephants, rhinoceroses, sharks and manta rays and the creation of a passport for musical instruments made in the past with animal parts that are now protected. Traveling abroad with the instruments requires a CITES permit that can take months to receive approval.