Last fall, the United States and China came together to crack down on the ivory trade. Both countries—the two biggest markets for illegal ivory—banned the import and export of the stuff, hoping to save some of the elephants being poached for their tusks. No more alabaster piano keys, no more intricately carved jewelry. At least not made of ivory. In the absence of elephant tusks, trinket makers in China are shifting to a new medium. And they’re threatening a new species in the process.

Giant clamshells—made of lustrous calcium carbonate, sometimes streaked with green or gold, and weighing up to 450 pounds—are the new quarry of fishermen in port towns like Tanmen, on the southern island province of Hainan. Harvesting used to be an art: A man dove, held his breath, teased the clam, and wrestled it to the surface. But with the help of new technology and bolstered by the ivory ban, giant Tridacna clams have become a full-blown industry in parts of China.

In the afternoon, trawlers haul hundreds of clams back to port, harvested with the help of scuba tanks, new breathing techniques, and outboard motors that the fishers rev to kick up sand around reefs. Craftsmen carve the shells in their workshops, selling the scrimshaw in hundreds of local shops. The “jade of the sea” can fetch prices upward of $12,000 per clamshell, supporting around 100,000 people on Hainan. “Even a few years ago, there were three, maybe four ships devoted to clam fishing,” says Zhang Hongzhou, an expert on the giant clam trade at Nanyang Technological University in Singapore. “Now, there are dozens.”

But the trade is taking a toll on the reefs. The fishermen aren’t just killing the giant clams—which are already extinct in some places. It turns out when you use rev your motor on a coral reef, you bust up its whole ecosystem. Clam flesh is a vital source of food for predators and scavengers. Their huge shells—up to four feet wide—serve as reservoirs for small invertebrates like tubeworms and a special phytoplankton called zooxanthellae. Without the clams’ protection, grazing animals quickly overfish the phytoplankton, eliminating a crucial food source for coral and other creatures in the reef’s ecosystem.

That’s not all. Even after they die, the clams function like an underwater giving tree. Scavengers pare the clam flesh away, leaving the calcium carbonate skeletons standing in an upright position. “I’ve seen new animals come in and colonize them on my dives,” says Neo Mei Lin, a marine biologist at the National University of Singapore. Later, the reef incorporates the shell material into its framework.

As fishermen whittle away the reefs closer to Hainan, these underwater poachers are spreading into areas contested by Taiwan and the Philippines in the South China Sea. On a visit to Tanmen in 2013, Chinese president Xi Jinping encouraged the fishermen to go farther and build bigger ships. “But I don’t think even Xi Jinping knows how much they’re harvesting,” says Zhang.

When the ivory ban went into effect, most Chinese citizens supported it: In one survey, 95 percent of respondents supported the ban. But it’s harder to care about the fate of a clam than a giant African elephant. On the trade website Tridacna Online, carvers and tradesmen gush about the industry’s growth potential. And on Alibaba’s popular business-to-business e-commerce site,, peddlers continue to move large volumes of Tridacna toys.

While the Tanmen government officially banned the harvesting of giant clams in March last year, shops are still thriving. Smugglers can still get the clams over the border and into the shapes those same ivory-hating consumers in Beijing, Shanghai, and Guangzhou adore: bracelets, soap dishes, bookends, and luxury sets for the game of Go.

Neo Mei Lin and her colleagues are working to raise awareness of the growing threat in the South China Sea. A colleague at the National University of Singapore noticed that the same satellite maps being drawn up to illustrate the Chinese military’s push to create artificial islands could be used to highlight damaged reefs. Combined with data from marine biologists close to the fishing sites, Neo is mapping out which populations are closest to extinction.

By sharing these findings and images on Chinese discussion forums, Neo hopes to avoid the fate the giant clams suffered in Singapore: The local population was extinct by the close of the 1800s when British and other colonizers scooped the clams up for display. But ultimately, it will be difficult to save giant clams without another sea change in Chinese public opinion. UN conventions protect Tridacnas from poaching—but officials can only enforce treaties if China exports the clams. For now, the shells are staying inside the country. It might just take a foreign taste for clams to save the species.

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Blame an Ivory Ban for China’s Vanishing Giant Clams