Save the Shark, Save the World WASHINGTON - In 1971, an unexpected series of interactions between international table tennis players turned out to be the first indication of China's willingness to engage with the United States after decades of estrangement. It presaged President Richard M. Nixon's watershed visit to the country. This unlikely set of events later came to be known as Ping-Pong diplomacy. Now we could be witnessing the equivalent - call it shark-fin diplomacy - by which China signifies to the world that it is ready to step forward into new arenas of environmental protection. The world's most populous nation faces serious issues: Air pollution has become a growing concern, with recent emissions of particulate matter so high in the northeastern city of Harbin that its official website stated, "You can't see your own fingers in front of you." Meanwhile, supplying wood for more than 80 billion sets of disposable chopsticks each year has decimated forests, and water pollution renders large sections of major rivers unfit for drinking and swimming. International concerns also loom large: Greenhouse gas emissions don't respect borders. And trade in endangered plants and animals threatens to undermine the global ecosystems. Oceans, in particular, are at great risk because they are increasingly overfished, polluted and stressed by rising temperatures and acidification resulting from climate change. Fortunately, China has begun to take steps. The country consistently ranks No.1 or 2 in attracting private investment in clean energy. It has a national renewable-energy standard and has adopted some of the strongest vehicle fuel efficiency regulations on the planet. People have been called on to reuse chopsticks. And the government has announced a policy that will help stem the killing of a crucial ocean species: sharks. The new attitude toward sharks is particularly instructive, since shark-fin soup has long been considered a delicacy in China, served at banquets and weddings. But its popularity has contributed to a sharp decline in the worldwide populations of these apex predators, which help maintain healthy marine ecosystems. It is estimated that 100 million sharks are killed each year, primarily for their fins. The first sign of a shift came in February, when President Xi Jinping issued instructions to all levels of the Chinese government that high-cost ingredients, including shark fins and specialties culled from other protected species, were not to be consumed at official meetings. In large part, this regulation stems from a crackdown on corruption and lavish spending, since shark-fin soup is expensive and has often represented a display of wealth. But language in the notice also acknowledged the importance of promoting "green, eco-friendly and low-carbon" consumption habits. Then, in September, came news from Hong Kong that the city government would ban shark fins from official functions there to "demonstrate its commitment to green living and sustainability." Since 50 percent of the world's annual trade in shark fins passes through Hong Kong, the move was highly encouraging. Together, those decisions are expected to reduce the global trade in fins and aid conservation initiatives, such as the establishment of shark sanctuaries. In those sanctuaries, which encompass 12.5 million square kilometers, catching, possessing and trading in shark products are prohibited. Open sea-dwelling species of sharks swim vast distances each year, passing in and out of national territorial waters where they are caught and killed. Sanctuaries will help to reduce the risk to these imperiled animals, which are slow growing, bear few young and play a vital role in ocean ecologies. Given China's immense size and expanding influence, it has the potential to play a key role in helping to solve the problems of climate change, overfishing, pollution and conservation. The new shark-fin diplomacy may prove to be a pivotal event - but only if China adopts the environmental leadership that the world so desperately needs. Joshua S. Reichert is the executive vice president of the Pew Charitable Trusts, directing Pew's environmental work.