HONG KONG — Scientists have long called for the creation of marine conservation programs in disputed areas of the South China Sea, arguing that the programs would help defuse tensions over competing territorial claims while protecting ecologically sensitive spawning grounds from commercial fishing fleets.
Leaders from China and Southeast Asian nations have mostly ignored the suggestion, even as the sea is threatened by overfishing and as tensions rise over China’s recent campaign to turn seven of the sea’s many disputed reefs into artificial islands.
But this could be changing in the Philippines, where the government said on Monday that President Rodrigo Duterte planned to declare a marine sanctuary and no-fishing zone at a lagoon within Scarborough Shoal, a reef China seized in 2012 that is not part of the island-building plan.
“That is a unilateral action,” the Philippine national security adviser, Hermogenes Esperon Jr., said of the proposed sanctuary in a brief statement, after a weekend in which Mr. Duterte met with President Xi Jinping of China on the sidelines of the Asia-Pacific Economic Cooperation summit meeting in Peru.
Mr. Duterte’s communications secretary, Martin Andandar, quoted Mr. Xi in the statement as having called for a “favorable environment” at Scarborough Shoal, which both countries claim. The statement did not specify what Mr. Xi thought of Mr. Duterte’s proposal, and the Chinese Ministry of Foreign Affairs did not respond to a faxed request for comment on Monday.
The announcement on Monday came about four months after the Philippines largely won an international arbitration ruling that had challenged China’s seizure of Scarborough Shoal, but also as Mr. Duterte, who took office in late June, attempts to reset frayed relations with China and publicly questions his country’s longstanding ties to the United States.
It also follows a similar statement about Scarborough Shoal by Wu Shicun, president of the National Institute for South China Sea Studies and an adviser to the Chinese government, who said last month that Beijing was open to making the lagoon within the shoal into an “environmental protection park.”
Experts said on Monday that it would be difficult to assess the feasibility of Mr. Duterte’s plan without further details, and that a crucial question is whether China would be involved in the implementation or enforcement of the proposed sanctuary.
“Until we have a management plan, we won’t know,” said Clive Wilkinson, a coral reef expert in Australia and the former lead coordinator for the nonprofit Global Coral Reef Monitoring Network. He added that the Philippines probably did not have enough ships to enforce such a ban, and that the lagoon sanctuary would offer only marginal fisheries protection in the absence of a corresponding fishing ban along the shoal’s outer flanks.
The South China Sea has some of the world’s most productive fisheries. A 2015 academic study found that the sea has 571 known species of reef corals alone, significantly more than most other global reef hotspots.
But the sea is also facing an overfishing crisis, and scientists say that China’s campaign to turn seven disputed reefs into artificial islands and build military facilities on some of them is damaging crucial spawning grounds. They say the establishment of port facilities at the new islands may also encourage Chinese fishing fleets to travel farther afield from the Chinese mainland, putting even greater pressure on beleaguered fish stocks.
Scarborough Shoal, known in the Philippines as Panatag Shoal and in China as Huangyan Island, is at the center of both the ecological and political dramas.
Although Chinese Coast Guard ships have granted Filipino fishermen access to the shoal in recent weeks as part of a rapprochement between the countries, the shoal is still widely seen as a potential part of the island-building campaign. Scientists say that is especially worrying because the shoal plays an important role as a site where countless fish and coral species can breed, helping to maintain the sea’s extraordinary biodiversity.
Mr. Wu, the Chinese government adviser, said in an interview last month that Beijing had decided that no fishermen from the Philippines or China should be allowed into the Scarborough lagoon because both sides had inflicted “huge” damage on it through dynamite fishing. He added that a Chinese-administered “environmental protection park” in the lagoon would represent an effort at bilateral cooperation, but he included an important caveat.
“A precondition for that is that the Philippines will respect China’s sovereignty and jurisdiction in Scarborough Shoal,” Mr. Wu said.
Ian J. Storey, a South China Sea expert in Singapore, said that scientists had been seeking multilateral conservation programs in the sea for decades. Despite that, and a call by Ma Ying-jeou, a former president of Taiwan, for joint management as part of a “South China Sea Peace Initiative,” Mr. Storey said the idea had so far been a diplomatic nonstarter because the sea is filled with so many overlapping territorial claims.
Mr. Storey said that a bilateral management plan of the Scarborough lagoon had a chance to succeed and would be a logical extension of the rapprochement between China and the Philippines. But he said China would almost certainly not respect a unilateral fishing ban by the Philippines, much in the way that Vietnam has long ignored a unilateral fishing ban that China sporadically enforces in another corner of the South China Sea.
The Philippine proposal is “a unilateral initiative,” Mr. Storey said, “and unilateral initiatives in the South China Sea have a history of going nowhere.”