MANILA — China’s island-building activities have destroyed about 300 acres of coral reefs and are causing “irreversible and widespread damage to the biodiversity and ecological balance” of the South China Sea, a spokesman for the Philippine Department of Foreign Affairs said on Monday.

“China has pursued these activities unilaterally, disregarding people in the surrounding states who have depended on the sea for their livelihood for generations,” the spokesman, Charles Jose, said during a news briefing in Manila.

He said China’s neighbors in the South China Sea could lose up to $100 million a year because of the loss of the coral reefs, which are breeding grounds for high-value fish harvested by countries surrounding the sea.

China has been undertaking land reclamation projects on the sand spits, islets and submerged reefs of the Spratly Islands in the South China Sea, according to satellite images released in the last year. United States and Philippine officials have said the newly constructed islands could serve as military outposts in the area, parts of which are also claimed by the Philippines, Vietnam and other governments.