The South China Sea cyanide dispute has added a new layer of tension between the Philippines and China, combining environmental risks with maritime security concerns. In early 2025, Philippine authorities reported the discovery of containers filled with cyanide near Second Thomas Shoal in the Spratly Islands. Laboratory tests later confirmed the presence of toxic substances, raising serious concerns about ecological damage in one of the region’s most sensitive and contested maritime zones.
Cyanide allegations raise environmental and security concerns
Manila claims the chemicals were deliberately used to damage the reef ecosystem and kill fish stocks, potentially affecting marine biodiversity and the safety of personnel operating in the area. Cyanide is often associated with illegal fishing practices, but Philippine officials describe this case as possible environmental sabotage. This incident follows a series of confrontations we analysed in our previous coverage of South China Sea maritime tensions.
A new escalation in the Philippines-China maritime dispute
The situation has quickly escalated into a diplomatic dispute, with China rejecting the allegations and describing them as unfounded. The waters around Second Thomas Shoal remain a key flashpoint, where Philippine resupply missions to the grounded BRP Sierra Madre regularly face pressure from Chinese coast guard vessels. As highlighted in our report on grey-zone tactics at sea, environmental pressure can also serve strategic objectives. The South China Sea remains a vital maritime corridor, with major shipping routes and overlapping exclusive economic zone claims. For a broader overview of the case and diplomatic reactions, see this external report detailing the incident.
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