美济礁
A 2014 United Nations Environment Programme (UNEP) report noted that "Sand is rarer than one thinks." "The average price of sand imported by Singapore was US$3 per tonne from 1995 to 2001, but the price increased to US$190 per tonne from 2003 to 2005". Although the Philippines and the PRC had both ratified the UNCLOS III, in the case of Johnson South Reef, Hughes Reef and Mischief Reef, the PRC dredged sand for free in the EEZ the Philippines had claimed from 1978, arguing this to be the "waters of China's Nansha Islands". "Although the consequences of substrate mining are hidden, they are tremendous. Aggregate particles that are too fine to be used are rejected by dredging boats, releasing vast dust plumes and changing water turbidity".