As more people move to coastal cities on the South China Sea, there has been a big increase in construction and land reclamation. These add to the erosion of beaches and sediment run-off that smothers the corals and leads to the degradation of the reef. Increased sedimentation also leads to a change in the composition of marine fauna, favoring more resilient species. Densities of fish are greatly decreased by overfishing. Coral is damaged by destructive fishing techniques and by removal for trade.
Fishing degrades the reef in several ways.
Destructive and illegal fishing methods are common, especially in the Philippines, Indonesia, and Malaysia. These methods include dynamite blasting and cyanide fishing. Overfishing not only depletes fish stocks of target species, but also changes the dynamics of the entire reef. Decreases in herbivores can lead to algal blooms which overtop coral growth and can cause mass mortality. Over 100,000 oil tankers and container and cargo vessels transit the Straits of Malacca and Singapore each year.