On Wednesday last week, Chinese ships once again entered Taiwan’s territorial waters to dredge sea sand illegally, this time near Linao Island (林坳嶼) in Matsu’s Juguang Township (莒光). Similar incidents have been reported almost every month and even several times in one month.

Chinese ships have been systematically dredging sea sand from Taiwan’s territorial waters, sector by sector, and not only around Matsu — dredgers have also been active around the island counties of Kinmen and Penghu.

If Taiwan does not take effective preventive measures, it might even see Chinese dredgers stealing sand off the coast of Taiwan proper, near the mouths of the Gaoping River (高屏溪) and Jhuoshui River (濁水溪).

Although China has banned dredging along the coast of its southeastern provinces, it turns a blind eye as its increasing large dredgers sneak into Taiwan’s territorial waters.

These Chinese dredgers and sand carrier ships often work in groups of 10 or more in a coordinated fashion.

Each dredger can dredge up a full load of about 2,000 tonnes in about two hours. The dredging business can sell NT$4 million to NT$5 million (US$131,300 to US$164,100) of sand per day of dredging. On each day of operation, the only risk they face is the detention of their ships and a fine of about NT$200,000 per case.

However, if several hundred thousand tonnes of sand are stolen from a single area in one day, it would not only damage the ecology of Taiwan’s sea and negatively affect fishery workers in the area, it would also cause the sandy surface layer of the Taiwan Strait’s seafloor to loosen, slip and sink.

The Taiwan Strait is the origin of the biological chain of the Kuroshio Current, which flows north to Japan, where it interacts with the Oyashio Current. The ecological damage caused by dredging in the Taiwan Strait might therefore have a devastating effect on the abundant fishing grounds that this ecosystem creates.

Eventually, the valuable sands around Penghu, Kinmen and Matsu might be completely exhausted.

After dredging the sand, these illegal Chinese dredgers haul it back to China, where it is used to construct offshore airports in Fujian Province or create artificial islands in the South China Sea. They even take advantage of the rising price of sand and gravel in Taiwan to sell it to unscrupulous Taiwanese merchants, who then transport it back to Taiwan proper and sell it for a profit.

Taiwan has a very high demand for sand, and this illegal sea sand is more than NT$100 cheaper per tonne than the river sand transported to Taiwan’s west coast from Hualien County.

Consequently, about 1 million tonnes of sand is imported to Taiwan from Fujian each month, accounting for about 70 percent of the demand for the construction industry in north and central Taiwan. About half of that amount is sourced from illegally dredged sea sand.

This imported sand, which is a mixture of sea sand and Chinese river sand, might have an excessive chloride content of more than 0.15kg per cubic meter. This is sure to cause serious and worrisome rust corrosion to steel rebar in buildings and steel tendons in bridges, leading to potentially unthinkable consequences for these “sea sand buildings,” including bridge collapses.

This latest discovery of illegal dredging is the third such incident in Matsu this year. If it is handled in the same way as the previous two instances — by simply confiscating the sand and putting the ships up for auction — there might be no point.