[1] In late 2013, the PRC embarked on very large scale reclamations at seven locations in order to strengthen territorial claims to the region demarcated by the nine-dash line.

[1] The PRC states that the construction is for "improving the working and living conditions of people stationed on these islands",[7] and that, "China is aiming to provide shelter, aid in navigation, weather forecasts and fishery assistance to ships of various countries passing through the sea.

[2] Aside from geo-political tensions, concerns have been raised about the environmental impact on fragile reef ecosystems through the destruction of habitat, pollution and interruption of migration routes.

13.5 square kilometres (5.2 sq mi)[citation needed] The PRC used hundreds of dredges and barges including a giant self-propelled dredger, the Tian Jing Hao.

[14][15] Built in 2009 in China, the Tian Jing Hao is a 127 m (417 ft) long seagoing cutter suction dredger designed by German engineering company Vosta LMG; (Lübecker Maschinenbau Gesellschaft (de)).

In the process of island building the sediment deposited on the reefs "can wash back into the sea, forming plumes that can smother marine life and could be laced with heavy metals, oil and other chemicals from the ships and shore facilities being built.

For back-filling these seven artificial islands, a total area of 13.5 square kilometres (5.2 sq mi), to the height of few meters, China had to destroy surrounding reefs and pump 40 to 50 million m3 (1.4 to 1.8 billion cu ft) of sand and corals, resulting in significant and irreversible damage to the environment.

Frank Muller-Karger, professor of biological oceanography at the University of South Florida, said sediment "can wash back into the sea, forming plumes that can smother marine life and could be laced with heavy metals, oil and other chemicals from the ships and shore facilities being built."

[42] Rupert Wingfield-Hayes, visiting the vicinity of the Philippine-controlled island of Pagasa by plane and boat, said he saw Chinese fishermen poaching and destroying the reefs on a massive scale.

He concludes: "However shocking the reef plundering I witnessed, it is as nothing compared to the environmental destruction wrought by China's massive island building programme nearby.

[44] John McManus, a professor of marine biology and ecology at the University of Miami said: "The worst thing anyone can do to a coral reef is to bury it under tons of sand and gravel ...

He explained that the reason "the world has heard little about the damage inflicted by the People's Republic of China to the reefs is that the experts can't get to them", and noted "I have colleagues from the Philippines, Taiwan, PRC, Vietnam and Malaysia who have worked in the Spratly area.