Before and after satellite images: What has been built on the reefs that China occupies in the Spratlys

Countries staking claims in the South China Sea have built airstrips and other structures - including military installations, helipads, lighthouses and even schools - on the disputed islands over the years.

China claims most of the South China Sea. The Philippines, Vietnam, Malaysia, Brunei and Taiwan also have overlapping claims.

Vietnam, for instance, started building an airstrip on Spratly Island in 1976, making it the first runway in the Spratly island group. Taiwan also built an airstrip in Itu Aba in 2008. China is the most recent claimant to do so in 2014 on the Fiery Cross Reef.

In the Spratly archipelago in the southern half of the South China Sea, China controls these reefs: Subi, Gaven, Hughes, Johnson South, Fiery Cross, Cuarteron and Mischief. Here's a  look through satellite images at how construction - in some cases, reclamation - has changed each of them.

Fiery Cross Reef

Where it is located: It lies on the west side of the Spratly Islands.

Who claims it: China (calls it Yongshu Reef), the Philippines (Kagitingan Reef), and Vietnam (Đá Chữ Thập)

What has been built on it: China started building an airstrip in 2014, and the 3,000m runway was completed in September 2015. In January 2016, it tested the runway for the first time by landing several civilian airliners.

The airstrip is capable of handling almost any type of aircraft in China’s inventory, including the Chinese H-6G bomber. The island reportedly houses a harbour large enough to dock military tankers. 

It also houses helipads, air defence guns and possibly has a radar tower under construction.

Experts say Fiery Cross could eventually become a command-in-control centre for the Chinese navy, and may allow China to enforce an Air Defence Identification Zone over the South China Sea.

Source: CSIS Asia Maritime Transparency Initiative / DigitalGlobe

Subi Reef

Where it is located: It lies in the northern Spratly islands.  It is 25km from Philippine civilian populations and 14km from the Thitu Reef cluster occupied by the Philippines.

Who claims it: China (Zhubi Dao), the Philippines (Zamora) and Vietnam (Đá Xu Bi)

What has been built on it: In its natural state, it is submerged at high tide. But China, which occupied the reef during its 1988 push to increase its footprint in the South China Sea, began land reclamation on Subi in 2014. 

Construction of a 3,000m airstrip is nearing completion after six or seven months of work. Satellite imagery indicate the presence of a surveillance tower and multiple satellite antenna. 

The Chinese were infuriated when the USS Lassen, a guided-missile destroyer, sailed within the 12-nautical-mile territorial limits of Subi Reef. 

Source: CSIS Asia Maritime Transparency Initiative / DigitalGlobe

Mischief Reef

Where it is located: The reef in Spratly Islands falls within what the Philippines claims to be its 200 nautical mile exclusive economic zone,  lying 129 nautical miles from Palawan. 

Who claims it: China (Meiji Jiao), the Philippines (Panganiban reef) and Vietnam (Đá Vành Khăn) 

What has been built on it: China has occupied Mischief Reef since 1995 and recent activity hints at the development of a naval base. Frigates and coast guard ships have been spotted in surrounding waters. China is building its third airstrip in the Spratlys here,  according to the CSIS Asia Maritime Transparency Initiative.

Source: CSIS Asia Maritime Transparency Initiative / DigitalGlobe

Cuarteron Reef 

Where it is located: In the London Reefs, on the western side of the Spratly Islands.

Who claims it: China (Huayang Jiao), the Philippines (Calderon Reef) and Vietnam (Bãi Châu Viên)

What has been built on it: Satellite images show what looks like a high-frequency anti-stealth radar installation under construction here. Other facilities include a buried bunker, a helipad, a quay and a lighthouse. 

Experts consider developments here particularly important as it would boost China's ability to monitor surface and air traffic across the southern portion of the South China Sea, especially traffic coming from the Strait of Malacca. China already has radar coverage of the northern portion of the South China Sea from the Paracel Islands.

Source: CSIS Asia Maritime Transparency Initiative / DigitalGlobe

Gaven Reef

Where it is located: It lies near the centre of the Spratly Islands.

Who claims it: China (calls it Huayang Reef), the Philippines (Calderon Reef) and Vietnam (Bãi Châu Viên)

What has been built on it: Chinese construction began sometime after March 30, 2014. A new building on Gaven Reef is almost identical to one on McKennan (Hughes) Reef, suggesting that China has standardised plans for its new island facilities in the South China Sea. China has had a troop and supply garrison here from as far back as 2003. There are a large supply platform where ships can dock, several gun emplacements, and radar and communications equipment.

Source: CSIS Asia Maritime Transparency Initiative / DigitalGlobe

Hughes Reef

Where it is located: It lies in the centre of the Spratlys.

Who claims it: China (calls it Dongmen Reef), Vietnam (Tu Nghia)

What has been built on it: Land reclamation activity on  Hughes Reef, began in May 2014. Reclamation work has expanded the reef by approximately 76,000 sq m. A large central structure, similar to one on Gaven Reef, and possibly an anti-aircraft system have been built.

Source: Maritime Awareness Project, CSIS Asia Maritime Transparency Initiative / DigitalGlobe

Johnson Reef

Where it is located: It lies in the north-west of the Spratlys.

Who claims it: China (calls it Chigua reef), the Philippines (Mabini Reef ), Vietnam (Gạc Ma)

What has been built on it: China took control of Johnson Reef from Vietnam after a clash in 1988.  Until early 2014 the only man-made feature on the reef was a small concrete platform that housed a communications facility, garrison building, and pier. Among the new additions are two helipads, a lighthouse and a solar farm.

Source: Maritime Awareness Project, CSIS Asia Maritime Transparency Initiative / DigitalGlobe