Sunday marks the fourth anniversary of the establishment of China's newest city, Sansha. Over the past four years, the region witnessed massive construction projects undertaken by China. The latest achievement is the successful trial flights on the two new airports on Zhubi and Meiji reefs, two of China's southmost reefs in the South China Sea. Our reporter Han Peng was there.

Q1: Han Peng, China's construction activities on the islands in the South China Sea have attracted global attention. You were on these islands to cover the trial flights. What have you seen?

A: Yes, I visited the two reefs, Zhubi and Meiji, where China is investing heavily in. Both of them are located in Nansha -- far from the mainland. What was impressive were the newly completed airports and lighthouses. Let's start with the airports. To cover the trial flights, our camera crew traveled for around 50 hours on a choppy waters before finally reaching reach Meiji. Most of us suffered from seasickness the entire time.

But with the success of the trial flights on these reefs, China now has three coral reefs in the South China Sea capable of receiving jumbo jets. (Map showing Meiji, Zhubi and Yongshu) This reduces the watery, two-day journey to a smooth flight of no more than two hours. The other project was the five newly-built lighthouses now illuminating the South China Sea. The lights can penetrate a distance as far as 22 nautical miles.

Engineers on Meiji told us that the South China Sea is one of the busiest regions for international trade and fishing. But it's also one of the most dangerous, with unexpected wind storms and submerged coral reefs all around. So these lighthouses provide much-needed navigation and protection to the Chinese and foreign vessels sailing in the region. To recall, most of these reefs were just about the size of a football field two years ago. And none of these new services are possible without China's land reclamation projects.

Q2: The South China Sea houses different kinds of ecosystems including those on coral reefs, mangroves and seaweed beds. They can be quite vulnerable to environmental changes. Will the land reclamation cause any harm to the ecosystems?

A: If the land reclamation attempts were all about dumping rocks and cement on the top of the coral reefs, then yes, of course it would destroy ecosystems.

But China's Oceanic Administration says the current construction methods are an innovative way of simulating the natural regeneration process of coral reefs. The idea was to pump up dead or unconsolidated coral reefs, and then heap them up on the land like how the winds and sea waves would. This is like accelerating the natural formation of coral reefs. After the initial reclamation stage, what's next is to urgently introduce various plants and animals, in order to build up an ecological system.

According to what we have learned from Zhubi and Meiji, tree planting is a top priority. Workers transport fertilized soil from the mainland and develop innovative ways to raise the survival rates of the plants. And as for the presence of animals like sea gulls and insects, workers say they arrived on their own.

Some US experts claim that the coral reefs in the South China Sea are facing large-scale destruction due to the construction. But the Chinese foreign ministry denied such accusations, and said that once the construction is completed, ecological protection on relevant islands and reefs will be notably enhanced, and that such actions and projects would stand the test of time.