China's southernmost city is preparing to plant 500,000 trees within the year in a new "greening of the islands" initiative.

Sansha's island location in the South China Sea means the city's forest-building plans will face challenges, including the transportation of seedlings, limited fresh water supplies and extreme weather, including typhoons.

But the tree planting project is seen as vital because the forests will provide a windbreak and prevent shoreline erosion, improve the area's ecology and benefit residents, officials said.