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

Sansha's geography in the South China Sea means the city's forest-building plans face challenges, including transportation of tree seedlings, limited fresh water supplies and extreme weather, such as typhoons, Xinhua reported.

But the tree planting is vital as the forests will provide a good windbreak and prevent shoreline erosion, improving the city's ecology and benefiting residents, officials said.

Coconut and casuarina trees are the plants of choice, as they have a high survival rate in the area's hot, humid, salty and high-radiation conditions.

Last year, about 300,000 trees were planted on islands and reefs, and 90 percent survived, turning the desert islands into green ones.

Sansha also promoted an "Internet plus tree" adoption activity to netizens. For 300 yuan ($46) per year, participants could own a coconut tree on the city's Zhaoshu island, according to media reports.