An insect pest has made a surprise attack on mangrove forest mainly distributed in south China's coastal areas since this May.

The insect pest was initially seen in Beihai Mangrove Reserve located in southern China's Guangxi Zhuang Autonomous Region at the end of May, and later found in other places of the autonomous region, as well as some areas in Guangdong and Fujian provinces.

According to Fan Hangqing, director of research center on mangrove forest, the destruction was caused by a kind of caterpillar, which reproduced four generations in less than a week.

The pest attacked the back of leaves first, preventing the regular process of photosynthesis on the mangrove trees.

As a result, the attacked plants shrink and dry, and if no new sprouts grow out, they will die out completely, Fang said.

Statistics showed that 9,800 mu (653 hectares) of mangrove forest was raided by the insect pest only in Guangxi, and so far, the death rate of the affected mangroves in the autonomous region has reached as much as 70 percent.

Dr. Zan Qijie, another mangrove expert with Futian Mangrove Reserve in Shenzhen City of Guangdong Province, attributed the pest's arrival not to changes of climate but the gradually deteriorated ecosystem.

"Since 1992, the insect pest attacks mangrove trees in the reserve every year," Dr. Zan said. "Destroyed surroundings is the main cause."

Compared with that in Beihai, the situation of mangroves in Qinzhou and Fangchenggang, another two coastal cities along Beibu Gulf, is relatively better thanks to its well-protected vegetation, which offers a sound environment for such natural enemies of caterpillar as birds, spiders and hermit bees to be inhabited and breed.

Mangroves trees, named "forest at sea," grow at interface of ocean and land, appearing every now and then along with flood or ebb tides.

Mangrove forest is also considered the most productive ecosystems in the sea by the experts.

Densely scattered along the shoreline of Guangxi, mangroves can help hold back 80 percent of tidal waves and provide plenty of food and fine resting places for birds and marine creature.

Experts say expanding offshore aquatic breeding has imposed negative impacts to growth of mangrove trees.

"People have applied too many pesticides, which in turn polluted the offshore, killed caterpillar's natural enemies and gradually broke the ecological balance, mangrove forests required,"Fang Hangqing said.

Warning such negative impacts came slow but were cumulative, Fan said the pest attack should be a sign of a destroyed mangrove ecosystem.

Investigation from forestry department of Guangxi, the area of mangroves in the country has dropped by over 50 percent from 22,000 square kilometers since 1950s due to overheating in filling sea area to create farmland and expanding aquatic breeding.

(Xinhua News Agency July 6, 2004)