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SHANGHAI, Dec. 1 -- Chinese botanists have found that 515 invasive plant species have taken up residence in the country, covering both inland and coastal areas.

The species, more than half of which are native to South and North America, are seen in all of China's provincial-level regions and even in national nature reserves, Chen Xiaoya, director of Shanghai Chenshan Plant Science Research Center under the Chinese Academy of Sciences, told Xinhua on Sunday.

Chen's team, along with scholars from seven other institutions, spent three years researching the number and distribution of invasive plant species in the vast country.

According to the researchers, Yunnan Province in the country's southwest registers the most: 334 species, and the country's southeast coast has 108. About 40 percent of the species belong to the families of sunflowers, legumes and grasses.

The alien plants threaten their local counterparts. For example, Solidago Canadensis, also known as Canadian goldenrod, was introduced to east China in the 1930s as an ornamental plant and, in Shanghai alone, it has led to the elimination of over local 30 species.

Previous studies showed that among the 100 worst invasive alien species identified by the International Union for Conservation of Nature, 50 have been brought to China.

China has five climate zones, which can provide suitable habitats for most alien species, Chen said. "Invasive species are a global problem. It has been worsened by globalization."

In mid-November, the Ministry of Science and Technology launched a project to create a data base of invasive plants. Nearly 30 researchers are expected to detail the species' history, distribution and dangers in China within four years.