An inspector from the Sichuan Entry-Exit Inspection and Quarantine Bureau tells students from Sichuan Agricultural University why woodcarvings cannot be brought into China without being quarantined first. [Photo by Huang Zhiling/chinadaily.com.cn]

Students from Sichuan Agricultural University's Wenjiang campus were shown a display of seized plants and plant products on Thursday afternoon by staff from Sichuan Entry-Exit Inspection and Quarantine Bureau.

The items had been confiscated from passengers arriving at Shuangliu International Airport in Chengdu, Sichuan province.

Many of the students were curious about a woodcarving that was on display and asked a bureau employee why it had been seized. They were shown wormholes in the piece that might have caused by a nonnative species.

The display of confiscated plants and plant products was one of many events staged by the bureau to mark China's first National Security Education Day, said bureau chief Sun Yingjie.

April 15 was designated National Security Education Day by the Standing Committee of the National People's Congress, China's top legislative body, under the National Security Law passed in July.

Other events held at the university included a well-attended lecture on nonnative species given by an inspector from the bureau, said Leng Jun, a university official.

The number of prohibited objects seized by the bureau has been on the rise in recent years. In the first three months of the year, more than 252 kilograms of bird's nests, pet food, ham, garlic, plants and lavender were seized, said Chen Bingyu, an information officer with the bureau.

Since the mid-1990s, invasive, nonnative species such as the pine wood nematode have done much harm to China's ecosystem, with the country's biodiversity, agriculture, forests, animals and fisheries all affected.

"Of the globe's 100 most dangerous alien species on the list of the International Union for Conservation of Nature and Natural Resources, more than 50 have invaded China," said Chen Hai, chief of the Chengdu Airport Entry-Exit Inspection and Quarantine Bureau.

"Each year, direct economic losses from them surpass 50 billion yuan ($7.7 billion)."