Alien plants believed to have been unwittingly transported by tourists to Mount Fuji are threatening to destroy or damage the ecosystem of the nation’s newest World Heritage site and even its landscape, researchers say.

In a recent study of plants along the Fuji Subaru Line toll road, which winds 2,300 meters up to the fifth station and nearby trekking trails, researchers found 56 foreign species likely brought in from elsewhere in Japan or overseas.

“Actually, it has been said for more than 15 years that a considerable number of alien species are growing on Mount Fuji,” said Takashi Nakano, chief researcher at the Yamanashi Institute of Environmental Sciences.

Nakano, who specializes in plant ecology, headed the research conducted in summer 2012 with Yasuo Yamamura, an Ibaraki University professor and researcher at its Institute for Global Change Adaptation Science.

Nakano explained that in light of the fact that the majority of the plants were found growing alongside the Subaru Line, seeds or plant parts are likely being picked up and carried by tourists on their clothing, shoes or car tires.

Some of them, such as some species of Artemisia, have already grown along the trekking trails and are likely to spread further, the researchers said.

“We need to monitor the growth situation on a regular basis and pull some up,” Nakano said.

Each year, more than 300,000 tourists from both home and abroad climb Mount Fuji, which was finally named a World Heritage site by UNESCO in June after people stopped using it as a garbage dump.

Concerns are growing that an expected influx of tourists will cause further damage to the volcano’s environment.

In similar efforts, a nonprofit organization called Fujisan Club — working with the governments of Yamanashi Prefecture and the town of Fujikawaguchiko — has been extricating bur cucumbers from Lake Kawaguchi, one of the Fuji Five Lakes.

Bur cucumbers, which are native to North America, are fast growers that climb and engulf plants around them, often strangling them. In mid-August, the club launched its fifth campaign of the year to exterminate the species.

A total of 15 members and volunteers looked for the plants’ roots by the lake and pulled them up. In about two hours they had collected enough bur cucumbers to fill 20 45-liter plastic bags.

“There is a report that the plant is growing along the Chikuma River in Nagano Prefecture like a carpet, and we have to prevent Lake Kawaguchi from following the same path,” said Naoko Aoki, director of the organization.

To prevent foreign species from getting out of control, the Environment Ministry has stressed the importance of curtailing the habitats in which they grow.