A three-day conference on preserving UNESCO World Natural Heritage sites opened Saturday in Aomori Prefecture, which is known for the Shirakami-Sanchi mountain range.

Delegates from Australia, China, India, Malaysia, the United States and 11 other countries are attending the second International Conference on World Natural Heritage, along with representatives from Hokkaido, Kagoshima and other prefectures. The first conference was held in Kagoshima Prefecture in 2000.

Hokkaido's Shiretoko area was added to the U.N. Educational, Scientific and Cultural Organization list earlier this year, while the ancient cedar forest on Yakushima Island in Kagoshima, believed to be among the largest in the world, was added in 1993.

The event is being held in three municipalities, including the city of Hirosaki and the village of Nishimeya, where part of the Shirakami mountain range, which straddles Aomori and Akita prefectures, is located.

The conference will hold three subcommittee meetings to discuss the preservation of world's natural heritage, creation of local communities and how to pass down heritage sites to future generations.

The participants will adopt a Shirakami-Sanchi declaration at the end of the three-day gathering Monday.

The Shirakami-Sanchi beech forest was added to the UNESCO list in 1993 together with Yakushima Island's ancient cedar forest.

Since becoming a world heritage site, however, the number of tourists visiting the mountain range in northeastern Japan has soared, affecting the local ecological system.

One ominous example is the spread of nonindigenous plants, which are believed to have come from seeds attached to tourists' clothing or bears coming down the mountains to eat crops near human settlements.

Aomori Prefecture and other entities say some areas of Mount Shirakami, are strewn with plantain weeds, which are not native to the area.