Grasslands are quickly vanishing in Japan, threatening to destroy the habitats of plants and wildlife there, a group of researchers found.

For about 100,000 years, about 10 percent of Japan was made up of grasslands, but the area has declined to about 1 percent over the past century, the group from the Forestry and Forest Products Research Institute, based in Tsukuba, Ibaraki Prefecture, Kyoto University, and other entities said.

The researchers said the decrease in grasslands in recent years "was a major development even when considered in units of tens of thousands of years."

They added that the disappearance of grasslands would ruin the habitats of living organisms in the areas.

Yuichi Yamaura, a senior researcher at the forestry institute, and others in the group collected leaves from four plants with deep ties to the Japanese from 25 locations around Japan, including Hokkaido in the north and Kyushu in the south.

They calculated the changes in the number of such plants and the land area they inhabited by looking into differences in DNA alignment. While the four plants, including "ominaeshi" (Patrinia scabiosifolia) and "waremoko" (Sanguisorba officinalis), had different life spans and heights, their numbers remained virtually unchanged for about 100,000 years.

Until about 10,000 years ago, the Japanese archipelago had a colder climate, making it difficult for forests to develop.

However, even after it became warmer, grasslands were maintained by humans cutting down forests and through controlled burning.