Kyoto, the old capital of Japan, is famous for two things: its Buddhist temples and the 1997 treaty that set out, with mixed results, to tackle global warming. Now the failure of the second is threatening the first as accelerating climate change eats away at Kyoto's ancient heritage.

Temples across the city, including some of its most famous, are reporting the rapid erosion of the delicate moss that forms an essential component of their famous Zen gardens.

A rise in temperatures and a change in the patterns of rain that nourish the moss are destroying a plant that is as essential to Japanese gardens as grass is to English horticulture.

Panicked monks have resorted to watering their moss gardens, which risks further damage, and even importing moss from other areas of Japan. Hideki Sunahara, of the 1,200-year-old To-ji temple, said: “We were shocked to discover this, which we never expected. This is a serious problem, and I believe that it is attributable to global warming. For me, a Japanese garden without moss is nothing.”

The damage has been documented by Kyoto University, which conducted a survey of those Buddhist temples and Shinto shrines designated World Heritage Sites by Unesco. They include Kinkaku ji, informally known as the “Golden Pavilion Temple”, and Ryoan-ji, home of the world's most famous Zen rock garden.

Nine out of the thirteen temples in the study reported a deterioration in moss quality, a change that the university attributes to climate change and also the “heat island effect”, whereby cars and buildings in urban areas drive up average temperatures by absorbing daytime heat and emitting it at night.

Yoshitaka Oishi, who carried out the research, said: “Moss needs mist and morning dew to survive, but these are disappearing as a result of the falling gap between daytime and night-time temperatures. At some temples, gardeners have to bring common hair cap moss from Tokyo and replant gardens.”

Josho Toga, head priest of Tenryu-ji temple, said: “Moss is the essence of the Japanese garden. It produces an appearance of such mellowness. For moss to survive, it needs soft rain, morning dew and sun. But the weather these days is like that of a subtropical region.”

The largest Kyoto moss gardens, such as at Koke-dera, known as the “Moss Temple”, contain 120 varieties, whose contrasting colours and textures appeal to the Japanese aesthetic of wabi-sabi — a melancholy appreciation for the impermanent that has its roots in Zen Buddhism.

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