Swiss forests are suffering increased defoliation, according to a new study, which found that nearly 30 per cent of trees across the country lost up to a quarter of their foliage in 2000.
The latest "Sanasilva" report from the Federal Institute for Forest, Snow and Landscape Research, released on Monday, said defoliation had risen in Swiss forests for the first time since 1995.
It said that overall nearly 30 per cent of 1,100 trees examined across the country showed a loss of more than a quarter of their foliage in 2000.
On average, trees lost 26 per cent of the foliage in 2000, compared to just over 21 per cent in 1999. This is the biggest increase since 1985, when the first inventory was carried out.
Pine and spruce trees suffered most, while beeches were virtually unaffected. Tree mortality did not increase.
The cause of defoliation is partly blamed on Hurricane Lothar - a violent storm that devastated many forests across the country at the end of 1999.
However, the researchers who carried out the study say Lothar is not entirely responsible because defoliation has increased in areas where the storm had little or no effect.
The researchers believe that the particularly dry spring in 2000 could also have contributed to defoliation.
The report says Swiss forests are not in any immediate danger, but it warns that there is a long-term risk. They say too much nitrogen and acid is still entering the soil, causing a nutritional imbalance for trees.
swissinfo with agencies