Mosses found on rocks and trees in cities around the world can be used to measure the impact of atmospheric change and could prove a low-cost way to monitor urban pollution, according to Japanese scientists.
Moss responds to pollution or drought-stress by changing shape, density or by disappearing, allowing scientists to calculate atmospheric alterations.
Mosses are a common plant in all cities so this method can be used in many countries; they have a big potential to be bio-indicators.
The scientists studied the effect of nitrogen pollution, air quality and drought-stress on moss found over a 3 sq km area in Hachioji City in north-west Tokyo. The study showed severe drought-stress tended to occur in areas with high levels of nitrogen pollution, which raised concerns over the impact on health and biodiversity.
The World Health Organisation says 88% of city dwellers are exposed to annual pollution levels that exceed its air quality guidelines.