Delicate 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.
The “bioindicator” responds to pollution or drought-stress by changing shape, density or disappearing, allowing
scientists to calculate atmospheric alterations, said Yoshitaka Oishi, associate professor at Fukui Prefectural University.
“This method is very cost-effective and important for getting information about atmospheric conditions,” Oishi told the Thomson Reuters
Foundation.
“Mosses are a common plant in all cities, so we can use this method in many countries they have a big potential to be bioindicators,” said Oishi, who analysed nearly 50 types of moss for the study.
Oishi said humid cities where moss thrives could benefit most from using bryophytes, a collective term for mosses, hornworts and liverworts, as bioindicators, adding that moss could be monitored in its natural environment or cultivated for analysis.
In a research paper published in the Landscape and Urban Planning journal, Oishi and a colleague described how they studied the effect of
nitrogen pollution, air quality and drought-stress on moss found over a 3 km2 area in Hachioji City in northwestern Tokyo.
The study showed severe drought-stress tended to occur in areas with high levels of nitrogen pollution, which it said raised concerns over the impact on health and
biodiversity.
However, the scientists could not effectively measure air purity, which affects the number of moss types as pollution levels in the sample area were not high enough, said Oishi. “If the air pollution is severe, the purity is also evaluated by moss the change of the moss is very diverse according to the environmental problem.”
Bioindicators such as mosses, which generally absorb water and nutrients from their immediate environments, were often cheaper to use than other methods of environmental evaluation, and can also reflect changes to ecosystems, said the scientists.
The World Health Organisation says 88% of city dwellers are exposed to annual pollution levels that exceed its air quality guidelines.
South-East Asia and the eastern Mediterranean have the worst air quality, followed by countries in Latin America and Africa.
“We believe this method can contribute to the evaluation of atmospheric pollution in other areas.”