How Moss Can Solve Japan's Major Pollution Problem

Scientists have found a new low-cost way to monitor urban pollution and atmospheric change, and it has nothing to do with technology. No, this method grows readily right on the rocks and trees: moss. 

Moss is a natural bioindicator that responds to pollution and drought by changing shape and density or disappearing altogether. Mosses absorb water and nutrients from their immediate surroundings, which can be a good indicator of changes to ecosystems. By monitoring these changes in the moss's natural environment (or even in cultivated scenarios) scientists can ascertain the levels of pollution in the air that might cause harm to human health. 

These findings were published in the Landscape and Urban Planning journal by Dr. Yoshitaka Oishi, an associate professor at Fukui Prefectural University. The study described the effect of nitrogen pollution, air quality and drought on moss found over a 1.9-mile area in Hachioji City in northwestern Tokyo. The study showed that severe stress from drought occurred on the moss in areas with high levels of nitrogen pollution, which raised concerns for Dr. Oishi over the impact on health and biodiversity in the region. 

While the study focused on Japan, the potential for this new discovery is worldwide: Moss is prevalent in urban centers across the world, and 88 percent of city dwellers are exposed to levels of pollution every year that exceeds the World Health Organizations air quality guidelines. Southeast Asia and the eastern Mediterranean are particularly affected, as are countries in Latin America and Africa. Moss could be the cost-effective answer to monitoring just how bad these areas are getting.

"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," Oishi told the Thomson Reuters Foundation.

This isn't the first time moss has been implemented as a solution to urban pollution. Brussels-based company Green City Solutions plants mobile walls of moss around cities, which act as small, portable CO2-catching planters called Citytrees. Measuring around 3.5 meters (about 3.8 yards), each Citytree cleans as much air as 275 trees, according Green City, as are designed to be self-watering, self-monitoring and aesthetically pleasing. So far, around 20 Citytrees have been installed in cities around the world.

Like Dr. Oishi, Green City is using moss because it is easy to grow, resilient, and are absorbent. Or as Zhengliang Wu, co-founder of Green City Solutions, put it, "Moss cultures have a much larger leaf surface area than any other plant. That means we can capture more pollutants."