BY KYNA RUBIN

Portland scientists tap the bryophyte Orthotrichum lyellii to test urban air quality.
From the October 2016 issue of Landscape Architecture Magazine 
For decades, mosses and lichens have been used to gauge forest health, and in Europe they have been used to measure and map urban pollution across countries. But a recent study of air quality in Portland, Oregon, is said to mark the first time that U.S. scientists have used moss to collect and map fine-grained data on toxic metals in the air of a city. ?This kind of high-density sampling on a large area is unique, at least in North America,? says Bruce McCune, a professor of botany and plant pathology at Oregon State University who is not associated with the study. ?It allows you to make inferences and find surprises that you wouldn?t otherwise.? Sometimes those surprises are unpleasant. Earlier this year, harnessing the bryophyte Orthotrichum lyellii to test the air quality of communities throughout Portland, U.S. Forest Service scientists found unexpectedly high levels of cadmium, nickel, lead, and arsenic in neighborhoods surrounding two stained glass plants. The study?s results sparked a local outcry that led to political fallout and enhanced regulatory attention.
Mosses are effective air-quality monitors because they lack roots. Living on trees, rocks, and roofs, they gather nutrients and water from the air alone. Few species grow in soil, leaving them unaffected by soil chemistry. And they are highly abso...