02/28/2026
Lichens are tiny, but have a BIG story to tell about the air we breathe — and they're vanishing.
Lichens, the colorful crusts, tufts, and leafy growths often found on tree trunks and rocks, are far more than biological oddities—they are nature’s air quality sensors.
These composite organisms, formed by a symbiotic relationship between fungi and algae or cyanobacteria, absorb nutrients directly from the air.
Because they lack roots and protective barriers, lichens are incredibly sensitive to airborne pollutants like nitrogen oxides and sulphur dioxide. Their presence, variety, and growth patterns offer scientists a powerful, natural method to monitor and understand air pollution’s effects on ecosystems.
Researchers, including teams at the Natural History Museum, are now using lichens to assess the impact of agricultural pollution, particularly nitrogen-based fertilisers. In Sri Lanka’s tea-growing regions, excess nitrogen escapes into the air and drifts into neighboring mountain cloud forests. There, scientists have set up long-term plots to track how lichen communities respond to varying nitrogen levels over time. This research not only reveals how far-reaching pollution from farming can be but also underscores lichens’ vital role in both ecological monitoring and ecosystem stability.