A living air quality ledger
In the northernmost part of Myanmar, the Kachin Hills contain the world's highest-quality jadeite jade, fueling a multi-billion dollar industry. This intensive extraction, centered around the town of Hpakant, has dramatically altered the area, turning forested mountains into barren pits. Beyond the visible damage to the land, the mining operations release a constant plume of atmospheric pollutants. Heavy machinery emits nitrogen oxides (NOx) and sulfur dioxide (SO2), while the constant excavation and movement of earth create immense quantities of airborne particulate matter. These pollutants settle on the surrounding environment, and one group of organisms, lichens, record this contamination.
Lichens are composite organisms, a symbiosis between a fungus and a photosynthetic partner, either an alga or a cyanobacterium. Lacking roots or a protective cuticle, they absorb water and nutrients directly from the atmosphere. This direct exposure makes them exceptionally sensitive to air quality. Different lichen species possess different tolerances to specific pollutants. By observing which species are present and which are absent, scientists can build a detailed picture of local air quality, a technique known as biomonitoring.
Reading the pollution signals
Near active jade mines, the air is thick with dust and chemical emissions. In these highly polluted zones, only the most robust lichen species can survive. Crust-like (crustose) lichens, which grow tightly pressed to tree bark or rock, tend to be more tolerant. Species in genera like Pyxine have been identified in other industrial areas of Southeast Asia as tolerant to pollutants and changes in substrate pH caused by nitrogen deposition. These tough species may be the only lichens found in the immediate vicinity of the Hpakant mining operations.
Moving away from the epicenters of mining, the composition of the lichen community changes. In this transitional zone, more complex, "leafy" (foliose) species might appear. The most delicate forms, the "shrubby" and hair-like (fruticose) lichens, remain absent. Species from the genus Usnea, which often resemble small beards hanging from tree branches, are famously sensitive to sulfur dioxide and other pollutants and disappear quickly from contaminated areas. The disappearance of these sensitive species, and the dominance of a few tolerant ones, is a biological signal of degraded air quality. Studies in other mining regions have shown that lichens accumulate heavy metals like lead, chromium, nickel, and arsenic in their tissues, with concentrations reflecting the levels in the environment.