The story
The abundant beard lichens draping Sol Duc Valley trees indicate exceptionally clean air, as many lichen species cannot survive in polluted conditions and serve as natural bioindicators of air quality. The valley's remoteness and the park's protection give the Olympic interior some of the cleanest air in the contiguous United States.
Notice those pale lichen beards once more on the way down. They only grow that thick where the air runs clean, and up here it runs about as clean as it comes. The forest wears its air quality on its sleeve, and the report is glowing. Take one more deep breath of it before the highway. You won't find better. Roll on out.
Photo: Niagara66 · CC BY-SA 4.0
