Methuselah beard lichen or old man’s beard lichen (and known often scientifically by its synoynm, Usnea longissima) was once more widespread than it is today. Throughout much of its historic range, a patchy distribution of circumboreal forests in Europe, Asia and North America, it is now either threatened or extirpated. Populations remain strong in the Pacific Northwest of North America, however. Declines are attributable to habitat loss (clear-cutting) and air pollution.
In one of my favourite natural history books, The Lichens of North America, reference is made both to its pollution-sensitivity: “Its presence can be used as an indication of pure air” as well as its outstanding potential length: up to 3m (10ft) (“easily the longest lichen in the world“).
A photographic note: the vertical streaks in the background of the image are rain drops.