The world's rags

In Book III of his History of Plants, Theophrastus describes lichens as "rags hanging from the trees". Today, it seems as if the whole of nature, so mistreated by our civilizations, is hanging in rags over the rest of the world. Lichens, pioneering ecosystems, act as scrolls of the "critical zone" that we find so hard to imagine. Forgotten sentinels that can stay alive for more than 8,000 years, ill-defined organisms clinging to dwarf birch trees in the Arctic, they are incomparable biomarkers that reveal the extent of global warming. World and part, they draw a landscape that reconsiders the traces and impacts of living organisms.