lichen

In recognition of their vulnerability, the lichen fields have been marked off on maps and with fences.

In particular, your reading mentions lichens.

Lichens are plants you'll find growing on rocks in the far north, sometimes referred to as reindeer moss.

In industrialized areas, lichens are destroyed by pollution, tree barks become darker, and dark moths are the ones birds have difficulty detecting.

That's right, and in winter, lichens are crucial for reindeer because their supply energy, but they don't have all the proteins and minerals the reindeer need.

Further, nearly all of the ice-age fauna had teeth that indicate an adaptation to grasses and sedges; they could not have been supported by a modern flora of mosses and lichens.

Lichens were probably the first successful flora.

Lichens helped to speed the decomposition of the hard rock surfaces, preparing a soft bed of soil that was abundantly supplied with minerals that had been carried in the molten rock from the bowels of Earth.

Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants.

Like if a cow or a sheep eats lichens, they're only gonna get like half as much nutrition out of them as a reindeer would.

Yeah, somehow when reindeer eat lichens they're able to draw a lot more nutrients from them than other animals.

Anyway...Okay, reindeer, um, oh, oh yes, and one more thing about lichens.

But lichens are actually quite complex.

Not far upslope were three rounded boulders, lichen-covered, with a hole beneath.