In short, a moss is a simple plant, and a lichen is a fungi-algae sandwich. Mosses are multicellular organisms with leaflets made of photosynthetic cells, just as with trees, ferns and wildflowers.

In patches of soil where mosses were present, there was more nutrient cycling, decomposition of organic matter and even control of pathogens harmful to other plants and people. On top of that, the authors say mosses may be instrumental in reabsorbing carbon dioxide.

Mosses will grow on any hard surface, including the sides of trees, but they prefer to grow on North-facing surfaces because they like the darker, more humid environment. If you don't see any moss growing on trees, also check on rocks. Mosses love to grow on hard surfaces, so trees and rocks are perfect homes for them.