Along the trails, you may notice patches of black crust on the soil (through early stages of development are nearly invisible). Known as "cryptobiotic crust," it is a mixture of cyanobacteria, mosses, lichen, fungi and algae. This remarkable plant community holds the desert sands together, absorbs moisture, produces nutrients, and provides seedbeds for other plants to grow. This crust is so fragile that one footprint can wipe out years of growth. Please don't walk on it. Stay on trails!