Lichen and what they tell you

Lichen is a plant that mostly grows on trees but can grow on other things like concrete and grass.Lichen is a bio indicator which tells you is it is clean or not.There are different types of lichen yellow lichen tells you that the air is dirty white,green lichen tells you that the air is clean gray lichen tells you that the air is in the middle. We went to two places the Easter inch moss and the main road we went to the Easter inch moss first and we found a lot of white lichen a small amount of yellow and one patch of grey lichen when we went to the main road we found a lot of yellow lichen no white lichen and no grey lichen which tells us that the air in the Easter inch moss was cleaner then the air in the main road so lichen is really important to tell if the air is clean or not.