What if there existed something in nature that could gauge air quality? There is. Though they have a preference for rough bark, lichens grow on most of the trees here. Consequently, most of the tree trunks in the woods around my home are a light grey. This is a good thing, as lichens are bioindicators of high quality air in the environment. The more three-dimensional the lichens are, the better the air quality.
Lichens are not plants. They are a mutually beneficial relationship between a fungus and algae. For more information about this relationship, see my previous post about Lichens.
When it rains, lichens act as a sponge by absorbing as much water as possible. After the rain stops, they slowly release the water back into the environment. This process keeps humidity levels in the forest more stable than if the water was simply allowed to fall directly onto the ground.
The three-dimensional properties of lichens also make them ideal places for arthropods to survive. It’s no wonder then, that birds are especially attracted to tree trunks covered in lichens. Even chickadees that have access to seed in the winter will consume arthropods for 50% of their diet.
Considering the above benefits, wouldn’t it be helpful to promote lichen growth on trees in the city?