• Saturday, February 19th, 2011

I was walking in a park I’ve never visited before with some colleagues who work there and one of them pointed out a lichen growing on a tree outside the nature center. She said up until a few years ago, there were no lichens in the park. Hmmm. How could that be? How did she know? Light bulb over head! A topic for Nature Niche!
I’m sure all of you have seen lichens, unless you never left the city, but perhaps mistook them for a moss or fungus. They are usually light green and grow on trees, rocks, really anything. Some grown in lacy patterns that remind me of the doilies my grandmother used to put on furniture.
Lichens are a combination of an algae and a fungus that grow together in a symbiotic relationship. The fungus offers moisture and a place for the algae to grow. The algae photosynthesizes to make food which the fungus consumes. The reason my colleague was remarking on the return of the lichen, was because they are extremely sensitive to air pollution. They can actually be used as air quality indicators. Lichens grow in three forms— crustose, foliose and fruiticose; each of which is progressively more sensitive to poor air quality. Crustose is most common around here and is flat and well, crusty. Foliose is leafy looking and fruiticose is almost shaggy. It is difficult to find fruiticose lichens where there is any industry since they are for the most part, intolerant of air pollution.
So good news for Bristol, Pa. The lichens are returning. You can all literally breathe a little easier.
Aren’t you now wondering if there are lichens growing in your habitat? Why not go out and take a look. Here are some photos of crustose and foliose lichens.

Crustose Lichen on Silver Maple bark

Foliose lichen on oak tree

Crustose lichen on rock

Crustose lichen on brick

Category: Nature Education
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