What is a lichen?

what is a lichen?

lichen covered tree

What is a lichen?

Ever wondered what is a lichen? They often appear as light green covering on trees so clear during winter months when the leaves have fallen. These are lichens and are made of 2 parts, an alga and fungi. Other living organisms cover trees too including ferns, mosses, fungi and plants. These are all collectively known as epiphytes.

These mysterious organisms are fascinating and come in a range of colours and sizes.

what is a lichen?

flavoparmelia type lichen

A lichen consists of 2 or more partners living together with both benefiting from the association. One partner is a fungus the other either an alga or a cyanobacteria (also known as blue-green alga although it is more closely related to bacteria than algae).

The alga produces nutrients from the suns energy by Photosynthesis. The fungus creates a body (thallus) in which they both live and produces chemicals that may act as sunscreen to protect the alga.

what is a lichen?

Cladonia spp. Fairy cup lichen

Lichens are an ancient type of organism dating back over 400 million years. They are very successful and cover over 8% of the world surface and over 30,000 species have been identified. They grow on the highest mountains to tidal coasts and from polar regions to the tropics.

Some are tiny and encrust rocks, trees or soil. There are some which resemble beards and are bushy, sometimes growing up to 3m, whilst others are lobed and leaf-like.

what is a lichen?

Devil’s matchstick lichen – Cladonia spp

Colours range from dull grey-browns to brilliant yellows and bright orange reds.

Lichens tell us about the health of the air we breathe. They are sensitive to pollutants from agriculture, power stations and car fumes. Burning coal for power produces acidic rainfall killing lichens and agricultural nitrogen compounds significantly change the lichens present as some are very sensitive whilst others thrive in the nitrogen rich air.

Some lichens are edible and used to flavour pizza in Morocco!

what is a lichen?

Usnea spp. lichen

Others are used by drug companies to make antibiotics or sunscreen cream.

Litmus paper, used to tell if a solution is acidic or basic, uses a water-soluble mixture of different dyes extracted from lichens.
They have also been used as indicators of ancient woodlands to show that they have never been clear-felled.

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