Lichens

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Lichens first appeared about 400 million years ago. They are now threatened by logging and climate change.

They show an amazing array of colours and shapes. They are particularly diverse in Britain because of our cool wet climate.

In Britain they are now being preserved by careful management of our woodlands.

Biology

Lichens can incorporate 3 kingdoms of living things: fungi, algae and cyanobacteria.

A symbiotic relationship is formed between each component. The fungi are dependent on the alga but the alga might live by itself.

The alga or cyanobacteria use light to produce carbon food for the fungus (a process called photosynthesis).

Many shapes and colours

Squamulose - lichens with scale-like lobes.

Foliose - leaf-like lichens.

Fructose - lichens with many different forms, usually with cylindrical branches.

Crustose - crust-like lichens

Lichens come in many different colours. Some have been used as natural dyes in specialist clothes. Some are fragrant, and large amounts are used in the perfume industry.

Old-growth forests - a haven for unusual lichens

Welsh woodlands have high rainfall and a mild climate. This provides a refuge for oceanic species restricted to western Europe.

Woodland lichens have become scarce in Wales as old-growth forests have been felled.

Commercial woodlands are unsuitable for old-forest lichens as a result of clear-felling, a lack of old trees and excessive shading.

Early warning systems

Lichens are very vulnerable to pollution and nutrients in the atmosphere. They also react to changes in climate and in woodland management.

They can be used as early warning indicators to show rising pollution. In Britain they have shown that pollution has declined with the decline in heavy industry.

Lichens can be chemically analysed to find what toxins are in the atmosphere.

Article Date: 24 July 2007