IMPORTANCE OF LICHENS

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Lichens are common food for insects and slugs. In the arctic tundra, reindeer and caribou rely on lichens during the winter, when no other food is available. Several species of lichens that sprout up through the snow are called reindeer mosses.

Humans rarely eat lichens except in cases where no other food is available. The Bible may chronicle one such example: Some scholars believe that the manna or bread that the ancient Israelites ate in the desert when they fled Egypt was made of lichen. In Japan, where algae as well as fungi are prized foods, certain lichens are eaten as delicacies.

Although lichens have been used in folk medicine as purported cures for many ills, from headaches and toothaches to tuberculosis, diabetes, and asthma, their use in modern medicine is recent. The discovery in the 1940s that some fungi produce potent antibiotics stimulated an extensive screening of fungi and lichens. Since then, lichen extracts have found limited use in Europe, where lichen antibiotics have been used to treat tuberculosis and some skin diseases.

Lichen extracts are also used to add color or scent. Many lichens have earthy red, brown, russet, and blue pigments, and these pigments have been used as clothing dyes since the time of ancient Greece. Native Americans use boiled lichen extracts to dye cloth and baskets. Even the famous Harris tweeds, woolen textiles from the Scottish islands, are still dyed with Scottish lichens. A number of dark, oily extracts from European and African lichens are used to add scents to soaps and perfumes.

Lichens are used as living indicators of environmental problems because of their sensitivity to atmospheric pollution. Despite their hardiness in severe conditions, many lichens are damaged by the chemicals found in polluted air and by acid rain produced from the burning of coal, oil, and gasoline, and other industrial processes. Comparisons of lichen damage from industrialized and nonindustrialized areas provide an index of air pollution. Studies spanning the past 50 years have found that the variety and number of lichens have declined in many industrialized cities in both Europe and North America. Fortunately, studies have shown that when a pollution source is shut down, lichens can make a comeback, providing hope for their long-term survival.

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