An Introduction to Lichens

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Lichens are a fascinating part of all our garden spaces, here you will find a basic introduction to these prehistoric life forms.

Introduction to Lichens

If I were to tell you that a body far more advanced and complex than our own, formed with no less than two species and continuing to breed at the ripe old age of 400 million years, had been discovered swarming in it’s millions right here on earth, I should imagine you may become intrigued if not alarmed. Indeed, it would appear that the closest thing to alien existence that the public have ever heard of has at last come to light. However, should I then tell you that this alien race was in fact made up of the different types of lichen which exist in their millions here on earth, that excitement would undoubtedly be extinguished. This truth is what privileges me to enlighten you in the fascinating subject of lichen and the extraordinary ways in which it has been used.

What is Lichen?

The subject of lichen is not renowned for being the most fascinating or stimulating topic of interest; in fact, lichen is not well known at all. Commonly confused with moss or fungus, lichen is an organism that is more often than not completely ignored by society. A lichen is a unique and specific structure, formed primarily by a mycobiont (fungus) and a photobiont (alga or cyanobacterium) and is admired as the one of the most efficient colonisers on the planet. As lichens are able to survive in harrowing environments, for example the sub zero conditions of mountain ranges, they have proven to be some of the most tolerant, advanced and important structures in existence – so it’s would be extremely difficult to find one growing in your garden or garden sheds. And with an estimation of more than 25,000 different species of lichen, it is unquestionable that we will all encounter a lichen species at some stage during our every day activities – and yet they remain unnoticed. Easily overlooked, the most fascinating qualities of lichen have not been brought to the public’s eye, despite the fact that 8% of the world today is covered in lichen. Nonetheless, scientists have investigated the organism, and as a consequence lichen has been discovered to be an invaluable tool to our world’s industry.

Lichen in industry.

The variety of different uses of lichen are astonishing; ecologists in Europe rely on lichen as a reliable source to determine the levels of air quality and pollution – lichens are extremely sensitive to man-made gases and pollutants, therefore providing a good measure of how contaminated an area may be. Furthermore, in Japan it is not uncommon to find lichen on the dinner menu: the lichen species Umbilicaria esculenta is frequently used in soups and salads. Remarkably, lichen is predominantly a carbohydrate and yet is 0% in fat. Equally partial to this unusual diet, reindeer will often be found feeding on Cladonia rangiferina (shown above), which is found primarily in areas of alpine tundra. Indeed, deer in general are unique in that they contain a specific enzyme known as ‘lichenase’ which enables them to digest lichen effectively. The benefits of lichen stretch as far as the fashion industry; ‘Roccella’ is a dye used to create blue and red fabrics and is formed by numerous lichen species (most likely Xanthoria and Cladonia), it is estimated that 9,000 tonnes of lichen (largely from Evernia prunastri and Pseusdevernia furfuacea) are used in the perfume commerce alone.

Perhaps one of most extreme and expensive lichen experiments to take place was in 2005 as a part of a space investigation. That year the European Space Agency embarked on a mission to test the versatility of lichen in the space environment. The test formed part of an investigation of the panspermia theory (the transferring of a species to another planet). Previously, certain forms of bacteria had proven to be too weak to stand the extreme conditions of space; however, it was suggested that certain species of lichen (Rhizocarpon georgraphicum and Xanthoria elegans) would be more successful. Therefore on the 31st of May a Russian Soyuz rocket transported the two species into space, where scientists subjected them to photon 2 emissions, high UV ray exposure and extreme cosmic radiation- all of which the species endured successfully and suffered no changes. The break-through gave an enormous boost to the panspermia theory, and encouraged the idea that scientists one day would be able to transport living organisms to Mars.

 

Further Reading

http://www.earthlife.net/lichens/reproduction.html

http://www.theecologist.org/how_to_make_a_difference/cleaner_air_water_land/363298/

http://www.esa.int/Our_Activities/Human_Spaceflight/Lichen_survives_in_space

http://www.sharnoffphotos.com/lichensNH/human_uses_dyeing.html

http://people.duke.edu/~bph8/VirginiaLichens/index.html

http://blogs.discovery.com/news_animal/2009/04/lichen-named-after-barack-obama.html

 

Lichen in medicine & further research

Due to their adaptability, lichens have been discovered and utilised on almost every continent, with many cultures finding their own use for the organisms. The relationship between lichen and human has its own branch of research known as ethnolichenology, further reiterating its importance in our environment. As a medicine, lichen is most useful when certain elements, known as secondary compounds, are extracted from the species and exploited as a particular treatment. This is commonly in the form compounds such as usnic acid, an antibiotic compound found in many lichen species – approximately half of all lichens contain this compound and/or other antibiotic properties. Other secondary compounds include bacteria killing toxins and pigments which can help reduce the effects of harmful exposure to sunlight. Lichens are commonly mistaken as the causes of Lichen sclerosus, though the skin condition is thought to be due to an overactive immune system and unrelated to lichens themselves.
The field of lichenometry has given scientists valuable tools when researching into the age of geological entities.  It is estimated that lichen can be preserved for up to 10,000 years and due to our understanding of its growth, one can extract information about the body it is using to grow on. A variety of methods allow us to determine the ages of rocks, changes in water levels, glacial deposits, rock falls and more.

In sum therefore, the utility, flexibility and commercial wealth of the seemingly lowly lichen should not be under estimated.  Whilst its uses and benefits do not enjoy widespread exposure, the remarkable existence of such an unusual life form should be neither over-looked nor marginalised.  From essential nutrition, to ground breaking scientific expansion, lichen is responsible for an extremely diverse number of modern day developments.

 

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