Learning to love lichens


This article was written in 2014. On 2 April 2016 Judith will be running a lichens workshop at Horton-in-Ribblesdale Churchyard, and  will update this post shortly to publicise this too.

Judith Allinson writes:

Lichens can tell us so much about the world we live in.

They are fun to study – buy a hand lens. (If you live  near me,  I’ll sell you one)

It is a simple hobby that does not produce much pollution (unless you travel the world by plane to see new species).

Three ways learning about lichens can improve your life: 

  1. Lichens can become your friends – when I see  Map Lichen (Rhizocarpon geographicum) it reminds me of going on walks in the Lake District and North Wales.   Lichens tell me about the environment and I feel happy to understand about how things work.
  2. Lichens are studied by interesting people – people like you maybe, who like a challenge and like to learn things. Lichen people are usually very helpful. – so you can make interesting friends, and become more interesting yourself.
  3. Lichens get you outside – whether up mountains or in the town park or churchyard.

Joseph Priestly in Birmingham


Here is a picture of a statue of Joseph Priestly (one of the discoverers of Oxygen), in the centre of Birmingham that I visited whilst on the CEL Joy in Enough conference in March 2014 – It has lichens on the plinth.


Xanthoria parietina

  They happen to be: Xanthoria parietina and Physcia adscendens.  Xanthoria parietina is sometimes known as Bird Perch Lichen, because it  will grow where there are lots of bird droppings. ..These lichens are indicators of Nitrogen pollution – the second biggest planetary limit we have exceeded – bigger than climate change – but not as big as biodiversity loss. (More on planetary limits at the foot of post)


Physcia adscendens


(Chemistry lesson to explain nitrogen fertilizer, algal blooms and why nitrogen pollution is the second biggest planetary limit) : Nitrogen gas N2 makes up 78% of the air and it is fairly inert. Plants cannot use it as fertilizer. Fertilizer Nitrogen compounds are made out of Nitrogen gas from the air by the Haber Bosch industrial process. Fertiliser compounds contain nitrogen – e.g. ammonium nitrate – NH4NO3- and break down to form Nitrogen Oxides. Cow urea is broken to to form ammonia . These various compounds cause haze and pollution which causes respiratory diseases and add “Extra fertiliser” to the trees, water systems etc. I shall just call these all these compounds  containing nitrogen “Nitrogen” here.). This “extra fertilizer” causes algal blooms in lakes in late summer and when the algae die, and the bacteria break them down, all the oxygen in the water gets used up so all the fish and other water organisms die.

No surprise to find these two lichens in the centre of Birmingham

But here is a tree branch in a country churchyard (Ingleton)  near the Yorkshire/Lancashire/Cumbria border:


Xanthoria parietina and Physcia adscendens

The very same two lichens.  This shows there is nitrogen pollution in the open countryside

Other studies of lichens (and chemical analysis of the air) shows that there is blanket pollution caused by the increasing and excessive use of nitrogen fertilizers. (It is exactly 100 years ago that the Haber- Bosch process was developed to make chemical fertilizers, and our vastly increased agricultural output is due to them. But much of the fertilizer runs through the soil into the rivers, or gets blown into the air, or gets converted to nitrogen oxides which are gases and go into the air.)

Many people know that we do not get big fruticose lichens in the centre of cities (compared to what you find in the Lake District, Wales and West Scotland.) This is because 150 to 30  years ago we had big problems in this country due to Sulphur dioxide pollution caused by burning coal. Now as city air is cleaner with respect to Sulphur dioxide these large lichens are increasing slowly, in built up aeas.   It is only recently that lichenologists have noticed how Nitrogen tolerant lichens such as Xanthoria and Physcia are spreading rapidly throughout Britain.


Learn more about lichens and you will be able to see where nitrogen pollution occurs. Or  just enjoy learning about the world around you and the beautiful shapes and colours.

  1. Opal Lichen project – do anytime this with your  WI,  Your youth group, your U3A group or by yourself.
  2. British Lichen Society – Lots of useful information about lichens

Planetary Boundaries

There are are nine planetary boundaries – which we must not exceed if life as we know it is to continue – according to a group in Sweden – (e.g. Fresh water use and Ozone depletion / hole in the ozone layer)

So far we have exceeded three of these boundaries by a long way:
Climate Change
Biodiversity Loss
Nitrogen Pollution

There is lots on this website, and other Green Christian Websites about Climate Change (e.g. Operation Noah), and there is a little on this website on Biodiversity loss (CEL encourages churches to raise money to save biodiversity through the CEL’s 100 Churches project . )

But what do you know about Nitrogen Pollution?


293px-Planetary_boundaries.svgPlot of the planetary boundaries according to the Nature paper by Rockström et al.[1] The colored star-like area represents the estimated current state and the corners of the red octagon circumscribed by the Earth are the estimated boundaries. Systems whose safe operating space could not yet be determined were left out.

Learn more about lichens and you will be able to see where nitrogen pollution occurs

  1. Opal Lichen project – do anytime this with your  WI,  Your youth group, your U3A group or by yourself.
  2. British Lichen Society – Lots of useful information about lichens



Author: | Date: 9 April, 2014 | Category: Biodiversity | Comments: 0

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