Ancient and mysterious. Here is a picture of the planet’s ancient past and if we are very good: a vision of our future.


When I discovered this group of lichens I couldn’t help but feel wonder. This tiny ecosystem is the end result of a whole lot of tricky connections. A lichen isn’t one organism but a perfect marriage of algae/cyanobacteria and fungi. How do tiny compatible organisms manage to find each other in a big world without an online dating service?

Yet, somehow they do find each other. And then they find a way to meld and cooperate to create something bigger and better than each alone could ever be. The process is mysterious. People try to grow lichens in labs and often fail miserably ending up with gross looking blobs instead of the amazing structures anyone can find growing wild.

As a complete newb I can only guess at what is growing in the photo above. I think the orange parasols are Teloschistes. The black circle with a white outline might be Tephomela or Lecanora. Maybe Phaeophysica? shrug Anyone know a good lichenologist?

Mixed in is the leafy-like stuff and paint-splotchy stuff that I have seen often enough but typically overlook.

More of the orange parasols below. I found these communities at Willowbrook Reach growing on living trees.


Car Pollution

Many lichens are not pollution tolerant and our neighbourhood has seen a substantial increase in traffic. It isn’t my paranoid imagination speaking. Not only does it take longer to cross the road as a steady stream of traffic flows by but I have seen chemical changes too. Limestone surfaces that were clean when I moved here are collecting that characteristic black stain created by car pollution. These stains are different from the soot I can wash off my house; they are the product of a chemical reaction involving nitrogen dioxide and sulphur dioxide from car emissions. In some places the rock surfaces are pitted showing where they are starting to dissolve.

Stone wall facing east and relatively little traffic. The white limestone is beginning to discolour.
Stone wall facing north and a steady stream of traffic.. The surfaces show much more discolouration and pitting.

Limestone blocks are more than an expensive pieces of cut rock. I kind of think of them as compressed fossils. Limestone forms when calcite from ancient corals and tiny microscopic skeletons accumulates in warm shallow seas over an unthinkable stretch of time. It is kind of like rock made from bones and sea shells.

Have you ever seen what happens to a chicken bone stored in a vinegar solution?

First you’ll see bubbles rise as trapped carbon escapes. Let the bone sit and it will become so soft you can twist it — sometimes even tie it into a knot. That is kind of what is happening to this limestone wall. Our oceans. And soil.

 What This Means for Gardeners

Gardening in Austin is already really difficult. When I first moved here I thought I was a good gardener with a decent skill set. Apparently not. I had more failures than successes and if it wasn’t for my insanely stubborn nature I would have given up long ago.

I used to think that the problem was in learning how to adjust to working with extreme heat and summer drought. But I think I just discovered a new layer to the problem. The problem isn’t ‘merely’ increasing temperatures — I need to add air and soil acidification into the mix.

That discolouration on limestone surfaces is evidence that the air here is already acidic. The increase in traffic suggests it will become worse. This means the sweet (basic pH) clay soil on this side of the city is probably also undergoing big changes.

For people living on the west side dealing with caliche soil acidification means an already difficult situation can only get drastically worse.

How much of a pH change will the native plants tolerate? Change the chemistry of the air and soil and you change everything.

I already knew I’d need to choose plants that can cope with extremes in moisture and temperature. But now I see that if I want my garden to last I will need to find plants that will tolerate a range in soil pH too. And air pollution. That sounds like big trouble over the long term. Acid loving plants tend to have evolved in forests with a lot of water and cool temperatures. Hmmm.


Meanwhile I think I will continue to seek out and appreciate our local lichen colonies while they last. Some lichens grow at a rate of .5 mm every year. I am from Canada. I know just how small one mm is. The next time I visit the cemetery I am going to bring along a ruler. I remember seeing lichens growing on the tombstones there. The dates on those tombstones could come in handy for appreciating the growth rate of these organisms.

How old are lichens in general? One source said they were already present about 400 million years ago. I am going to start calling that period of time The Age of Cooperation. That is when the leaf cutter ants also created a mutually beneficial relationship with fungi.

No wonder people are so bad at this cooperating business! Modern humans have only been around for about 50,000 years. We are as clumsy as toddlers. As terrible as a two year old. And somehow we’ve found ourselves in charge of the place …

40 thoughts on “Lichens

  1. I did not have time to read your post properly last week Debra and have come back this morning to read again and I am glad I did, great informative post and wonderful photos. I really enjoy observing Lichens and mosses and so happy you do to.


  2. A very enjoyable and informative post, thank you! I’m also fascinated by mosses, lichen and mushrooms but not an expert. It’s just so complex. The yellow mushroom reminds me of the red elf cup which we find around our woods. We also have plenty of lichen…and to think that some people think they’re a sign of pollution, oh dear!


    1. Thanks so much for the comment! and encouragement! There is a lot to love out there. Your red elf cup sounds interesting. Love the name. I’ll have to look it up. I can see why some people might connect lichens to polluted areas. I live in an older area. Where there are old materials there will inevitably be signs of decay. That is how it is supposed to be. Lichens will move in because they are the first organisms to start the process of succession. And well some lichens are so specific that polluted areas are what they need.


        1. It really depends on the kind of lichen. They each have really exact needs and can handle almost no deviation. And I just recently found this out too. But that species variability allows some lichens to move into terrible death dealing places like where a volcano may have blown an area up to begin the process of building up a new ecosystem.

          Liked by 1 person

  3. Really enjoyed this post. <3
    I live in a fairly sparsely-populated part of Ireland and I love the abundance of lichen here. There is so much more than in the built-up places I've lived in before. There is a flat white lichen here that is very common on the stonework and also the trees get covered in branching lichen. I've been wanting to post pictures on my blog but haven't got around to it yet. Maybe this will inspire me to get my camera out.


  4. I adore lichens and wrote about those found on my maple tree….they are covered in these beautiful organisms. I loved learning more and look forward to hearing what you find in the cemetery. MAybe if we could cooperate think of all the magic we could make in this world….


    1. Thank you. I can’t believe how many treasures I have overlooked all my life. I think you are right: lichens are kind of miraculous and magical.


  5. Oh, lichen. Seeing it anywhere is a reminder to protect our air (water, and soil) since, as you point out, they are the poster children for eco-cooperation. Those are some especially spectacular shots, Deb. I’d never seen the orange parasolly ones in bloom that way before. Breathtaking. I’m a lichen admirer from way back, and next to moss, I believe lichen are perhaps the least well understood or appreciated organisms growing in these parts. Thanks for helping address that!


  6. Very interesting and worth further investigation. It would seem though that the air (moisture in the air – acid rain) is far more acidified and detrimental than would the soil be in changing pH due to pollution for affecting lichen. Porous rock like limestone makes sense to absorb the rain as does soil, but to change soil pH quite a lot of that type of rain would be necessary. As acid rain falls on a substrate like tree bark for instance, one kind of lichen growth form may be replaced by another more tolerant form, so using it as a barometer would make it hard to determine how bad is the pollution I would guess.

    Also, I think the acid rain immediately affects a herbaceous plant’s leafy parts – killing the plant. It is really evident seeing burnt plants. Calcium and magnesium – base nutrients, are found in soil and are necessary for plant growth. These nutrients also neutralize acids. Buffering is a process that helps soil resist the effects of acid rain and these salts are buffering agents. Places that have thin, nutrient poor soils are not as effective at buffering the rain though, and these soils can become increasingly acidic which would reduce ability to support a healthy plant life. Over a very long time, aluminum which is in soil, will dissolve and be carried into wetlands and streams. That becomes very toxic to all the aquatic life living in those places. Wetlands are some of the first places to notice the affects of acid rain. I know in areas of high pollution, lichen is often found on tree wounds and on sandstone walls. In architecture, we have to deal with biodegradation and conservation of structures.


    1. Great info! Thank you. One of the things I recently learned was that these pollutants don’t even need rain — they can be deposited just by humidity. And trust me this is a VERY humid place in the summer. And as you say, as bad as acidification might be for soil it is far far worse for aquatic life.


    1. Back in the day we called it acid rain. haha. I feel like one of those old grannies shaking her cane. But the lichens are seriously beautiful. I am starting to get obsessed with them.


  7. Our city has installed some roundabouts to smooth out traffic flows. They have install huge limestone blocks as decorative elements. We have a lot of limestone as bedrock here from the Devonian seabed we once were. In about two years, the blocks got ugly dark stains streaking down them. I imagine it is the same chemical you point out in the lichens and rocks above. The city now goes around and power washes the blocks to give them a fresh look.


    1. Oh thank you! Great photo. And that looks like a great place for a science fair project. Is the stuff washing off tar and soot? That alone is a problem since soot was the very first carcinogen ever identified. If it is soot — how much builds up between washings? That could be measured. And where does the soot ‘go’ when it is washed off the rock? If it is the chemical reaction how much of the stone surface gets eroded with each power wash? Harder to measure but not impossible. Either way, those stones are a great indicator for air quality. That investigation could lead to discussions about cars and how they erode human and environmental health.

      Liked by 1 person

  8. Beautiful. I usually notice lichens on rocks rather than trees, and I’ve been better at noticing them in the last few years. This was a fun post to read.

    As to the limestone, our region is built of coral limestone. Limestone is used decoratively all over — it’s beautiful and available. And I do see the darkening of stone over time. I’d assumed it was sooty residue. Thanks for explaining the real reason.


    1. Thank you! We also have a lot of limestone present and people frequently use it as a building material. It is so much nicer than concrete in my opinion.

      Liked by 1 person

  9. A fascinating post! Lichen are curious things. I love your photos of them – especially the orange parasols. I’d love to see some as impressive as those! The effect of pollution is a sad truth. Mankind’s influence on the planet is a worrying one.


    1. Thank you. =) From what I can see a lot of these lichens have a global distribution. These guys were tiny. Each parasol was about the size of a letter O in print — super easy to overlook.

      Liked by 1 person

  10. Your photos of the lichen are brilliant. As much as we proclaim the beauty of the plants and flowers we see everyday on a larger scale, these small colonies are simply beautiful examples of the different types of life on our planet.

    As to your point that changing the chemistry of the air and soil changes everything, you’re so correct! And it’s been happening for eons. Just check out the history of various regions following cataclysmic volcanic eruptions. A cursory study of Yellowstone Park’s volcanic area or Mount St. Helens since it’s eruption proves that. The growth of deserts is another example. Our air and soil, AND our water, have changed and will continue to change, for better or worse. And as they change, so will the plant and animal life that depends on them. That includes human beings as well!

    Thanks for such a thought-provoking post!


    1. Glad you liked it. It is true that natural forces also contribute to air pollution. Though not nearly as much as human interference and they aren’t things we can control as we can with the use of automobiles. I have visited Yellowstone and that is a pretty hellish vision of the future. But as you say life prevails. Even there you will find lichens that are pollution tolerant busy wearing down rocks to make soil one half mm at a time. haha


  11. A lovely header and I’ m likin’ your lichen. What a beautiful and complex structure. I have noticed some amazing lichens growing on ancient gravestones in churchyards round here. You have inspired me to go and have a closer look.


  12. As to your first question, some of the people I’ve known who use online dating services, well, let’s just say that maybe they didn’t have the intellectual capacity of lichen. Which probably brings me to your last point–how do we, the toddlers (at best) in the world, find ourselves in charge? Hmmm. Lots of answers to that one, I guess.

    It’s interesting what you’re observing in your east Austin neighborhood. I have similar soil as you do–I think–I’m east of MoPac, with decent depth, not the thin caliche of those west of MoPac. I haven’t seen the discoloration of limestone that you’re observing, but that doesn’t mean there isn’t plenty of pollution. Nor have I seen the changes in soil you’re observing. I do think that many of our native plants are remarkably valiant and resourceful, but they have evolved for specific climate and soil limits. If you’re correct, many could succumb in time to changes in air and soil composition.

    I love your photos, as always, I especially love your descriptors: “leafy-like stuff and paint-splotchy stuff “. Nice.


    1. I doubt we will see changes to our soil in a hurry but I could be wrong. The old blackland prairie soils are going to buffer and buffer until poof one day they will hit the tipping point or critical load or whatever you want to call that phenomenon. It will happen much more quickly to the caliche. And just because we can’t see it doesn’t mean it isn’t happening. Remember when we used to have Ozone Action Days? Nearly every day one summer I got to ride the bus for free. Nobody even talks about ozone anymore since they dropped that program but when I go out where there is a vista I can see a pretty dense haze most summer mornings. We have a pretty serious car pollution problem here.

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