A Short Ecology Lecture

Just a quick one from me. A few days ago Mark linked to an essay about mycorrhizae on the BBC, “Friendly fungi help forests fight climate change.” Naturally I read it, and have a few in-line comments and excerpts to share.

A Brief Primer

If you have never heard of mycorrhizae, that’s not surprising. But you will have seen mushrooms and toadstools: some of these are the fruiting bodies of a certain kind of mycorrhiza, “ectos.” Ectomycorrhizae. (Hard name to remember? Not really. Ecto, outside, mycor, fungus, rhiza, root. Fungus that lives outside the root. Geddit? There are “endos” too, which…. you guessed it.

Fungi come in a variety of forms, many of which we encounter day to day, sometimes without realising quite what they are: yeast that makes bread rise is a unicellular fungus. The black pin mould that later causes the demise of the same bread is also a fungus. Dry rot* is a fungus, and so is athlete’s foot. Those fungi with large obvious fruiting bodies we call mushrooms and toadstools get their carbohydrate in a variety of means – from consuming dead wood to destroying living wood (honey fungus as a good example) to actually getting a tree to give it to them in exchange for inorganic soil nutrients.

Ectos are in the latter group. They surround tree roots and set up with them a little swap shop. Who brings what? What does each party want?

Well, the tree has an excess of simple carbohydrates and is wanting nutrients like phosphorus. The ecto has access to plenty of soil phosphorus via its vast network of hyphae. It could of course engage in chemical warfare for what it wants, via the production of destructive enzymes. But a mutualistic enterprise seems to work better in some circumstances.

Figure 2-1 from Jackson & Mason 1984

A classic ecto is fly agaric, a familiar toadstool to anyone who has set foot in a woodland or watched Fantasia.^ According to wiki, this either gets its name from its use as a primitive insecticide, or owing to the fact that if you eat it your mind feels as if it is full of bluebottles. And contrary to good sense, people do actually eat it. Wiki describes its use as an “entheogen,” not a term I had heard, but you can guess what it means by its parts and their use in other words. In a perhaps overenthusiastic attempt at recycling, some folk would drink the urine of those who had earlier eaten the fly agaric. My question: did they take it warm, or let it get cold first? (I cannot abide clearing up warm cat sick, so whenever one of our furries has an accident, I cover it with a paper towel and wait for it to go cold first.)

The Essay

So with that as a primer, with some perhaps interesting but non-essential info added, let us move on to the essay itself.

Its second sentence is:

While we know that forests play a major role in countering global warming – acting as reservoirs for carbon – what is less well understood is how tiny organisms that dwell hidden in the soil help lock away our greenhouse gas emissions.

Here I would like to draw your attention to the way this is put. The use, or perhaps misuse, of active verbs immediately set my teeth on edge. Do forests counter global warming? Do soil organisms help to lock away carbon? If these things happen (and see below for a discussion about that) they have no beneficial intent. They have no intent at all, save to reproduce. That is ecology lesson #1. Nature has no motivation. It is callous, indifferent, ruthless, red in tooth and claw, amazing, beautiful, etc. Nothing that Nature does is for us.

Trees photosynthesise, and:

This is how trees naturally combat the planet-warming greenhouse effect. In the last 20 years, the Amazon rainforest alone is estimated to have taken in 1.7 billion metric tons of carbon dioxide.

Trees combat the greenhouse effect? No. Trees just rollin’. Is that 1.7 billions tonnes a real figure? I don’t know. In any case, is it net? Let us also in passing note that the Amazon rainforest has about the hottest average temperature on the planet.

Trees though do not act in isolation; they are entangled with – and work alongside – a vast community of micro-scale fungi.

A 2016 study led by researchers from Imperial College London revealed that one particular type – ectomycorrhizal fungi – enables certain trees to absorb CO2 faster (and therefore grow faster) than others. This is known as the “CO2 fertilisation effect”.

Aha, now in come the ectomycorrhizae. Unfortunately the association described was known about decades before this Imperial College study. It was discovered long ago that trees grown without their ectos – er, well, they didn’t grow. And when I say long ago… I mean 1917, roughly a century before 2016. This was when Melin discovered that seedlings of pine and spruce in newly-drained bogs only grew normally in the presence of ectomycorrhizae. Naturally, this discovery transformed the practice of forestry. But it didn’t happen in 2016.

The CO2 fertilisation effect, meanwhile, has nothing at all to do with ectos, and everything to do with the higher concentration of CO2 in the atmosphere making it easier for plants to photosynthesise.

Ectomycorrhizal fungi have also been found to slow down the process of rotting; decomposition breaks down all that locked-away carbon and releases it into the atmosphere. So the fungi, in effect, have two methods of fighting global warming.

I have no data on this, but it seems unlikely. It might refer to the fact that a symbiotic relationship is better for the tree than a pathogenic one.

Now is perhaps the moment to mention that decay in woodland is generally rather fast. Certainly litter does not survive long, hardly even from one autumn to the next. In the absence of permanent waterlogging or desert-level dryness, wood will also be devoured in a handful of years. What this means is that unless the above-ground biomass is increasing, there is no net fixing of carbon going on. In other words, a growing plantation fixes carbon but a mature forest does not. Of course, if you cut down the plantation, turn it into pellets and burn them, you can hardly say that a plantation fixes carbon either. The only way this can happen is if you make permanent use of the wood (e.g. by making it into a table). Probably sinking logs to the bottom of the ocean would have a similar effect.

Research conducted into planting one particular variety – Arbuscular mycorrhizal fungi, or AMF – in soil has shown how it can not only help enrich soil fertility, but also reduce CO2 levels in the atmosphere.

OK, so consider a modern farm: what sort of thing do we spray on the farm or coat our seeds with… well, fungicide to name but one thing. Kill them mycorrhizae thar! Oh, and pour a load of PNK over the soil to make it easier for the plant to get these nutrients, so they don’t need the symbiosis anyway. This much is obvious. It is not obvious to me how this would reduce CO2 levels in the atmosphere, unless the writer is referring to the reduced production of fertilisers.

Research has also shown a link between the loss of soil fungi and a reduction in carbon content of forest soil. Meanwhile, deforestation, which annihilates the fungi along with their host trees, disrupts this whole underground, climate change-fighting ecosystem.

Climate change-fighting ecosystem? (Picture me making a sour expression here.) As I have just explained, mature forests are not a carbon dioxide sink. Gone are the halcyon days that gave rise to the coal measures, because there are now saprophytic fungi that gobble up fallen timber as soon as it hits the ground.

These fungi might be tiny and hidden beneath the ground, but they form a network that is protecting our planet. Scientists who study them say we can do more – particularly through sustainable farming methods – to protect them.

Well, the fruiting bodies are not hidden, except for truffles. [Unlike fly agarics, the spores of truffles are not wind-dispersed. They get about thanks to the efforts of things like wild boar. Truffles are, however, ectos.]

As to the idea that any “protecting our planet” is going on, well, it’s erroneous.


A+ for the essay, simply because the author is only 14. Were she 41, the mark would have been C-.

The idea that Nature is working for the benefit of humanity is as erroneous as the idea that climate change activists are working for the benefit of humanity. But at least in the former case, coincidental advantages sometimes result.

Notes and References

*The latin name of dry rot is Serpula lacrymans, which as I translate it means “creeping weeping one.” (It used to be called Merulius lacrymans, which sounds like it has something to do with crying blackbirds, dunno.) Anyway, this rather fine beast, once established on damp wood, is able to grow on even if the wood subsequently dries out, hence the common name. It makes its own water by digesting the wood’s long-chain polysaccharides and eventually “weeps.” Nemesis to humanity’s hubris, its destructive power seems to be unrivalled. There was an outbreak after World War 2, following (among other measures) the stopping up of ventilation bricks to prevent the ingress of poison gas. Insulation authoritarians beware.

^I read that Walt Disney sent a still of the ring of fly agarics in Fantasia (one such is the featured image) to Chiang Kai-Shek, inscribed “From Fantasia. To Chiang Kai-Shek – In admiration. Walt Disney.” This was back before Pearl Harbour, when the US was neutral-ish; what Generalissimo Chiang Kai-Shek made of the gesture, I don’t know, nor what became of the still.

Richard M. Jackson & Philip A. Mason (1984). Mycorrhiza. The Institute of Biology’s Studies in Biology no. 159. Edward Arnold, London. Available at Archive.org.


  1. When you wrote that, “The idea that Nature is working for the benefit of humanity is as erroneous,” I misunderstood it.
    I misread it as, “The idea that Nature is working for the benefit of humanity is as erroneous.”

    My thought was, “how is this news?”

    Liked by 2 people

  2. JIT in general I have to agree with you, nature does not act in ways that benefit us humans except by chance or by our deliberate design. However I think that with some mammals the jury might be out. Certainly dogs have protected us or helped us tame other parts of nature. And if you have ever experienced a wild cavorting dolphin doing tricks for onlooking humans for sheer joy (ie not for fish) you might revise your statement that nature doesn’t do anything for us. But I have to agree that you have to really search for instances of this.

    Liked by 1 person

  3. Unless we find someone fluent in dolpinese, we have no way of telling whether they are doing their tricks out of pure joy or as a practice for their next interstellar jump.*

    * see HHGTTG


  4. Jit, thanks for the very necessary corrective; and also thanks for going easy on the young author of the essay which prompted the BBC article. The essay is well-written for a 14 year old, and my sadness is that “fighting climate change” is now so entrenched in the education system that it means that an obviously intelligent girl almost inevitably used the language that she did.

    Liked by 1 person

  5. On the chance that Ms. Zara Hussan might someday read this page, I have a message & suggestion for her:

    Zara, climate change is a highly politicized issue, so, as is the case for any politicized issue, if you want to understand it, you need to seek out balanced information. If you want to learn about the SCIENCE of climate change, instead of political spin, here’s a list of resources which can help:


    It has:
    ● accurate introductory climatology info
    ● in-depth science from BOTH skeptics & alarmists
    ● links to balanced debates between experts on BOTH sides
    ● info about climate impacts
    ● links to best blogs on BOTH sides

    Liked by 1 person

  6. Mark, exactly as you say. I did give the essay an A+, and I’m sure it is better than I would have crabbed out with my Berol pen and small town high school library when I was her age!

    The thing that struck me was not just the way that climate change is now seemingly ingrained, it is also that (a point I laboured) there is this strange yet compelling belief that Nature is wonderful and somehow on our side, when it clearly isn’t. (Nor is it against us.)

    As a thought experiment, try returning the UK to its pristine state, drop 70 million people into it, and see how much we love Nature then. We modern humans have modified our environment to such a degree that we have very little idea what Nature is like. I would not rate my own chance of surviving in the wild for very long. I have a little theoretical knowledge about things like wild plants and fungi… but have a horror of the very idea of picking and eating a wild mushroom.

    Just in case I eat a destroying angel by mistake.

    Liked by 1 person

  7. Jit

    The trick is to NEVER eat a ‘mushroom’ with white gills. Edible mushrooms have pink/brown/black gills, so if you stick to those you will be OK.


  8. Profound issues raised here, thanks. The relationship the Celtic church of these islands reportedly had with birds – and with the recovery from the “new dark age” of their time through sanctuaries like Iona (given that Alan used that phrase in another thread today) … a role that Kenneth Clark celebrated in our own time … this is what came to mind. And I haven’t even eaten any magic mushrooms.


  9. Bill, I can recall news reports of SE Asian refugees being poisoned by eating local (U.S.) mushrooms that look just like the edible mushrooms that they used to eat back in SE Asia. I don’t know what color the gills were, but those unfortunate incidents suggest that visual appearance alone is not a foolproof way of distinguishing between edible and poisonous mushrooms, everywhere in the world.


  10. JIT I’m sure you will agree that parts of Nature are exceedingly beautiful, but other parts are downright and squeamishly horrible. Also it must never be forgotten that we humans are fully part of nature and inevitably are subject to its strictures. Those people who “live close to nature” know this better than most.

    In your imaginary reconstituted world, I probably would have done quite well a decade ago (but my weakened knees would let me down now) because I was taught how to make flint hand axes, which I suspect would come in very handy. The person who taught me was a real expert. Her party piece was to create a flint comb.

    Liked by 1 person

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