Are Hordes of Mushroom Fanatics Wrecking British Woodland?

Every autumn the tabloids churn out their stories on how our native forests are being decimated by vanloads of fungal thieves. The Guardian, often championed as one of the papers that avoids employing scare tactics, regurgitates the same article year after year. The eradication of fungi from our green spaces would certainly be a crying shame, but do heavy picking pressures actually drive declines in the abundance of our favourite species?

Why do we care?

I am often asked the question, “why do you love mushrooms”? As a mycological nerd, I think there are a million answers to this; the primary reason I became interested in fungal identification is not dissimilar to that which made last summer’s hit game Pokémon Go™ explode. The thrill is in exploring new areas and discovering psychedelic colours, alien forms and rare beauties. From lurid red fly agarics, to squat little puffballs and the brain-like cauliflower fungus, the fungal world is full of surprises.


From left to right: the fly agaric (Amanita muscaria), the common puffball (Lycoperdon perlatum) and the cauliflower fungus (Sparassis crispa) demonstrate the high diversity of colour and form found in British mushrooms.

Images by Onderwijsgek, Stu’s Images and James Lindsey, used under CC BY-SA Licenses from Wikimedia commons

I firmly maintain that people are happier when they have (and use) access to natural spaces. As George Monbiot argues brilliantly, any child that grew up denied of the wonders of diving through the branches of fallen trees, peering into badgers’ sets and hurtling through the kaleidoscopic hues of autumn bracken was denied some of the most fundamental, yet exhilarating hours of their lives.

But the simple joy of fungal discovery is only the beginning of a plethora of services that these humble organisms can give us. Fungi are not only beautiful, but are a vital facet of our natural ecosystems. They are the decayers of organic matter, the source of sustenance for many critters and the purveyors of soil nutrients to most plants. In fact, plants are thought to be so reliant on their fungal neighbours that some rather antagonistic mycologists have described plants as ‘parasites of fungi’.

They have even been used for thousands of years in our treatment of disease, from the ancient Greeks rubbing mouldy bread into wounds, to modern-day fungally-derived chemicals exhibiting anti-cancer1, antimicrobial2 and cholesterol-lowering3 properties.

Isn’t it like picking fruit from a tree?

One of the most frequent claims on foraging and identification forums across the internet is that mushrooms are like fruit on a tree. Picking most of, or even all, the apples on an apple tree won’t kill it, thus the same should be true of mushrooms. This analogy is in some ways useful, but doesn’t really cut the mustard. It is true that mushrooms are not individuals, i.e. one button mushroom is not equivalent to one whole fungus. Rather, mushrooms are fruiting bodies for a larger organism that lives in the organic matter from which they emerge.

The fungal mycelium, a branching network not dissimilar to roots on a tree, lives under the soil, acquiring nutrients so that the organism can grow, reproduce and disperse. These networks often spread uniformly from a central point creating a circular shape below the surface. The centre of this circular mycelium ceases to produce mushrooms once the available nutrients are exhausted, sometimes leaving a ‘fairy ring’.

A fairy ring is formed when a mycelium grows outwards from a central point and produces fruiting bodies (mushrooms) where soil nutrients are not yet exhausted.

Image by James Lindsey, used under a CC BY-SA 2.5 License from Wikimedia commons

When you pick a mushroom, you are not damaging the mycelial network, but rather removing the fruiting body, the organ used for dispersal. The gills of a chestnut mushroom you can buy in Tesco create spores that will colonise new substrates and produce new mycelial networks. In this way, people are correct – picking a mushroom is similar to picking a fruit from a tree.

However, the differences are twofold: firstly, it would be extremely difficult to make a significant dent in the number of fruit in British woods; many are too hard to access and are highly abundant, unlike some uncommon and edible fungi. Secondly, fruit often rely on being picked for their dispersal by woodland animals, whereas fungi are reliant on being in situ and ejecting their spores into the wind, something they are unable to do if picked before reaching maturity. If too many fungi are picked before they have dropped their spores, then it stands to reason that the next generation of mushrooms might have fewer individuals, but is there any evidence to support this?

Where is the evidence?

The short answer to this question is that there isn’t really any. That’s not to say that picking pressure isn’t having a negative effect on our woodlands, just that not many people have attempted to do the research yet. In fact, instead of being an argument in favour of letting anyone, anywhere, pick mushrooms, this is actually quite the opposite. Until there is a scientific consensus on a sustainable level of mushroom foraging for UK woodlands, commercial picking should be illegal. At the bare minimum, individuals and/or companies should need a license to sell them. Small quantities of picking for personal use, I would argue, should be a right of those that live in the area, unless it is a site of specific scientific interest (SSSI).

Another argument often proffered in favour of picking is that people forage mushrooms all over Europe with no significant environmental impact, therefore, we should be able to do the same here. This may be true (although again there is little to no data to prove it), however the UK has a higher population density than many countries in mainland Europe. Coupled with a relatively low proportion of forest cover, an increase in picking pressure here could have more devastating effects than we have seen elsewhere.

One paper published in 2006 looking at Swiss ecosystems did appear to find that long-term mushroom picking was safe, having no effect on fungal diversity or mushroom abundance4. However, I would debate the validity of these findings, and their value as a guide for UK conservation practices. Without getting too technical, the authors divided up woodland into small plots, and subjected some of them to foraging pressure (picking and/or trampling), leaving others untouched. But this method is unrealistic for real mushroom picking. Commercial mushroom pickers are not targeting 10x10m plots of forest and leaving healthy woodland nearby, but clearing much larger swathes of forest that may not be so easily recolonized by drifting fungal spores. Mushrooms disperse extremely long distances. In the ‘70s it was reported in the journal Nature that coffee leaf rust fungus, which destroys vast swathes of Coffee arabica, may have been wind-dispersed across the Atlantic Ocean from West Africa to Brazil (an astonishing 2900km)5! In the Swiss study, it is likely that spores from the surrounding patches could rapidly recolonise foraged patches, thus masking any damage being done by picking.

The Swiss authors recognised this problem in their article, and additionally found that trampling, something that often goes hand-in-hand with picking, does significantly decrease the number of fruiting bodies found in plots. Therefore, we cannot use this paper as an excuse to justify potentially dangerous practices, rather it may even emphasise the need for more research to establish safe foraging levels.

It is true that the same process of long-distance dispersal may mean that fungi are resilient to the pressures of picking, as small source populations may repopulate heavily foraged areas, however, this has also yet to be demonstrated, and caution is warranted once again.

The diversity and abundance of British fungi is an important element of the magic that makes up our native woodlands. Without due care, we may be decimating them in a way from which they will struggle to recover.

More research is needed to find out how these fragile organisms are standing up to the increasing pressure that we are placing on their brittle stems. If we want our own children to enjoy the same delights of the natural world that we have, instead of chasing Pokémon through a lifeless, concrete city, then it is imperative we exercise caution before it is too late.

References

1. Gangadevi, V., and J. Muthumary. “https://link.springer.com/article/10.1007/s11274-007-9530-4Taxol, an anticancer drug produced by an endophytic fungus Bartalinia robillardoides Tassi, isolated from a medicinal plant, Aegle marmelos Correa ex Roxb.” World Journal of Microbiology and Biotechnology 24.5 (2008): 717.
2. Mygind, Per H., et al. “Plectasin is a peptide antibiotic with therapeutic potential from a saprophytic fungus.” Nature 437.7061 (2005): 975-980.
3. Manzoni, M., and M. Rollini. “Biosynthesis and biotechnological production of statins by filamentous fungi and application of these cholesterol-lowering drugs.” Applied Microbiology and Biotechnology 58.5 (2002): 555-564.
4. Egli, Simon, et al. “http://www.sciencedirect.com/science/article/pii/S0006320705004726Mushroom picking does not impair future harvests–results of a long-term study in Switzerland.” Biological conservation 129.2 (2006): 271-276.
5. Bowden, J., P. H. Gregory, and C. G. Johnson. “Possible wind transport of coffee leaf rust across the Atlantic Ocean.” Nature 229.5285 (1971): 500-501.

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