It’s the season (in the northern hemisphere), and I’ve noticed over the years that the “yields” are decreasing in some places while in other places they remain constant. It’s hard to find data on iNat to assess the population of edible mushrooms and see any trend.
Naturally, there are certainly many factors at play in addition to the variability of each year’s conditions; but some forests seem to be much more resilient to “over-harvest” than others. To your knowledge, is there any research on this topic that could lead to some insights?
As far as I know there isn’t. It would be a very difficult thing to research because the fruits are so finicky about appearing. Genetic testing of soil samples could prove which mycelium are still present, but even that wouldn’t tell us why some of them haven’t fruited well in years. Nor would it tell us whether those that are missing were wiped out by persistent over harvesting, or some other change to forest conditions.
Just logically speaking it should depend on the species of mushroom and what stage people are picking them at. Mature mushrooms harvested after releasing most of their spores should be basically impossible to over harvest, unless of course harvesting them has starved out a beetle or snail they relied on to spread the spores, or something else we don’t fully understand.
Puffballs, any mushroom desirable at button stage, or morels picked too young because people are worried the competition will get to them, are obviously going to be more vulnerable to over harvest.
It is hard to say whether anecdotal reports (including our own) of fewer edible mushrooms in over harvested woods are even accurate, or just a result of more people out picking them.
For the sake of illustration, imagine a woods that magically produces exactly 10,000 edible mushrooms a year regardless of the weather. Now imagine that 30 years ago, only 10 locals knew about it and each came away with a fantastic haul of 1,000 mushrooms. A few of them made the unfortunate mistake of bragging about this woods. Plus human population has increased drastically. Plus mushrooming has become more popular. Now, 2,000 people a year each find 5 measly mushrooms out there, and go home complaining about the poor crop, even though the woods is still producing it’s magic quota of 10,000.
Maybe the way to study it would be to fence off a study area in the middle of a highly harvested forest (thinking high voltage electric and guard towers, lol) then count the mushrooms that come up in it. Then I guess destroy them before they go to spore, to mimic over harvest so they don’t interfere with future results. For the results to be meaningful, this study would have to go on for many years to find an average. And of course compared to a control plot in a less harvested but otherwise similar woods.
For the vast majority of mushrooms, doesn’t the mycelium live on and produce next year’s crop? So the negative effect of mushrooms not surviving long enough to produce spores will be more on the dispersal of the fungus to new sites rather than a decline in mushroom production in the place of origin.
To my mind, an unsustainable mushroom harvest from a mushroom harvester’s point of view would be where the harvesting damages the mycelium, such as use of rakes which strip off the leaf litter in a wood.
A more holistic view of sustainability would include effects on other species. As I have mentioned before in the forum, there are thousands of insect species which breed in fungi and intensive collecting removes their habitat, so would be counted as not sustainable on those grounds.
Yes, the same mycelium produces next year’s crop, but some are fairly short lived and don’t spread easily. We are worried about the next hundred years’ crop.
Particularly with fungi that feed exclusively on dead wood, the mycelium dies when it finishes digesting it’s food source, unless there happens to be a fresher log of it’s host species touching the one it’s colonized. The “new site” it’s spores need to disperse to might be the latest dead tree of a compatible species, even if that’s only 50’ away.
Mycorrhizal fungi can be longer lived, but those that depend on partnership with specific trees still need spores to spread to widely scattered saplings of that species in a mixed forest. Otherwise they eventually die without progeny when the partner tree dies.
Even in conditions that do allow a single mycelium to spread over a wide area (rather than a patchwork of genetically distinct mycelium spawned from spore) it may be more vulnerable to disease spreading through the whole patch, or less able to adapt to changing climate. I don’t think that’s been studied in mushrooms, but genetic diversity in a population is usually good for any species’ ability to adapt and evolve.
Obviously these concerns only apply in a large area. I don’t think it would be possible to over-harvest a few acres, if there were spores blowing in from next door.
True… this is indeed an useful bias to actually be aware of. That’s why I was thinking in terms of local markets who group the source from many profiles harvesters, although not including the non-commercial ones. And as it turns out, they don’t collect much data about it where I’ve been looking about it.
The Oregon chanterelle study linked to on the modern-forager site was a very interesting read. It pointed out a challenge I hadn’t thought of - the difficulty in accurately measuring biomass in the unharvested control plots without, you know, harvesting them.
I know this wasn’t the only aspect they were studying, but I felt like from the perspective of understanding the possible impacts of real-world over harvesting, the design was fundamentally flawed because they “over harvested” some small plots and not others in a forest otherwise protected from mushroom hunting. That’s very different than the public combing hundreds of contiguous acres of state land removing everything they find.
Assessing any factor individually is quite a daunting endeavour in itself, but perhaps citizen science could help a bit. Although it seems unlikely that people harvesting mushrooms will willingly share much about their finds in an accurate manner.
Perhaps time would be better spent in pedagogical activities to prevent damaging the mycelium and altering their habitats. I have found many habitats destroyed for unknown reasons in a forest than don’t usually get damaged to that extent. I didn’t take pictures everywhere but you get an idea from those below:
There are no squirrels in this island (Tenerife) but mostly nearby the area was extensively combed with rakes, so I would speculate that it’s done by the same people. All these mushrooms were obviously not boletes though, so I don’t see what would be the point of it.
Part of my approach to collecting mushrooms for consumption is to field clean, reducing time at home. Any trimmings go back in the hole and the hole covered. If you leave a pile of trimmings you are flagging others that “they grow here.” This assumes you know exactly what you are collecting.
Here they didn’t use to sell them in local markets. The locals didn’t really eat them in the past. But perhaps restaurants… there is definitely some increased harvesting including some more “industrial” approach.
On the other hand, the local authorities have enforced a mandatory permit to be authorised to pick up mushrooms, so they know something is going on.
