Rare British fungi: genuinely uncommon or simply ignored?

Around 15,000 species of fungi have been reported from the UK, with over 2,000 recorded on only a single occasion. Does this mean that many fungi are genuinely rare and in need of conservation, or simply rarely recorded?

Shaggy parasol (Chlorophyllum rhacodes). Mushroom on woodland floor with a shaggy cap.

Fungi in the UK are highly diverse and are critical to our survival due to their role in recycling of nutrients and in water uptake by plants. Currently, we know that around 15,000 species are present (5-6 times the number of plant species), and the UK list is increasing steadily as new fungi are discovered. Fungi need conservation just as much as animals or plants. However, our poor state of knowledge means that we are almost always unsure whether species that have only been found on one or a few occasions are genuinely rare, or just rarely observed. This is a major barrier to their inclusion within conservation management plans. 

The Lost & Found Fungi Project 

With generous financial support from the Esmée Fairbairn Foundation, Kew has embarked on the Lost & Found Fungi Project, a five-year UK fungal research programme in partnership with the volunteer science community. With support from Kew, local fungus recording groups will carry out surveys and monitoring exercises for a set of 100 species that are currently assumed to be rare, to establish whether they are still extant in the UK, and if so whether their distributions are larger or smaller than are known at present and whether they are threatened. 

Selection of the 100 will be according to several criteria; they will be eligible if their current known distribution is less than five sites, or if they have not been recorded at all for the last fifty years. Alternatively ,they may be of known conservation concern or valued by local communities. The list of species will not be static. Some will be found to be commoner than previously thought, and thus of lesser conservation concern. Probably, others will not be found at all, providing indications that they may be extinct in the UK. Species removed from the list for these reasons will be replaced to maintain the overall number. 

The project presents us with a number of challenges. Most fungi exist principally as networks of microscopic filaments within soil or plant tissues, and are only detectable when their fruit-bodies (such as mushrooms and toadstools) are visible. These may only appear for short and unpredictable periods, and perhaps not at all when conditions are not optimal. Molecular detection methods are technically feasible, but are expensive and cannot be used by non-specialists. Proving that species are extinct and not just non-fruiting is therefore problematic, but either situation would be a cause for conservation concern.  

A second challenge is that most candidate species for the List of 100 will almost by definition be poorly known and difficult to recognise. Our task at Kew will be to bring together all useful information on the species concerned and present it in an accessible format. We also need to provide information on when and where to look, as well as what to look for. This will include ecological as well as geographical data; for example if a species is known to grow only on the underside of fallen oak branches, knowledge of this niche will greatly improve the chances of detection. Very many fungi have such tightly-defined habitats. 

Once candidate species have been re-discovered, conservation assessments will be made to determine the risk of extinction in the future. Protection plans for those found to be threatened will then be developed, with the support of landowners and other local stakeholders, and the health of their populations will be monitored. Such approaches are routine for well-known groups of organisms such as birds and mammals, but this will be one of the first established programmes in Britain for the protection of fungi. 

Threats to UK fungi 

Through this project, we hope also to learn about the more general threats to the continuing existence of fungi in the UK. We believe that fungal species are threatened in the same way as animals or plants, and that the proportion of species that are threatened is not less than for well-known taxa. Indeed, fungi face particular threats from human activity, which almost certainly substantially increases the proportion of species that are endangered. Such threats include habitat loss (especially of ancient woodlands and other habitats with long ecological continuity), pollution (especially caused by nitrogen deposition), and direct persecution through the widespread use of fungicides. Many fungal parasites of food crops and forest trees cause insignificant economic damage, but are destroyed as by-catch in the attempt to control those species that compete effectively within human-mediated environments. 

A further major threat to UK fungal species is that of the globalisation of agriculture and horticulture, combined with suboptimal mechanisms for pest control. A good example here is the fungus causing ash dieback in the UK (Chalara fraxinea / Hymenoscyphus pseudoalbidus); it was probably introduced from eastern Asia into eastern Europe via the horticultural trade, and has then spread to the UK via a combination of natural airborne spore dispersal and movement of infected planting material. But it doesn’t only threaten ash trees; it has been shown to compete aggressively with a native non-pathogenic fungus that occupies the same ecological niche, and there is a long list of fungi and lichens dependent for survival on ash trees that are also likely to disappear to the invasion. 

Perhaps the biggest threat to native fungal populations is caused by climate change. The impact of this phenomenon on fungi in the future is perhaps even less certain than for better-known organism groups, but we know that many fungi are sensitive to climatic extremes such as drought and flooding, and that many face human-created barriers to population movement as their natural habitats have become fragmented. There may of course be winners as well as losers; we have seen what we believe to be recent arrivals in southern Britain that may have taken advantage of a warming climate, and some species appear to have a longer fruiting period when modern and historical records are compared. 

Our new project will not provide solutions to all of these problems, but it will inform the conservation community and the general public of threats to a wide range of fungal species. Fungi have a very bad press in the UK; there is a widely held misconception that they are inconvenient or even malevolent. Humans pose a far more potent threat to fungi than fungi do to humans, and their eradication would pose an ecological catastrophe even greater than that posed by climate change. If we can show that fungi may be the victims rather than the perpetrators of evil, our project will have been a success.