Waxcap fungi

Overall vulnerability

Feature assessed:

• Waxcap fungi (Hygrocybe spp.)
• Waxcap grasslands with grassland fungi assemblages

Special qualities:

• Internationally important and locally distinctive wildlife and habitats

Feature description:

Waxcaps are a distinctively colourful group of fungi found on grazed and mown grasslands. There is a diverse assemblage in the PDNP, and grassland fungi from various groups including earthtongues, fairy clubs, and pinkgills grow alongside them in so called ‘waxcap grasslands’.

Waxcaps are thought to be mycorrhizal fungi - forming a symbiotic relationship with plant roots by providing soil nutrients in exchange for organic carbon. Much of the PDNP contains grazed landscapes, and a few sites such as the Longshaw Estate are internationally recognised for grassland fungi diversity. 1081.5 hectares of waxcap grassland have been mapped, but this certainly under-records where waxcaps can be found.

Waxcaps benefit from livestock grazing and mowing, as a short grass sward benefits their fruiting bodies. Intensive management such as nitrogen fertilisation, overgrazing, and ploughing can have severe negative impacts. As such, waxcaps have been lost from many agricultural areas, but less intensively managed parkland, including estate land and churchyards, still contain some interest. Waxcaps are a striking and characteristic feature of traditionally managed pastureland, and a sign of historical agriculture persisting. Waxcaps in the PDNP are of conservation importance in the UK, and internationally. Many sites of international, national, and regional importance have been found, and the UK British Action Plan (UK BAP) priority species the date-coloured waxcap can be found here.

How vulnerable are waxcap fungi?

Waxcaps in the PDNP have been rated ‘high’ on our vulnerability scale. This score is due to high sensitivity and exposure to climate change variables, with a variable and often unknown current condition, and only a moderate adaptive capacity.

Waxcap grassland condition in the PDNP is variable, with some sites of national importance, but many others unknown or under-recorded. The impact of climate change on waxcap grasslands is unclear, as they are a habitat more dependent on management than climate. One factor that will be likely to have an effect is increased nitrogen deposition, which may act to reduce the extent and abundance of waxcaps. Waxcaps are not particularly adaptable as a genus, but management knowledge and application has some potential to reduce the impact of climate change.

Current condition:

It is difficult to assess the current condition of waxcaps even at the national level because they are so under-recorded. Within the PDNP there are many areas that have some records, but many will also go unnoticed and unrecorded. Of the known sites, several are of national importance following Joint Nature Conservation Committee (JNCC) guidelines, with at least 19 waxcap species present. These include the Longshaw Estate, Alport Valley grasslands, Chatsworth House Lawns, Coombes Dale and Hucklow Edge.

Due to their specific habitat requirements, waxcaps are generally dependent on a narrow band of management intensity. A cessation of management will allow the grass sward to increase and disadvantage waxcap fruiting, but intensification of management will have severe negative impacts. This often occurs through ploughing of fields, which can destroy the underground hyphal networks that are the main body of the fungi. Nitrogen fertiliser application and liming also disadvantage fungi generally, and overgrazing can damage fruiting bodies and increase nitrogen enrichment through dung. As waxcap communities are slow to establish, only fields that have not seen ploughing or improvement in living memory are likely to have high waxcap interest. As a result, many fields that were once waxcap grasslands will have lost their communities as agricultural intensification became more commonplace. Waxcap communities on mown lands are also at risk as the increasingly common practice of leaving cuttings to lie increases nutrient enrichment.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Nitrogen deposition may increase as a result of greater winter rainfall. Waxcap and other macrofungal communities are sensitive to high soil nitrogen levels. The cause of this sensitivity is unclear, and likely is due to multiple effects, but is well documented in upland sites. This could lead to a loss of waxcaps from some sites, especially upland sites and those near roads. Data Certainty: High

Hydrological changes may also affect the suitability of waxcap habitats. Some grassland may become flooded for parts of the year, waterlogging the hyphal network. Waxcaps require well-drained soils, so this could damage the hyphal network and cause the loss of waxcap communities from some sites. Drought could be more significant, drying out some sites during the summer months. This could damage hyphal networks and reduce fruiting in affected sites, causing the loss of waxcaps from some sites or slowing their growth and dispersal. Data Certainty: Moderate

Increased average annual temperatures may have a positive effect on waxcap fungi. Higher temperatures due to climate change are predicted to be generally beneficial for fungi, and so waxcaps may spread and fruit more often. However, dry conditions can be devastating for fungal communities, as was seen in the 2018 summer drought. Therefore, any benefit from increased temperatures could be countered by the accompanying drier summer conditions. Data Certainty: Moderate

Changes in annual precipitation cycles may have a large impact on waxcap populations. Fungi are dependent on high soil moisture levels, especially during the fruiting season when wetter conditions allow their fruiting bodies to last and spread spores for longer. Wetter autumn conditions may therefore benefit some fungi. As later fruiters, waxcaps could be well placed to take advantage of this - fruiting closer to the wetter winter than the drier summer. However, this could be offset by the action of summer droughts. Drier summer conditions reduce fungal growth and reduce the likelihood of fruiting. As a result, any benefits of wetter autumn conditions would be lost as fruiting bodies may not be present to take advantage of them. Data Certainty: Low

Invasive or other species interactions

Increased average annual temperatures may result in larger populations of burrowing mammals such as moles and badgers. This would result in increased disturbance of the ground in fields. In waxcap grassland, this could result in damage to the hyphal network of the soil. As the hyphal network is slow to recover from damage, this could result in some waxcaps being lost, and reduced fruiting in some sites. Increased aeration of the soil could however be beneficial. Data Certainty: Low Increased nitrogen availability may increase the growth rate of surrounding grasses, reducing the fruiting rate of waxcaps due to the adverse microclimate created under the long sward. While the effects on the underlying hyphal network are unclear, this would lower the presence and visibility of waxcap fruiting bodies and reduce their dispersal ability. Taller grasses can also change the composition of the bryophyte layer with which some grassland fungi are thought to have a symbiotic relationship, potentially changing the fungal composition. Data Certainty: Low

Other indirect climate change impacts

Warmer winter conditions will mean fewer frost events. Early frost events have strong negative effects on fungal fruiting bodies, preventing their occurrence and causing die-off in those already present. Fewer frost events will therefore result in a greater number of fruiting bodies being produced, generating spores for longer. This would increase the visibility of waxcaps and promote their dispersal. However, the associated group of earthtongues benefit from cold weather of 3°C or lower, so overall grassland fungal diversity may be reduced. Data Certainty: Moderate

An increase in wildfire associated with hotter summer temperatures and droughts may be damaging to some waxcaps. Where less diverse waxcap communities are found growing in long sward purple moor-grass moorland in the Dark and South West Peak, wildfire is a significant risk. If the hyphal network is damaged by fire as it chars the soil, the fungi could take decades to recover. While the more diverse sites on pasture and estate land are unlikely to be affected by wildfire, these sites containing a few specimens are more widespread across the PDNP, and so may represent an equally large resource. Data Certainty: Low

Human behaviour change

Hydrological changes may change land use on pastureland. Some fields will become less suitable for livestock at certain times of the year due to waterlogging or drought. The grazing intensity on those fields unaffected by this could increase. Increased grazing pressure can negatively affect waxcap communities by ground compaction and trampling, as well as increase nitrogen deposition through dung. Overgrazing of fields also encourages mat grass dominance, an unsuitable sward for waxcap fruiting bodies. This disturbance, even if for only short periods, could severely damage slow to recover waxcap communities, causing a reduction in their extent. Data Certainty: Low

Nutrient changes or environmental contamination

Increased winter rainfall and severity of summer storm events may lead to greater runoff in the PDNP. This has the potential to spread fertilisers and enriched soil from more intensively farmed land onto waxcap grassland and other pastureland. This nitrogen enrichment would cause a reduction in abundance and extent of waxcap communities. Data Certainty: Low

What is the adaptive capacity of waxcap fungi?

Overall adaptive capacity rating

Waxcap hyphal networks grow extremely slowly, and as a result, they are difficult to recover once damaged. Once lost entirely, a waxcap community can take up to 50 years to re-establish. This is compounded by the specific management requirements for a diverse waxcap community, meaning that a beneficial management regime must be implemented for some time before results are felt. Data Certainty: High

There are over 40 species in the waxcap assemblage, though at least 19 must be present on a site before habitat is considered waxcap grassland of national importance. Most species have broadly similar sward and drainage requirements, though soil preferences can vary in terms of acidity and composition. As a result, there is limited diversity in ecological niche within the waxcaps. However, one or two species are well adapted to disturbance and so can be found in places where others are unlikely to be, including newly created and wetter grasslands. Data Certainty: High

Although the most important waxcap habitat covers small areas of high diversity, much of the PDNP is grassland and so has the potential for some waxcap value. Improved grassland is unlikely to contain much interest for waxcaps and allies, but some species may be present in low concentrations. This habitat has high connectivity throughout the PDNP and extends out of the boundary, so the less visible waxcap populations are likely to cover a large area. Soil genomic studies show that waxcap hyphae can be found in areas that have never had records of their presence, meaning that waxcaps may be present in many soils but only fruit occasionally or in some parts of the network. If true, changes in management could yield results quickly as a hyphal network will already be established. Connectivity is lower in parklands and lawns separated by urban areas. Data Certainty: Low

Limited financial resources are available for the conservation of waxcap grassland mostly due to lack of knowledge and awareness resulting in no specific prescription within environmental land management schemes. The economic incentive for intensive management is also greater than that for low intensity conservation management, and so uptake of any potential projects may be reduced. However, waxcaps are in a unique position in that much PDNP pastureland could be increased in ecological value with relative ease by managing for waxcaps. Waxcaps will also benefit from other changes in management to benefit soil health and sustainability. Data Certainty: Low

Some institutional support is available for waxcaps and their habitats, with sites such as Longshaw Estate having been managed for waxcap communities for decades. As recognition of the value of waxcaps in the PDNP grows, more sites may benefit from better waxcap management. Some species are recognised as UK BAP priority species, with the date-coloured waxcap a PDNP priority species. Only a few sites of high value fall within Site of Special Scientific Interest (SSSI) or Special Area of Conservation (SAC) designation, leaving many without statutory protection. Data Certainty: Moderate

Management techniques for waxcaps are reasonably well known, with traditional farming methods likely to be the most beneficial. Lowering grazing pressure, ceasing ploughing and tillage, and reducing chemical inputs are known to produce high value waxcap grasslands in the long term, provided a spore source is available. This management can be worked into existing land use across large areas of the PDNP with benefits to soil health and other ecological benefits. Data Certainty: Low

Key adaptation recommendations for waxcap fungi:

Improve current condition to increase resilience

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are aimed at improving the condition of the feature at present, therefore making it better able to withstand future changes to climate.

• Survey greater areas of PDNP grassland to assess true extent of waxcap grassland.
• Alter management of pastureland to increase waxcap populations. Cease ploughing and ensure appropriate grazing levels, and lower inputs of fertiliser and lime. Introduce measures to reduce compaction and waterlogging. Concurrent benefits of improved soil health and ecological condition mean this is desirable even disregarding waxcaps.
• Management of large lawns such as those on estate land should have a greater focus on waxcap assemblage.
• Promote PDNP waxcap grasslands, as they are already some of the finest internationally. An increase in awareness and knowledge may lead to wider benefits for waxcap grassland resilience and soil health.
• Encourage further uptake of environmental land management schemes by farmers within the PDNP.

Improve current condition to increase resilience: Targeted conservation efforts for important sites and at risk areas

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are conservation measures aimed at those sites that will have the biggest impact for this feature – either because they are particularly important for the feature or because they are most at risk from climate change.

• Training on identification of CHEGD fungi (Clavaroids (club and coral fungi), Hygrocybe spp. (waxcaps), Entoloma spp. (pinkgills), Geoglossum and related genera (earthtongues), and Dermoloma spp. (as well as Porpoloma and Camarophyllopsis spp.) will increase the pool of surveyors to identify and designate sites of importance.

Adaptations that could aid other features

These recommendations are changes that could be made to this feature, which will have a positive impact on the ability of other vulnerable features to withstand future climate change.

• Focus of future assessments and management should be broadened from just waxcaps to include the wider grassland fungi assemblage that associates with waxcap grassland. This is often known as the CHEGD group.