Dutch forest mushrooms decline by 20% in 15 years, signaling ecosystem stress
A significant drop in forest mushrooms across the Netherlands over the past 15 years raises concerns about forest health and environmental conditions. These fungi, vital for nutrient cycling and tree growth, are sensitive indicators of climate and soil quality changes affecting ecosystems and biodiversity.
| Key Data Point | Details |
|---|---|
| Decline since 2010 | 20% reduction in forest mushroom distribution |
| Species most affected | Cooperating fungi (e.g., fly agaric, chanterelle) |
| Initial growth period | 80% increase in cooperating fungi (1994–2010) |
| Litter decomposers decline | Dropped to 85% of 1994 levels (2004–2024) |
| Wood-inhabiting species trend | Stable after earlier 25% increase (1994–2010) |
| Nitrogen-sensitive species | 136% growth (1994–2010), then sharp decline |
| Monitoring network | 119 species tracked in forests on sandy soils |
| Primary causes | Nitrogen deposition, acidification, dry summers |
| Data source | CBS and Mushroom Research Netherlands |
Statistics Netherlands (CBS) and Mushroom Research Netherlands monitor environmental health through forest mushroom trends. These organizations provide critical data to policymakers and researchers, helping assess the impact of environmental policies and climate change on ecosystems.
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Forest mushrooms have declined by a fifth over the past 15 years
Since 2010, the distribution of forest mushrooms has been declining. Between the mid-1990s and 2010, however, there was still an increase. Species that closely cooperate with trees, and thus play an important role in forest health (such as the fly agaric), saw their distribution area grow by about 80% between 1994 and 2010. But over the past fifteen years, these species have also experienced the steepest decline. This is evident from new calculations by Statistics Netherlands (CBS) based on data from the forest mushroom monitoring network of Mushroom Research Netherlands.
In this monitoring network, part of the Ecological Monitoring Network (NEM), 119 (out of approximately 1,600) species of forest mushrooms are recorded in forests on sandy soils. Mushrooms are the fruiting bodies of fungi and emerge from fungal threads (mycelium) that grow in the soil, between leaves, or in wood. Because mushrooms respond quickly to changing environmental and climatic conditions, they are good indicators of the quality of their habitat. The state of the mushrooms thus says a lot about the composition and health of forests.
In the 1970s and 1980s, many species of forest mushrooms declined sharply. This was due to the emission of substances (sulphur dioxide, ammonia, nitrogen oxides) that acidified and eutrophied the environment (water and soil) [1]. Environmental measures subsequently led to a reduction in emissions of these substances. As a result, from the mid-1990s onwards, there was temporary recovery of forest mushrooms, mainly of nitrogen-sensitive species.
Three groups of forest mushrooms
Forest mushrooms perform three key functions in the forest and are therefore divided into three groups: litter decomposers, wood-inhabiting species, and cooperators.
The ‘litter decomposers’ (saprotrophic species of the forest floor), such as the stinkhorn and the common stinkhorn, break down dead plant material, such as leaves that have fallen to the forest floor. This group of mushrooms increased by an average of 15% between 1994 and 2004, but between 2004 and 2024, their distribution declined to 85% of the level in 1994.
Wood-inhabiting species stable after earlier increase
Wood-parasitic fungi, such as the coral fungus and birch polypore, live at the expense of living but often already weakened or old trees and plants, and can gradually make them sick and cause them to die. Once a tree is dead, there are mushrooms that break down the dead wood, the so-called wood-saprotrophic species. These two groups of ‘wood-inhabiting’ mushrooms (the parasites and the saprotrophic species) increased by more than 25% between 1994 and 2010, but have since declined again to roughly the 1994 level.
Cooperators of the forest
Cooperating fungi (ectomycorrhizal), such as the fly agaric and chanterelle, grow around the fine roots of trees and exchange nutrients and water for sugars produced by the tree through photosynthesis. These fungi promote tree growth while also benefiting from this cooperation (symbiosis). After an increase of about 80% between 1994 and 2010, this group has since declined. Nevertheless, the distribution of this group of mushrooms in 2024 was still about 35% higher than in 1994.
Cooperators most sensitive to environmental changes
The ‘cooperators’ (ectomycorrhizal species) increased from 1994 onwards, partly due to a reduction in nitrogen emissions from agriculture and the near-disappearance of acid rain. Within this group of mushrooms, two subgroups can be distinguished: nitrogen-sensitive (the majority of species) and nitrogen-tolerant species. The nitrogen-sensitive species increased by 136% between 1994 and 2010. Since then, there has been no further reduction in nitrogen deposition, and these mushrooms have declined sharply again (dry summers played a role in this). The distribution of nitrogen-tolerant ‘cooperators’ remained virtually unchanged during this period.
Sources
- Compendium for the Living Environment – Trend in forest mushrooms
Relevant links
- [1] Van Strien et al, 2017 - Woodland ectomycorrhizal fungi benefit from large-scale reduction in nitrogen deposition in the Netherlands
- Dashboard – Sustainability
- Website - Forest Barometer