Threats
Press coverage around SPUN and mycorrhizal fungal networks.
Mycorrhizal fungi support life on earth, yet we are destroying them at an alarming rate. In doing so, we destabilize ecosystems and lose access to a vast nutrient capture system that could help reform agriculture, forestry, and carbon capture.
Habitat destruction is the #1 threat to global fungal diversity
HABITAT DESTRUCTION
Habitat loss is the largest driver of biodiversity loss world-wide. Without their plant partners, mycorrhizal fungi cannot survive. Logging, agriculture, and urbanization cause drastic disruption to the structure and physical integrity of underground fungal networks. This impairs their ability to sequester carbon, move nutrients, and promote soil aggregation.
When habitats are destroyed, the fungal community structure is dramatically altered because of (i) shifts in local microclimate, (ii) loss of plant partners, and (iii) massive increases in soil erosion. The damage can take decades to recover. The loss of grasslands and forests is of particular concern. Grasslands contain 20-30% of the world’s soil carbon, largely thanks to many trillions of kilometers of fungal networks that actively pull carbon into deep soil layers under grass roots. But degradation of grasslands is widespread and accelerating. Networks under forests are also being lost: logging is associated with massive decreases in fungal diversity which can take more than 50 years to recover.
SOURCES
Ammitzboll, H. et al. “Diversity and abundance of soil microbial communities decline, and community compositions change with severity of post-logging fire.” Mol. Ecol. 30, 2434–2448 (2021)
Bardgett, R.D. et al. “Combatting global grassland degradation.” Nat. Rev. Earth Environ. 2, 720-735 (2021)
Chen, J. “Historical logging alters soil fungal community composition and network in a tropical rainforest.” For. Ecol. Manage 433, 228-329 (2019)
Hartmann, M. et al. “Significant and persistent impact of timber harvesting on soil microbial communities in Northern coniferous forests.” ISME J 6, 2199–2218 (2012)
Lughadha, E.N. et al. “Extinction risk and threats to plants and fungi.” Plants, People, Planet 2, 389-408 (2020)
Song, P. et al. “Effects of historical logging on soil microbial communities in a subtropical forest in southern China.” Plant Soil 397, 115-126 (2015)
Sterkenburg, E. et al. “The significance of retention trees for survival of ectomycorrhizal fungi in clear-cut Scots pine forests.” J. Appl. Ecol. 56, 1367-1378 (2019).
AGRICULTURAL EXPANSION
Nearly all crops depend on mycorrhizal fungi. Yet industrial agriculture employs aggressive tillage, and vast quantities of chemical fertilizers, fungicides and pesticides which devastate fungal networks. Without their fungal partners, crops require more chemical inputs and are more vulnerable to drought, soil erosion, pests, and pathogens.
Industrial agriculture relies on tillage and huge inputs of fertilizer, pesticides and fungicides – all of which decrease the abundance, effectiveness, and diversity of mycorrhizal fungal networks. A recent study found the abundance of fungal networks was higher in organically managed fields, and the fungal communities were also far more complex: twenty-seven species of fungi were identified as highly connected, or ‘keystone species’, compared with none in the conventionally managed fields. Frequent and aggressive tillage disrupts fungal communities, leading to significant decreases in biomass and diversity compared to no-till systems. Application of fungicides further impairs fungal networks, reducing phosphorus uptake in croplands by more than 40%. The negative effects of agricultural practices spill out far beyond farmers’ fields. A large study published in 2018 suggested that the ‘alarming deterioration’ of the health of trees across Europe was caused by a disruption of their mycorrhizal relationships, brought about by nitrogen pollution.
SOURCES
Banerjee, S. et al. “Agricultural intensification reduces microbial network complexity and the abundance of keystone taxa in roots.” ISME J 13(7), 1722-1736 (2019)
Edlinger, A. et al. “Agricultural management and pesticide use reduce the phosphorus uptake capability of beneficial plant symbionts.” PREPRINT (Version 1) available at Research Square (2021)
van der Linde, S. et al. “Environment and host as large-scale controls of ectomycorrhizal fungi.” Nature 558, 243-248 (2018)
Wang, Q. et al. “The impact of cropping system, tillage and season on shaping soil fungal community in a long-term field trial.” Eur. J. Soil Biol. 102, 1164-5563 (2021)
~40%
of Earth’s land surface is used for agriculture
Fires reduce fungal biomass by up to 96%
CLIMATE DISRUPTION
Extreme temperatures, drought, and floods threaten the ability of global mycorrhizal fungi to move nutrients and store carbon. Disruptions arising from climate breakdown, like intense wildfires, destroy plants and the mycorrhizal fungi underground.
Wildfires and other extreme weather events are becoming more intense and more frequent. Severe fires are particularly destructive to soil organisms like fungi. After fire, it can take more than a decade for soil microorganisms to reach pre-fire levels. Fungal networks are more vulnerable to wildfires than other soil biota, and suffer massive reductions in diversity. These changes in the composition of fungal communities can alter plant community structure and have cascading effects across trophic levels decreasing the richness of fungal feeders, such as arthropods, in forests and grasslands. Mycorrhizal networks in forests are becoming even more important under increasing temperatures because of their ability to provide water to plant hosts. Mycorrhizal fungi can help plants withstand extreme drought.
SOURCES
Bowd, E.J. et al. “Long-term impacts of wildfire and logging on forest soils.” Nat. Geosci. 12, 113-118 (2019)
Bowman, D.M.J.S. et al. “Vegetation fires in the Anthropocene.” Nat. Rev. Earth Environ. 1, 500–515 (2020); Certini, G. et al. “The impact of fire on soil-dwelling biota: A review.” For. Ecol. Manage. 488, 118989 (2021)
Dove, N.C., Hart, S.C. “Fire Reduces Fungal Species Richness and In Situ Mycorrhizal Colonization: A Meta-Analysis.” Fire Ecol. 13, 37–65 (2017)
Gehring, C.A. et al. “Tree genetics defines fungal partner communities that may confer drought tolerance.” Proc. Natl. Acad. Sci. 114, 11169–11174 (2017)
Pellegrini, A. et al. “Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity.” Nature 553, 194–198 (2018)
Pressler, Y. et al. “Belowground community responses to fire: meta-analysis reveals contrasting responses of soil microorganisms and mesofauna.” Oikos 128, 309-327 (2019)
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