Fungi learn how to cope with drought, but at a cost

Understanding what climate change will do to belowground ecosystems helps us predict what will happen aboveground, too

Matthew Vandermeulen


University at Buffalo

Climate change is a stress that all organisms must deal with. One major stress from rising temperatures is an increase in droughts

One reason the risk of drought is climbing is that warmer temperatures dry out soil, especially during periods of low precipitation. Dry soil creates a snowball effect by killing plants, which yields more dry soil. But the effects of drought do not stop at plants – some fungi suffer as well.  

It might appear as though fungi are not important because they are only scattered here or there when you see them in the woods or in the grass. That is because most fungal growth is underground. Fungi are dominant members of the community of microscopic organisms that live beneath our feet. In many soil communities, fungi represent an average of 55%-89% of all microbes. Because fungi strongly impact ecosystem health, how fungi respond to drought is an important ecological question.

We know other immobile organisms, like plants, can deal with drought by stress priming. Stress priming is a process where exposure to a stress, such as extreme cold or pathogen attack, helps an organism to respond better to future stress events. In some microbes, stress priming can lead to 10 times better survival rates. Plants have been studied extensively for their ability to stress prime for drought, however, filamentous fungi (meaning fungi that grow in long, thin strands) have not.

A pair of researchers at Germany's University of Bayreuth have now investigated if filamentous fungi have the ability to stress prime for drought. They used two different species of fungi that are found ubiquitously in soil as models: Penicillium chrysogenum (a source of penicillin) and Neurospora crassa, a bread mold. 

To prime them, the fungi were exposed to a mild simulated drought by allowing the soil they grew in to dry out, after which they were allowed to recover. Then the researchers hit them with another, more severe drought. They measured the growth and activity of the fungi, and compared those that were primed before the severe drought stress to other fungi that were not. They found Pencillium was able to stress prime and maintain their "primed" state for at least seven days. Neurospora showed no ability to stress prime. 

a dry, dead flower

Climate change-induced droughts could have devastating effects on plants and fungi

Photo by Paweł Czerwiński on Unsplash

But stress priming comes with a cost. The researchers saw that fungi that were primed, but not exposed to severe drought, grew less than fungi that were not exposed to stress at all. This is because stress priming redirects resources that could otherwise be used for growth, a concept seen in other studies. This means the intensity, frequency, and time frame between drought events could favor some species over others, causing a shift in fungal community composition. Filamentous fungi that stress prime would most likely have a competitive edge in an environment where there is a shorter time lapse between droughts. Non-stress primers, however, could have an advantage in environments with longer time spans between drought stresses because stress priming wastes resources for a memory that may not last long enough to benefit them. 

Filamentous fungi get their name because they grow in branching filaments, called hyphae. The hyphae expand outwards to form large networks of tissue that traffic nutrients from distant places, making filamentous fungi expert scavengers. One of the dominant roles of scavenging fungi in maintaining a healthy ecosystem is nutrient cycling by decomposition. By breaking down organic molecules, fungi release nutrients into the ecosystem that would otherwise be unobtainable to other organisms. 

Another important role for some filamentous fungi is establishing a symbiotic relationship with plants by invading into their roots so both organisms can exchange nutrients with each other. These fungi are referred to as mycorrhizae. Many plants are dependent on nutrients provided by mycorrhizae to grow and thrive. 

Changes from drought in the growth, activity, or composition of the fungal community could thus have a rippling effect on an ecosystem. They could also have negative impacts on overall climate. 

For example, these changes could disrupt the ability of fungi to store carbon in soil. Soil contains over three times more carbon than the atmosphere and four times the amount in all living plants and animals, and fungi are a critical part of that. In boreal forests, which account for about 30% of total forest area in the world, 50-70% of stored carbon comes from dead roots and fungi growing in the soil. If soil cannot hold on to as much carbon, then more carbon dioxide will be released into the atmosphere. Changes to fungal community composition could also have direct environmental impacts by altering fungal roles in decomposition and plant-fungi relationships. 

To us, fungi are small and often invisible organisms. But they are critical components of ecosystems, and living mostly underground won't protect them from the effects of climate change. Studying how they respond to environmental stressors will help us better predict how all of the important ecological processes fungi contribute to will change as the world warms –and, ultimately, what that means for those of us aboveground.

Comment Peer Commentary

We ask other scientists from our Consortium to respond to articles with commentary from their expert perspective.

Raj Rajeshwar Malinda

Cell Biology and Developmental Biology

Climate change is real and gradually affecting all the living  organisms, and if not addressed properly, it will be a disaster for our planet. We have already started to see the effects such as seasonal changes, rising sea level and temperature  variations around the global. You nicely explained the effect  on healthy ecosystem in reference to fungi. If healthy ecosystems start to suffer because of climate change, I think  it would severely affect the lives of humans. Thanks for a nice read! 

Matthew Vandermeulen responds:

 I appreciate your comment and am happy you enjoyed the article. This is a really important topic for everyone to keep thinking about and I appreciate you taking the time to leave a comment and take the conversation further. 

Marnie Willman


University of Manitoba Bannatyne and National Microbiology Laboratory

While fungi and ecosystem biology are certainly not my fields, I can appreciate the importance stated in this article. The effects of climate change go much deeper than the earth simply getting warmer, and fungi are a great understated example of this. It’s true that they play a incredibly important role in the environment, and if they’re unable to  survive droughts and climate shocks that come with climate change, big  problems are coming down the pipeline.

I am wondering if fungi could eventually “learn” to becoming  resistant to droughts. For the species named that cannot survive a drought or prime themselves for adverse weather, I wonder if you could condition them to do so. This would likely be a downstream experiment,  but what are your thoughts on this?

Matthew Vandermeulen responds:

Because there are many fungi that are at least somewhat drought resistance, I would think with time you could artificially select other fungi to be more drought resistant like the one in this article. To make it so a fungus that cannot currently stress prime into one that can is a much harder question to answer because we do not fully understand the molecular regulations behind how stress priming is achieved in fungi. It might be a simple genetic rewiring after a couple generations or it could be much more complex than that. I think it would be a great  downstream experiment to try and artificially select for a  strain of N. crassa that could potentially stress prime and be more drought resistant, and if successful, see what changed genetically to understand what the  programming would look like in this organism. If it could be done artificially, it would suggest that it could possibly occur naturally  too. 

Rebecca Dzombak


University of Michigan

Thanks for shedding light on the underground, Matthew! I have a couple questions. One is only tangentially related to your article, but I’m curious: how sensitive are soil fungi/mycorrhizae to soil CO2, and how might this affect their C cycling capabilities & therefore soil C storage? Do they cycle nutrients more efficiently at increasing CO2, or vice versa? So as drought may affect the mass of fungi growth, would there be changes in how efficiently they can operate from drought, high temps, or changing CO2

Matthew Vandermeulen responds:

One study has found  that mycorrhizae fungi respond positively to increased CO2 levels, increasing their growth by up to 47%. This positively impacts their ability to act as a carbon storage. Plant species that associate with  some mycorrhizal fungi also increase their biomass when CO2 levels rise, which would increase the ecosystems ability overall to store more carbon. In some environments, scientists have found that higher CO2 levels have lead to an increase in fungal species  richness in areas where there is also an increase in plant root  production. It appears that overall, the response of both mycorrhizal fungi and plants to higher CO2 levels are tightly correlated and should  generally be considered together. This can make it difficult to completely disentangle the effects of just mycorrhizal fungi.

One factor scientists have found that influences soil fungi response to CO2 levels is the type of soil  the fungi are found in. The different water, phosphorus, and nitrogen availability in different soils can lead to different fungal community  composition and activity levels. Rising CO2 levels may affect fungi  differently depending on what type of soil they come from. In some soils, decomposition rates do somewhat correlate positively  to fungal species richness or biomass, which means there would be an affect on nutrient cycling in that environment that is at least partially dependent on CO2 levels.

So, fungal and plant biomass can increase due to rising CO2 levels, which would help with carbon storage, but increased decomposition rates and activity could release more CO2 into the atmosphere. When you add to that all the other variables from climate change, such as rising  temperature and more extreme weather events, it is difficult to know for sure how the future of soil fungi will play out without more research.

Adriana Romero-Olivares


University of New Hampshire

This is a great piece that shows how important, yet overlooked, fungi are in our ecosystems. This topic is especially relevant to me because I study the response of fungi to global climate change, and look into adaptation strategies fungi undergo to survive environmental stress. I’m  glad you touched on the subject of ecosystem-scale effects of fungal responses to drought because indeed the responses could go to simple community shifts with no major effects to the environment (unlikely, but you never know) to massive effects that could end up creating a  positive feedback (worsening) to global warming. I thought Marnie's questions about fungi learning to become resistant is very interesting, and I agree that this could be done artifically in a lab experiment (i.e. using racing tubes for example and some sort of culture media that simulated water stress), but it is very likely happening in the wild as well.