Martinez-Suz’s research focuses on mycorrhizal fungi – a immense group of fungi that coexist with plant root systems. Mycorrhizal fungi form networks that can circulate around and sometimes inside plant roots, passing nutrients and water to the plants in exchange for carbon. About 90 percent of plant species are known to form symbiotic trade networks with various species of fungi. “These plants are covered in these fungi. It’s amazing. They are small, but they are everywhere,” says Martinez-Suz.
This has grave implications for tree planting programs. Planting modern forests is the main hope for carbon sequestration, but there is growing evidence that mycorrhizal networks may be crucial to the success of these attempts. One replanting study found that a birch and pine forest planted on moorland in northern Scotland did not enhance soil carbon stocks even after almost 40 years in the ground. The scientists who carried out the study believe this may be due to the influx of modern trees disrupting existing fine mycorrhizal networks on the moorlands.
“Replacing the entire set of fungi with other fungi has long-term impacts on soil carbon sequestration and biodiversity,” says Martinez-Suz. Her current project involves comparing samples from forests in low-polluted areas, such as northern Finland, with samples from highly polluted regions, such as Belgium and the Netherlands. In her opinion, mushrooms in polluted regions are less diverse, which may affect the ability of forests to store carbon dioxide.
The main culprit is nitrogen pollution, which enters the soil through the burning of fossil fuels for electricity generation and transportation, as well as through agriculture. Excess nitrogen changes the composition of soil fungi, reducing the number of fungi that are best at retaining nutrients and pumping carbon into the soil.
However, there is hope that forests can change the situation. One study in the Netherlands found that when nitrogen pollution decreased, beneficial fungal species began to return to forests. The danger, says Martinez-Suz, is that if ecosystems are pushed too far, there may be no fungal spores left to boost the population.
If we are to better understand how these fungi impact critical ecosystems, we need to come to grips with all of these species. Mycologists believe that almost 90 percent of the world’s mushroom species are yet to be discovered, and Kew archivists are only halfway through a long process of digitizing their collection so that researchers can easily find out where and when a species has been found.
About 5,000 additional specimens arrive at the funarium every year, and the shelves are cluttered with samples waiting to be dehydrated and stored. Many of them, says Davies, are sent by amateur mycologists fascinated by the world of mushrooms. “People in such academic institutions will send them materials to work with and identify because they are world experts, even though they have no formal education. They’re just obsessed. It’s so frosty.”
The article was published in the July-August 2024 issue WIRED Magazine UK.