Friendly fungi help forests fight climate change

This award-winning essay by young British science writer Zara Hussan explores the hidden, underground networks of fungi that are quietly helping plants and trees retain carbon and fight climate change. Winner of the 2022 Association of British Science Writers (ABSW) Young Science Writer of the Year award, her essay explores a microscopic realm: Earth’s fungal “life support system”.

Indonesian rainforest: trees naturally absorb carbon dioxide

A forest is home to billions of living things, some of them too small to be seen with the naked eye. Collectively, these microscale species contribute more to our planet than most of us could imagine.

While we know that forests play an important role in combating global warming – acting as carbon sinks – what is less understood is how tiny organisms that live hidden in the soil help to block our greenhouse gas emissions.

Trees in our forests absorb carbon dioxide from the atmosphere as they photosynthesize; its leaves, powered by sunlight, convert this carbon dioxide into oxygen and sugar. As a tree grows, carbon becomes part of its woody “biomass”.

This is how trees naturally fight the greenhouse effect that warms the planet. In the last 20 years, it is estimated that the Amazon rainforest alone has absorbed 1.7 billion metric tons of carbon dioxide.

Trees, however, do not act in isolation; they are entangled in – and working alongside – a vast community of fungi at the microscale.

A 2016 study led by researchers at Imperial College London revealed that a specific type – ectomycorrhizal fungi – allows certain trees to absorb CO2 more quickly (and therefore grow faster) than others. This is known as the “CO2 fertilization effect”.

Illustration showing the cross section of useful fungi that live on tree roots

Illustration showing the cross section of useful fungi that live on tree roots

These fungi live in the root system of a host tree. In a symbiotic relationship, fungi help the tree to absorb more water, carbon and other nutrients. In return, the tree provides food for the fungi through photosynthesis.

Ectomycorrhizal fungi have also been found to retard the decay process; decomposition breaks down all this blocked carbon and releases it into the atmosphere. So fungi actually have two methods for fighting global warming.

Insights into the critical and driving role of fungal growth have already been applied to agriculture. Sowing the soil with “friendly fungi” is considered a promising technology for future sustainable agriculture.

Research carried out to plant a particular variety – arbuscular mycorrhizal fungi, or AMF – in the soil has shown how it can not only help to enrich soil fertility, but also reduce CO2 levels in the atmosphere.

Fungal net on dead wood

A mesh of subterranean fungi plays an important role in energy and nutrient recycling

The use of these fungi can also provide a more sustainable alternative to chemical fertilizers, which can reach and pollute nearby water sources.

The benefits of so-called “biofertilizers” such as AMF have resulted in the global biofertilizer market reaching a value of over US$2 billion.

Switching from chemical to organic fertilizers comes at a financial cost. Biological fertilizers are also often crop-specific and generally do not increase crop yields as much and as quickly as chemical fertilizers. They are understood to be far more beneficial to the soil and the environment, although in the UK the government has developed a scheme called the Sustainable Agriculture Incentive (SFI). It is intended to provide financial assistance to farmers who opt for more sustainable and nature-enhancing practices.

Moving away from chemical fertilizers on farmland can give these useful fungi a boost in our forests as well.

illustration showing the application of biofertilizer to a plant

illustration showing the application of biofertilizer to a plant

Scientists say naturally occurring forest fungi are being put at risk by some chemicals. Colin Averill, senior scientist at ETH Zurich in Switzerland, says that chemical fertilizers – which are rich in nitrogen, phosphorus and potassium – really break the symbiosis between fungi and plant roots.

Research has also shown a link between the loss of soil fungi and a reduction in forest soil carbon content. Meanwhile, deforestation, which annihilates the fungi along with their host trees, disrupts this entire underground climate change-fighting ecosystem.

The system can be repaired, however. Dr. Averill says that by transplanting soil from rich and biodiverse “donor” sites to places where the soil is depleted, it is possible to restore fungal networks.

He argues that taking these steps is necessary to help protect microbial communities.

More recently, a project led by the Society for the Protection of Underground Networks (Spun) set out to map these microscopic networks of fungi and understand their essential role in protecting our soils. The project is the start of what scientists call an “underground climate movement” aimed at protecting this ancient life support system and helping it fight climate change.

These fungi may be tiny and hidden under the ground, but they form a network that is protecting our planet. Scientists studying them say we can do more – particularly through sustainable farming methods – to protect them.

portrait of zara

portrait of zara

Young Science Writer of the Year 2022, Zara Hussan, 14, is from the Plashet School, East Ham, London. The ABSW Young Science Writer of the Year award invites students ages 14-16 to submit an 800-word essay. The competition, supported by BBC News, is designed to get young people writing and thinking about the big questions in science, technology, engineering and/or mathematics.

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