Researchers have proposed an unusual agricultural solution that could meet the protein needs of millions of people, while actively sequestering large amounts of carbon: grow mushrooms in amongst the roots of trees.
This is an emerging practice called mycoforestry, which introduces fungi spores into the root systems of sapling plants. The fungi grow symbiotically, receiving carbohydrates from the tree, in return for nutrients which they gather through their far-reaching network of underground filaments, and funnel back to the tree.
“Once the tree and fungus are growing together happily, they are then planted into the field,” explains Paul Thomas, a professor at the University of Stirling in the UK, and lead author on a new study about the practice. “It’s essentially new woodland creation, but with trees that have a symbiotic edible fungus growing on the roots.”
Together with colleagues, Thomas looked at the potential of this forest-and-food combo to meet humanity’s protein needs, using as a test case one popular mushroom species called Lactarius deliciosus, or the saffron milk cap.
First, Thomas and team calculated the emissions and sequestration potential of different tree-planting methods, based on data from 637,000 ground plots spread across multiple forest biomes, ranging from boreal to tropical. Next they combined this with yield data on the saffron milk cap, to determine the overall environmental footprint of mycoforestry. This, they compared to the farming systems of nine other protein-rich foods such as beef, pork, milk, cheese, seafood, and pulses.
Most strikingly, they found that mycoforestry is the only form of protein production that actually sequesters carbon, mainly on account of the trees that make this growing system unique. Even pulses, which had the lowest emissions footprint besides fungi, still produce between 4 and 10 kilograms of CO2-equivalent per hectare each year.
Mycoforestry, on the other hand, could lock away tons. Farming in boreal regions of the northern hemisphere showed the most promise, where tree-fungi farms could capably sequester 12.8 tons of carbon dioxide equivalent, per hectare, per year. Depending on the habitat type, tree-planting method, and plantation age, this could grow to almost 900 tons per hectare annually—equivalent to sequestering the annual emissions of 194 gasoline-fueled cars.
In temperate ecosystems the potential was smaller, around 6.1 tons per year. Meanwhile, the researchers found that farming in tropical landscapes brings a risk of increased emissions due to higher rates of deforestation there for commodities like soy and beef. (Though they do note that the mycoforestry landscapes might actually be protected from deforestation, by the relatively high value of the fungi crop.)
In a measure of real-world potential, the researchers showed that combining fungi production with existing afforestation projects—efforts to plant trees where previously there were none—could feed millions without using up any land.
In China where afforestation is taking hold, mycoforestry on afforested plots planted between 2010 and 2020 could have produced enough calories to feed 4.6 million people annually, they found. Globally, the 4.7 million hectares of afforested land could have provided enough mycoprotein to feed almost 20 million people.
This is a “missed opportunity” the researchers believe, but one we can take now.
Threats to forests are growing, and agricultural expansion is the biggest driver. But mycoforestry is a legitimate form of food production that can occur without deforestation, and in fact by adding trees to the landscape. (Provided it’s well-managed, and bearing in mind the well-documented risks of large scale afforestation projects).
What’s more, mycoprotein “could absolutely replace protein produced by other sources,” says Thomas—perhaps even displacing a share of livestock farming to further ease the pressure on wild forests.
As odd as it may at first seem, growing mushrooms on trees could be a powerful agricultural solution, say the researchers. They urge more research and investment in this idea—which may simply be too good an opportunity to miss. “We present a system that can mitigate climate change, whilst also producing a lot of food,” Thomas says.