Global Map Revealing the Vast Underground Network that Connects Trees, Fungi and Bacteria Created by Scientists

In recent years, scientists have begun to understand that trees rely on complex underground networks of fungi and microbes which interact symbiotically with the roots, facilitating the transfer of nutrients.

Now, an international team of scientists has created the first global map of these vast subterranean systems, known as "mycorrhizal fungi networks" or, colloquially, the "wood wide web," according to a study published in the journal Nature.

For their paper, the researchers created a computer algorithm to analyse a database belonging to the Global Forest Initiative, which has information on 1.2 million forest trees, representing 28,000 species in over 70 countries, the BBC reported.

To produce models of these fungal networks around the world, the algorithm took into account local environmental factors, as well as data regarding the different microbes that are most closely associated with each tree species.

For example, the roots of oak and pine trees are often surrounded by ectomycorrhizal (EM) fungi, Science Magazine reported. Meanwhile, those of maple and cedar trees tend to found alongside arbuscular mycorrhizae (AM) fungi—which can penetrate the roots. Still others—mostly in the legume tree family—are often associated with "nitrogen fixing" bacteria, which take the gas from the air and turn into food.

The team's analysis showed that local climate has a big role to play in the composition of these networks. In regions characterized by a cool temperate climate and boreal forests, EM fungi are more common. In the warmer tropics on the other hand, AM fungi are found in higher proportions. Finally, nitrogen-fixing bacteria tend to be clustered in very hot dry, areas.

"It's the first time that we've been able to understand the world beneath our feet, but at a global scale," Thomas Crowther, an author of the study from ETH Zurich, told the BBC. "Just like an MRI scan of the brain helps us to understand how the brain works, this global map of the fungi beneath the soil helps us to understand how global ecosystems work.

"What we find is that certain types of microorganisms live in certain parts of the world, and by understanding that we can figure out how to restore different types of ecosystems and also how the climate is changing," he said.

The authors say that the latest findings highlight not only the significant role that mycorrhizal networks play in mitigating climate change, but also how vulnerable they are to its effects.

According to the study, AM fungi accelerate the recycling of carbon into the atmosphere, whereas EM fungi help to remove the greenhouse gas and keep it locked away in the ground. The problem is that EM fungi are at greater risk from climate change, thus we could see significant declines in future—which could increase the "feedback loop of warming temperatures and carbon emissions.

"The types of fungi that support huge carbon stores in the soil are being lost and are being replaced by the ones that spew out carbon in to the atmosphere," Crowther told the BBC.