AI-rewritten: This is a summary of an article from Quanta Magazine, rewritten by AI (Qwen, running locally) to make it easier to read. The facts come from the original article – read it for the full story.

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Mycorrhizal fungi form a vast underground network that trades minerals with plant roots, helping enrich soil and sequestering 13 billion tons of atmospheric carbon dioxide each year. This process is roughly equivalent to one-third of the world’s fossil-fuel emissions. Scientists know these organisms partner with 80% of all plant species on Earth in a relationship that evolved some 450 million years ago. While researchers understand how this trading system works, they do not yet fully grasp how brainless fungi decide whom to trade with or what terms to offer.

Toby Kiers, an evolutionary biologist at Vrije Universiteit Amsterdam, studies these hidden networks using tools like fluorescent quantum dots and imaging robots. She explains that fungi break up rocks by digesting them outside their bodies, often partnering with bacteria to dissolve hard-to-access minerals into forms plants can use. In return, plants feed the fungi sugar and lipids. Kiers describes this partnership as Earth’s circulatory system, noting that these fungal networks act like open-pipe systems rather than individual cells because they lack septa that divide them into compartments.

These microscopic threads are thinner than hair on a human head and connect roots across terrestrial ecosystems. The relationship was so fundamental for plants that the fungus effectively served as their root system for tens of millions of years before true roots evolved. Kiers emphasizes that plants and fungi are very different kingdoms of life, yet they rely on this intimate association to build the ecosystems humans depend on today.