The early ancestors of plants were simple forms of algae, which drifted rootless through fresh waters. Most biologists believe that, only when algae partnered with a very different life form – fungi – some 470 million years ago, was it able thrive on land.

Indeed, today some nine in 10 land plants exist in symbiosis with what’s known as ‘mycorrhizal’ fungi, which helps their roots to extract nutrients from the ground. This animation from the Society for the Protection of Underground Networks and the Fungi Foundation details how this hidden relationship operates, the vital role these underground fungal networks play in ecosystems worldwide, and the threats they currently face due to human activity.