Beneath every forest is a complex underground web that plants use to communicate. The network is so intricate that we are only just starting to understand it. What is the language of trees?

What is the Wood Wide Web? It's common knowledge that animals communicate. People talk, dogs bark, babies cry. Plants do as well, but in a slightly different way. Hidden under our feet is a world of countless pathways created by roots and fungiFungi are a group of living things including mold, mushrooms, and yeast. They eat organic material - usually dead things, like fallen trees and old fruit - and reproduce by spreading spores. . Plants use it to exchange water and essential nutrientsSubstances that plants and animals need to live and grow. The six essential nutrients our bodies need are vitamins, minerals, protein, fats, water, and carbohydrates. . The network has been nicknamed the Wood Wide Web. This social network is far older than the internet, though, at nearly 500 million years old.

How does it work?: It all comes down to fungus. For centuries, fungi growing on trees were thought to be harmful. In reality, certain kinds of fungi combine with the roots of plants to form a relationship called a mycorrhizaThis difficult word comes from the Greek for "fungus" and "root".. The bond is mutually beneficial: plants provide the fungi with sugars and water. In return, the fungi share important nutrients like phosphorus and nitrogen.

Why is it good for plants? As well as gaining useful nutrients from the fungi, trees are also connected to each other through the network. Sometimes, older plants use the network to send products of photosynthesisThe process in which green plants use sunlight and carbon dioxide to create sugar and oxygen. to smaller trees with less access to sunlight.

The Wood Wide Web even allows plants of different species to send and receive messages. Occasionally, if one plant has been attacked by insects, it can send warning signals out to others nearby. When a tree dies, it can use the network to give away its final nutrients to surrounding plants.

Is it all friendly? No. Connected through fungi and roots, plants are never truly alone. This makes them vulnerable to nasty neighbours that use the network to their advantage. Some plants release toxic chemicals to harm others while fighting for a space on the forest floor. Other plants steal from each other. The phantom orchid can't photosynthesise, so it sucks the food it needs from nearby trees.

Is a forest just one, big organism? Some people believe that trees live in a sort of society, sharing and exchanging food and information. It might not be quite so simple though. Others believe that the network linking thousands of different species may have come about by mistake. Trees have adapted to send signals to other plants of the same species. Somewhere along the way, messages are picked up by foreign plants.

Is the network good for the environment? Yes. The fungi that support tree growth also store carbon. This makes the web essential to slowing down climate change. But the fungi only grow in cooler climates. As global temperatures rise, they could be in danger.

In 2019, scientists made a global map of the web that tracks the effects of climate change. They hope the map will alert people to the dangers of global warming, as well as show them the beauty of the Wood Wide Web.