A lot, it seems.
For humans, communication normally equates to talking. Trees don’t talk by using language or forming words and so for many years, people have believed that it means that trees don’t say anything to each other. How wrong we were.
What researchers have since discovered is that trees communicate not by sound but by scent. The first place they noticed this was in Africa by watching the way that giraffes feed. When the tree becomes aware that it is being browsed upon, it starts to pump tannin into its leaves, which make the tree unpalatable and drives off the hungry ungulate. What is fascinating though is that the giraffes the researchers were watching tended to walk upwind or a distance of about 100 meters before resuming their feeding. What was happening was that the tree was also releasing a warning gas called ethylene, which was carried on the wind and would warn other trees of the same species nearby to start producing tannin too.
Not only could they communicate but it seems they were looking out for each other’s wellbeing. This is something we’re beginning to understand more deeply with terms such as “forest wisdom” and “mother trees” being coined by forest researchers.
The problem though is that this form of communication, although fast, is weather dependent. What if trees wanted to say something to one another and there wasn’t any wind to carry their message? Well, that’s where some help comes in in the rather bizarre form of fungus. Dr. Suzanne Simard of the University of British Columbia discovered that they warn each other using chemical signals as well as electrical impulses sent through the fungal networks around their root tips. As the trees’ root systems grow together and overlap, it allows them to share information with their neighbours. These electrical impulses travel at about a third of an inch per second, which compares to that of a jellyfish or a worm. It seems that trees also share valuable nutrients with one another through their root tips, helping to care for sick or young neighbours.
What happens if there are loner trees in an area though? Does this block the alarm signal being passed through the forest? Luckily not. As described by Peter Wohlleben in his extraordinary book The Hidden Life of Trees, fungi act like “fiber-optic internet cables”, disseminating news around the forest. As Wohlleben says, “over centuries, a single fungus can cover many square miles and network an entire forest”. They share information about insect, droughts and other dangers, even between competing species of trees as well as with shrubs and grasses.
This is rather comically referred to as the “wood wide web”.
What fascinates me is that if trees are weakened, they seem to lose their communication skills, which results in them being unable to defend themselves. It seems that insects listen to the chemical warning signals and then test a tree that doesn’t pass the message on by taking a bite out of its leaf. Because the tree has been unable to hear the rest of the forest warning it, it will not have produced any tannins and will become inundated with hungry insects wanting to devour its sweet leaves.
This fact is pertinent to us as a social species. It reminds us that we too are designed to look out for one other and to share information, resources and support. Trees that stand alone are weakened and the same can be said for humans. It’s a reminder too that communication doesn’t always mean talking. Like trees, our imaginary root systems are connected in weird and wonderful ways and regardless of physical distance, language or even the ability to speak, we should protect and care for our neighbours.