In 1999, a team of scientists led by Christian Körner did what thousands of people do every Christmas: they wrapped Norway spruce trees in tubes. Except this was in March, not December. And the trees were 40-metre-tall giants in the middle of a Swiss forest, not 2-metre pipsqueaks in a living room. (The team had to use a crane). And the tubes had no lights or baubles on them. Instead, they had a series of tiny holes, which pumped out carbon dioxide.
For years, the team fumigated five of these wild spruces. They wanted to see how trees will cope with the high levels of atmospheric carbon dioxide that we’re pumping into the atmosphere. But in the process, and almost by accident, they showed that trees of different species exchange huge amounts of carbon via an internet of fungi—a “wood-wide web” that secretly connects their roots.