There's increasing evidence to show that trees are able to communicate with each other. More than that, trees can learn. When you discover how trees talk to each other, feel pain, nurture each other, even care for their close relatives and organise themselves into communities, it's hard to be sceptical. The support they give each other is not random. Research by Professor Massimo Maffei at the University of Turin shows trees can distinguish the roots of their own species from other plants, and even pick out their own relations from other trees. Some are so tightly connected at the roots that they even die together, like a devoted married couple. Diseased or hungry individuals can be identified, supported and nourished until they recover. They can also send warnings using chemical signals and electrical impulses through the fungal networks that stretch under the soil between sets of roots. These fungi operate like fibre-optic internet cables. Their thin filaments penetrate the earth, weaving through it in almost unbelievable density. One teaspoon of forest soil contains many miles of these tendrils. Over centuries, if left undisturbed, a single fungus can cover many square miles and create a network throughout an entire forest. Through these links, trees can send signals about insects, drought and other dangers. News bulletins are transmitted by chemical compounds and also by electricity. Most of us see trees as practically inanimate. But the truth is very different. They are just as intensely alive as we are ... and for much, much longer.