I’VE been reading a rather disturbing book, called The Hidden Life of Trees. The subtitle, What They Feel, How They Communicate, made me particularly uneasy.
It’s by Peter Wohlleben, who manages a large forest in Germany. Over his career he has not only learned the scientific facts about trees but has developed an empathy with them. He never goes quite as far as saying they have feelings, but the question lingers.
It came as a surprise to me that trees have a social system. The roots, which extend twice the spread of the crown, grow into each other, enabling them to transfer nutrients to each other if one tree is suffering, say from insect attack or damage. This happens only within the same species, leading to the conclusion that the sensitive root tips are capable of distinguishing their own family from others. The point of this mutual support is that a group of trees is much less at risk from wind and weather than a single one, and they create a humid micro-climate which benefits them.
They also warn each other about enemies. When a caterpillar takes a bite out of a leaf, the damaged area registers pain in the form of an electrical current, though this is not transmitted in milliseconds like a human but goes at the stately pace of a third of an inch a minute. After a few minutes or even an hour the tree starts to pump toxic substances into its leaves which deter the caterpillars. At the same time it releases chemicals into the air which are picked up by neighbouring trees so that they can marshal their defences in good time. Some of these chemicals are attractive to predators of the caterpillars and they soon arrive for a juicy meal. But here is the amazing thing – trees can distinguish between pests by their saliva, and send out the appropriate information to their neighbours. This means they must have some sense of taste.
They also broadcast messages via the interconnected root system. Even if there is a gap between the roots (Wohlleben says there are occasional loners which avoid social interaction) there are fungi in the soil which transmit the news. Wohlleben envisages this as an internet of the ground. The ultra-thin filaments of the fungi weave through the soil with such intensity that one teaspoon contains many miles of them. Thus the entire forest is networked and the trees exchange news about predators, drought and no doubt lumberjacks. This ‘wood wide web’ extends between species, as it is in the fungus’s interest to keep as many trees healthy as it can.
Peter Wohlleben writes of parent trees ‘educating’ their young by restricting the amount of light and water they get, to make them grow slowly, while ‘nursing’ them with nutrients via the roots. This results in dense, strong, healthy wood which will live for hundreds of years. Although a beech sapling would grow 18 inches a year with unlimited light and water, in a forest it grows so slowly that a sapling the height of a man may be 70 or 80 years old. It may have to wait another 200 years until the mother tree dies.
Spare a thought, then, for street trees. Grown fast in nurseries, their roots trimmed to keep them small enough to handle, then planted in holes dug out of compacted earth, they are isolated from all the forest support system and discipline of growing slowly. There is no cooling humid microclimate, only burning hot asphalt in the summer, salt spray in the winter and exhaust fumes all year round. They are easy targets for pests and are easily blown over, and nearly all die prematurely – of course, being replaced by a younger victim.
One topic Wohlleben does not cover, perhaps mercifully, is whether trees suffer when they are felled. He does however call for the restoration of mixed forests with a substantial proportion of trees allowed to live their full span so that they can pass their knowledge on to the next generation.
He writes: ‘I for one welcome breaking down the moral barriers between animals and plants. When the capabilities of vegetative beings become known, and their emotional lives and needs are recognised, then the way we treat plants will gradually change as well. Forests are not first and foremost lumber factories . . . completely the opposite in fact.’
I hope I have not made the writer sound nutty – it all made perfect sense to me. There is so much more to learn about the amazing world we live in.
PS: A note of praise for the translator, Jane Billinghurst, who gets hardly a mention but has made the book immensely readable.
Gunnera news: We just escaped frost this week but it has been cold every night. The left-hand plant has got a couple of strong new leaves coming up, hidden behind the frost-damaged ones.
This is last week’s picture:
And this is yesterday: