DO TREES HAVE FEEL­INGS?

Can you hear whis­per­ing in the woods? Are trees talk­ing to each an­other via vast un­der­ground fun­gal net­works? Sara Mait­land ex­plores the fas­ci­nat­ing claims of au­thor Peter Wohlleben

Countryfile Magazine - - Contents -

A con­tro­ver­sial new book sug­gests that trees ‘talk’ to each other. Is it be­yond be-‘leaf’?

Last year Peter Wohlleben, a Ger­man forestry ecol­o­gist, pub­lished a book that swiftly be­came a mas­sive best­seller not just in Ger­many, but in Bri­tain and the USA, too. It was called The Hid­den Life of Trees: What They Feel, How They Com­mu­ni­cate.

In the book, the au­thor makes some pretty rad­i­cal claims. Among them are that trees com­mu­ni­cate with each other, ex­change use­ful in­for­ma­tion, are ca­pa­ble of learn­ing from ex­pe­ri­ence, have a pos­i­tive so­cia­bil­ity, pro­tect and nur­ture both their young and their very old, come to col­lec­tive de­ci­sions about is­sues like pop­u­la­tion growth or fer­til­ity and feel pain.

In this view, trees are cer­tainly sen­tient and pos­si­bly (al­though he does not say this ex­plic­itly) have con­scious­ness – or some­thing very like it. And from here, it is not a long step to ar­gu­ing that any fixed boundary be­tween an­i­mals and trees – even hu­mans and trees – is ar­bi­trary.

To reach these con­clu­sions, Wohlleben does not evoke any kind of folk­loric an­i­mism – the nymphs and spir­its of clas­si­cal Greece, the World Tree of the Norse sagas or the end­less dark forests of fairy sto­ries – but two very dif­fer­ent kinds of ev­i­dence.

The first is his own ex­pe­ri­ence over sev­eral decades of work­ing in forests – 20 years with the Ger­man forestry com­mis­sion, and lat­terly in the com­mu­nity-owned beech woods of Hum­mel, where they are work­ing for the re­turn of primeval forests. The ev­i­dence from this source is in­vari­ably au­thor­i­ta­tive, and of­ten touch­ing and beau­ti­ful.

The other source of his ev­i­dence is new sci­en­tific re­search, and this is where things be­come more com­pli­cated. Trees com­mu­ni­cate, ap­par­ently, by a num­ber of tech­niques. Wind-borne chem­i­cal re­lease is one of them. When a tree is at­tacked by preda­tors of var­i­ous kinds – nib­bling gi­raffes in the case of African aca­cias, or in­sect lar­val in­fes­ta­tions of Ger­man beech trees, for ex­am­ple – it emits a chem­i­cal essence that the wind car­ries to other neigh­bour­ing trees and they re­spond by pro­duc­ing de­fences that, for in­stance, make their leaves less tasty to the in­vaders. But can such a trans­mis­sion of chem­i­cals be called com­mu­ni­ca­tion, as it is in­vol­un­tary?

An­other, even more cru­cial com­mu­ni­ca­tion tool used by trees is through the sym­bi­otic re­la­tion­ship known as ‘my­c­or­rhiza’ formed be­tween trees and funghi.

My­c­or­rhizal fungi live in the roots of all trees (in­deed of al­most all plants) to the bi­o­log­i­cal ad­van­tage of both. The fungi stretch out del­i­cate threads called ‘hy­phae’, which, be­cause they are finer and fur­ther-reach­ing than the tree’s own roots, are able to sup­ply the tree with ni­tro­gen, phos­pho­rous and other vi­tal nu­tri­ents. Mean­while, the tree sup­ports the mycelium with car­bon and su­crose, which the fungi needs but can­not make.

The hy­phae criss-cross with each other, cre­at­ing a some­times-huge un­der­ground net that puts each in­di­vid­ual tree in con­tact with its neigh­bours, seem­ing to al­low for the trans­fer of vi­tal re­sources be­tween them. This is ex­tra­or­di­nary and deeply fas­ci­nat­ing, but new it is not. The ex­is­tence of fungi within root sys­tems has been known about for over a cen­tury and a half, and their

“The un­der­ground net­work puts each in­di­vid­ual tree in con­tact with its neigh­bours”

mu­tu­ally ben­e­fi­cial re­la­tion­ship was de­scribed by Fran­ciszek Kamieński be­tween 1879–1882. The name ‘my­c­or­rhiza’ was in­tro­duced in 1885. Oliver Rack­ham de­scribes the process fully in Wood­lands (2006). What Wohlleben adds is not so much new re­search as a vivid nar­ra­tive of com­mu­ni­ca­tion; the mem­o­rable term the ‘wood-wide web’ (which, as he makes clear, he did not orig­i­nate) and a hu­man­is­ing lan­guage.

FULL COV­ER­AGE

It is in the evo­lu­tion­ary in­ter­est of large de­cid­u­ous trees of the sort that grow in groups (woods or forests) to main­tain a full canopy. This con­serves wa­ter sup­plies, re­duces the force of winds and moder­ates tem­per­a­ture.

In an old and well-es­tab­lished wood, the trees have both the link­ing web of mycelium and of­ten in­ter­con­nected root sys­tems, and healthy trees will pro­vide nec­es­sary nu­tri­ents to young saplings or to trees that are, through age, dis­ease or other cir­cum­stances, short of them. The fre­quency with which this hap­pens is in­deed fas­ci­nat­ing – and the sug­ges­tion that nearby trees con­tinue to pro­vide sug­ars to the stumps of trees felled cen­turies ago and there­fore no longer able to cre­ate their own through pho­to­syn­the­sis cre­ates a rich mys­tery.

How­ever, is it jus­ti­fi­able to de­scribe such ex­changes in terms of friend­ship, com­pas­sion or ma­ter­nal care, as Wohlleben does? (It is al­ways ma­ter­nal, by the way – there are no fa­ther trees for the au­thor.) Or, more gen­er­ally, to speak of trees in terms of con­scious emo­tions – fear, pain, ten­der­ness, parental in­stincts panic – even if they seem to ex­hibit be­hav­iours that in hu­mans might in­di­cate those feel­ings? Does the re­build­ing of new bark over a ‘wound’ – such as one caused by the break­ing of a branch – demon­strate that the tree is re­spond­ing to pain?

De­spite an­thro­po­mor­phis­ing trees, Wohlleben in­sists he has his lim­its, telling a Ger­man news­pa­per: “I don’t hug trees and I don’t talk to them.”

BE­SPOKE OAK

Bri­tain’s old­est forests are pre­dom­i­nantly oak forests, not the Ger­man beech forests that Wohlleben writes about. There are vis­i­ble dif­fer­ences – the most ob­vi­ous one is that beech forests tend to have clear floors and the beech seeds ger­mi­nate un­der the ‘par­ent’ trees. This rarely oc­curs with oak trees – to ger­mi­nate, they need to be car­ried away (by jays, squir­rels or streams) some­where else.

This means that Wohlleben’s talk of par­ent­ing, nur­tur­ing, ed­u­ca­tion and train­ing does not nec­es­sar­ily ap­ply to British woods. All his re­search into chem­i­cal in­ter­ac­tions, in­for­ma­tion ex­change and ‘so­cia­bil­ity’ has not been tested in our forests. For ex­am­ple, where do the flow­ers – such as blue­bells, which grow un­der oak trees – fit into his ob­ser­va­tions? We do not know. Beech trees may well be dam­aged, if not killed, by cop­pic­ing. Hazel, how­ever, an­other very com­mon British wood­land tree, ap­pears to live longer un­der cop­pice man­age­ment.

Ear­lier this year a group of Ger­man bio­sci­en­tists and other forestry ex­perts took the un­usual step of launch­ing a pub­lic pe­ti­tion against The Hid­den Life of Trees, on the grounds that they felt it was pseu­do­science. Wohlleben re­sponded to the crit­i­cisms by stat­ing that all his facts are “based on sci­ence”.

I am not sure that for Wohlleben the sci­ence is the im­por­tant thing: I think he deeply loves trees and wants them to be pro­tected, nur­tured, hon­oured. This is a good agenda but it raises more ques­tions of its own – a cen­tral one here is what is the ev­i­dence that we, hu­man be­ings, are more likely to pro­tect, hon­our or nur­ture be­ings that we iden­tify with? We are not do­ing very well with our own species – or with pri­mates who are surely much eas­ier to an­thro­po­mor­phise than trees are. It seems to me we should pro­tect trees pre­cisely be­cause they are not like us, but so very dif­fer­ent.

Ac­cord­ing to au­thor Peter Wohlleben, beech forests (such as this plan­ta­tion in Ar­broath) com­mu­ni­cate, sup­port one an­other and feel pain TOP, IN­SET Peter Wohlleben in Hum­mel For­est

OAK CHANGE Mys­te­ri­ously, around 1900, oak trees seemed to stop grow­ing from acorns in canopied wood­lands, a phe­nom­e­non that au­thor Oliver Rack­ham re­ferred to as Oak Change. Sci­en­tists still de­bate the rea­son for this. Oaks now de­pend on third par­ties to trans­port the acorns – squir­rels and jays not only move but bury (or plant) acorns – of­ten at quite a dis­tance from the ‘par­ent’ tree. So the ‘nur­tur­ing’ be­hav­iour of beeches is not seen among oak trees to­day. SUP­PORT NET­WORK Wohlleben re­ports that stumps of trees felled hun­dreds of years ago may live on, if neigh­bour­ing trees – which are likely to be their off­spring – pro­vide them with es­sen­tial sug­ars via the my­c­corhizal net­work. THE WOOD-WIDE WEB Ev­ery tree in the wood is linked via a net­work of fun­gal threads, called mycelium. These mi­cro­scop­i­cally slen­der threads stretch across the wood. In­di­vid­ual trees are con­nected via this my­c­or­rhizal net­work, or wood-wide web.

Sara Mait­land is a monthly BBC Coun­try­file Magazine colum­nist and the au­thor of A Book of Si­lence and Gos­sip from the For­est.

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