The Week - UK (2021-02-06)

Briefing NEWS 13

6February 2021 THE WEEK

HowwastheEarth’ssoilformed?
Althoughourplanetis4.54billionyears
old,whatwethinkofassoiltodaydidn’t
formuntilabout 450 millionyearsago,
thankstothecombinedactionof
percolatingwaterandlivingorganisms.
Essentially,soilconsistsofamixof
materialsthathavebeenbrokenupfrom
rocksandminerals,combinedwithmore
orlessdecomposedorganicmatterand
water.It’salsofilledwithliving things:
tinymicro-organismssuchasbacteria,
archaeaandfungi;largerfaunasuch
asinsectsandearthworms;andthe
mammalsandreptilesthatmaketheir
homesinit.Onegramofsoilisestimated
toholdanythingbetween4,00 0 and
50,0 00 speciesofmicro-organisms,while
thegroundbeneathourfeetishometoa
quarterofallanimalspeciesonEarth.

Whyisitsoimportant?
Thecomplex food webs insoilrecycle nutrientsfromtheorganic
materialin it,and fixnitrogen fromtheair.Soiliscentraltolife
on Earth:obviously, allhuman lifedependson it–soilcontains
the nutrientsfor cropsandvegetation togrow,and providesthe
foothold fortheirroots.Butsoildoes plentymorebesides.Itis
hometobacteriaand fungiwhich areused inthe productionof
foods rangingfromcheesetowineandevensoysauce,andwhich
arecrucial tothedevelopment ofdrugs andvaccines,fromwell-
knownantibiotics like penicillintobleomycin (used fortreating
cancer) toamphotericinfor fungalinfections.Soil also imparts
hugeenvironmental benefits.It filters rainwaterandstoresit,
regulatingthedischargeofmoistureto preventflooding.And
it acts asavastandcruciallyimportant storeofcarbon.

How does it store carbon?
Theworld’ssoilscontainanestimated2,500 gigatonsofcarbon

• more thanthreetimestheamountin theatmosphere andfour
  timeswhat isstored inalllivingplants and animals.Scientists
  estimate that soil removessome25% offossilfuelemissions
  fromtheEarth’satmosphereeach year,makingitanessential
  componentinthefight againstglobalwarming.Infact, it’ssuch
  aneffectivecarbon sink thatif we
  couldincreasetheamountitcan store
  byjust0.4%,we couldhaltthe build-
  up ofCO 2 in theair.But the ability
  of soiltoeffectivel ystorecarbon
  depends onit bothremaining intact
  andinahealthy state. And,
  unfortunately,that hasn’tbeen
  happening foralong time.

How fast is soil disappearing?
Very fast:theworld is losing about
30 football pitchesof fertile soil
everyminute, accordingtothe Soil
Association.Sincethe industrial
revolution, about 135billion tonnes
of soil is estimatedtohavebeenlost
from farmland, according tosoil
scientist ProfessorRattanLal. In
Iowa’s fertile farmland, for instance,
the average topsoil depthdecreased
from14-18inches atthestart of
the 20th centuryto6-8 inchesbyits
end. Andit’snot just thespeed at
which soil is disappearing that’sthe

problem; it’s the quality of the soil

that remains.“Manytypesof soil

degradation areinvisible,”saysRonald

Vargas,ofthe UNFood andAgricultural

Organisation. “Youjust don’tsee the

lossof organiccarbon fromsoilsor

pollutionbuilding up init unti lyou

try to plantcrops there.”The ability

of soil to support plant life is being

reducedby erosion, compaction,

nutrient imbalances, acidification and

water-loggingaroundthe world.

Why is that happening?

Severalof themost significant causes

are climate-related. Some29 million

acres ofland arelost every year to

desertification,the loss of vegetation

often broughtabout byshiftsinclim ate

and by over-grazing.Risingtemperatures

also increasethefrequency of droughts and wildfires,which

degradethe quality of soil. Othercauses arestill more directly

linked withhuman behaviour.Oneisurbanisation,asthe growth

of towns, citiesand road networksseals soil beneathlayersof

asphalt andconcrete. Andanotherisdeforest ation:vegetation is

beingremovedon amass scalearoundthe world, exposing soil

to eros ionfromwindand rainand meaning thatitcannotbe

repl enishedbyorganic matter.But perhaps the mostimmediate

threat to theworld’ssoilcomesfromagriculture.

Howdoes farming harm soil?

It isn’tfarming per s ethat’sthe problem; it’s theway in which

agriculturehas evolved in recent history.Farmshave increasingly

come to rely on heavy tilling,multipleharvests andlarge-scaleuse

of agrochemicals i norder toincrease yields andmaximise profits.

In the past 20 years, theworld’s agricultural productionhas

increasedthreefold andtheamountofirrigated landhasdoubled,

according tothe EuropeanCommission’s Joint Research Centre.

But thathascome atacost: theJRC haswarned thatproductivity

hasdecreased on20%ofthe world’scropland,16%offorest

land,19%of grassland,and 27%ofrangeland.Heav yploughing

not only disrupts soil ecosystems; it also releases carbon into the

atmosphere, hindering thefightagainst climate change.

What can be done about this?

There isagrowingawareness ofthe

need to start looking afterthe Earth’s

soil. In 2017,then-Environment

SecretaryMichael Gove warned that

intensivefarminghad leftthe UK

30 to 40years awayfrom the

“fundamental eradication of soil

fertility” in parts of the country.

“Countries canwithstand coups

d’état, wars andconflict,even leaving

the EU,” hesaid,“butnocountry

can withstandthe loss of its soil

and fertility.” It’scleartha tdrastic

changes in landuse will berequired,

but the questionishow toreduce

pressure on thesoilwhile feed ing a

growingworld population (seebox).

On pres enttrends, the future looks

“bleak”, warnedalead author

of aUNFoodand Agriculture

Organisationreport in December

–but they added that “it’s not too

late to introducemeasures now”.

Our disappearing soil

The earth beneath ourfeet is the sourceofagreat deal of thelife onthis planet–butit’s under threat

Home toaquarter of all animal species on Earth

Howtofeed theten billion

The world’s population–now about 7.8 billion–is

expected to hit ten billion in 2050. Food production will

have to rise vastly to feed humanity; so agriculture will

have to be made much more sustainable if the soil is to

be protected. There are any number of ways of doing

this: from taking modest steps that prevent erosion

–plant ing hedges, terracing slopes–tor eplacing

monocultures with crop rotation; to adopting systems

that preserve soil quality, such as organic farming,

permaculture (the creation of self-sufficient farming

eco-systems) or “no-till” agriculture, where farmers

plant new crops over the remains of the last, instead

of ploughing over their land, keeping soil intact. Each

of these systems has advantages and disadvantages:

yields in organic farming, for instance, tend to be lower.

But there is one step that could be taken, globally,

to preserve the Earth’s soil, according to the UN’s

Intergovernmental Panel on Climate Change: to eat

less meat. Around 80% of the world’s farmland is used

to raise livestock or to grow plants to feed animals –

but that land produces just 18% of food calories. If

meat and dairy consumption were cut out entirely,

global farmland could be reduced by more than 75%.

Even modest cuts would reduce pressure on the land.