Deep, Down and Dirty: The Science of Soil (2014) Movie Script
'Every spring,
our planet is transformed.'
A riot of new life
bursting from the ground.
'And it's all made possible by one
rather misunderstood material.'
From early childhood
we're told that this stuff, dirt,
is best avoided.
But as someone with a lifelong
passion for soil and
everything that grows in it, it's a
rule I've always enjoyed breaking.
'I'm Chris Beardshaw. I spend my
life designing and planting gardens.
'Everything I do depends on soil.
'And I'm going to try and convince
you that it's an unrecognised
'wonder of the natural world.'
For billions of years
our land must've looked
pretty much like this.
Bare rock. A barren place.
Apparently devoid of life.
But something transformed it
into a vibrant, living planet.
'And that something was soil.'
But what fascinates me
is where did the soil come from?
What is it composed of
and why is it so essential to life?
So I'm going to get down
and dirty with soil.
I want to investigate its secrets.
And reveal it as you've never seen
it before. An intricate
microscopic landscape...
..teeming with
strange and wonderful life forms.
I'm going to reveal a world
more complex
and fragile than anything that
exists above ground.
A substance so remarkable,
you'll never walk on the grass
in the same way again.
'As a gardener, I spend my life
among plants.
'I see them emerge from the soil.
'But I've never really had
the chance to discover what gives
'soil its amazing, life-giving
force.
'So now I want to find out.
'And I'm starting by doing
what comes naturally.
'I'm going out to dig.'
Ask any gardener and they'll tell
you that the soil
provides their plants with the
nutrients that are needed for life.
And if you grow anything
intensively,
on farms or gardens,
you have to apply fertiliser
to replace and replenish those
nutrients in the soil.
In a natural landscape like this,
all of these trees are being
supported by the nutrients that
are just inherently in the ground.
But we shouldn't take these
nutrients for granted.
Like our fertilisers,
they also need to be replenished.
And how that happens is the first
great mystery of soil.
Even at the end of winter
there's plenty of evidence of life
on the woodland floor, or at least
last season's life.
Leaf litter,
coming from the canopy above.
But this is of no use at all
to the surrounding plants
in its current state.
That's because most plants simply
can't feed on dead leaves and twigs.
They're too tough to break down
and digest.
And this creates a problem.
Any nutrients
they hold are locked in
so the plants can't get at them.
'But hidden beneath the surface
of the soil
'is a very different picture.'
This modified-looking spade is
actually a scientific instrument.
The soil corer gives us
the perfect cross section through
the layers of the topsoil.
At the top we can see here this
unrotted layer of leaf litter.
It's last season's leaves just
sitting on the surface.
But below that is a much darker
layer where the
particles are much more broken down,
much smaller and quite compact.
Beneath that is what
we would recognise as topsoil.
These are described by soil
scientists as different horizons.
'Collectively, the horizons
are known as a soil profile.'
And the deeper down the profile
we go, the smaller
the pieces of leaf and twig become
until they just disappear.
So somehow the tough plant matter
is eventually broken down,
releasing its trapped
nutrients into the soil.
This is one of the most vital
processes in nature.
'And it's begun by a rather
unlikely hero.
'To help track it down,
'I'm joined by Lynne Boddy,
Professor of Mycology
'at Cardiff University.
'We're on the hunt for an organism
that prefers to stay
'out of the light.'
This is a likely-looking candidate,
plenty of moss on the surface.
Let's turn it over gently
and see what we can see.
Look at that.
Oh, it's wonderful, isn't it?
Absolutely covered, it's almost like
a spider's web under here, isn't it?
It is. This is fungus.
The crucial thing about the fungi
is that they release nutrients
which allow plants to
continue to grow.
The main body of the fungus is
called the mycelium, which is
made up of very, very,
very fine filaments,
they're too small to see by the naked
eye. But here they're aggregated
together to form cord- or root-like
structures that we can clearly see.
What do these threads do?
They grow out from this wood
in search of new resources,
so maybe the resources would be dead
leaves, more wood.
When they find them they exude
enzymes that break down the structure
of the wood or the leaves or any
other bits of dead plant material.
It's easy to overlook fungi.
But, to me,
they're true champions
of the natural world.
They begin the process
of breaking down dead wood
and leaves to release
the nutrients trapped inside.
It's an extremely rare ability.
The thing about the wood decay
fungi is that actually
they are the only organism or almost
the only organism that can
actually break down wood on this
planet, and that is one
of the reasons why they're
so important, because otherwise
we'd be up to our armpits in dead
stuff. And, in fact, plants
wouldn't be able to
grow because all the nutrients
on this planet would be locked up
in the dead plant material.
As the fungus breaks down the leaves
and twigs, it produces a rich
substance we call humus that becomes
part of the soil itself.
But the fungus is doing another
crucial job.
It's feeding an entire world
most of us don't even know exists.
Using specialist microphotography,
we can catch a rare glimpse
of an astonishing hidden kingdom...
..teeming with weird,
almost alien-looking life.
Millions of tiny creatures,
all of which are dependent
on nutrients being
released by the fungi.
These are nematodes,
tiny, round worms.
Scientists think there may be up
to half a million
species of these
wriggling in the soil.
There are mites, tiny
relatives of spiders and scorpions.
Tardigrades, often called 'water
bears' due to their cute appearance.
And rotifers, fascinating little
creatures that can propel themselves
through the soil using special hairs
that appear to revolve like a wheel.
This is the first great
secret of the soil. A vast,
living kingdom of tiny animals.
As they move around, eat
and are in turn eaten themselves,
they spread the essential nutrients
released by the fungi.
Helping to make the soil a more
fertile place for growing plants.
'Yet so far
we've only seen how fungi
'begin the process of unlocking
those nutrients.
'Breaking down all the tough remains
of dead plants is too large
'a job for fungi alone.
'But they have a secret ally
underground.
'An animal whose impact on the soil
is greater than any other.'
When it comes to ecosystems,
not all organisms are created equal.
By that, what I mean is the work
of one or two species will allow
hundreds of others to thrive.
One such animal is so important it's
been called an ecosystem engineer.
In this field, there might well be
over two million of them.
There are no prizes for guessing
which animal I'm seeking out here.
It's one that's inspired
generations of horticulturists
and agriculturists.
It is possibly the greatest
gardener on earth.
And it's this, the humble earthworm.
As a gardener,
I've long known that worms play
an important role in soil.
The great Charles Darwin devoted
over 40 years of study
to them, culminating in the
publication of his seminal work,
The Formation Of Vegetable Mould
Through The Actions Of Worms
With Observations On Their Habits.
You may not have heard of it,
but it sold faster
than On The Origin Of Species.
Darwin's studies, lesser known
than his work on evolution,
revealed an organism that was
essential for the life of the soil.
He became obsessed by them.
He fed them different diets,
tested their intelligence
and even tested their senses
by playing a bassoon to them.
What is about the earthworms
that beguiled Darwin?
Just why are they so important?
Well, first of all the sheer
scale of the worm operation.
As they tunnel into the ground
in their millions,
their burrows permeate the earth
like a vast ventilation system,
providing essential supplies of air
to everything else that
lives in the soil.
But that's not the earthworms'
only talent.
They also continue
what the fungi began.
They eat and digest dead leaves
underground,
unlocking their trapped nutrients.
The way they do this reveals
one of the most fundamental
secrets of soil.
But it's hard to see.
'So I've come to meet
Mark Hodson, Professor
'of Environmental Science
at York University.'
I find they're very fun creatures,
you see them a lot.
If you walk around after the rain
you see them crawling around.
'He's spent years studying what
and how worms eat.'
They go up and down.
During the day, they stay in
the bottom of their burrows.
At night they come out onto
the surface, they look round,
sort of, sometimes they keep their
tails anchored in their burrows.
They sort of stretch out
and eat or grab organic material,
they pull it down into their
burrows to eat later on.
And the undigested material gets
squirted out of the back end and that
helps make all of this black, browny
stuff which is the soil.
Nothing is quicker at breaking down
dead leaves than an earthworm.
It's thought that in the average
field the worms get through
a staggering one and a half
tonnes of plant matter every year.
They're like leaf-processing
factories,
operating on an industrial scale.
Yet they look nothing more than
a simple, fleshy tube.
So what's going on inside?
To help answer that, Mark has been
doing a rather unsavoury experiment.
This Petri dish contains
a sample of plain soil.
And this one was made using earth
that has passed through
an earthworm.
In other words, worm poo.
Mark's been comparing the two
and he's uncovered
evidence of a hidden army of secret
agents at work within the worm.
Bacteria.
So each of these spots is
a bacterial colony. You can see
there are far more growing here
from the material that's just
come out of the earthworm gut.
So the earthworm ingests the soil,
there are bacteria in there already,
and the earthworm gut environment
is good for bacteria.
It's moist, its got the right pH,
the earthworm is secreting mucous
full of polysaccharide sugars,
which the bacteria love to eat.
So it's bacteria
that finish the job of breaking down
dead plant matter.
There are billions of them
naturally present in the ground,
like workers on a production line
turning dead plants into new soil.
But inside the earthworm
this activity is magnified to levels
that are truly mind-blowing.
If you do counts on the soil
in earthworm guts
you can have 1,000 times more active
bacteria in that soil
than the bulk soil
surrounding the earthworm.
What it's proving is
the earthworms have ramped up
the bacterial activity in the soil.
And it's this army of bacteria,
hidden in the guts of earthworms,
that completes the vital cycle.
Unlocking all
the nutrients from dead leaves
and releasing them
back into the soil.
We very often think of soil as being
brown, solid, inert stuff.
But there's more life within in it
than flies, swims or walks above it.
And, far from being a haphazard
array of organisms,
this is a complex
range of interconnected structures
that support the life above.
As we've seen, it takes
a combination of plants, fungi,
animals and bacteria all working
together to keep nutrients
flowing from the dead to the living.
In the process, new soil is created
which in turn supports
even more life, making a cycle that
keeps the soil fertile.
Yet so far we've only scratched
the surface of the soil.
Everything we've seen happens within
just the topmost layers.
'Look deeper and there's
far more to soil than this.
'To reveal just how much,
I first need a bit of heat.'
What I have here is dried topsoil.
I want to find out
how much of this is
derived from plants by setting
fire to it.
If it's 100% plant material,
there should be nothing left.
So I'm starting with 100g.
'Let's see how much remains.'
As this is burning away, the soil is
completely transforming colour.
It's going from a soft brown
to almost a carbon colour.
Very similar to the
embers in a barbecue.
The soil particles are fracturing,
breaking apart. The organic matter
binding them together is burning
away and the soil particles are
just falling to pieces.
'The plant matter is turning
into gases like carbon dioxide
'that are lost into the air.
'After about 15 minutes of intense
heat, I'm going to weigh it again.'
See how much we've lost?
We started off with about 100,
it's now down to 70.
So about 30% of this original soil
was plant based.
It's burnt away.
Clearly, there's more to soil than
just plant material.
To see what that is, we need to get
beneath the topsoil
and look deeper down.
'This is Scolly's Cross
in Aberdeenshire, where
'a landslide has exposed the layers
of soil beneath the pine forest.
'It's something we rarely
get to see,
'as all this is usually hidden
underground.'
In a landslip situation like this
we get to examine perfectly
the soil profile, the horizons or
layers of various materials.
At the top we've got the vegetation
and, below, the various layers or
horizons of soil,
each with a different characteristic
in terms of colours and textures.
The topsoils, going down into
the subsoils with the roots
penetrating,
this is what we saw in the forest.
But, as we go further down, the dark
organic plant material disappears.
We seem to have left
the soil behind.
These deeper layers are mainly
made up of fragments
of the underlying rock.
And then further down
we're into bedrock.
Collectively, these layers form
the foundation of soil development.
Rock fragments permeate the soil
from the bedrock
all the way to the surface.
It's mainly this stuff that
was left behind
when I burned the plant matter
away from the topsoil.
But, though these
particles are from lifeless rock,
that doesn't mean
they have no purpose.
In fact, they are fundamental
to how soil works.
Soil particles are divided into
three different categories
depending on the size
of the particle.
The largest being sand.
There you can see them
just coming into focus,
wonderful, rounded particles.
The next size down, well, it's silt.
And there you can start to see
the individual silt particles.
And the very smallest are the clays.
Search for the clay. There they are,
much smaller.
Relatively speaking, if the sand was
the size of a beach ball
then the clay particles would be
the size of a pin head.
Incredibly small and
flat in their profile.
What's curious about the particles
is that the relative
proportions of them in any
soil fundamentally affect
how that soil behaves, and, more
importantly, how it supports life.
'To see exactly how, I've come to
the James Hutton Institute
'in Aberdeen.
'I'm here to meet soil
scientist Dr Jason Owen.'
Jason, what will this
experiment demonstrate?
What we have here are three
cylinders. One with a sand, one
with a silt-dominated soil
and one with a clayed soil.
When we pour water in the top
what we'll see is the water
percolating through the soil
profile.
With the sand it'll go very quickly.
With a clay it'll go very slowly.
And the silt will be
somewhere in between.
To me, this is familiar stuff,
as it will be to any gardener.
It's the age-old question
of drainage. How well water
moves through different
types of soil.
With the sand, large particles,
there's quite large gaps,
comparatively speaking,
and water can
go down through the profile.
With the clay, very small particles,
and as a result the gaps
where water can penetrate
are exceptionally small.
The silt is somewhere in between
the two extremes.
But to really see what's
going on inside the soil
we have to look at it in far
greater detail.
Here, they're using cutting edge
technology to examine soil
on an incredibly small scale.
We're joined by Evelyne Delbos,
operator of the Scanning Electron
Microscope at the Hutton Institute.
She's looking at soil
magnified 400 times.
I have the three main
parts of the soil.
The sand grains here.
On the right is the silt
and the clay at the bottom.
Well, you can sort of see with
the clay, for example,
it's stacked so tightly together
that you can actually not see
discernible gaps between them.
Whereas here we've got these very
large sand particles
and even through they're
right on top of each other
you can still see the far larger
gaps.
That allows air,
for aeration of the soil,
and it also allows water movement
through the soil.
But there's more going on here
than just how the particles
are packed together.
Let's imagine this is
a grain of sand.
And the surface area of that
grain of sand is that surface,
that surface, that surface,
and that's it.
It we take, by comparison,
the same volume of clay
then you have that surface plus that
surface plus that surface, so you
can imagine already that the surface
area is much, much, much larger.
So what does the surface area
do to the water?
What's the relationship
between those two things?
What's interesting about many clays,
it has an electric charge
associated with its surfaces.
Many nutrients that are dissolved
within the water can be
attracted to these clay sites, to
this large surface area,
and then held,
basically for root systems
then to uptake for plant growth.
So clay particles have an electrical
charge that can bind nutrients
and water to them.
This allows soil to
act as both larder
and reservoir for plants
and animals.
Sounds ideal, but there's a catch.
Too much clay and the soil can act
like a sponge
and can quickly become waterlogged.
At the other end of the scale,
too much sand
and the water can run through
too quickly,
washing the nutrients out and
leaving behind soil that's dry.
Have we got an image of what
a good soil should look like?
Here you can see some grains
of sand, they are different sizes.
It's a mixture and you can also have
there and there the clay
and the silt all mixed up.
So this is demonstrating the ideal,
in terms of soil. It would
be free draining,
retain sufficient moisture,
sufficient nutrients,
what about microbial activity?
This is a very,
very complicated 3D structure
which gives all of the microbiota
within the soil effectively a niche,
a home to live, and as a result
the ecosystems that exist in the soil
are exceptionally complicated.
This is a classic example where
you've got the mix between the
large particles, the clay particles
and silt all working together.
So the elements that make up soil
come from two very different places.
The chaos of life,
and the inert world of rock.
Together, they create an intricate
substance that can naturally
feed and water all
plant life on earth.
And it makes me wonder just how did
this strange
alliance between rock
and life begin?
'How did the very first soil
come to exist?'
To find out, we need to go back
to a time
and place before the first soil
appeared on the planet.
That's not quite as difficult as it
might sound.
This is Malham Cove, an inland cliff
deep in the Yorkshire Dales.
It's a striking landscape,
built from limestone
and sculpted by the awesome
power of ice.
This place offers a wonderful
window into the Earth
billions of years ago,
before there was soil.
That's because at the end
of the last Ice Age,
as temperatures rose and the ice
retreated, it left this
naked rock. Any soil that had been
here had been scoured away
and deposited somewhere in that
direction.
And as a consequence any soil
you see here is relatively new,
in fact, it's still forming.
Making this one of the best
places in the country to discover
how we get from this naked rock,
to this. Soil that supports life.
I'm joined by Professor Steven
Nortcliff from Reading University.
Landscape is fascinating in terms of
the soil.
First, I want to know what could
possibly start to break up
something as seemingly
permanent as rock.
We've got to break it down.
And we've got evidence here in this
landscape
of those early stages of breakdown.
We have ice forming in the fissures
in the rock and as the ice expands
it forces the rock apart. And that's
the first form of disintegration.
When water freezes, it expands.
If that expansion
happens within a crack,
it can exert a force strong enough
to break rock apart.
And you can witness this in your own
freezer at home.
You fill the ice tray and when it
freezes there's expansion.
But it seems remarkable that
that expansion is powerful enough
to blow rock apart.
Well, you're expanding in a confined
space.
It only has one way to expand
and that's sideways.
That forces the rock apart and it's
the beginning
of the disintegration
to give us the soil.
This process is called
physical weathering.
It breaks down rock by sheer
brute force.
But we're still a long way
from soil.
Next comes a different process
entirely.
And it starts with rain.
We'll just drop some
hydrochloric acid onto limestone.
You can see it fizzing.
You can hear it fizzing.
It's really going at it.
What Stephen's showing me
is an exaggerated version of what
happens every time it rains.
Rain is slightly acidic
and, with limestone,
when this slightly acidic water
falls on the surface it weathers it.
And is that what we're seeing here,
on the surface of the rock?
That is exactly
what we're seeing here.
So rain reacts with the rock,
gradually dissolving it. This is
chemical weathering.
The second key step towards soil.
Using a stronger acid to speed
the process up,
we can see just how powerful it is.
Here, a piece of rock is almost
entirely dissolved. Leaving
behind nothing but insoluble,
sandy remains known as sediments.
And that's the beginning
of the soil.
It's a very small
amount of insoluble residue,
but that's where the soil
development starts.
But sediment isn't yet soil. There's
something fundamental missing.
Life. But look closely,
and this rock is not bare.
It's covered in this, lichen.
And this is what causes the final,
almost magical metamorphosis from
inert rock, to life-giving soil.
In this environment they are key
because the lichen will attack the
rock, very much like the chemical
weathering we saw, but it will break
it down, release nutrients.
Lichen is actually two organisms,
algae and fungus,
living in one body.
And though it seems almost
incredible, the fungus part is able
to break down the rock to release
nutrients that it can feed on.
Much as we saw the fungi do
with the wood in the forest.
Over time, generations of lichen
grow over one another,
the new on top of the dead.
The dead remains form
organic matter.
And when this mixes with sediment
the result is soil.
And so from an apparently barren
limestone pavement up here
we have the complete story
of the generation of our soils.
Bare rock through the various
weathering processes, the biological
processes and eventually the
formation of soil. It is all here.
Condensed into just a few
square metres.
Yeah, it's a wonderful example
of soil development in motion.
And what we've got is different areas
representing different timescales -
some it's just starting,
others it's been going on
for a few thousand years.
Soil is the place where the
relatively inert world of rock meets
the riot of life above.
It's a complex,
staggeringly complex ecosystem,
but it also offers
something of a conundrum
because the life creates soil,
breaking down organic matter and
forcing rocks apart, but that life
is also dependent upon the soil
for nutrients, moisture, habitat,
anchorage, somewhere to live.
That means there's a delicate
balance between the life
and the soil.
Challenge one and you inevitably
challenge the other.
And today that ancient balance
between rock and life
is being challenged
as never before in history.
A new force has entered the world
of the soil. Humankind.
In geological terms,
human civilisation is a mere
blink of the eye, at around about
9,000 years. And in that brief
moment in time we've arguably done
more to change our soils than
in the previous 400 million years.
We've mined it.
Built on it.
Farmed on it.
And, in places like this,
drained it.
And our actions have had
consequences we never imagined.
East Anglia is famed for its fenland
landscape. One of rivers,
marshes and streams.
But what we have left is just
a fraction of what was once here.
Largely because this is a habitat
that's prone to flooding
and since the 17th century
generation after generation have
been progressively draining it.
The great system of canals
and ditches have been dug.
To drain the unwanted water
into the sea.
Over the past 300 or so years,
the population of the UK has
grown rapidly.
This put huge pressure on places
like the fens.
To help feed all those extra mouths,
we needed to dry out
the waterlogged land to make way
for the business of agriculture.
Rivers and lakes were drained
and crops planted.
The few people who lived there were
thought rough and unfriendly.
Old ways of life and traditional
pastimes that had grown up
around the flooding
were swept aside.
But this progress came with
a sting in the tail.
As the rivers
and meres were drained,
something unexpected happened.
The land began to sink.
This is Holm Fen,
drained in the 1850s.
It was the home of Whittlesea Mere,
once thought to be the second
largest lake in England.
This is all that's left.
Previous experience had demonstrated
that if you drain the fens
the land would sink.
So a local landowner
here at Holme Fen, William Wells,
decided to measure that process.
He took a post
and pushed it into the ground
until the top was completely
covered. And that post today?
Well, here it is.
The top of the post was originally
ground level.
Since 1850 this whole tract of land
has sunk somewhere in
the region of four metres,
making this one of the lowest
places in Britain.
There can surely be no clearer
indication of the effect
of human interference on soil.
But why did it sink?
And what are the consequences?
'I'm joined by Dr Ian Homan.
'He and his colleagues at
'Cranfield University have
extensively studied the area.
'We're going to take a look
at a rather special type of soil
'found here in the fens.
'This is peat.'
Pretty good profile. It is indeed.
Peat forms in a wetland environment,
so the soils are waterlogged.
It's low in oxygen under the surface
and it's quite acidic.
So the combination of the
waterlogged nature,
the lack of oxygen and acidity slows
down the rate of decomposition.
The soil bacteria and
the microbiological
components of the soil aren't able to
decompose that organic material.
So it accumulates very slowly.
So in peat, instead of being broken
down, plant material builds up.
And this has an important effect.
Plants grow using carbon dioxide
from the air.
And if they're not broken down
when they die
they and the carbon they contain
become trapped within the soil.
This is what's
known as a carbon sink
and peat bogs are some of the best.
But remove the water,
and the balance changes.
Oxygen enters the soil, allowing
bacteria and fungi to breathe.
This is what happened
when the fens were drained
and it had profound consequences.
That allows the micro-organisms
to use the carbon within this peat
as an energy source, converting
the carbon into carbon dioxide
and energy.
The fens, we think, are losing about
four million cubic metres of
peat soil every year and that equates
to an emission of carbon dioxide
of about 1, 1 million
tonnes of carbon dioxide a year.
We've gone from being an environment
that should be storing carbon
dioxide into the soil
into an environment now that
is emitting carbon dioxide.
So the story of the fens really is
that it's the worst possible,
for both ends of the spectrum.
Not only are we losing
the carbon sink,
but the carbon dioxide is being
released into the atmosphere.
Indeed.
So as a result of human activity
four metres of peat,
which took thousands of years to
form, disappeared in mere decades.
And this old post is a monument
to what can happen
when we upset the balance
within the soils.
It's a story that's repeated
throughout human history.
Archaeological records very
clearly demonstrate
that, as our nomadic ancestors began
to settle and farm the land,
populations increased dramatically.
And in order to feed the population
the area of land that was turned
over to the plough also increased.
Those early farmers tilled
and ploughed, fertilised
and irrigated in the best way
they knew how.
But, as we've seen,
human interference can have
unexpected consequences.
Ploughing and tilling can destroy
the soil's structure.
Intensive farming will deplete
the soil of nutrients
and over-irrigation can cause
high levels of toxicity.
When these factors combine
the soil becomes degraded
and prone to erosion from wind
and water.
For me, recent history provides
a stark warning.
By the 1930s, vast swathes
of the North American prairies
were turned over to the plough.
All the way from Canada
down to Texas.
But this would lead to catastrophe.
High winds and sun. A country without
rivers and with little rain.
Intensive farming techniques had
weakened the structure
of the soil till it could no longer
hold itself together.
So when a drought came the soil
dried out then simply blew away.
Turning the prairies into a huge
dustbowl.
The rains failed and the sun baked
the light soil.
It affected 100,000,000 acres
of land. By 1940,
over 2 million people had been
forced off the prairies.
Their stock choked to death on the
barren land.
Their homes nightmares
of swirling dust night and day.
Many went to heaven.
It was one of the biggest
environmental disasters
in American history.
But today the problem is
potentially worse than it ever was.
There are now more than seven
billion human beings on the planet.
There are more of us alive today
than there have been
up to the 20th century.
So it comes as no surprise more is
being taken from the soil.
We're more reliant on the soil
than ever before.
In trying to satisfy that need
we're cultivating, tilling,
fertilising to keep our soil
productive.
In doing so, we're destroying
the delicate structural
balance of the soil.
That can be hugely costly.
So when we talk about an impending
food crisis
what we should actually be
talking about is a soil crisis.
And that crisis is being felt as
keenly in the UK as anywhere else.
It's brought this farm in
Ross-on-Wye to the brink of ruin.
Asparagus farmer John Chinn
has seen massive gullies
open up in his fields.
Weakened by farming, the soil was
washed away by the rain,
taking his crop with it.
So what is it about the
conventional way of managing
a crop like asparagus that was
causing that degree of erosion?
It's two sides.
The first is that we have soil
exposed the whole time.
Then, secondly, because we didn't
want water standing in the crop
we would plant the rows up and down
the slope so the water would run off.
Of course, what was happening
was that the water was
running off faster and faster and
as it went it picked up the soil
because it was just there on the
surface. Carried that soil out to
the bottom of the field, maybe into
a stream, a road, leaving behind it
a gully that as you came
down the slope got deeper and deeper.
We have an amber warning in force
for the Somerset Levels.
Water erosion has become
a devastating problem in the UK.
Could be another 20mm or perhaps
a bit more in this area.
Over the past five years,
we've experienced an unusually high
number of storms,
culminating in the winter of 2013.
It was the wettest on record.
Vast swathes of the UK suffered
rainfall on an almost biblical
scale, leaving many areas like the
Somerset Levels deluged for months.
It's this kind of rainfall
that was partly to blame
for the destruction of John's
asparagus fields.
In desperation,
he sought the advice of soil
specialists at Cranfield University.
One of them was Dr Rob Simmons.
'He's investigating the huge problem
of water erosion on the smallest
'possible scale.
'By studying the energy
within individual raindrops.'
The raindrop has a certain
mass and a velocity
which affects its kinetic energy.
When that raindrop with that kinetic
energy impacts on the soil surface
it will damage the soil and cause
breakdown at the soil surface.
As you start to get extreme rainfall
events you get short-duration,
high-energy events with a larger
drop size, more kinetic energy
and they're going to cause more
damage to your soil surface.
And it's those that we're
having more of?
And it's those that we're
having more of. Yep.
Rob is testing what happens
when rain hits soil.
It's immediately apparent that
excess water quickly starts
to flow across the surface, what the
scientists call run-off.
Right, what we can see here is that
run-off is being generated
almost straight away.
So expanded out onto a large field
situation
this could cause major problems.
This is all well and good in a lab,
but is there anything you can
do about it out in the field?
Absolutely, but the best thing to do
is to go out in the fields.
Where the sun is shining.
Where the sun is shining.
By understanding exactly what
happens when raindrops hit soil, Rob
has been able to help John make some
big changes to the way he farms.
And they're surprisingly low-tech.
Instead of planting straight up
and down the hillside,
John now plants his rows
on the diagonal.
And he plants grass
strips between them.
The combined effect is to
slow down the run-off of water,
reducing its power to
erode the soil.
But that's only the beginning.
Now Rob's come up with an ingenious
new idea to take the energy
'out of the rain itself.
'To test it, he's set up rainfall
simulators
'and dug a series of channels,
or wheelings.'
We've got two rainfall simulators.
We've got
a wheeling which is bare on the
left-hand side. And on the
right-hand side we've got a wheeling
which has got straw mulch in it.
What the straw will do is it will
absorb the energy of that rainfall.
It will also act
as a blanket effectively
and it will absorb some of that
water, slow down the run-off.
It seems an incredibly simple
solution, basic straw.
Comparing the two scenarios side
by side reveals a big difference.
Raindrops hit the bare earth with
force and break up the soil.
Run-off water soon begins to flow
and carry the soil away.
But here the large drops are broken
up before they can hit the ground.
It's the straw, not the soil,
that takes the brunt of the impact.
And the run-off is reduced
to a trickle.
By having that canopy it absorbs
all the energy, you don't have
the detachment, you don't have
the run-off and erosion problems.
What's your reaction to the
technology which is now being
deployed in the field?
Well, I suppose as a farmer it
started off as scepticism,
you know, here's a chap from the
university. Yes, he can solve
civil engineering problems,
mining quarrying problems, but
this is farming.
And so it's taken a little while,
I think, hasn't it, Rob?
You've worked on me, you've shown me
that it works. Now that's starting
to snowball. That's going out to
other farmers and I think that
in 10 years' time the sort of things
were doing now
will become standard practice
and frankly to not do them will
become unacceptable.
We have to look after the soil,
it's a valuable resource.
To me, it's astonishing that
a potentially huge threat to soil
can be averted using
something as low-tech as straw.
All it needs is a little thought
and a willingness to change.
I believe these are vital if we're
to avoid the mistakes of our past
and preserve this most precious of
resources.
And research like this
and the commitment of farmers
like John give me
hope that we'll achieve that.
So, whilst we have a chequered
history when it comes to our
relationship with soil,
it does seem at last we're beginning
to understand and
appreciate what an amazing substance
it is.
'Exploring soil, we've uncovered the
secrets of its life-giving force.'
We've revealed an intricate living
system, where life meets rock
at the microscopic scale.
Each acting on the other in complex
and surprising ways to form what
to me is, without doubt,
the most fascinating and important
material on the face of the planet.
So the next time you
walk on the grass
give a nod of thanks to the
hidden rainforest beneath your feet.
our planet is transformed.'
A riot of new life
bursting from the ground.
'And it's all made possible by one
rather misunderstood material.'
From early childhood
we're told that this stuff, dirt,
is best avoided.
But as someone with a lifelong
passion for soil and
everything that grows in it, it's a
rule I've always enjoyed breaking.
'I'm Chris Beardshaw. I spend my
life designing and planting gardens.
'Everything I do depends on soil.
'And I'm going to try and convince
you that it's an unrecognised
'wonder of the natural world.'
For billions of years
our land must've looked
pretty much like this.
Bare rock. A barren place.
Apparently devoid of life.
But something transformed it
into a vibrant, living planet.
'And that something was soil.'
But what fascinates me
is where did the soil come from?
What is it composed of
and why is it so essential to life?
So I'm going to get down
and dirty with soil.
I want to investigate its secrets.
And reveal it as you've never seen
it before. An intricate
microscopic landscape...
..teeming with
strange and wonderful life forms.
I'm going to reveal a world
more complex
and fragile than anything that
exists above ground.
A substance so remarkable,
you'll never walk on the grass
in the same way again.
'As a gardener, I spend my life
among plants.
'I see them emerge from the soil.
'But I've never really had
the chance to discover what gives
'soil its amazing, life-giving
force.
'So now I want to find out.
'And I'm starting by doing
what comes naturally.
'I'm going out to dig.'
Ask any gardener and they'll tell
you that the soil
provides their plants with the
nutrients that are needed for life.
And if you grow anything
intensively,
on farms or gardens,
you have to apply fertiliser
to replace and replenish those
nutrients in the soil.
In a natural landscape like this,
all of these trees are being
supported by the nutrients that
are just inherently in the ground.
But we shouldn't take these
nutrients for granted.
Like our fertilisers,
they also need to be replenished.
And how that happens is the first
great mystery of soil.
Even at the end of winter
there's plenty of evidence of life
on the woodland floor, or at least
last season's life.
Leaf litter,
coming from the canopy above.
But this is of no use at all
to the surrounding plants
in its current state.
That's because most plants simply
can't feed on dead leaves and twigs.
They're too tough to break down
and digest.
And this creates a problem.
Any nutrients
they hold are locked in
so the plants can't get at them.
'But hidden beneath the surface
of the soil
'is a very different picture.'
This modified-looking spade is
actually a scientific instrument.
The soil corer gives us
the perfect cross section through
the layers of the topsoil.
At the top we can see here this
unrotted layer of leaf litter.
It's last season's leaves just
sitting on the surface.
But below that is a much darker
layer where the
particles are much more broken down,
much smaller and quite compact.
Beneath that is what
we would recognise as topsoil.
These are described by soil
scientists as different horizons.
'Collectively, the horizons
are known as a soil profile.'
And the deeper down the profile
we go, the smaller
the pieces of leaf and twig become
until they just disappear.
So somehow the tough plant matter
is eventually broken down,
releasing its trapped
nutrients into the soil.
This is one of the most vital
processes in nature.
'And it's begun by a rather
unlikely hero.
'To help track it down,
'I'm joined by Lynne Boddy,
Professor of Mycology
'at Cardiff University.
'We're on the hunt for an organism
that prefers to stay
'out of the light.'
This is a likely-looking candidate,
plenty of moss on the surface.
Let's turn it over gently
and see what we can see.
Look at that.
Oh, it's wonderful, isn't it?
Absolutely covered, it's almost like
a spider's web under here, isn't it?
It is. This is fungus.
The crucial thing about the fungi
is that they release nutrients
which allow plants to
continue to grow.
The main body of the fungus is
called the mycelium, which is
made up of very, very,
very fine filaments,
they're too small to see by the naked
eye. But here they're aggregated
together to form cord- or root-like
structures that we can clearly see.
What do these threads do?
They grow out from this wood
in search of new resources,
so maybe the resources would be dead
leaves, more wood.
When they find them they exude
enzymes that break down the structure
of the wood or the leaves or any
other bits of dead plant material.
It's easy to overlook fungi.
But, to me,
they're true champions
of the natural world.
They begin the process
of breaking down dead wood
and leaves to release
the nutrients trapped inside.
It's an extremely rare ability.
The thing about the wood decay
fungi is that actually
they are the only organism or almost
the only organism that can
actually break down wood on this
planet, and that is one
of the reasons why they're
so important, because otherwise
we'd be up to our armpits in dead
stuff. And, in fact, plants
wouldn't be able to
grow because all the nutrients
on this planet would be locked up
in the dead plant material.
As the fungus breaks down the leaves
and twigs, it produces a rich
substance we call humus that becomes
part of the soil itself.
But the fungus is doing another
crucial job.
It's feeding an entire world
most of us don't even know exists.
Using specialist microphotography,
we can catch a rare glimpse
of an astonishing hidden kingdom...
..teeming with weird,
almost alien-looking life.
Millions of tiny creatures,
all of which are dependent
on nutrients being
released by the fungi.
These are nematodes,
tiny, round worms.
Scientists think there may be up
to half a million
species of these
wriggling in the soil.
There are mites, tiny
relatives of spiders and scorpions.
Tardigrades, often called 'water
bears' due to their cute appearance.
And rotifers, fascinating little
creatures that can propel themselves
through the soil using special hairs
that appear to revolve like a wheel.
This is the first great
secret of the soil. A vast,
living kingdom of tiny animals.
As they move around, eat
and are in turn eaten themselves,
they spread the essential nutrients
released by the fungi.
Helping to make the soil a more
fertile place for growing plants.
'Yet so far
we've only seen how fungi
'begin the process of unlocking
those nutrients.
'Breaking down all the tough remains
of dead plants is too large
'a job for fungi alone.
'But they have a secret ally
underground.
'An animal whose impact on the soil
is greater than any other.'
When it comes to ecosystems,
not all organisms are created equal.
By that, what I mean is the work
of one or two species will allow
hundreds of others to thrive.
One such animal is so important it's
been called an ecosystem engineer.
In this field, there might well be
over two million of them.
There are no prizes for guessing
which animal I'm seeking out here.
It's one that's inspired
generations of horticulturists
and agriculturists.
It is possibly the greatest
gardener on earth.
And it's this, the humble earthworm.
As a gardener,
I've long known that worms play
an important role in soil.
The great Charles Darwin devoted
over 40 years of study
to them, culminating in the
publication of his seminal work,
The Formation Of Vegetable Mould
Through The Actions Of Worms
With Observations On Their Habits.
You may not have heard of it,
but it sold faster
than On The Origin Of Species.
Darwin's studies, lesser known
than his work on evolution,
revealed an organism that was
essential for the life of the soil.
He became obsessed by them.
He fed them different diets,
tested their intelligence
and even tested their senses
by playing a bassoon to them.
What is about the earthworms
that beguiled Darwin?
Just why are they so important?
Well, first of all the sheer
scale of the worm operation.
As they tunnel into the ground
in their millions,
their burrows permeate the earth
like a vast ventilation system,
providing essential supplies of air
to everything else that
lives in the soil.
But that's not the earthworms'
only talent.
They also continue
what the fungi began.
They eat and digest dead leaves
underground,
unlocking their trapped nutrients.
The way they do this reveals
one of the most fundamental
secrets of soil.
But it's hard to see.
'So I've come to meet
Mark Hodson, Professor
'of Environmental Science
at York University.'
I find they're very fun creatures,
you see them a lot.
If you walk around after the rain
you see them crawling around.
'He's spent years studying what
and how worms eat.'
They go up and down.
During the day, they stay in
the bottom of their burrows.
At night they come out onto
the surface, they look round,
sort of, sometimes they keep their
tails anchored in their burrows.
They sort of stretch out
and eat or grab organic material,
they pull it down into their
burrows to eat later on.
And the undigested material gets
squirted out of the back end and that
helps make all of this black, browny
stuff which is the soil.
Nothing is quicker at breaking down
dead leaves than an earthworm.
It's thought that in the average
field the worms get through
a staggering one and a half
tonnes of plant matter every year.
They're like leaf-processing
factories,
operating on an industrial scale.
Yet they look nothing more than
a simple, fleshy tube.
So what's going on inside?
To help answer that, Mark has been
doing a rather unsavoury experiment.
This Petri dish contains
a sample of plain soil.
And this one was made using earth
that has passed through
an earthworm.
In other words, worm poo.
Mark's been comparing the two
and he's uncovered
evidence of a hidden army of secret
agents at work within the worm.
Bacteria.
So each of these spots is
a bacterial colony. You can see
there are far more growing here
from the material that's just
come out of the earthworm gut.
So the earthworm ingests the soil,
there are bacteria in there already,
and the earthworm gut environment
is good for bacteria.
It's moist, its got the right pH,
the earthworm is secreting mucous
full of polysaccharide sugars,
which the bacteria love to eat.
So it's bacteria
that finish the job of breaking down
dead plant matter.
There are billions of them
naturally present in the ground,
like workers on a production line
turning dead plants into new soil.
But inside the earthworm
this activity is magnified to levels
that are truly mind-blowing.
If you do counts on the soil
in earthworm guts
you can have 1,000 times more active
bacteria in that soil
than the bulk soil
surrounding the earthworm.
What it's proving is
the earthworms have ramped up
the bacterial activity in the soil.
And it's this army of bacteria,
hidden in the guts of earthworms,
that completes the vital cycle.
Unlocking all
the nutrients from dead leaves
and releasing them
back into the soil.
We very often think of soil as being
brown, solid, inert stuff.
But there's more life within in it
than flies, swims or walks above it.
And, far from being a haphazard
array of organisms,
this is a complex
range of interconnected structures
that support the life above.
As we've seen, it takes
a combination of plants, fungi,
animals and bacteria all working
together to keep nutrients
flowing from the dead to the living.
In the process, new soil is created
which in turn supports
even more life, making a cycle that
keeps the soil fertile.
Yet so far we've only scratched
the surface of the soil.
Everything we've seen happens within
just the topmost layers.
'Look deeper and there's
far more to soil than this.
'To reveal just how much,
I first need a bit of heat.'
What I have here is dried topsoil.
I want to find out
how much of this is
derived from plants by setting
fire to it.
If it's 100% plant material,
there should be nothing left.
So I'm starting with 100g.
'Let's see how much remains.'
As this is burning away, the soil is
completely transforming colour.
It's going from a soft brown
to almost a carbon colour.
Very similar to the
embers in a barbecue.
The soil particles are fracturing,
breaking apart. The organic matter
binding them together is burning
away and the soil particles are
just falling to pieces.
'The plant matter is turning
into gases like carbon dioxide
'that are lost into the air.
'After about 15 minutes of intense
heat, I'm going to weigh it again.'
See how much we've lost?
We started off with about 100,
it's now down to 70.
So about 30% of this original soil
was plant based.
It's burnt away.
Clearly, there's more to soil than
just plant material.
To see what that is, we need to get
beneath the topsoil
and look deeper down.
'This is Scolly's Cross
in Aberdeenshire, where
'a landslide has exposed the layers
of soil beneath the pine forest.
'It's something we rarely
get to see,
'as all this is usually hidden
underground.'
In a landslip situation like this
we get to examine perfectly
the soil profile, the horizons or
layers of various materials.
At the top we've got the vegetation
and, below, the various layers or
horizons of soil,
each with a different characteristic
in terms of colours and textures.
The topsoils, going down into
the subsoils with the roots
penetrating,
this is what we saw in the forest.
But, as we go further down, the dark
organic plant material disappears.
We seem to have left
the soil behind.
These deeper layers are mainly
made up of fragments
of the underlying rock.
And then further down
we're into bedrock.
Collectively, these layers form
the foundation of soil development.
Rock fragments permeate the soil
from the bedrock
all the way to the surface.
It's mainly this stuff that
was left behind
when I burned the plant matter
away from the topsoil.
But, though these
particles are from lifeless rock,
that doesn't mean
they have no purpose.
In fact, they are fundamental
to how soil works.
Soil particles are divided into
three different categories
depending on the size
of the particle.
The largest being sand.
There you can see them
just coming into focus,
wonderful, rounded particles.
The next size down, well, it's silt.
And there you can start to see
the individual silt particles.
And the very smallest are the clays.
Search for the clay. There they are,
much smaller.
Relatively speaking, if the sand was
the size of a beach ball
then the clay particles would be
the size of a pin head.
Incredibly small and
flat in their profile.
What's curious about the particles
is that the relative
proportions of them in any
soil fundamentally affect
how that soil behaves, and, more
importantly, how it supports life.
'To see exactly how, I've come to
the James Hutton Institute
'in Aberdeen.
'I'm here to meet soil
scientist Dr Jason Owen.'
Jason, what will this
experiment demonstrate?
What we have here are three
cylinders. One with a sand, one
with a silt-dominated soil
and one with a clayed soil.
When we pour water in the top
what we'll see is the water
percolating through the soil
profile.
With the sand it'll go very quickly.
With a clay it'll go very slowly.
And the silt will be
somewhere in between.
To me, this is familiar stuff,
as it will be to any gardener.
It's the age-old question
of drainage. How well water
moves through different
types of soil.
With the sand, large particles,
there's quite large gaps,
comparatively speaking,
and water can
go down through the profile.
With the clay, very small particles,
and as a result the gaps
where water can penetrate
are exceptionally small.
The silt is somewhere in between
the two extremes.
But to really see what's
going on inside the soil
we have to look at it in far
greater detail.
Here, they're using cutting edge
technology to examine soil
on an incredibly small scale.
We're joined by Evelyne Delbos,
operator of the Scanning Electron
Microscope at the Hutton Institute.
She's looking at soil
magnified 400 times.
I have the three main
parts of the soil.
The sand grains here.
On the right is the silt
and the clay at the bottom.
Well, you can sort of see with
the clay, for example,
it's stacked so tightly together
that you can actually not see
discernible gaps between them.
Whereas here we've got these very
large sand particles
and even through they're
right on top of each other
you can still see the far larger
gaps.
That allows air,
for aeration of the soil,
and it also allows water movement
through the soil.
But there's more going on here
than just how the particles
are packed together.
Let's imagine this is
a grain of sand.
And the surface area of that
grain of sand is that surface,
that surface, that surface,
and that's it.
It we take, by comparison,
the same volume of clay
then you have that surface plus that
surface plus that surface, so you
can imagine already that the surface
area is much, much, much larger.
So what does the surface area
do to the water?
What's the relationship
between those two things?
What's interesting about many clays,
it has an electric charge
associated with its surfaces.
Many nutrients that are dissolved
within the water can be
attracted to these clay sites, to
this large surface area,
and then held,
basically for root systems
then to uptake for plant growth.
So clay particles have an electrical
charge that can bind nutrients
and water to them.
This allows soil to
act as both larder
and reservoir for plants
and animals.
Sounds ideal, but there's a catch.
Too much clay and the soil can act
like a sponge
and can quickly become waterlogged.
At the other end of the scale,
too much sand
and the water can run through
too quickly,
washing the nutrients out and
leaving behind soil that's dry.
Have we got an image of what
a good soil should look like?
Here you can see some grains
of sand, they are different sizes.
It's a mixture and you can also have
there and there the clay
and the silt all mixed up.
So this is demonstrating the ideal,
in terms of soil. It would
be free draining,
retain sufficient moisture,
sufficient nutrients,
what about microbial activity?
This is a very,
very complicated 3D structure
which gives all of the microbiota
within the soil effectively a niche,
a home to live, and as a result
the ecosystems that exist in the soil
are exceptionally complicated.
This is a classic example where
you've got the mix between the
large particles, the clay particles
and silt all working together.
So the elements that make up soil
come from two very different places.
The chaos of life,
and the inert world of rock.
Together, they create an intricate
substance that can naturally
feed and water all
plant life on earth.
And it makes me wonder just how did
this strange
alliance between rock
and life begin?
'How did the very first soil
come to exist?'
To find out, we need to go back
to a time
and place before the first soil
appeared on the planet.
That's not quite as difficult as it
might sound.
This is Malham Cove, an inland cliff
deep in the Yorkshire Dales.
It's a striking landscape,
built from limestone
and sculpted by the awesome
power of ice.
This place offers a wonderful
window into the Earth
billions of years ago,
before there was soil.
That's because at the end
of the last Ice Age,
as temperatures rose and the ice
retreated, it left this
naked rock. Any soil that had been
here had been scoured away
and deposited somewhere in that
direction.
And as a consequence any soil
you see here is relatively new,
in fact, it's still forming.
Making this one of the best
places in the country to discover
how we get from this naked rock,
to this. Soil that supports life.
I'm joined by Professor Steven
Nortcliff from Reading University.
Landscape is fascinating in terms of
the soil.
First, I want to know what could
possibly start to break up
something as seemingly
permanent as rock.
We've got to break it down.
And we've got evidence here in this
landscape
of those early stages of breakdown.
We have ice forming in the fissures
in the rock and as the ice expands
it forces the rock apart. And that's
the first form of disintegration.
When water freezes, it expands.
If that expansion
happens within a crack,
it can exert a force strong enough
to break rock apart.
And you can witness this in your own
freezer at home.
You fill the ice tray and when it
freezes there's expansion.
But it seems remarkable that
that expansion is powerful enough
to blow rock apart.
Well, you're expanding in a confined
space.
It only has one way to expand
and that's sideways.
That forces the rock apart and it's
the beginning
of the disintegration
to give us the soil.
This process is called
physical weathering.
It breaks down rock by sheer
brute force.
But we're still a long way
from soil.
Next comes a different process
entirely.
And it starts with rain.
We'll just drop some
hydrochloric acid onto limestone.
You can see it fizzing.
You can hear it fizzing.
It's really going at it.
What Stephen's showing me
is an exaggerated version of what
happens every time it rains.
Rain is slightly acidic
and, with limestone,
when this slightly acidic water
falls on the surface it weathers it.
And is that what we're seeing here,
on the surface of the rock?
That is exactly
what we're seeing here.
So rain reacts with the rock,
gradually dissolving it. This is
chemical weathering.
The second key step towards soil.
Using a stronger acid to speed
the process up,
we can see just how powerful it is.
Here, a piece of rock is almost
entirely dissolved. Leaving
behind nothing but insoluble,
sandy remains known as sediments.
And that's the beginning
of the soil.
It's a very small
amount of insoluble residue,
but that's where the soil
development starts.
But sediment isn't yet soil. There's
something fundamental missing.
Life. But look closely,
and this rock is not bare.
It's covered in this, lichen.
And this is what causes the final,
almost magical metamorphosis from
inert rock, to life-giving soil.
In this environment they are key
because the lichen will attack the
rock, very much like the chemical
weathering we saw, but it will break
it down, release nutrients.
Lichen is actually two organisms,
algae and fungus,
living in one body.
And though it seems almost
incredible, the fungus part is able
to break down the rock to release
nutrients that it can feed on.
Much as we saw the fungi do
with the wood in the forest.
Over time, generations of lichen
grow over one another,
the new on top of the dead.
The dead remains form
organic matter.
And when this mixes with sediment
the result is soil.
And so from an apparently barren
limestone pavement up here
we have the complete story
of the generation of our soils.
Bare rock through the various
weathering processes, the biological
processes and eventually the
formation of soil. It is all here.
Condensed into just a few
square metres.
Yeah, it's a wonderful example
of soil development in motion.
And what we've got is different areas
representing different timescales -
some it's just starting,
others it's been going on
for a few thousand years.
Soil is the place where the
relatively inert world of rock meets
the riot of life above.
It's a complex,
staggeringly complex ecosystem,
but it also offers
something of a conundrum
because the life creates soil,
breaking down organic matter and
forcing rocks apart, but that life
is also dependent upon the soil
for nutrients, moisture, habitat,
anchorage, somewhere to live.
That means there's a delicate
balance between the life
and the soil.
Challenge one and you inevitably
challenge the other.
And today that ancient balance
between rock and life
is being challenged
as never before in history.
A new force has entered the world
of the soil. Humankind.
In geological terms,
human civilisation is a mere
blink of the eye, at around about
9,000 years. And in that brief
moment in time we've arguably done
more to change our soils than
in the previous 400 million years.
We've mined it.
Built on it.
Farmed on it.
And, in places like this,
drained it.
And our actions have had
consequences we never imagined.
East Anglia is famed for its fenland
landscape. One of rivers,
marshes and streams.
But what we have left is just
a fraction of what was once here.
Largely because this is a habitat
that's prone to flooding
and since the 17th century
generation after generation have
been progressively draining it.
The great system of canals
and ditches have been dug.
To drain the unwanted water
into the sea.
Over the past 300 or so years,
the population of the UK has
grown rapidly.
This put huge pressure on places
like the fens.
To help feed all those extra mouths,
we needed to dry out
the waterlogged land to make way
for the business of agriculture.
Rivers and lakes were drained
and crops planted.
The few people who lived there were
thought rough and unfriendly.
Old ways of life and traditional
pastimes that had grown up
around the flooding
were swept aside.
But this progress came with
a sting in the tail.
As the rivers
and meres were drained,
something unexpected happened.
The land began to sink.
This is Holm Fen,
drained in the 1850s.
It was the home of Whittlesea Mere,
once thought to be the second
largest lake in England.
This is all that's left.
Previous experience had demonstrated
that if you drain the fens
the land would sink.
So a local landowner
here at Holme Fen, William Wells,
decided to measure that process.
He took a post
and pushed it into the ground
until the top was completely
covered. And that post today?
Well, here it is.
The top of the post was originally
ground level.
Since 1850 this whole tract of land
has sunk somewhere in
the region of four metres,
making this one of the lowest
places in Britain.
There can surely be no clearer
indication of the effect
of human interference on soil.
But why did it sink?
And what are the consequences?
'I'm joined by Dr Ian Homan.
'He and his colleagues at
'Cranfield University have
extensively studied the area.
'We're going to take a look
at a rather special type of soil
'found here in the fens.
'This is peat.'
Pretty good profile. It is indeed.
Peat forms in a wetland environment,
so the soils are waterlogged.
It's low in oxygen under the surface
and it's quite acidic.
So the combination of the
waterlogged nature,
the lack of oxygen and acidity slows
down the rate of decomposition.
The soil bacteria and
the microbiological
components of the soil aren't able to
decompose that organic material.
So it accumulates very slowly.
So in peat, instead of being broken
down, plant material builds up.
And this has an important effect.
Plants grow using carbon dioxide
from the air.
And if they're not broken down
when they die
they and the carbon they contain
become trapped within the soil.
This is what's
known as a carbon sink
and peat bogs are some of the best.
But remove the water,
and the balance changes.
Oxygen enters the soil, allowing
bacteria and fungi to breathe.
This is what happened
when the fens were drained
and it had profound consequences.
That allows the micro-organisms
to use the carbon within this peat
as an energy source, converting
the carbon into carbon dioxide
and energy.
The fens, we think, are losing about
four million cubic metres of
peat soil every year and that equates
to an emission of carbon dioxide
of about 1, 1 million
tonnes of carbon dioxide a year.
We've gone from being an environment
that should be storing carbon
dioxide into the soil
into an environment now that
is emitting carbon dioxide.
So the story of the fens really is
that it's the worst possible,
for both ends of the spectrum.
Not only are we losing
the carbon sink,
but the carbon dioxide is being
released into the atmosphere.
Indeed.
So as a result of human activity
four metres of peat,
which took thousands of years to
form, disappeared in mere decades.
And this old post is a monument
to what can happen
when we upset the balance
within the soils.
It's a story that's repeated
throughout human history.
Archaeological records very
clearly demonstrate
that, as our nomadic ancestors began
to settle and farm the land,
populations increased dramatically.
And in order to feed the population
the area of land that was turned
over to the plough also increased.
Those early farmers tilled
and ploughed, fertilised
and irrigated in the best way
they knew how.
But, as we've seen,
human interference can have
unexpected consequences.
Ploughing and tilling can destroy
the soil's structure.
Intensive farming will deplete
the soil of nutrients
and over-irrigation can cause
high levels of toxicity.
When these factors combine
the soil becomes degraded
and prone to erosion from wind
and water.
For me, recent history provides
a stark warning.
By the 1930s, vast swathes
of the North American prairies
were turned over to the plough.
All the way from Canada
down to Texas.
But this would lead to catastrophe.
High winds and sun. A country without
rivers and with little rain.
Intensive farming techniques had
weakened the structure
of the soil till it could no longer
hold itself together.
So when a drought came the soil
dried out then simply blew away.
Turning the prairies into a huge
dustbowl.
The rains failed and the sun baked
the light soil.
It affected 100,000,000 acres
of land. By 1940,
over 2 million people had been
forced off the prairies.
Their stock choked to death on the
barren land.
Their homes nightmares
of swirling dust night and day.
Many went to heaven.
It was one of the biggest
environmental disasters
in American history.
But today the problem is
potentially worse than it ever was.
There are now more than seven
billion human beings on the planet.
There are more of us alive today
than there have been
up to the 20th century.
So it comes as no surprise more is
being taken from the soil.
We're more reliant on the soil
than ever before.
In trying to satisfy that need
we're cultivating, tilling,
fertilising to keep our soil
productive.
In doing so, we're destroying
the delicate structural
balance of the soil.
That can be hugely costly.
So when we talk about an impending
food crisis
what we should actually be
talking about is a soil crisis.
And that crisis is being felt as
keenly in the UK as anywhere else.
It's brought this farm in
Ross-on-Wye to the brink of ruin.
Asparagus farmer John Chinn
has seen massive gullies
open up in his fields.
Weakened by farming, the soil was
washed away by the rain,
taking his crop with it.
So what is it about the
conventional way of managing
a crop like asparagus that was
causing that degree of erosion?
It's two sides.
The first is that we have soil
exposed the whole time.
Then, secondly, because we didn't
want water standing in the crop
we would plant the rows up and down
the slope so the water would run off.
Of course, what was happening
was that the water was
running off faster and faster and
as it went it picked up the soil
because it was just there on the
surface. Carried that soil out to
the bottom of the field, maybe into
a stream, a road, leaving behind it
a gully that as you came
down the slope got deeper and deeper.
We have an amber warning in force
for the Somerset Levels.
Water erosion has become
a devastating problem in the UK.
Could be another 20mm or perhaps
a bit more in this area.
Over the past five years,
we've experienced an unusually high
number of storms,
culminating in the winter of 2013.
It was the wettest on record.
Vast swathes of the UK suffered
rainfall on an almost biblical
scale, leaving many areas like the
Somerset Levels deluged for months.
It's this kind of rainfall
that was partly to blame
for the destruction of John's
asparagus fields.
In desperation,
he sought the advice of soil
specialists at Cranfield University.
One of them was Dr Rob Simmons.
'He's investigating the huge problem
of water erosion on the smallest
'possible scale.
'By studying the energy
within individual raindrops.'
The raindrop has a certain
mass and a velocity
which affects its kinetic energy.
When that raindrop with that kinetic
energy impacts on the soil surface
it will damage the soil and cause
breakdown at the soil surface.
As you start to get extreme rainfall
events you get short-duration,
high-energy events with a larger
drop size, more kinetic energy
and they're going to cause more
damage to your soil surface.
And it's those that we're
having more of?
And it's those that we're
having more of. Yep.
Rob is testing what happens
when rain hits soil.
It's immediately apparent that
excess water quickly starts
to flow across the surface, what the
scientists call run-off.
Right, what we can see here is that
run-off is being generated
almost straight away.
So expanded out onto a large field
situation
this could cause major problems.
This is all well and good in a lab,
but is there anything you can
do about it out in the field?
Absolutely, but the best thing to do
is to go out in the fields.
Where the sun is shining.
Where the sun is shining.
By understanding exactly what
happens when raindrops hit soil, Rob
has been able to help John make some
big changes to the way he farms.
And they're surprisingly low-tech.
Instead of planting straight up
and down the hillside,
John now plants his rows
on the diagonal.
And he plants grass
strips between them.
The combined effect is to
slow down the run-off of water,
reducing its power to
erode the soil.
But that's only the beginning.
Now Rob's come up with an ingenious
new idea to take the energy
'out of the rain itself.
'To test it, he's set up rainfall
simulators
'and dug a series of channels,
or wheelings.'
We've got two rainfall simulators.
We've got
a wheeling which is bare on the
left-hand side. And on the
right-hand side we've got a wheeling
which has got straw mulch in it.
What the straw will do is it will
absorb the energy of that rainfall.
It will also act
as a blanket effectively
and it will absorb some of that
water, slow down the run-off.
It seems an incredibly simple
solution, basic straw.
Comparing the two scenarios side
by side reveals a big difference.
Raindrops hit the bare earth with
force and break up the soil.
Run-off water soon begins to flow
and carry the soil away.
But here the large drops are broken
up before they can hit the ground.
It's the straw, not the soil,
that takes the brunt of the impact.
And the run-off is reduced
to a trickle.
By having that canopy it absorbs
all the energy, you don't have
the detachment, you don't have
the run-off and erosion problems.
What's your reaction to the
technology which is now being
deployed in the field?
Well, I suppose as a farmer it
started off as scepticism,
you know, here's a chap from the
university. Yes, he can solve
civil engineering problems,
mining quarrying problems, but
this is farming.
And so it's taken a little while,
I think, hasn't it, Rob?
You've worked on me, you've shown me
that it works. Now that's starting
to snowball. That's going out to
other farmers and I think that
in 10 years' time the sort of things
were doing now
will become standard practice
and frankly to not do them will
become unacceptable.
We have to look after the soil,
it's a valuable resource.
To me, it's astonishing that
a potentially huge threat to soil
can be averted using
something as low-tech as straw.
All it needs is a little thought
and a willingness to change.
I believe these are vital if we're
to avoid the mistakes of our past
and preserve this most precious of
resources.
And research like this
and the commitment of farmers
like John give me
hope that we'll achieve that.
So, whilst we have a chequered
history when it comes to our
relationship with soil,
it does seem at last we're beginning
to understand and
appreciate what an amazing substance
it is.
'Exploring soil, we've uncovered the
secrets of its life-giving force.'
We've revealed an intricate living
system, where life meets rock
at the microscopic scale.
Each acting on the other in complex
and surprising ways to form what
to me is, without doubt,
the most fascinating and important
material on the face of the planet.
So the next time you
walk on the grass
give a nod of thanks to the
hidden rainforest beneath your feet.