Original subtitles

The relationship between plants and humans is extraordinary.

We've been adapting to each other

for as long as we've been on the planet.

We rely upon plants for almost everything.

The air we breathe, the water we drink, the food we eat,

much of the clothes we wear,

in some parts of the world, the very buildings in which we live.

But that relationship is now changing.

How it changes next will shape the future of our green planet.

Some plants have the ability to live alongside us...

..even when we make it extremely difficult for them to do so.

This is Piccadilly Circus in the heart of London.

It would be difficult to imagine a more hostile place for a plant.

And yet, even here, plants will find a way.

Plants like this may seem to follow us wherever we go.

We call them, perhaps a little unkindly,

weeds.

In fact, these plants are pioneers,

the ones that are most able to take advantage of new habitats,

even very harsh ones.

This wall is at least 100 years old.

It's like a sheer cliff face with no sign of soil,

and yet this ivy-leaved toadflax thrives here.

How?

The plant grows towards the light with its flowers facing outwards

to attract pollinators.

But once they've succeeded in doing that

and the seed pods start to develop,

its behaviour changes.

For now, the pods turn and grow away from the light,

seeking the darkest place they can find.

A crevice, perhaps, like this one.

It's all the toadflax needs.

It can now germinate and start to produce a new plant.

Other pioneers have a different strategy.

They instead distribute their seeds far and wide in great numbers.

Sow thistles are masters of this trick.

Each of its seeds is equipped with a tiny downy parachute,

which will catch the slightest breeze.

And they can travel extraordinary distances.

They can rise a mile high in the sky

and reach places hundreds of miles away from the parent plant.

The seeds only need to find the tiniest chink

and they can take hold.

We barely notice many of these plant invaders.

But here in the heart of Hong Kong,

strangler fig seeds that landed on a stone wall generations ago,

have spread their flexible branching roots far and wide.

They can be anchored so firmly

that they become a part of the city's architecture.

This is perhaps the ultimate weed.

But there are places where the extraordinary abilities of fig trees

have created a very different relationship with human beings.

Meghalaya in north-east India,

a high altitude plateau riven by dizzyingly steep valleys.

It's home to the Khasi people...

..who've learned how to use the remarkable properties of fig trees

to help them live in such difficult country.

As in Hong Kong, the tree's numerous roots anchor it firmly,

here to steep mountainsides.

These roots can grow up to 2.5cm a day.

They are unusually strong,

flexible, and can develop into a multitude of shapes.

The Khasi persuade them to provide them with stairs.

The monsoon season brings a seemingly insurmountable challenge

for Khasi communities.

This is the wettest place in the world.

Nearly 30cm of rain can fall in a day.

Rivers become lethal torrents,

dividing communities from each other.

This is when the relationship between fig trees and the Khasi

becomes most important.

They deliberately plant fig trees near the rivers.

When they're mature enough to have developed many hanging roots,

Shining Star Kongthaw begins working with them.

He guides the roots through bamboo tubes

that are pointed towards the opposite river bank.

These strands will combine as they grow, sharing nutrients

and resources and becoming stronger than a lone strand could ever be.

As the years pass, the growing roots become a living bridge.

As they grow, they become ever stronger and more stable.

This unusual relationship has allowed the people here to thrive

in an otherwise challenging landscape.

But there are plants that have found a deeper partnership with us,

and in doing so, have changed landscapes across the globe.

It began over 10,000 years ago,

with plants that we found especially good to eat.

At first, this relationship created challenges of its own.

Many of the ancestral grasses,

like these wild oats from Israel,

have a trick to ensure that their seeds are planted

in the perfect place.

Each seed head, at the top, carries two long bristles called awns,

and when a seed drops to the ground,

these awns do something truly extraordinary...

..they walk.

The awns twist as they dry out during the day,

and then when they get wet...

..they untwist.

Tiny hairs grip on to the ground,

keeping the individual moving forward.

In this way, the seeds work their way along the ground

until eventually they find a rock to hide under

or a crack to drill in to.

This adaptation is useful for the plant,

but not for us.

It's hard to collect seeds when they drop off and walk away.

So our ancestors selected plants whose seeds don't drop off,

don't have legs

and don't bury themselves out of reach.

They also selected those individuals which put their energy

into developing much larger seeds.

Close relationships like this have developed all over the world,

producing the plants that are now our crops.

This may seem a poor deal from the point of view of plants,

but not so.

We eat their seeds,

but in return, we cherish and cultivate them,

and now they are widespread and far more abundant

than their wild ancestors.

You might call this a bargain between ourselves and plants,

and over the years, it's proved extraordinarily powerful.

In the beginning, the bargain operated on a small scale.

Plant, tend and harvest by hand in small patches.

Over time, these plants produced more food,

increasingly efficiently...

..and the partnerships became more exclusive.

We started doing more and more for a small number of chosen species.

These few persuaded us to eliminate their competitors,

cure their diseases,

poison their enemies,

and keep them well-watered,

even when other species faced drought.

Fewer and fewer plant species,

like soy, wheat and rice,

now occupy more and more land.

And so now whole landscapes are dominated

by a single species of plant.

A monoculture.

This is the Central Valley of California,

the biggest orchard in the world.

A million acres of just one type of tree,

almonds.

Each flower, if it's fertilised by pollen

from a different almond tree,

will produce an almond nut.

The flowers, patterns and scent have evolved to attract insects

and bribe them to do that job for them.

The pollen doesn't have to move far,

it just needs to reach a neighbouring tree.

There are about 20,000 flowers on each tree...

..and 140 million trees.

That is billions of flowers all calling out at once.

But here, the beauty of the blossom is wasted.

To make way for these almond trees,

the land was, in effect, wiped clean.

Countless wild species of plants and animals were removed,

including, critically, pollinators.

So now the flowers need help, and lots of it.

ENGINE REVS

MACHINERY WHIRS

LOUD BUZZING

40 billion honeybees...

..trucked in from all over the United States.

The orchard is only in bloom for a few weeks,

so the almonds need the bees to get to work immediately.

Each bee can visit thousands of blossoms a day.

And while they take most of the pollen they collect back

to the hive, they also drop some pollen at each stop.

And, so, with luck,

the flowers are all eventually fertilised.

Day after day, the process is repeated.

Flower after flower.

Tree after tree.

By the time the petals fall,

2.5 trillion flowers have been successfully pollinated

and will now grow in to 2.5 trillion almonds.

This type of intensive, streamlined agriculture

produces amazingly high yields.

But monocultures are fragile.

While they can function effectively when conditions remain stable,

it only takes a small change to create catastrophe.

Lodgepole pine,

a very valuable timber tree grown extensively in western Canada.

Millions of acres of the same species,

all the same age and the same size.

For centuries, lodgepole forests have lived in a natural balance

with their enemies,

including this one,

the mountain pine beetle.

In summer, female beetles start hunting for a suitable nursery

in which to lay their eggs.

The ideal site is a mature lodgepole pine

with bark thick enough to feed a female's brood

and, critically, to protect them from the bitter cold

of the coming winter.

Once under the bark, she tunnels upwards...

..laying her eggs as she goes.

A single female beetle can lay 100 eggs in a season.

When the larvae hatch,

they grow by feeding on the inside of the bark.

As they do, they damage the channels that transport water and nutrients

between the roots and needles.

For centuries, the freezing northern winters

killed the majority of larvae,

so tree and beetle remained in balance.

But now, with the climate changing, the winters aren't cold enough

to control the beetle numbers.

Needles turning red are a sure sign that the trees are dying.

The beetle plague spreads like wildfire across a landscape

covered by a monoculture of similarly vulnerable trees.

Since the first mass outbreak 40 years ago,

trillions of trees in North America have been killed

by the mountain pine beetle.

Loss of plant diversity makes any habitat more vulnerable

to changing conditions.

Now, with climate changing so fast,

we are losing plant diversity just when we need it the most.

Two out of five plants are now facing extinction.

Of course, the loss of any one species is in itself a tragedy,

but such a loss erodes the stability of a whole ecosystem,

and that should be of great concern for all of us.

We need an insurance policy, a hedge against extinction.

This is Kew's Millennium Seed Bank.

Packets of seeds arrive here from all over the world.

These are from a relative of the yucca plant,

which grows in central Mexico on the slopes of volcanoes,

and nowhere else.

Most of the seeds are from plants that are threatened.

Some indeed, have gone extinct since their seeds arrived here.

But here, at least, those seeds are safe.

When they arrive, they're processed

and sealed in to airtight jars.

Seeds are then brought underground to be stored in a vault,

like this one, at -20C.

Since the bank was founded,

two billion seeds from 40,000 different species

have been brought and stored here.

Because a seed contains everything it needs to start a new plant,

each and every one of them represents a little grain of hope...

..hope that one day we will make it possible for the seeds

of these rarities to grow in the wild once again.

The seed bank certainly gives us options when a species becomes rare

or even extinct.

But around the world, people are trying ways to keep

natural plant populations healthy where they should be,

in the wild.

Hawaii.

90% of the plant species here

are found nowhere else in the world.

Many are threatened by a plant invader called Miconia.

It was brought to the island of Maui in the '70s as an ornamental plant.

In its native Mexico,

it grows in balance with a rich variety of predators,

competitors and diseases.

It grows taller than most native Hawaiian vegetation,

and little can grow beneath it.

On the island of Maui, with nothing to keep it in check,

it creates a stifling monoculture.

Miconia, it would appear,

is doing very well for itself.

But today it's under attack.

On level ground, a single dedicated team can keep Miconia in check.

But unfortunately, this plant can spread to places impossible

for people to reach on foot.

Just one plant can produce around ten million seeds a year,

enough to cover this entire landscape.

With so much at stake, the team have come up

with an extraordinary plan.

It's too dangerous to land here,

but they don't need to.

A marksman with great skill can shoot the Miconia

with paint balls full of herbicide.

A perfect shot is one that hits the stem,

so ensuring that the herbicide spreads throughout the plant.

The method is so precise

that with careful flying and accurate aim,

they can kill the intruders without damaging any wild plants.

Destroying alien invaders is not the only way to help

the native plants here.

This is Waikamoi Preserve, the last surviving fragment

of a high-altitude Hawaiian rainforest,

and home to one of the world's rarest plants.

Holokea.

There are only 57 fully-grown individuals left in the wild.

Their peculiar flowers evolved to suit the beak

of a bird found only in Hawaii,

the 'i'iwi.

The bird is now so rare itself that, today,

these partners seldom, if ever, meet.

So the chances of holokea getting pollinated are very slim.

But a strange new partnership might just save it.

I look at losing a plant as flying in a plane and taking a screw out

and, yeah, the plane will fly and you might be able to take a couple

of screws out and keep flying,

but eventually you're going to crash.

Hank knows where to find every one of the last 57 plants,

and he returns every year to act as their pollinator.

We have to step in and play that role as pollinator or matchmaker.

Hank collects the pollen from the male flower

and dusts it onto a female flower of a different plant.

He's currently their life support,

but his goal is for holokea to thrive without him.

So, before he leaves, he plays the call of the 'i'iwi bird.

'I'IWI BIRD CALLS

Hank hopes the sound will attract the living birds,

and if they come, that they will reconnect with the last holokea

and rekindle their vital relationship.

I believe all species are important

and I believe we have a duty to act.

We need to act, not only in the wild places,

but even in those where we live

and where we farm.

Like much of the world,

Kenya is losing thousands of native trees annually.

Ones that local people rely on for so much,

especially fuel.

But here, people have come up with an ingenious way to reverse

some of that loss around them.

At a factory in the outskirts of Nairobi,

workers collect and sort waste charcoal dust.

Seeds of carefully selected native trees are mixed with the dust.

This carbon coat will protect the seeds from hungry animals

until the rains arrive.

These are seed balls.

In the village of Kibwezi,

acacia trees are becoming scarce,

cut down by previous generations to make charcoal.

But the students at this school make forest restoration child's play.

The nutrients in the dissolving char dust

will give each little seed a good start.

If only a handful of these seeds grow into a tree,

the effort has been well worth it.

Every mature acacia tree can itself produce thousands of seeds a year.

13 million seed balls have been distributed in Kenya alone...

..and the methods by which they're dispersed...

..are ever more inventive,

to say the least.

This technique is being repeated around the globe.

Seed-ball-making workshop.

People are choosing seeds of local native plants,

giving them a little initial help

and bringing some wild plants back into the world around them.

But is it possible, even in our most extreme monocultures,

to invite a bit of wildness in

and, with it, a bit of resilience?

I have two different kinds of forage growing in my orchard.

The yellow that you see behind me is a variety of different mustards.

And then after the bloom,

we're going to see some clover blossom.

This mix of plants means the bees can feed

before and after the brief almond bloom.

And they also get a more balanced, healthier diet.

In the meantime, it's going to provide habitat for all sorts

of insects and the bees, and probably some rabbits.

It's a step towards establishing a better, more stable system.

It's about finding balance.

That's what we're trying to do here.

Find a balance.

Can humanity globally find a new balance between wild plants

and those we have domesticated?

Around half the usable land on Earth is taken up by agriculture.

Do we really need that much?

Maybe not.

It's a remarkable fact, but around 80% of all cultivated land

is used for raising livestock for us to eat.

Raising animals can be a sustainable way to create food,

but in many places, plants can produce the same amount

of protein on a fraction of the land that animals need.

What could it mean for wild plants if the global balance

between plant-eating and meat-eating shifted?

It may sound odd, but the more plants we eat,

the more space there will be for wild plants.

Remarkably, it's possible to restock even highly degraded land

with wild plants.

In Brazil, the needs of cattle ranching drive most deforestation.

30 years ago, the owners of one former cattle ranch

wanted to restore their land to the Atlantic rainforest

that once covered it.

They had no idea if it could be done...

..the land was so bare and eroded.

But they were determined to try.

First, they cleared the introduced African cattle grasses,

invasive plants that outcompete most of the native plants.

The grasses were replaced by seedlings grown from seeds

gathered in nearby remnants of Atlantic rainforest.

The Earth Institute, or Instituto Terra,

as the ranch is known now,

was encouraged by early success and expanded its scope and ambition.

In five years, trees covered the land again,

and within ten,

it was clear something remarkable was happening.

When rain falls, it now no longer simply runs off the land,

leaving it parched.

Instead, it clings to the plants,

to every root, stem and leaf...

..and then slowly filters to the forest floor.

..and, so, previously dry streams burst into life

for the first time in decades.

The Institute never introduced animals or plants

other than the trees.

The animals came back on their own.

Small ones came first.

And then, very recently,

camera traps left in the forest captured images

beyond the hopes of everyone involved.

A maned wolf,

an animal that is being driven from its native habitat by deforestation,

drawn to its favourite plant,

the wolf fruit tree.

Not only that...

YAPS

..a puma...

..with cubs!

The arrival of these precious top predators and their young

shows what can happen when we make space for wild plants.

We have, for centuries,

robbed wild plants of the space and time they need to thrive.

That has certainly not been to their benefit.

Nor, ultimately, is it to ours.

Our relationship with plants has changed throughout history,

and now it must change again.

Whether it's what we eat and cultivate

or whether it's what we like,

we must now work with plants and make the world a little greener,

a little wilder.

If we do this, our future will be healthier

and safer

and, in my experience, at any rate, happier.

Plants are, after all,

our most ancient allies, and, together,

we can make this an even greener planet.

Throughout the Human episode,

the Green Planet crew sought

to capture the lives of plants confronted with the human world.

But they also heard the stories of people deeply connected

to the plants around them...

..such as those at the front line of the battle to save Hawaii's native

endangered plants from invasive species.

If we don't get a handle on Miconia,

we could lose everything that makes Hawaii special and unique.

But before the Green Planet team could start work,

they had to undertake some rigorous preparation.

We're going into somewhere that has very...

It's a very sensitive ecosystem.

They're trying to protect it from invasives.

Filming in a place so ravaged by invasive species

meant they had to be 100% sure that they were not spreading

any non-native stowaways themselves.

They had to scrub and disinfect every item of equipment.

With kit clean, the team first focus on filming

the rare holokea plant...

..accessible only on foot.

There are a few pristine areas like this left in Hawaii,

only 40% of the land still has native vegetation,

most of it wiped out by invasive species like Miconia.

Next on the list was to film the team waging war on Miconia,

known locally as the purple plague.

For crew member Aja,

the work is not just a physical battle

against this invasive species,

it's deeply personal.

I've been to the pristine areas,

so I know what it looks like and feels like,

you know, to be in the presence

of all that mana and spirituality.

Those aren't just plants.

Those are ancestors' spirits, you know?

Controlling these invasive plants is a relentless job,

and Aja is not just doing this for native Hawaiian ecosystems,

but also to protect her ancestral relationship

to this fragile landscape.

So, going through this, it feels good to hack 'em

and pull them out and be like,

"Yeah, OK, take that!" You know?

We can sort of fight back.

Aja's fierce passion to protect these native forests is evident,

but the purple plague has spread to places

Aja could never reach on foot.

Taking to the sky is the only way to reach the front line

of this battleground.

With only enough fuel to stay airborne for two hours,

the window for capturing this aerial battle is uncomfortably small.

We have one day of doing the heli operations.

The weather could completely mess us up

if we get a system that comes in,

heli to heli is always dangerous and difficult.

This flight is not just tense for Liz,

for plant sniper Brooke Mahnken,

these short flights represent his only opportunity

to hold back the invasion.

Miconia left unchecked can be terribly damaging.

The potential for one seeding plant,

if it were to get far away from the population,

reach maturity and put seeds out,

then it's starting a whole new infestation.

And once it occupies that entire area,

then it's completely wiped it out.

The helicopter is really important because you can fly in extreme

terrain with these, like, 1,000ft cliffs

and find Miconia that...

There would be no other way to get to these plants.

The Miconia team are used to the aerial challenges

of this battle, but for producer Liz,

the pre-fight talk from the helicopter pilot

brings home the lengths that this team go to

in order to complete their work.

So, you're just going to be in the back here

and it's a hurricane in the back seat,

literally a hurricane, so nothing loose,

you don't want to put an arm ahead, a leg or a hand out

cos it's going to blow behind you

and you don't want to stick your head out

because if the headset comes off,

then it's into the tail rotor and then it's bye-bye, Maui.

Pre-flight checks completed,

the clock is now ticking to get into the air.

This matters so much to everyone here.

I definitely feel the pressure to get this right.

INDISTINCT SPEECH

To get within shooting distance of the plants,

the helicopter pilot must carefully manoeuvre in

to one of the area's deepest canyons.

See the light-coloured rock? Yep.

Follow that up, to the right.

You see it?

The target is in sight.

Oh, yeah. There it is.

OK, I'm live and ready.

With high winds gusting up from the waterfall,

getting into position is tricky enough in one helicopter,

let alone two.

To give Brooke the best chance of hitting the Miconia,

the pilot must get him within 20 metres of the plant

and ideally at eye-level.

Any missed shot threatens to become friendly fire,

harming the species he aims to protect.

Ready? Yeah. Here we go.

Brooke must strike the stem of the plant

to have the best chance of completely killing it.

Whoa! My God, nice fire!

Yeah, worked really, really well. Thanks, guys.

This has been a successful mission for both teams.

The pilot's skills and Brooke's sharp shooting

has saved another patch of forest,

and Liz is relieved that she has the shots

she needs to do the story justice.

It's over. It's over.

It just looked amazing.

Yeah, it looks good.

It looks good.

For Brooke and Aja, however, their work doesn't stop.

Just holding back the tide of invasive species in Hawaii

is more than a lifetime's work.

But Aja believes that her fight is worthwhile.

Everything we do is for the next generation,

just like our ancestors and kupuna.

It wasn't for them, it was for the next generation.

And just to have my kids go into areas, like, where they can see

there are still natives,

where we don't have to go through all this invasive vegetation.

You know, it's not just my responsibility,

it's everyone's responsibility.

You know, the Earth takes care of us, so we have to do the same,

we can't just let it go by.

We've got to take care, too.

The Open University had produced a poster

that explores the vital role that plants have for our planet.

To order your free copy, call...

or go to...

..and follow the links

to the Open University.