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[man] You could think of yourself driving in a mountainous area
with the road circling up the mountain.
An overpowered engine driving much, much too fast,
driving without any headlights.
Cliffs that you're at risk of falling over.
[engine revving]
You want, of course, to turn on the headlights,
and that is what science tries to do all the time.
To give us the headlights so we can see what risks we're facing.
Recent discoveries made by scientists
studying the ways in which our planet works
are surely of the greatest importance for all of us.
Their insights are deeply troubling.
Nonetheless, they also give us hope,
because they show us how we can fix things.
One of those who has devoted his life
to studying these globally important problems
comes from Sweden.
Johan Rockström.
What he and his colleagues around the world have discovered
is perhaps the most important scientific insight of our times.
Johan has given us hope.
Hope that there is a way out of this crisis.
And once you too have heard it,
you may never look at the world in the same way again.
[Johan] This is not about the planet.
This is about us. It is about our future.
We still have a chance.
The window is still open for us to have a future for humanity.
That I think is the beauty of where we are today.
[David Attenborough] Our understanding of how our planet works
is always advancing.
We can now see more clearly than ever
how life's intricate complexity is essential for our own survival.
But biodiversity is collapsing, and our climate is changing.
Johan Rockström has focused on what keeps our planet stable.
We're the first generation, thanks to science,
to be informed that we may be undermining
the stability and the ability of planet Earth
to support human development as we know it.
This comes from ice core data,
and I think that this is the most important graph we have today.
[David] The graph is a revelation.
It shows global temperature variability
over the past 100,000 years
since the first appearance of modern humans.
We were jumping between plus-minus ten degrees Celsius in a decade.
We had, to put it simple, a rough time.
[David] What's critical is that the temperature stabilized
just 10,000 years ago.
[Johan] You can just see from the graph that this is a remarkable,
not to say almost miraculously stable, interglacial period.
[David] Geologists have given this period of stability
its own special name.
It's called the Holocene.
The Holocene is remarkable.
It is a warm period where the planet's global mean temperature
varies between just plus-minus one degree Celsius
during the entire period.
Plus-minus one.
…is plus-minus one degree Celsius.
This is what established the modern world as we know it.
[David] The Holocene's stable temperatures
gave us a stable planet.
Sea levels stabilized.
For the first time,
we had predictable seasons and reliable weather.
This stability was fundamental.
For the first time, civilization was possible,
and humanity wasted no time in taking advantage.
We domesticated rice, wheat,
teff, maize, sorghum,
on different continents roughly at the same time.
And off we go on the civilizational journey as we know it.
This is the interglacial stage that has enabled us
to develop modern civilizations as we know it.
The Holocene is the only state of the planet we know for certain
can support the modern world as we know it.
[David] Since the dawn of civilization,
we have depended on this stable state of the planet.
A planet with two permanent ice caps,
flowing rivers,
a cloak of forests,
reliable weather,
and an abundance of life.
Throughout the Holocene,
this stable planet has given us food to eat,
water to drink, and clean air to breathe.
But we have just left the Holocene behind.
The exponential rise in human pressures on planet Earth
has now reached a stage
where we have now created our own geological epoch.
[David] Scientists recently declared that the Holocene has ended
and that we are now in the Anthropocene,
the age of humans,
because we now are the primary drivers of change
on planet Earth.
We have converted half the world's habitable land
to grow crops and rear livestock.
We move more sediment and rock than all the Earth's natural processes.
More than half of the ocean is actively fished.
Nine out of ten of us breathe unhealthy air.
And, in a single lifetime,
we have warmed the Earth by more than one degree.
I would say that perhaps the most dire message to humanity
is the following.
So we have, in just 50 years,
managed to push ourselves
outside of a state that we've been in for the past 10,000 years.
Are we at risk of destabilizing the whole planet?
It's just a mind-boggling situation to be in.
For the first time, we have to seriously consider
the risk of destabilizing the entire planet.
[David] Johan's ambition has been to see the big picture.
To draw from a global network of knowledge,
to learn what keeps the entire planet stable.
What are the systems that determine the state of the planet?
And if they are five or if they were 30,
we did not know when we started.
We just open-ended asked the question,
"Can we identify the systems that regulate the state of the planet?"
[David] Those systems have held the planet in its stable state
throughout the Holocene.
As we increase our pressures on Earth,
there is a danger that those systems will start to break down.
That we will break through Earth's boundaries,
causing the stability that we depend on to collapse.
[Johan] I was absolutely convinced that we wanted
to dig into this challenge of defining planetary boundaries,
and can we identify a quantitative point
beyond which we risk triggering nonlinear changes?
And that becomes your boundary.
[David] If scientists could define our planet's boundaries,
could they also give us the road map to guide us out of our current crisis?
To show us not only how to avoid collapse,
but how to secure our own thriving future on planet Earth?
The first and most obvious boundary is well known to us all.
With global temperatures now warmer
than they've been since the dawn of civilization,
there is a danger that we have already crossed the boundary in Earth's climate.
Perhaps the most alarming evidence of this
is in the change of our planet's ice.
As a Swede, Johan feels this more keenly than most.
[Johan] As a kid in Sweden, like all children in Sweden,
we learn that the south top at Kebnekaise is the highest peak in this country.
And it's something that is just ingrained
in the identity of being a Swedish citizen.
So, of course, it's…
You know, with sadness,
one comes to realize that that will no longer be the case.
[David] The south peak of Kebnekaise
has recently lost its status as the highest peak in Sweden.
The glacier that makes up its highest point
has been shrinking roughly at the rate of half a meter a year
for the last 50 years.
[Johan] What we're seeing here at Kebnekaise
on its own will not destabilize the planet.
But having two caps of a permanent ice
in the Arctic and in Antarctica is
the very precondition for the planet to stay in this state
that has enabled us to develop civilizations as we know it.
And that's why it's such an enormous concern
to see glaciers melting,
irrespective of whether it's a small glacier at Kebnekaise,
or whether we're talking about Greenland,
because they all add together
to this fantastic capacity of cooling the planet.
[David] This cooling effect was fundamental
in keeping the Earth's temperature stable throughout the Holocene.
The planet's ice was reflecting just the right amount of the Sun's energy
back into space.
A permanent white surface like what we can see around us here
is reflecting back 90, 95% of incoming heat from the Sun.
When these ice sheets start melting,
not only do they shrink in size
so the fringe areas are very dark and absorb heat,
but even just the fact that you get liquid surface on the ice
changes the color so significantly, so you can come to a point
where the ice sheets tip over from being self-cooling
to becoming self-warming,
and that is the most dramatic tipping point
in the Earth's system.
[David] A tipping point is a point
beyond which a change becomes irreversible.
[man] It's like a train that's parked on a slope,
and it's beginning to move.
We're losing the brakes on the train,
and so the train is accelerating,
getting faster and faster, and at some point, we lose control.
[water splashing]
[David] We are already losing the brakes
that could prevent the melting of the Greenland ice cap.
[man] When I first came here, aged 20,
it felt like kind of a dream,
because I was seeing landscapes that I had only kind of seen in textbooks.
[David] Jason is one of the many scientists around the world
whose evidence and insights were fundamental to Johan's research.
The millennia snowfall onto Greenland has accumulated,
produced this dome of ice.
It's two miles thick and, you know, well up in the atmosphere.
It's really cold up there.
[David] As it melts, the surface of the ice cap
lowers into warmer air,
speeding up the melt.
The more it melts,
the cooler the climate would need to become in order to reverse it.
But today's climate is already too hot for Greenland.
So in the current climate, Greenland is already beyond its threshold,
er, where it's now losing 10,000 cubic meters of ice per second.
That's the average loss rate.
Now, that loss rate will only continue
as the climate heats up.
So is Greenland lost?
Evidently, it is.
[David] Unless we can significantly cool the Earth's climate,
the melting of the Greenland ice cap will inevitably continue.
[Johan] The drama here is that one characteristic of tipping points
is that once you've pressed the on button, you cannot stop it.
It takes over. It's too late. It's not like you could say,
"Oops. Now I realize I didn't want to melt the Greenland ice sheet.
Let's… Let's back off."
Then, it's too late.
When you cross these tipping points, you can enter a point of no return
that you basically commit the planet to an irreversible sliding away
from a state that, in our case, can support us humans.
[David] The melting of Greenland's ice cap
would raise sea levels around the world by seven meters.
[Jason] Imagine a world where sea level is not static.
Where it's changing.
Cities, hundreds of coastal cities now are threatened by rising seas.
Er, that stability in sea level was key
to the development of civilization.
It's… It's a… It's a Mad Max future that we're facing.
[David] But Greenland is just one of Earth's polar ice caps,
and it's dwarfed by its southern twin.
Not so many years ago,
it was thought that Antarctica was the resilient system.
This was the ice sheet that was not very much affected by climate change.
But today, that has changed completely.
Today we're seeing accelerated loss of mass
and loss of ice into the ocean in Antarctica.
West Antarctica would lead to sea-level rise of more than five meters
if it were to melt down completely,
and then east Antarctica actually holds the tenfold of that,
so more than 50 meters worth of sea-level potential.
[David] Ricarda is one of Johan's colleagues,
and she studies how tipping points can interact.
The important point to make here is that everything
in the Earth's system is connected.
If one part of the climate system
crosses its tipping point,
then that might make it more likely
for other parts of the system to also cross their critical threshold,
so you can think of this in terms of dominoes.
If you tip one of them over,
then this might lead to a cascading effect.
What is clear is that with ongoing global warming,
we're increasing the risk
of crossing tipping points in the Earth's system.
When we cross tipping points, we unleash irreversible changes
that would mean that the planet will go from our best friend
to a position where it dampens and reduces the stress,
sucking up carbon dioxide,
taking up heat, absorbing impacts,
and tipping over to a point where it could self-reinforce warming
and become a foe.
[David] The climate is, of course, being warmed by greenhouse gases,
so it's in our emissions of these gases
that we find a global tipping point.
Since long before human beings appeared, the Earth's average temperature
was closely tracking the concentration of carbon dioxide in the atmosphere.
During the Holocene,
this concentration remained relatively steady,
but that all changed with the Industrial Revolution.
In 1988, we passed 350 parts per million
of carbon dioxide in Earth's atmosphere.
This was the moment we crossed the boundary.
Ever since then, we've been at risk of triggering changes
that lead to runaway warming.
[Johan] You go past 350 PPM
in the concentration of carbon dioxide in the atmosphere,
and you enter the danger zone.
[David] So 350 parts per million is the first of Johan's boundaries,
and we're already well beyond it.
[Johan] Right now, we've reached a point of carbon dioxide concentration
in the atmosphere of roughly 415 parts per million.
We're starting to see the impacts of being
in the middle of the danger zone in the climate boundary
in terms of rising frequency of droughts,
and heatwaves, and floods,
and accelerated melting of ice,
and accelerated thawing of permafrost, and higher frequency of forest fires.
[David] Up ahead is a second threshold.
We are rapidly approaching 450 parts per million carbon dioxide.
[Johan] The planetary boundary danger zone is defined
by the uncertainty range in science.
Today, our assessment is that the uncertainty range in science
lies between 350 PPM,
which is the boundary
between the safe zone and entering the danger zone,
up to 450 PPM,
which is when you exit the danger zone and go into a really high-risk zone.
[David] If we enter the high-risk zone,
irreversible tipping points become highly likely, if not inevitable,
and this is a conservative estimate,
given that the signs of tipping points are all around us now.
In simple terms, the climate planetary boundary
is equal to 1.5 degrees Celsius warming,
and it just provides all this evidence
that we take a huge risk if we allow ourselves to go beyond 1.5.
We are at 1.1, we're rapidly moving towards 1.5,
and our only chance to stay within the planetary boundary on climate
is that we, you know,
reach a fossil-fuel-free world economy within the next 30 years.
[David] While that target for global temperature
may have grabbed all the headlines,
Johan knew that this was only one part of a bigger picture.
For our planet's stability relies on more than just its climate.
More research and evidence had to be brought forward
to conclude that we also have four biosphere boundaries.
Boundaries that are in the living Earth.
These include the land configuration.
How… How is the composition of biomes on Earth?
Er, the three rain forests, the temperate forest,
the boreal forest,
the grasslands,
the wetlands.
Second is biodiversity.
So all the species in water and on land.
And then the third one, of course, the bloodstream, the hydrological cycle.
And then, finally, the injection of nutrients
that are fundamental for the functioning of the living biosphere.
The nitrogen and phosphorus cycles.
[David] The first of the biosphere boundaries,
the composition of the habitats on Earth,
is concerned with how we are now transforming those natural habitats.
We are fast approaching a major tipping point
in one of the planet's largest remaining wildernesses.
The Amazon.
Carlos Nobre has been studying
the rain forest's importance to our planet's stability for decades.
He was the first to sound the alarm.
[in Portuguese] I saw the Amazon in 1971-72 undisturbed.
I saw the forest
and the rivers.
I would swim in the Rio Negro with the piranhas,
And nothing ever happened to me.
[David] Since that time, large swathes of Amazon have been cleared
for livestock and soya farming.
Carlos has discovered that this is pushing us closer
to triggering irreversible change across much of what remains.
[in Portuguese] In 1998, we began the largest scientific experiment
ever conducted in a tropical rain forest.
[David] Many towers were built in the rain forest
to study how it creates its own climate.
The data shows large parts of the rain forest are drying out.
[Carlos in Portuguese] In the Amazon,
the dry season lasts a maximum of three months.
But with global warming
and also forest degradation, due to human activities,
in particular, livestock and soya farming,
the dry season has become six days longer
each decade since the 1980s.
[David] As the forest is reduced and fragmented,
its ability to recycle water
and generate rain into the dry season is diminished.
If the dry season becomes longer than four months,
the jungle trees die and are replaced by savanna.
A process called savannization.
There are signs that parts of the Amazon are already changing.
[in Portuguese] If deforestation goes above 20 to 25% of the forest,
with global warming increasing,
we are likely to experience an irreversible process of savannization
that could affect 50 to 60% of the entire Amazon forest.
[David] We have already lost close to 20% of the Amazon rain forest.
We could be about to tip the Amazon from planetary friend to planetary foe.
As the jungle turns to savanna, many trees die,
and carbon is released into the atmosphere.
Carlos has calculated the Amazon could release
200 billion tons over the next 30 years.
That's equivalent to all the carbon emitted worldwide
for the past five years.
[Carlos] We are very, very close to the tipping point.
Are we concerned about fighting the climate crisis?
Are we, er, concerned about keeping the carbon in the forest?
Or "I don't care"?
There is reason to be deeply concerned at this point.
We're still expanding agricultural land into natural ecosystems.
We are still cutting down the rain forest
at a pace that puts the whole system at risk.
[David] And it's not just the rain forests.
Trees of every description are invaluable in maintaining planetary stability.
So much so that a loss of just 25% of the world's forest cover
risks triggering catastrophic tipping points.
But we have already cleared almost 40%.
We are well into the danger zone for this boundary.
A second major consequence of deforestation
is a loss of biodiversity.
Of nature.
Biodiversity is the second of the biosphere boundaries,
because it underpins our own ability to thrive on Earth.
But we are not treating it well.
Nature is being degraded at a rate and a scale
that is unprecedented, er, in human history.
[David] Anne Larigauderie is an ecologist alarmed by the growing flood of evidence.
Everywhere around the world, nature is in decline.
One million of species of plants and animals
out of an estimated total of eight million
are threatened with extinction.
If we continue with this negative trend,
we might be headed towards a sixth mass extinction.
[David] In just 50 years,
humanity has wiped out 68% of global wildlife populations.
It's clear that we are in the midst of a biodiversity crisis.
Losing all of this fabric of life,
all of this biodiversity, is threatening our own life on Earth.
With current negative trends in biodiversity,
we are not going to be able to feed the planet.
For that, you need nature that functions well.
[David] For Johan, it was a story close to home
that really hit him.
I opened the newspaper and read this story about UK scientists coming over to Sweden
and stealing, you know, short-haired bumblebee queens.
And it read like they had, you know, sneaked over at night
and basically snatched these hundred bumblebee queens
to bring them back into the UK
and to basically save what they had been destroying.
[David] Across Europe, short-haired bumblebees
are key pollinators for food crops.
But by the 1990s, they had been classed as extinct in the UK.
Here, we have, you know, a country that feels forced to go to another country
and then steal back some of its pollinators
to have a functioning ecosystem.
That's a… Then, you know, to me personally,
that was a moment of, er, of realization that
this is serious.
[David] Around 70% of the world's crop species
rely to some extent on insect pollination.
But the expansion of intensive monoculture is leading
to a drastic decline in insects.
The irony is that our global production of food is,
in essence,
wiping out the very thing our food production relies on.
It was not only proof of one of the fundamentals
in biodiversity research,
which is that biodiversity is not something
we need to protect just because of the beauty
or some kind of moral responsibility from one species, humans,
to another species like flora and fauna.
Oh no, it's the toolbox for the functioning of our societies.
It is a fundamental piece of the puzzle
to make food production, clean air, clean water,
carbon sequestration, nutrient recycling, to work.
[David] Scientists have tried to calculate the benefits that insects provide
simply by going about their daily business in large numbers,
each kind providing a subtly different service.
But their value is mostly incalculable until suddenly…
they're gone.
A planet without insects is not a functioning planet.
And, of course, the decline is not just confined to insects.
Wildlife has been squeezed out
as our agriculture has expanded across much of Earth's habitable land.
Today, of all the birds on Earth, only 30% are wild.
And of all the mammals on the planet,
wild species now make up, by weight, only 4%.
So where is the boundary for biodiversity?
How much more of the natural world can we afford to lose
before our own societies collapse?
There are many different tipping points in the natural world,
and it's difficult to translate concretely
the planetary boundary when it comes to biodiversity,
because life is very complicated.
[David] A single boundary for the loss of nature
may be hard to pinpoint because of nature's complexity,
but one thing is clear.
We've already crossed well beyond it.
[Johan] We are so deep in the red.
We are in such a dangerous point
when it comes to losing species on Earth and destroying ecosystems on Earth
that we have to halt the loss of biodiversity
as quickly as we ever can.
Now is the time to set as a target
for 2021, 2022,
I mean really at the early parts of this decade,
that we must aim at a zero loss of nature.
The equivalent of 1.5 degrees Celsius maximum allowed warming
would be zero loss of nature from now onwards.
[David] The third biosphere boundary relates to the planet's bloodstream,
for fresh water is another of the fundamentals
that society depends on.
Did you know that you and I need roughly
something like 3,000 liters of fresh water per person every day for us to stay alive?
And you say, "My God, 3,000 liters? Three tons of water? How can that be?"
Yes, we only need 50 liters for hygiene and drinking.
We, in the rich world, use roughly another hundred
for washing, our household needs.
And then industry needs another 150, so that's like 300 liters.
But the rest, the 2,500 or so, is for food.
That's the fresh water we need to produce everything that we have on our plates
when we eat our food.
[David] Fresh water has a special significance for Johan.
It was the subject of his PhD
and many years of research in the semi-arid regions of Africa.
I spent from, you know, sunrise to sunset walking around, sweating like crazy,
collecting data, you know.
Digging profiles in the soil,
taking soil samples, doing soil moisture measurements.
Just getting wind speed data and rainfall data.
I've measured so much leaf area.
You don't, you won't imagine, you know,
how careful a scientist has to be in just measuring in square millimeters
the size of all the leaves on a plant.
[David] It was the details he needed to answer a much bigger question.
How much water do we need to feed the world?
My tentative answer when I was doing my MSc was,
was that, "Yes, there seemed to be enough water."
[David] But there's another side to the coin.
Is there a global threshold for fresh water use
beyond which the system starts to collapse?
[Johan] We actually scanned off all the river basins in the world
and then, you know, defining what's the minimum amount of runoff water
any given river basin must have to maintain the wetness in the system
so that you have thriving ecosystems,
good supply of water, functioning river basins.
[David] The volume of water currently being extracted from each river
reveals why many are now in danger of running dry.
[Johan] Globally, we're still, as far as our assessment shows today,
in the safe zone on fresh water,
but we're rapidly moving towards a danger zone.
[David] The last of the biosphere boundaries
involves the flow of nutrients, nitrogen, and phosphorus.
They are the essential components of all living things,
the key ingredients in fertilizers.
Johan has witnessed firsthand the impacts of their increasing use.
He spent his childhood summers on an island in the Baltic Sea.
[Johan] We loved fishing.
Most often, I fished with my closest friend here, Anders,
and my little brother Nicklaus. And…
So there was often the three of us.
Almost being able to tell my mother and dad that,
"So you want some fish for dinner?"
and we would come home with a catch, basically.
One of the adventures was going out
one, two nautical miles out in the open Baltic,
and that's where we could, by hand, fishing cod.
I was, at that time, the best at rinsing the fish,
so, after one hour, I had to abandon the fishing,
because we got so much cod that the only way to bring it home
was that we would actually cut up the fish on site.
So we would have the seagulls just engulfing us,
because there was so much, er, you know, entrails
and then pieces of fish that I was then cutting off
just to fit in the boat.
And that was a cause of great, great excitement as a kid to do that.
A few decades later, today, it's a completely different situation,
and you see nobody trying to go out to catch cod,
because, er, it's just literally empty.
It looks exactly the same, by the way, as it did in the 1970s, 1980s
when you look at it from above,
but when you look at it from below, it's something completely different.
[David] When Johan was a boy, the Baltic was a healthy environment
dominated by predatory fish like cod.
But while overfishing removed many of the fish,
it was fertilizers washed off the surrounding fields
that tipped the Baltic into disaster.
It's now the world's most polluted sea.
[Johan] It is when you have many Baltic Sea equivalents across the planet
that there is reason for deep concern,
because it's a…
It's a signal that the entire planet is gradually losing its resilience
and gradually becoming weaker and weaker.
[David] Elena Bennett is an expert on the impacts of fertilizers.
We take nitrogen out of the air and chemically convert it
into a form that is able to be used by plants,
or, in the case of phosphorus, we dig it up out of the ground.
We mine it.
We developed these chemical pathways or ways to mine phosphorus
that were much, much more efficient,
and that basically doubled, tripled,
or even quadrupled the production of food around the world.
[David] This was invaluable in feeding a growing population,
but we got into the habit of applying far more fertilizer
than the crops could actually use.
The unused nutrients wash into rivers,
over-fertilizing them too.
A process called eutrophication.
What we see are these algal blooms.
Sort of looks like a blue-green scum on top of the lake.
They often smell terrible
because we're smelling the rotting of that algae.
As it's decomposing, it uses up oxygen.
[David] Reduced oxygen changes the chemical composition
of the sediment on the bottom of the lake, causing it to release more phosphorus.
[Elena] Soon as you have a eutrophication problem,
the lake sort of says,
"Oh good, we're gonna make it worse,"
and it just creates a positive feedback cycle
that creates more and more and more phosphorus
going into that lake and essentially keeps it in that state.
We also have the same issue of eutrophication in oceans,
where we get what are called dead zones from the same nutrients,
and we see those dead zones now
in a few hundred places around the world.
[David] Eutrophication in the ocean may have been an important contributor
to one of the world's five previous mass extinction events.
Already today, some dead zones have expanded
to cover tens of thousands of square kilometers.
Our overuse of phosphorus and nitrogen
is one of the least known, but most critical impacts
we're having on the biosphere.
We are already deep into the danger zone.
[Elena] We are well across the nutrient boundary.
It's… It's not a thing that we think about very often.
I think we need to be taking this boundary much more seriously than we currently are.
[David] Nutrients, water, our forests, biodiversity, and the climate.
Five big components of our planet that regulate stability
and underpin our own survival.
But Johan and his colleagues knew that this still wasn't the full picture.
They hadn't yet accounted for a little-known drama
that's playing out in the oceans.
Its impact on our planet's stability could outplay all others.
When we emit CO2 into the atmosphere,
about a third of that emissions has ended up in the ocean.
[David] Terry Hughes has been a close collaborator with Johan
over many years.
[Terry] That has changed the chemistry of the ocean.
It has changed the pH
and made it less alkaline, or more acidic.
Hence the name "ocean acidification."
[David] When carbon dioxide dissolves in water,
it creates carbonic acid.
[Terry] The vulnerability is in colder waters.
[David] Over the past few decades,
the world's ocean has become 26% more acidic,
and, for as long as carbon dioxide concentrations
in the atmosphere remain high,
the ocean will continue acidifying.
The acid reacts with chemicals in the water called carbonate ions,
reducing their concentration.
[Terry] It affects a broad suite of organisms,
particularly those that need
carbonate to grow their skeletons.
Things like mollusks, oysters, mussels.
[David] Ocean acidification has an ominous history.
Global changes in the acidification,
the pH of the ocean, can actually cause mass extinctions.
We've seen that repeatedly in the geological record.
So as we manipulate
the planet's climate, we're literally playing with fire
in terms of the unforeseen consequences
of moving past these planetary boundaries into uncharted territory.
[David] We are still in the safe zone for ocean acidification,
but we're pushing towards the danger zone
and potentially a catastrophic mass extinction.
For all the complexities of Earth,
Johan and his colleagues discovered that there are just nine systems
that keep our planet stable.
But they've not yet identified where the boundaries lie for two of them.
The first one is an assortment of human-made pollutants.
We call it "novel entities," and it is everything from nuclear waste
to persistent organic pollutants
to loading of heavy metals
to microplastics.
[David] Humans have created 100,000 new materials,
any number of which could interact with the environment in catastrophic ways.
As of yet, this boundary is not quantified.
We simply don't know the long-term or cumulative impacts
of these polluting substances.
But most have the potential to cause planet-wide disruption
if not controlled in some way.
There's one form of pollutant that is already having a global impact.
So much so that it has a boundary of its own.
Aerosols are basically particles in the atmosphere.
They are what's called air pollution particulates.
75% of the aerosol pollution is from fossil fuel combustion.
We see them as hazy sky,
because they intercept sunlight and just scatter it like mirrors.
And they cause what's called "global dimming."
[David] Veerabhadran has spent a lifetime studying the air around and above us.
The other way aerosols impact climate,
because you're cutting sunlight, which is the major energy source
for driving the temperature of the planet, these aerosols have caused some cooling.
When you hear climate scientists like me say that aerosols are cooling the planet
and mask the warming, you may think, "That's a good thing."
But unfortunately, it's not.
Because of this masking,
we are still not seeing the full greenhouse beast.
[David] This cooling effect from aerosols is masking
about 40% of the effects of global warming.
And it comes at a high price.
Air pollution kills over seven million people every year
and takes, on average, three years off the life expectancy of each one of us.
Where the boundary for air pollution lies
has not yet been scientifically determined.
Just based on the 7.5 million deaths by these particles,
I would say we have already crossed the boundary
as far as aerosols are concerned.
[David] Finally, the ninth boundary is the ozone layer.
It has the unique distinction of being the only boundary
where we're moving in the right direction.
[Veerabhadran] The ozone intercepts harmful ultraviolet radiation,
which directly impacts our DNA
and causes deadly diseases like skin cancer.
That is why,
when the Antarctic ozone hole was discovered in the 1980s,
there was a global panic.
[David] The discovery of the ozone hole
caused by chemical pollutants being released into the atmosphere
persuaded nations to phase out these chemicals.
[Johan] It was quite fantastic how the scientific warnings
translated into political action.
This is the first and only example
that we can actually manage the whole planet.
We can actually return into a safe operating space
for a planetary boundary that we had seriously gone into the high-risk zone,
and we returned back into a safe operating space.
It was indeed fantastic to witness.
Scientists raised the alarm, and the world acted.
Thanks to Johan and his colleagues,
we now know the planet has nine boundaries
and the risks we face by crossing them.
Together with the ozone layer, we are, at least for now,
within the safe zone for ocean acidification and fresh water.
We don't yet know how close we are to the danger zone for air pollution,
or for all the other pollutants, the novel entities.
But most worryingly, we have already exceeded
at least four of the nine boundaries.
Climate, forest loss, nutrients, and biodiversity.
We are now crossing irreversible tipping points,
and we are perilously close to tipping the Earth
into a state that is unable to support our own civilizations.
What we're seeing in the world today verifies the planetary boundary framework.
We can see so clear evidence that,
because we're in the danger zone on climate,
because we're in the deep high-risk zone on biodiversity loss,
we start seeing increased drought, impacts on the rain forest,
the forest fires in Australia and in the Amazon,
the accelerated ice melt, the collapse of coral reef systems.
[David] For the scientists bearing witness to these planetary changes,
the loss is much more than just numbers.
Terry Hughes has spent a lifetime studying coral reefs.
[Terry] A bleached coral is very, very sick.
[David] Corals bleach when the waters around them get too warm,
something that's happening with increasing frequency and intensity
as a consequence of global warming.
In big thermal extremes, like we've been seeing
during mass bleaching events in recent decades,
they can actually die very, very quickly.
They cook.
The footprint of a bleaching event is ten times bigger
than the most extreme Category 5 tropical cyclone.
So they're off the scale in terms of the size of the impact,
and in terms of how frequently they are occurring.
[David] Terry studies the Great Barrier Reef,
the largest reef system in the world.
Bleaching events used to be localized and rare,
but over the past two decades,
marine heatwaves have caused widespread bleaching.
Three of the five biggest bleaching events have occurred in the past five years.
[Terry] We're worried about that shrinking gap
between one bleaching event and the next one.
We've already seen back-to-back bleaching events
occur for the first time on the Great Barrier Reef
in two consecutive summers in 2016 and 2017.
[David] Those gaps are critically important if the corals are to recover.
Half the reef's corals have already died.
Terry's work involves conducting aerial surveys
to record the extent of each bleaching event.
[Terry] When we do our aerial surveys, we fly as slowly as we can,
as low as we can, so we can see individual corals,
and we can assess how many of them are bleached white or not.
[Terry] All the coral's bleached.
[man] Yeah, that's bad.
[Terry] You can actually see a bleached reef from kilometers away,
because it virtually glows.
There's so much white coral on it.
[Terry] So I've got very broad crest, and just about everything's bleached.
Those surveys have now been done five times,
and I have led three of those.
The last three in 2016, 2017, and 2020.
It's, um…
It's a job I'd hoped I'd never have to do,
because it's actually, um, very confronting.
Sorry.
[David] We're heading for a future in which the Great Barrier Reef
is a coral graveyard.
[Terry] The climate modelers are telling us, the biologists,
that business-as-usual carbon emissions
will result in back-to-back bleaching events
every consecutive summer by the end of this century.
We've gone past the tipping point for coral bleaching.
Scientists and ecologists like myself
have been talking for decades now about global warming,
and it has been frustrating, um, that we haven't been listened to.
I get angry.
I don't get depressed. I get angry.
There is a real reason to be frustrated,
because the science is clear
and has been communicated for the past 30 years,
and still we're not moving in the right direction.
I want you to panic.
I want you to feel the fear I feel every day.
And then I want you to act.
I want you to act as you would in a crisis.
I want you to act as if the house was on fire.
Because it is.
[woman] The bush fires in Australia have raged for months,
destroying so much of the country's east coast--
[David] In 2020, Australia endured a summer from hell.
[man] And our only way out is now
a treacherous gauntlet of fallen trees and flames.
[David] Fueled by record-breaking temperatures and months of severe drought,
50 million acres of lands were incinerated.
People fear this will become the new normal.
But the science says there will be no normal.
Daniella Teixeira studies glossy black cockatoos,
one of Australia's most vulnerable birds.
[Daniella] Glossy black cockatoos let you get really close to them.
They will learn who you are, and, in places where you visit regularly,
they actually, I think, get to know who you are,
and so you can actually go up to them,
sit underneath the tree where they're feeding,
and get to know the individual birds.
[David] As soon as it was safe to do so,
Daniella returned to one of her main study sites
on Kangaroo Island off South Australia.
It's February. Nesting season for the cockatoos.
[exhales]
There's no sign of any wildlife at all.
Um…
There's nothing left here.
It just looks like
complete carnage.
It's almost like I'm not looking at the spot that I know.
Like it's almost like this can't be the same spot,
because it's so starkly different.
Yeah, I've spent the last four years
working in this very location, so this is…
This is about, um…
Yeah, this is about as hard as it gets. This spot was really, um…
Like there was a big commotion every evening.
We would have had young chicks by this point.
[sighs]
This is… This is heartbreaking.
Jesus.
[sighs]
[sniffs]
I know this nest
pretty well.
It's absolutely horrible to see it like this.
And all that's left is…
Is the iron collar just burnt on the ground.
Like, the iron collar is…
Is what we put on the nest trees to save them.
To stop the possums
from…
From predating on the chicks.
And just to see all around me these iron collars just
open on the ground.
You know, they weren't enough to save them.
This is an ecological catastrophe. There's no doubt about it.
[David] The 2020 bushfires
were the most devastating in Australia's history.
[Daniella] Climate scientists have been talking about these events
for a long time,
and we were expecting that this might happen,
but I don't think anybody expected it to be so soon
or so severe.
[David] Scientists estimate that the fires killed or displaced three billion animals.
[Daniella] 1.43 million mammals,
2.46 billion reptiles,
180 million birds,
and 51 million frogs.
These figures are so enormous,
so consequential…
I don't know how to make sense of them.
That's not what we should be dealing with as conservationists.
I think this is a wake-up call.
These black summer fires really showed us that it's now,
it's affecting us today,
and this is gonna have long-lasting consequences.
Like, where can he go?
[David] Wildfires and coral bleaching
are caused by us overstepping the climate boundary.
But it is the destruction of nature that lies behind what has been by far
the most far-reaching impact of our destabilizing planet.
The COVID-19 pandemic.
It affected your life as it affected mine.
COVID-19 was a planetary impact we were ill-equipped to deal with.
It overwhelmed health services
and brought the global economy to its knees.
Though it surprised many,
the World Health Organization had forewarned that it was coming.
I think it was a question of time.
Er, we were destroying nature. We were destroying our ecosystems.
We have been doing very aggressive agricultural practices.
We were doing an incredible, very aggressive deforestation.
If you add to that the fact that we live in very polluted cities
with a very high population density,
I think all of those elements were kind of contributing to create
the perfect scenario for any new virus to spread.
[David] Zoonotic diseases emerge and spread into the human population
when nature's resilience is weakened.
It's not healthy nature that causes pandemics.
In terms of transmission of the diseases,
it's only with certain species under certain circumstances
and when we invade their environment in a very aggressive way.
So, for the human health, animal health, and environmental health,
the three are so much linked.
Exposure to nature is good,
provided we do not destroy nature
and we not destroy the ecosystems where other species are able to live.
COVID-19, I feel, has made us understand
for the first time that,
"Oh my God, something that goes wrong somewhere else on the planet
can suddenly hit the whole world economy
and can change my life, like, immediately."
The appearance of COVID-19
was a clear warning that all is not well with our planet.
But it's also given us an opportunity to rebuild in a new direction.
Now that Johan and his colleagues have turned on the headlights,
we can clearly see the boundaries.
We can see the path back to a safe space,
to a more resilient future.
It is achievable.
It's not a question anymore of doing economic growth here
and then do some environmental impact reduction over here.
Oh no, now it's a question of framing the entire growth model
around sustainability,
and have the planet guide everything we do.
[David] An immediate priority is to reduce carbon emissions to zero
and stabilize global temperature as low as we possibly can.
The window is still open for us to be able to avoid passing two degrees.
It's even open to come to 1.5.
But the window is really just…
It's… It's barely open.
[David] Since the beginning of the Industrial Revolution,
we have emitted 2,400 billion tons of carbon dioxide.
To stay below 1.5 degrees,
we must emit less than 300 billion tons more.
If we continue to emit 40 billion tons each year,
our budget will run out within seven years.
Of course, we cannot shut down
all energy utilities in the world overnight,
so the only orderly way to do this
is to bend the global curve of emissions now,
because that's what all science shows.
Now is the last chance we have to bend the global curve.
What is the most rapid pace of emission reduction
that we can accomplish?
Well, there's no study that suggests that we can go faster than 6, 7% per year,
because 6, 7% per year, that is cutting by half in a decade.
[David] Cutting our emissions in half every decade
is an exponential rate of change.
[Johan] Anyone can adopt this pace.
I mean, you and I can do it as individuals.
We can say, "Okay, from now on, myself and my family
will try to cut emissions by half every decade,"
which would mean that you would be fossil fuel-free
in one generation, in 30 years' time.
And a company can do it, or a country can do it,
or the world can/must do it.
[David] Phasing out fossil fuels will, of course,
begin our journey back towards the safe space
within the climate boundary.
And it will also substantially reduce air pollution
and also slow down ocean acidification
as well as reduce pressure on biodiversity.
But zero emissions are not enough.
We must also draw down the carbon that's already overheating the planet,
and there's one very effective way to do this.
Plant more trees.
A global effort to plant billions of trees
could be one of the most cost-effective and achievable solutions
to the climate crisis.
And growing more trees is vital to offset the carbon we continue to emit
as we strive to reach zero emissions as fast as we can.
Of course, capturing carbon
is only one of the benefits that trees provide.
Cheikh Mbow has collaborated with Johan for many years.
He's an advocate for trees.
[in Wolof] Trees prevent soil erosion.
Without trees, there will be less rain.
If we plant trees in the fields,
the fertility of the fields and, therefore, production will increase.
We want to bring the tree back to its place
at the center of sustainable development.
Our job is to make sure that wherever a tree can grow,
we plant one.
[David] Planting trees and restoring our natural world
will, of course, have huge benefits for our planet's biodiversity,
but it will also help to stabilize our climate, our fresh water,
and have enormous benefits for our food production
and all the other services that nature provides for free.
Just imagine, for the first time since the dawn of humanity,
we could wake up one morning
on a planet with more wildlife than there was when we went to sleep.
There's another transformation that is almost unbelievably simple,
but it's key to staying within our planet's boundaries.
It can be adopted by you or me.
In fact, by anyone with the freedom to choose what food they eat.
[Johan] Now, the exciting thing is the diet that is more flexitarian,
less red meat, more plant-based protein,
more fruit and nuts, less starchy foods,
if you take that diet
and assume that all people would eat healthy food,
we could actually come back within a safe operating space,
not only on climate, but also on biodiversity,
on land, on water, on nitrogen and phosphorus.
Quite exciting that eating healthy food
might be the single most important way of contributing to save the planet.
There's one more transformation that is vital.
It would bring us back towards the safe zone
within all our planet's boundaries.
Imagine a world without waste,
with nothing to throw away.
Our waste is created by design.
When we make products,
we rarely build in the means to recover the raw materials.
If we turn that linear system into a circular one,
designing products so that the raw materials
can all be recovered,
our use of resources could be infinite.
[Johan] So more and more evidence shows that circular economies
are fundamental if we are to stand a chance
of providing good lives for all citizens in the world.
[David] Eliminating waste would bring us closer to the safe zone for climate,
biodiversity, and especially nutrients, novel entities, and air pollution.
The planetary boundaries have given us a clear path ahead.
Simple things, like choosing renewable energy,
eating healthy food, planting trees,
saying no to waste.
Together, these could transform our future on Earth.
And the magic in this is that these transformations
would also improve all our lives right now.
[Johan] Even if you don't care at all about the planet
and even if you don't care too much about equity in the world,
but rather are selfish, just focusing on yourself
and your family and your own life,
which I think is a very respectful position to have
as a human being struggling with everyday life,
still you would want to come back to a safe operating space.
Everyone would benefit immediately of having clean air,
giving more healthy and longer life expectancies.
Your children would be healthier.
Coming back within planetary boundaries
also means you are more likely to live in,
in societies with, you know, stable markets and stable jobs,
which then reduces risks of conflict and instability where you're living.
So, all in all,
you want to be in a safe space,
rather than being in a danger zone where everything is just in flux.
What we do between 2020 and 2030,
from the evidence we have today, my conclusion is,
it will be the decisive decade for humanity's future on Earth.
The future's not determined.
The future is in our hands.
What happens over the next centuries
will be determined of how we play our cards this decade.
[David] It's a remarkable time to be alive,
but it also carries great responsibility to act decisively.
We have no time to lose.
[Johan] What would we do if we had had a report tomorrow morning
saying that an asteroid is on its way to Earth?
Well, I'm sure that we would just put everything else aside
and just focus then on solving the problem.
Cost whatever cost it takes.
[David] It is now clear from the science
that the planetary crisis we are facing requires the same united response.
[Johan] I would say that we do not have
environmental problems in the world anymore.
Destabilizing the planet…
The risk of destabilizing the planet is a question of security and stability
for all societies in the world.
Therefore, it is a question for the Security Council.
I think one should put the planetary boundaries right at the center
of the most strategic top governance level we have in the world,
which is the United Nations Security Council.
[David] Such a global response is now within reach as never before.
There's something bigger happening right now,
which is that one species, we humans,
are such a dominant force on the planet
in a way that we haven't seen across the eons
over the past four billion years.
Mother Earth is under continuous diagnosis
and continuous observation.
The digitalization and the hyper-connectivity
in the world of science and in the world of observation
now means we've covered the whole planet with knowledge.
What if we're now entering
a new, unique geological epoch
that is not only geophysically defined,
but also defined by the fact that we have
a new consciousness embedded inside the planet?
Thanks to the work of scientists like Johan Rockström,
we now have the capacity to act as Earth's conscience, its brain.
Thinking and acting with one unified purpose
to ensure that our planet forever remains healthy and resilient.
The perfect home.