The Age of Sustainable Development" gives students an understanding of the key challenges and pathways to sustainable development - that is, economic development that is also socially inclusive and environmentally sustainable.
The Planetary Boundaries
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From the course by Columbia University
The Age of Sustainable Development
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From the lesson
Growth within Planetary Boundaries
Professor Sachs details the various planetary boundaries and their implications for growth dynamics.
Meet the Instructors
Jeffrey Sachs
Director, Earth Institute; Quetelet Professor of Sustainable Development; Professor of Health Policy and Management
We've been talking
about economic growth, how it started, how it diffuses, what the big
problems are, how countries still trapped in
poverty can spring free of the poverty trap.
But the problem, we know, is more complicated than that.
What if the world
achieves economic growth?
What if the poor countries, as they hope and
rightly deserve, catch up with the high income countries?
What then for the planetary boundaries?
What then for an environment already under tremendous stress?
Remember that sustainable development makes a
key point, that economic, social and environmental
systems are interlinked. So, I want to focus now more deeply on
how we might even conceive of bridging this terrible
problem of global economic growth, the good that we want, the
progress for poor countries, with a worsening environmental crisis.
We have to understand the environmental systems and
how humanity is effecting them.
Then we have to look for practical approaches.
How we can reduce the pressures that humanity is placing on
the climate, on the oceans, on the land, or other species.
So that we can reconcile these two objectives and indeed, make it
possible to achieve all three of the basic goals of sustainable development.
Economic growth, fairness and social inclusion and environmental
sustainability. Remember the concept of planetary
boundaries or the fact that we're living in as new geologic era, the anthropocene.
Both these concepts, planetary boundaries and anthropocene,
signify that humanity has become so numerous,
our 7.2 billion people and rising, and so effective one
could say, so productive in the capacity to mine and extract
resources. To transform resources for production
in industry, to consume, that we have suddenly,
unprecedentedly as a species, hit these planetary
risks and even dead ends if we're not careful.
The concept of planetary boundaries, I think it's
an extremely useful one, because when world leading
ecologist Johan Rockström and many, many other leading
ecologists got together, they asked the question in specificity.
What are the major challenges coming
from humanity's impact on the physical environment?
Can we identify those challenges?
Can we quantify them?
Can we identify what would be safe limits for human activity
so that we can begin rather urgently because we're late to this.
To redesign our technologies and our economic growth dynamics
so that we can have economic
improvement while staying within the planetary boundaries.
You'll recall the picture that we looked
at of the planetary boundaries around this circle.
And I want to say a few words about each of these so that we can begin
to look deeply at the question of how to reconcile growth and these
various environmental threats. The first of the challenges and
the biggest is climate change. This is being caused by
humanity's use of particular technologies. Especially
fossil fuels and the way we use land and grow animals
and food that produces atmospheric
change in the form of rising concentrations of
a few particular gasses. Carbon dioxide is the most important of
these. Nitrous oxide, methane and a few more
industrial chemicals are the greenhouse gasses that have the property
that they allow the sunlight in as ultraviolet radiation.
But then, when the earth would re-radiate its heat to space, they trap energy in the
form of the outgoing infrared radiation and thereby warm the planet.
So these greenhouse gases are very particular molecules
that have the property that they absorb infrared radiation.
And so when their concentration in the atmosphere increases, that warms
the planet.
It's because of these greenhouse gases that life
is possible in the way we know it, because
that envelope of the atmosphere has made the earth
warmer than say, the moon, which lacks an atmosphere.
And is very, very cold as a result.
But at the same time, if we perturb the greenhouse gas concentrations,
raise them by raising the CO2 or the methane or the nitrous
oxide in the atmosphere, then we endanger ourselves and other species.
The second of the planetary boundaries is related, ocean acidification.
This also comes from carbon dioxide in the atmosphere which is increasing because
of human use of coal, oil, and gas. The oceans are being
acidified, made more acid, by the fact
that the carbon dioxide in the atmosphere dissolves in the ocean
producing carbonic acid. And because of this acidity,
various kinds of animal life, corals and
shellfish and lobsters and and
very small plankton that also have these external
shells made of calcium are threatened by the
increasing acidity which makes it hard for the species to make their protective
shells. Now, the pH of the ocean
has already decreased by 0.1 unit on the pH
scale from zero all the way to 14,
the least acidic or basic end of the pH
spectrum. A change of 0.1 in the pH oceans doesn't
seem like all that much. But this is a logarithmic scale.
So, what a decline of 0.1 signifies is an increase of
protons in the ocean of 10 to the 0.1. Or about 0.3, 30%
increase of acidity in the ocean already with a lot more to come.
If you look at this map of the ocean, you can see the
changes that are already being noticed on average in different parts of the world.
The oceans are not uniformly
becoming more acidic. That depends on ocean dynamics.
But the shading of this colored map shows that we're already in
an environment on a trajectory of dangerously rising ocean acidity.
The third of these planetary boundaries is ozone depletion.
We learned a while ago
accidentally, but thank God, we learned it, that certain industrial
chemicals, those that were used at the time for refrigeration, mainly.
Chlorofluorocarbons, or CFCs, when put into the air,
would rise into the upper atmosphere, dissociate, and the chlorine in those CFCs
would then cause the ozone layer in the upper atmosphere to
dissociate. And a famous, horrifying finding was that
there developed a big hole in the ozone over Antarctica.
And when that was discovered by satellite of course people were rightly terrified.
Because the ozone layer in
the upper atmosphere protects us from too much ultraviolet
radiation, saves us from skin cancer and many other harms.
And humanity realized that this planetary boundary was already being
crossed, the ozone was already being depleted unwittingly by us.
This is what's so frightening, we didn't
even know it until some brilliant atmospheric
chemists unveiled the mechanisms by which these chlorofluorocarbons
deranged and destroyed the ozone level. The next
of the planetary boundaries is the heavy human caused
loading of nitrogen and phosphorus. When
farmers grow more food, you'll recall that they put soil
nutrients into the soil as organic fertilizers and as chemical fertilizers.
Either way, incidentally, the nitrogen goes into the soil,
some of it gets taken up by the crops.
But a lot of it runs off the farm into the water, into
the groundwater, and it collects in the rivers, and especially collects
in the estuaries, the point where rivers meet the ocean.
And that heavy pollution of nitrogen and phosphorus coming mainly from fertilizer
use is creating a tremendous amount of ecological destruction.
We'll have a look at that shortly.
The next big challenge of planetary boundaries comes from our overuse
of fresh water resources.
We need fresh water every day to stay alive.
Our crops need fresh water.
Of the total amount of fresh water that humanity uses, about 70%
is used for agriculture, to grow our food. About 20% is for industry.
And about 10% only, interesting enough, is for our household
use, for hygiene and sewerage and, and and the rest.
We use so much water, especially for our food production, that
we are depleting very, very important sources of fresh water.
For example, in the United States, in India, in
China and in other parts of the world, we're drilling
for water in, in ground water aquifers, we
are taking the water out, using it for irrigation.
But taking the water out at a much faster rate than the water is being replenished
by rainfall, and then by the water percolating back into the groundwater.
We're depleting the groundwater. When it runs out, disaster.
And that's happening in many places in the world and will happen in many other
places in the coming decades unless we are much more efficient in our water use.
To grow food to feed our animals of
course, humanity uses a massive amount of land.
We also use land for our cities, for our parking lots, for our streets.
But actually the urban areas, even though they seem to dominate, are
only a few percent of the total land area on the planet.
The farmland and the pastureland and the timberland that we use for forest
products is a much, much larger proportion of the total land area.
And humanity has been grasping over history for more and more
land, more and more pasture land, more and more crop land.
After all, the human population as we know
has increased roughly ten times since the Industrial Revolution.
That requires a lot more farmland to feed the 7.2 billion of us.
The problem with that is that we share
this planet with other species and as we grasp
this land for our farmland, for our pasture land, for our
timber land for our palm oil plantations and many many other uses.
We are literally chasing the other species away
and off the planet into extinction in many cases.
Our land use is having devastating consequences on biodiversity.
The next category identified
is aerosol loading. Small particles put up into the air
because of industrial processes, or households that are burning
coal into keep warm. And creating
tremendous amount of air pollution, very damaging for the lungs.
Claiming many, many lives per year. And with a heavy impact also
on changing climate dynamics.
Then there's a very broad category of chemical pollution.
Our petrol chemical industries, our steel industries, mining
industries, not only demand a tremendous amount of land
and water for their processing, but they add
a tremendous amount of pollutants back into the environment.
Many of these pollutants are persistent, they, they last in the environment, they
accumulate, they can be very deadly for humans, for other species.
And the range of chemical pollutants is so vast and the human and animal and plant
health consequence is so large that it's absolutely
impossible to summarize, except to say that the problems
are horrific in many places.
China, the world champion of economic growth over
the past 30 years, has also become the
champion of polluted waterways of major cities, because
of the extent of the heavy industrial processing.
And this all sums up to a final category of biodiversity loss.
The death, the extinction of other species.
We're killing more animals and plants than we even know, than we've even met
and catalogued scientifically, because we're chopping down
rain forest, poisoning environments, acidifying the oceans.
Creating so much pollution and poisoning. That species are disappearing even before
we're able to identify and catalogue the millions of other species
that share the planet with us and that we share with them.
We are not stewards of global biodiversity right now.
We are posing absolutely profound challenges.
And when it comes to biodiversity loss, one could say
that all of these planetary boundary threats, the acidification, the climate
change, the land use patterns, the pollution, they're all contributing to
the loss of species, probably by the millions.
It's actually hypothesized, shocking as it may seem, that humanity is now causing
the sixth great extinction wave of the planet earth.
The other five, the first, for example, 440 million years ago.
The next one, the second, 365 million years ago and so forth, weren't
caused by any species, weren't caused by human beings, since
we weren't there. These were natural dynamics, whether
it was, asteroid hits or whether it was the
internal dynamics of the earth itself. These were natural processes.
This sixth mega-extinction is not natural.
It is the result of one species, that would be us, causing so much damage
on the planet that we are putting millions and millions of other species at risk.
And, since we depend on those other
species, of course we are putting ourselves
at profound risk.
We are also creating a hugely unstable environment.
My colleague, professor James Hanson, recorded the extreme
heat events on the planet from the 1950s till now shown in this series of maps.
If you look at the map for 1955 and look at the
dark red areas, you see a few places on the planet where
there were heat waves in the June, July, August months of the
year. And when you see those, you see that
they were very particular places such as in, in Canada.
Because of climate change, the number of those red splotches
on the map which signify extreme heat, in that
location, unusual to a massive extent for that
locale, has been increasing in frequency very dramatically.
You look at the map of 1955, just a couple of red regions.
Have a look at the map of 1975, 20 years
later, now there are a few more dark red regions of the map
signifying places where extreme heat waves gripped
those places. But, now jump ahead another 30
years or so to 2006 or 2007,
suddenly the map is all red, it seems. The planet
has been in engulfed by what was an extraordinary shock 30 years
ago becoming common place now. We all know it, we're feeling
our own heat waves wherever we are. And being amazed
year after year as new and very uncomfortable
and often very dangerous records are set in very
high temperatures gripping different parts of the planet each year.
But what these maps are showing is that
the frequency of these extreme events is absolutely shocking.
Well, these are the planetary boundaries that have been identified.
We know that we are already pushing against the limits.
And our question,
in the coming analysis, is how can we think that
that growth that we've been trying to decipher and promote can
be reconciled with environmental sustainability and staying within these
planetary boundaries when we already have so much challenge.
That is our question, as we now delve more deeply into the
intersection of economic growth and planetary boundaries.
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