Is there a definition that would be easy to understand and that we could

all agree upon? Well let's get drawing!

Sustainability. Sustainable development.

You must have heard these words a lot over the last number of years.

Well, at least I did. And maybe just maybe

sometimes you were not totally clear as to what people really meant.

So you may be familiar with the Brundtland definition

which is quite common: sustainable development

is development that meets the needs of the present without compromising the

ability of future generations

to meet their own needs. Although this doesn't exactly tell us what to do on

Monday morning

it's a very easy definition to understand and to communicate.

There's another one, one that was created in the late

nineteen eighties that is more of a scientific definition

it was created by a Swedish doctor his name is Karl-Henrick Robèrt

and he was frustrated with the lack

of common language around sustainability so he thought

what if he managed to get a group of scientists together

and to agree on what sustainability means

based on science and thermodynamics and maybe

that will lead to understanding what the root causes of

unsustainability are. So that's what he did

he put together a group of 50 scientists: mathematicians, physicists,

chemists, etc.

and after 22 drafts they agreed on several things.

First they agreed on the fact that we live in the biosphere

so the biosphere is this very thin layer

at the surface of the earth where life is possible

proportionally speaking it's as

thin and fragile as the skin on an onion. And within this biosphere

there are plants and animals. Plants produce

oxygen and food which are consumed by the animals

and in return the animals produce fertilizer

and CO2 (carbon dioxide) which

are used by the plants and we have a cycle that is well balanced.

So this is a very quick cycle

we eat every day and we breath every second and it works very well

Then they agreed on the fact that this system,

the biosphere, is open with respect to energy

So this means that energy

from the Sun comes in and radiations come out

And they also agreed on the fact that this system

is closed with respect to matter so

maybe you remember this very famous phrase from Lavoisier that says

nothing is created, nothing disappears, everything is only transformed.

So this is also known as the first law of thermodynamics

the law of conservation of matter and

it means that except for a few satellites and meteorites

all the matter that was on earth

4 billion years ago is still here today

it has changed form and the molecules

reorganized themselves over time but

it is still the same matter and the other thing that comes with this

is that everything has a tendency to disperse

So for example take an iPhone

and wait for a million years, it's very likely that you will get a pile of dust.

Take a pile of dust and wait for a million years

you will never get an iPhone. It works only in one direction.

This is also known as the second law of thermodynamics,

the law entropy. So

if everything disperses all the time, how is it possible

that we live here in such a beautiful world

with beautiful nature, cities, people,

flowers and so on. Well this is what

photosynthesis does for us. Photosynthesis

pays the bills. It enables plants

to use the energy from the Sun in order to reorganize

matter and create new structure. So the group of scientists

also agreed on the fact that there are other cycles,

very slow geological cycles, that bring matter

from the lithosphere, that we also call the earth's crust,

to the biosphere and these cycles

are also very well balanced: some matter

moves from the earth's crust to the biosphere

through things like volcano eruptions and weathering.

And just about the same amount of matter goes back from the biosphere to the

earth's crust

via things like mineralization and sedimentation

and all this is well balanced. These cycles take millions of years

they're very slow unlike the previous ones and

they also work very well. So this is what the scientific community agreed upon

so this is the world we live in and

so we can ask a question what is sustainability? Well

sustainability is actually the capacity of

our human society to continue indefinitely within these natural cycles

and sustainable development would be

a development towards this state of sustainability. So you may be thinking well

this does not exactly tell us what to do on Monday morning either.

Well that's right but it enabled the group of scientists

to look at the things that we do to interfere with these natural cycles

and they found 4 root causes of

unsustainability and these are the 4 things

that we need to stop doing to be sustainable

And that will be the next video. Before moving to the next one, here are the key

points to keep in mind: all the matter that was on earth

four billion years ago is still here today there is no "away"

everything has a tendency to disperse and lose its structure over time

photosynthesis pays the bills it

uses the energy from the Sun to reorganize matter

left to their own devices natural cycles

are well-balanced and sustainability

is the capacity of our human society to continue indefinitely within

the natural cycles. So I hope this is helpful.

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