Sustainability: definition with simple natural science

Hi Alex here. What is sustainability? You must have heard a lot about sustainability and sustainable development over the last few years.

I know I did. And maybe, just maybe, sometimes you were not totally clear as to what people really meant. So here is a definition that my workshop participants have found very clear and useful over the years.

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 does not exactly tell us what to do on Monday morning, it's a very easy definition to understand and to communicate.

There's another one that was created in the late 1980s that is more of a scientific definition. It was created by a Swedish doctor who found that there was a lack of common language around sustainability. So he thought what if we 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, and chemists, etc.

and after 22 draft, they agreed on several things: First they agreed on the fact that we live in the biosphere. The biosphere is this very thin layer at the surface of the earth where life is possible. Proportionally speaking, it is a 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. In return, animals produce fertilizer and CO2 (carbon dioxide) which are used by the plants and we have a cycle that is well balanced.

This is a very quick cycle : we eat every day and we breathe every second, and it works well. Then, they agreed on the fact that this system, the biosphere, is open with respect to energy. This means that energy from the Sun comes in and radiations come out.

This is also known as the first law of thermodynamics. 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".

This is also known as the law of conservation of matter and it means that except for a few satellites and meteorites, the matter that was on Earth four billion years ago is still here today. It has changed form and the molecules have reorganized themselves but it is still the same matter. The other thing that comes with this, is that everything has a tendency to disperse.

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 of 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. Plants have the capacity to use the energy from the Sun in order to produce oxygen and sugar using carbon dioxide and water. Photosynthesis reorganizes matter and creates new structure.

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 very well balanced.

This cycles take millions of years, they are very slow, unlike the previous ones, and they also work well. So this is what the scientific community agreed upon. This is the world we live.

So what is sustainability? Well, it is actually the capacity of our human society to continue indefinitely within these natural cycles. And sustainable development would be a development toward this state of sustainability.

So you may be thinking "well this does not exactly tell us what to do on Monday morning either". That's right but it made it possible for our group of scientists to look at the things that we do to interfere with these natural cycles and they found four root causes of unsustainability. And these are the four things that we need to stop doing to be sustainable.

They are all equally important. They're all necessary and sufficient. The first one is that we extract large flows of materials from the Earth's crust, the lithosphere.

These materials are things like oil, like natural gas, heavy metals, etc. that are rare in the biosphere and that we extract in such large quantities that they accumulate and nature cannot cope. The second one is that we create, in our society, substances that accumulate in nature.

We create chemical compound that nature takes a very long time to break down but we also create substances that already exist in nature, like carbon dioxide for example, but in such large quantities, that they accumulate and nature cannot cope. The third one is that we physically inhibit nature's ability to run the natural cycles. How do we do that?

Well, for example, by chopping trees at a faster rate that they can grow, by systematically destroying ecosystems and replacing them with parking lots, roads, buildings etc. so that nature cannot run its cycles anymore. These are three ecological root causes.

Once again, there is no priority order. The fourth one is social and can actually be the most important of all. We create in our society barriers to people meeting their basic human needs worldwide.

Human needs are very interesting and you can watch our video about them if you are interested. There are things like creativity, identity, participation, and so o,n and so forth. So how do we do that?

Well, for example if you purchase a product that is manufactured in a sweatshop in a developing country, indirectly, you support the business, and indirectly, you contribute to poor working conditions in this factory, and to the fact that these people are unable to meet their basic human needs. So this is the scientific consensus on the four root causes of unsustainability. I hope it helps you understand better what sustainability means and the fundamental reasons why we're not sustainable today.

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