Sustainable development has been defined in various ways over the years, perhaps most famously by the World Commission on Environment and Development report in 1987, Our Common Future, which defined it as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” This points to both the needs of people, and the limits that the environment and society may impose on those needs. Great stuff… for the academics. So someone coined the rather folksy ‘three-legged stool’ model of sustainability that suggests sustainable development is about achieving a balance between environment, social needs, and economic growth. Do this, and the future will be golden.

But of course, it isn’t. The three-legged stool model is fundamentally flawed in suggesting the environment, society and economics are in any way equal. To explain, let’s consider a different analogy.

The Sustainability Stack

On the top of this model we have the Economy. It’s at the top not because it’s the most important, but because this simply does not exist without a society underpinning it. When social order collapses, the economy goes with it. And human society, in turn, exists within an environment which provides food, water and air. Take those fundamentals away, and everyone either leaves, or dies. And for this tower to remain stable, it needs to sit on a stable platform of governance.

So, what happens when we start to chip away at parts of the tower in the pursuit of a dollar? At first, nothing much. You can take away some equality and representation here, some health and safety there but, pretty soon, you have unrest on your hands.
Similarly, the more environmental services are compromised, the shakier society gets, either through straight up reduced life (air pollution kills 5.5 million people a year), or through civil unrest: nearly all protests in China in recent years have been related to pollution, which has been estimated to cost some 9% of GDP.

And, of course, if governance is poor, nothing can work well: environmental infractions won’t be punished, social services will be poor, and corruption rife. Governance is a critical element of sustainability, with its own Sustainable Development Goal, yet it is overlooked by the three-legged stool model and sustainability assessment methodologies.

In Pursuit of a Dollar

Unlike the three-legged stool model, the Stack model clearly shows the physical relationship between the four ‘pillars’ of sustainability and how the current global economic model gives undue preference to money (which has been shown to have a non-linear relationship to happiness). This is not to say that we should not develop or pursue economic returns but to do it in such a way that the blocks we take out are replaced.

This is challenging, it is true. But we are engineers, we are problem solvers and we have to be up to the task of solving the greatest problem of all.

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This concept was developed by me and first presented in 2017 at the Big 5 International Building & Construction Show, Sustainability Talks, in Dubai, in a talk titled Challenges in Sustainability. Quoted figures were correct at the time.

The Sustainability Stack