According to most economists – the west is in decline, the eurozone is in crisis and even emerging powerhouse countries like China and India have witnessed a slowdown in economic growth. With that in mind, a new phrase is starting to emerge in the vocabulary of some horizon scanners. That phrase is ‘peak GDP’.

All of us have heard of peak oil but in a stirring, if somewhat ideological, hypothesis the American documentary film-maker Dave Gardner suggests that humanity’s endless pursuit of economic growth and population growth is doomed. It could lead to peak food, peak water, peak biodiversity, peak energy and even peak gross domestic product – he argues.

It would be easy to throw anti-capitalist accusations at the GrowthBusters director and some would say his green stance has a definite red tinge, in terms of the socialist politics that could be said to inform his views. His points about our planet’s finite resources, though, are worth considering. “It seems quite logical to think that humanity cannot increase our population and economy forever if we are limited to planet earth as our life-support system,” says Gardner.

“Economist Kenneth Boulding described it rather articulately in 1966 when he wrote of the ‘spaceman’ economy. We can no more expect the earth to support 12 billion people – or seven billion living like millionaires – than we could expect one of today’s spacecraft to provide bunks, food, oxygen and water for 500 crewmembers.

“If we can understand this at the small scale of a spaceship, why is it that we cannot comprehend it on a global level? Growth optimists assure us the scale of the human enterprise on earth is not limited by natural resource supplies. This is based on a belief system rationalised by the observation that we have managed to ‘innovate’ our way around resource limits during 200 years of unprecedented growth.

“It is difficult, if not impossible, to change this kind of faith with words of logic – or even facts. Once we conclude our current values and practices are unsustainable or no longer delivering good lives, we are faced with the question of what should replace them.”

Certainly a great deal of common sense in that statement. But difficulties arise when you try to come up with an alternative to capitalism and consumerism. Communism failed miserably. As did neoliberalism. The compromise ‘Third Way’, writ large in social democracy, also died with a whimper. As a result, we find ourselves in the current economic malaise that today makes watching the evening news the most depressing of affairs – even for us story-seeking journalists.

Gardner does not offer a detailed prescription for the way forward. However, he has an idea of where to start the process of change. “A necessary first step is to alter the fundamental value or belief that underpins our civilisation’s policies and practices,” he says. “That is a crucial and will unlock a treasure trove of possibilities. We must move from a fundamental belief in the wondrous powers and possibilities of endless growth, to an understanding that we live in a spaceman economy.

“We need to believe in the wonders of nature, including its beauty but also its necessity, its fragility, and – most importantly – its limits. We must replace our emphasis on quantity with a focus on quality, give up more and embrace enough, jettison competition and value collaboration. Once we take that step, we turn the key and open the door to a world of possibilities.

“We will unleash creative minds to contemplate, experiment and try new ideas and models for practices, policies and systems that can allow our civilisation to live within its means on earth.” The message is a tough one to take. And he could be wrong, technological innovation may yet save us all by unlocking extra resources or multiplying those that already exist. Then again, he could be right. For now, we should at least start a public debate on these, the defining issues, of our lifetime.

Dean Carroll is editor of Policy Review