Setting aside whether global GDP itself can continue growing indefinitely, the growing volumes of materials used each year present significant threats to natural systems.

These threats arise from extraction of resources and the pollution created during production and after goods become wastes. Human ecological footprint analysis has found that our global economy is 1.7 times larger than our natural systems can support long-term.

Climate change is an example of where natural systems cannot remediate pollution as quickly as we create it.

While economic growth is a national priority in nearly all countries, some leading economists have foreseen that eventually the size of economies would need to level off.

Economic pioneer John Stuart Mill wrote that wealth could not increase indefinitely and that eventually a steady state would be reached. He actually thought that this would be a desirable development.

John Maynard Keynes also anticipated the possibility of a steady state economy as a desirable state of abundance in which more socially-just policies could be given priority. More recently, the leading proponent of a steady state economy has been Hermann Daly.

A steady state economy has a stable size or fluctuates slightly over time. Critically, a steady state economy operates within ecological limits.

To achieve this, population and per capita consumption would also be roughly constant, although temporary decreases in one would allow increases in the other. More efficient use of resources to minimise wastes, along the lines of a circular economy, would enable higher levels of consumption while staying within ecological limits.

To stay within ecological limits, renewable resources such as timber would only be harvested at the rates they can regenerate, and without damaging other ecological values. Non-renewable resources, such as minerals, would be harvested no faster than renewable substitutes can be developed.

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