It is sobering to be reminded of the transient nature of nations and empires ("Getting to the future with honour"; June 2).

As Singapore's fate is intertwined with the rest of the world's, perhaps we should consider how our present industrial and technological civilisation might play out.

Energy lies at the heart of our present civilisation, and it has been predicted that society will collapse when we can no longer generate sufficient energy to maintain our complex way of life.

The Industrial Revolution started with the exploitation of the readily available fossil fuel - coal, which the world then harnessed to tap other energy sources such as oil, thus driving further complexity and industrialisation.

But, fossil fuels are limited, and once the world runs out of cheap and readily accessible energy, society will quickly fray; political and economic institutions break down, production and trade wither, global supply chains get disrupted, and technology fails.

Society will fracture, with inevitable conflict as a result.

In the past, the world retained enough technologies and institutions for future generations to build upon and eventually supersede past civilisations.

However, unlike the past, when one civilisation rose to take the place of a fallen one, our globalised world today may find that there are no other external resources, capital or knowledge to fall back on once we run out of energy resources.

Researchers have calculated that if half of our energy comes from renewable sources, we would generate enough energy to maintain our current economies and surmount any energy crisis that may destroy our current system.

We need to build on such sources while we still have the energy capabilities to do so, and that would require investment in renewables 50 times the current level.

With climate change exacerbating energy shortages, we may return to the Dark Ages once society breaks down. Nuclear weapons may wrought such devastation that humans may be unable to recover.

Even if enough humans survive to start over again, all our knowledge and records could be obliterated and key institutions forgotten.

Hopefully, such a doomsday scenario will not materialise. But we should act now to safeguard our energy sources, as well as rein in climate change.

Maria Loh Mun Foong (Ms)