Our civilisation is powered by machines that use energy, mostly from oil and coal - fossil fuels laid down by biological activity in the distant past. Until recently that energy has been cheap, especially during the period of the last 60 years when oil rather than coal has been the main source of energy.

Oil is made in the earth at a very slow rate. If we used it at the rate it is made our skies would be clear and the air would be breathable, even in cities (which might be small).

Sheikh Zaki Yamani the former oil minister of Saudi Arabia predicted that there would be an oil crisis in the mid 1990s as several large sources of non-Arab oil become exhausted. (But perhaps he was wrong, as oil prices in 1994 were lower than in 1972). However, by 2005 they had risen considerably. Have we reached the time of Peak Oil?

But every other source of minerals which are taken into industry, turned into consumer goods and then dumped is finite. It would be wise not to remain dependent on these.

There will always be doubt as to the exact amount of resources available. There can be no doubt that they are finite.

One measure of the impact of the world population is the quantity of resources per person. At present it is said that 2% of the world's population - in the United States - uses 25% of the world's oil production. The least that can be said about this is that this is an unstable situation. Many of those not using the resources will tend to see it as unfair. Modern electronic communications make it likely that they will become aware of it. What they will do about it, if anything, remains to be seen. The Iraq-Kuwait war may be the first act of a struggle among increasing numbers of people for decreasing quantities of resources. The aftermath of this first Iraq war showed that Iraq had been actively developing nuclear weapons and already possessed the "poor man's nuclear weapon": poison gas. If the poor countries decide to force the west to pay attention to their needs they may develop means to do so. Already gas has been used by terrorists several times in Japan.

By 2005 we can see that a huge acceleration in the rate of use of oil by the rapid economic expansion of China and India is putting existing oil extraction and refining under pressure.

Does the market system automatically respond to signals of future scarcity? Probably not. Human intelligence is needed for that and non-market actions may be needed.

Some traditional societies believe that the land does not belong to us but to the ancestors and the descendants and that it is our duty to hand it on in as good condition as we received it. One formulation is that "It is only borrowed from our children" .

The most successful and long lasting human cultures are those which have lived on income from solar energy rather than capital.

Modern economies are dependent on oil and minerals which cannot be renewed. Our grandchildren won't need to argue about oil pollution. How many will there be of them?

If renewables are not in use to replace oil, coal and minerals when they run out, our civilization will go the way of Tyre and Nineveh, Greece and Rome. The future ought to belong to wind, solar, tidal, wave energy and such materials as wood, plastic from starch and so on. If these are developed now they can take over. If not, the picture we should have of the future is not pleasant.

Recent low prices of oil may have provoked a feeling of false optimism, replaced by the sudden rise of oil prices in 2004-5 and the spike of 2008. A low price of oil is likely to inhibit solar research and other developments which would reduce the effects of the fundamental problem.

Clearly, we need large scale investment in energy sources that do not use oil or coal. The European Union already has plans for building large solar thermal plants in North Africa, to be connected to Europe by a new electricity grid that would link North Africa in the south to Norway and Iceland in the north. Other large scale sources would be tidal and wave machines off the coasts of Britain and Ireland. Outside Europe there is scope for huge amounts of power from solar, Ocean Thermal, and several other technologies. But there is a need to start the large scale engineering needed. So far, the rather timid response has been to create a "market" in carbon - something that will probably benefit only the Financial Traders who are so keen to see it start. This is the Milton Friedman approach. There is no sign that it will have any effect on the physical generation of energy, or result in anything like the serious amounts of energy investment needed. A large scale OTEC and Solar project in Australia would be a good start.

Iceland would also be a useful source of energy that does not emit carbon, using its geothermal and hydro energy.