Hamish McRae: Habits build a better planet

Whatever emerges from the Earth Summit in Johannesburg, the fact that there is a summit at all will focus attention on the environment. The coming weeks will be filled with reports, demonstrations, communiqués, speeches and angst. But if it is extremely welcome that the world should focus on the damage that humankind is doing to the planet, there is a danger that the background noise will drown out whatever signals ought to be heard.

So what should the concerned outsider look for? We as individuals are not going to make a profound impact on the future of our planet or our species. But it would be nice to try to figure out what is happening, if only to know where to aim off when either side of the great environmental divide propounds its views. Here goes.

The debate splits into four interconnected areas: energy; climate change; food and water; and bio-diversity. They are connected because the use of fossil fuels is leading to climate change, which in turn puts pressure on food and water supplies and threatens bio-diversity.

The world will not run out of fossil fuels in any of our lifetimes. Though there is only about 45 years of proven oil reserves at present consumption levels, gas reserves are much larger and there is enough coal for several hundred years. There are, however, several reasons for concern.

One that is currently enormously important is that an overwhelmingly large proportion of the proven reserves are in the politically unstable Middle East, as the pie chart shows. Gas reserves are more broadly distributed, with the former Soviet Union having broadly comparable reserves to the Middle East. And of course more oil and gas will be discovered. Still, there is an obvious political concern.

Next there is the longer-term worry that, even allowing for new discoveries, oil production will tail off in the next generation. The world has been successful in finding new oil in the past 20 years (see bar chart) but most of the growth in proven reserves has again been in the Middle East. We are discovering more oil where we know there is a lot already; we have not been discovering vast new virgin fields.

Many of the "new" fields of the 1970s have already become mature. The UK's sector of the North Sea is now in decline, and it looks as though we will again become a net importer around 2007. US production is similarly in decline and, while there are promising fields in offshore areas, overall production will continue to fall.

Of course there are areas of the world where as-yet-undiscovered oil exists: for example, parts of Siberia and the Falklands basin. But from oil exports the impression I get is that there is nothing like another Middle East in prospect.

The world peak in oil production may be another 10 years away, and with gas production, currently shooting up, the peak may be 15 or 20 years off. But demand for both oil and gas is also rising. Note how limited the alternative sources of energy are when compared with oil and gas.

That leads to what is surely the greatest concern of all: the relationship between fossil fuel use and climate change. Don't blame the floods in Europe on changing weather patterns. That looks much more like a random event and there is certainly a huge random element in the world's climate. Nevertheless there is a general agreement in the scientific community that the present cycle of global warming is associated with the growing use of fossil fuels. There are long but unknown time lags between fossil fuel use, global warming and climate change more generally. Quite a lot of further climate change is, so to speak, in the pipeline.

Not all climate change is bad. Some 2,000 years ago North Africa enjoyed an unusually wet period and became the breadbasket for the Roman Empire. Over the past 30 years the Sahara has been unusually dry, even by more recent standards, and the desert has been advancing by a few miles each year. On the other hand, a warmer climate in, for example, southern England will enable it to increase output and grow Mediterranean crops. And while the area of the world covered by forests has been declining, the slight increase in temperatures has encouraged trees to put on more leaf cover, so the actual amount of forest may not be falling as fast as some surveys suggest. Nevertheless it is hard to adapt to rapid climate change and what is happening is very rapid by historical standards. That puts pressure on food supplies.

Providing there is enough fresh water the world can feed itself. Something like two-thirds of the additional food the world has grown over the past 30 years has come from irrigated land. But there is great pressure on water supplies, and ill-designed irrigation schemes have done dreadful damage to what could otherwise be valuable farmland. The most publicised environmental catastrophe of this nature has been the shrinking of the Aral Sea, the result of Soviet state direction that the region should grow cotton. But two generations earlier the creation of the Oklahoma dustbowl shows that the market system can create disasters too.

The obvious danger is that climate change will interact with ill-conceived irrigation schemes and large parts of the world will be hard pressed to feed itself.

Of the final concern, the threat to bio-diversity, economists find it hard to put numbers on that – how do you put a price on the survival of the Sumatra rhino? What we do know is that we are likely to lose several large mammal species and that the world will be a poorer place if our only memory of them is through nature films.

Johannesburg matters, not because summits fix things – they may make them worse – but because they make us think. And thinking leads to those small changes in habit that cumulatively could make a huge shift in the way we treat our planet.