If the Earth's entire population midway through the next century were to live as we in Britain do today, humanity would need about seven extra planets. Eight earths could provide our natural resources quickly enough, along with the capacity to assimilate all our wastes and pollution without critical environmental degradation.
So, says the book commissioned by Friends of the Earth UK, we need to make drastic cutbacks by 2050 - to allow others in poorer, developing countries their fair share of planetary resources and to bring already stressed life-support systems back within safety margins.
As well as an 88 per cent cut in the United Kingdom's fossil fuel use, we ought to use 73 per cent less timber, 15 per cent less water, and cut our consumption of aluminium, steel and cement by more than 70 per cent. We should halve our use of rock, sand and gravel by 2050 and eliminate the chlorine we use, mostly in the chemicals and plastics industry.
``Imagine a city enclosed in an enormous, impenetrable transparent dome,'' the book says. ``It would not be long before the accumulation of wastes and depletion of resources within it made life intolerable, or impossible. The entire planet is within such a `glass bubble' - there is a growing realisation that increasing population and increasing consumption are pushing at the limits of what Earth can take.''
Signs of abuse and stress are already visible around the world as water shortages, loss of soil fertility, dwindling fish stocks and rising temperatures caused by a build-up of greenhouse gases. In the next century, the threats will be much greater.
A quarter century ago, it was thought humanity would soon run out of basic, non-renewable resources like oil and metals due to the rapid growth in population and industrialisation. Now the dangers are seen as overwhelming nature's ability to absorb pollution, and using renewable resources like wood at a rate far beyond what can be sustained.
The authors estimated what the global consumption limits should be for key resources. Next they allocated Britain a share based purely on the size of its population and not its relative wealth. Then they calculated how much the UK would have to cut its consumption from current levels, and propose how that might be done.
The limits they came up with are mostly extremely rough and ready, because the science and economics of calculating just what punishment the earth can take are in their early infancy. Much depends on what degree of despoliation is regarded as tolerable, and what techniques are used to exploit natural resources.
Water is the only resource they treat as purely national - all the others can and are freely traded around the world. The book proposes a 15 per cent cut in the total quantity the water companies take, easing the strain on rivers and wetlands and giving some safety margin against declines in rainfall caused by man-made climate change.
The book accepts bringing about these changes will mean huge changes in attitudes, business and in government in Britain and internationally. A start must be made now. But, in the real world, it seems most likely that we will carry on with business as usual.
Tomorrow's World, by Duncan McLaren, Simon Bullock and Nusrat Yousuf, published by Earthscan; pounds 12.95.Reuse content