More people, higher expectations and dwindling food stocks all add up to a disaster we will be unable to ignore. Martin Ince reports

Global warming has caused a worldwide argument between the merely rich and poor worlds and between energy producers and consumers: the hole in the ozone layer has changed nothing but the product mix of the world chemical industry. But if Lester Brown is right, we are finally approaching the crunch that will convince everyone we have to do something about the world ecological crisis.

According to Brown, who is director of the Worldwatch Institute in Washington DC, the signs that we will not be able to ignore will be apparent in the supermarket queues of the developed world, the marketplaces of the south, and the commodities pages of the newspapers. The cause will be a collision between rising population, rising standards of living, falling acreages of agricultural land, peaking world fish catches and dwindling food stocks.

While the Worldwatch Institute's agenda covers everything from energy policy to green taxation, Brown's own interest in food supplies is central to its concerns. He was brought up on a farm in southern New Jersey and as a young man had his own tomato-growing business before deciding to work in United States agricultural aid projects in the third world and later founding Worldwatch. Now it gives him pleasure that the agricultural industry is paying attention to the message. In Europe this month to launch the 1996 edition of State of the World, Worldwatch's annual tome on the earth's environmental problems, he presented his key findings to the board of Norsk Hydro, the world's biggest fertiliser manufacturer, one of a number of key audiences he wants to reach in addition to the politicians and pressure groups he frequently addresses.

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The key to Brown's argument is in food stocks and food prices. In 1989, world "carryover stocks" of grain, the amount in stock as the harvest began to be collected, reached a high of over 100 days of consumption. This year the figure will be 49 days, the lowest on record. In 1973, the carryover went down to 55 days, the lowest previous record, and grain prices doubled. In 1995, prices for wheat, corn and rice went up by a third. This feeds into the costs of everything made from them, ranging from beer to eggs.

As Brown sees it, high food prices and food scarcity "could become the defining issue of the new era", replacing the ideological conflict of the cold war.

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The problem in part is that the increase in world population - by 450 million since 1990 - is not being matched by increases in grain production. The amount of cropland used for grain production fell from 732 million hectares to 669 million between 1981 and 1995 because of the abandonment of badly eroded land in the US and the former Soviet Union and the loss of farmland to industry, mainly in Asia. Elsewhere, set-aside schemes have cut into production and, if Brown is right, are likely to be reversed. In the European Union, setaside land could feed about 8 million people.

This problem is worsened, says Brown, by the falling use of fertiliser, which is admittedly due in part to its overuse in the former USSR, and the declining availability of water, one of the key inputs to all forms of agriculture. In Beijing, the water table has fallen by 45m: in the US, the Ogallala aquifer, which underlies the key farm areas of the midwest, is also falling, and in many countries once-proud rivers like the Colorado and the Yellow River sometimes fail to reach the sea because of water extraction for industry and agriculture.

The problems of growing food pressure are added to, Brown thinks, by global warming, which seems likely to be a contributor to the recent run of very hot summers. The effect of high temperatures during peak growing periods in areas such as the US midwest is to cut the productivity of crops like wheat and especially corn.

The economic effects of the end of the cheap food era are likely to be stark, and unpleasant for millions. But they could also be unexpected. The most interesting could be a change in the terms of trade between city and country. Cities import water and some, such as Beijing and Los Angeles, depend on mass pumping to remain viable. Cities can usually outbid farmers for water because of their denser economic activity. But as food prices rise, farming could become more lucrative, and the historic trend to leave the land could be reduced.

This collision between city and country is another trend, Brown thinks, in a world that is already changing too fast for the coping mechanisms of its people and institutions. "Nobody really knows what adding 50 million people a year to the earth's population means," he says, although he adds on an optimistic note that about 12 per cent of the world's population lives in countries that have achieved population stability (such as the UK). His favourite example is Japan, which had a strongly pronatalist population policy until after the second world war when it was abandoned as part of coping with postwar development. Its population growth fell by half between 1949 and 1956. Even Iran, the heart of militant Islam, has cut population growth by reducing tax breaks for larger families. "They are now closer to doubling than tripling population, which was where they were headed before," says Brown. He is less convinced about the Chinese one-child policy. "A one-child norm cannot be voluntary," he says, pointing out that the Chinese population has grown by 500 million. It might be preferable to have a less draconian policy. But in any country, the rules of compound interest mean that the earlier a rational population policy gets started, the better the results and the easier they are to obtain.

As perilous as the growing numbers of people are their growing expectations. As Brown points out in State of the World, the world economy grew by $4 trillion between 1985 and 1995. That is about the size of the world economy in 1950, so as much economic activity was added in that decade as in the millennia to that time.

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This economic activity is reflected, Brown points out, in record demands for pretty well everything - paper and wood, minerals and fossil fuels as well as food - and by the emergence of new areas of demand, especially in east Asia. He points out that the Chinese economy grew by 57 per cent between 1991 and 1995 and China has swung from exporting eight million tonnes of grain in 1994 to importing 16 million last year, a shift blamed in the markets for much of the enhanced demand for grain.

This increased economic activity is reflected in strongly increased world trade which, Brown says, brings very direct perils of its own. Twenty-three major new infectious diseases, of which HIV is but the best-known, have appeared since 1970. Others include Lyme disease, transmitted from deer to people, and the Ebola virus. Increased international travel makes it simpler for these diseases to get at populations that have no resistance to them, as new forms of flu have long spread from China.

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Related to this trend is the increasing spread of existing plant and animal species beyond their previous range, emboldened by global warming and enabled by the increasing flow of ships, trucks and aircraft to facilitate the journey. Historical examples range from the dull English sparrow to rats, wild oats and the Rinderpest virus. The sparrow has displaced native birds as far afield as Australia and south America, as well as eating crops. Rats, too, displace other animals and eat crops, but also carry disease. The Rinderpest virus started in India but has become a dangerous cattle pest in Africa. Wild oats, claims Brown's colleague Chris Bright, have spread in many cereal-growing areas reducing output by enough to feed 50 million people.

Current "bioinvasions" include less well-known examples such as the Zebra mussel, which started out in the Caspian and is driving out other species as well as fouling boats and pipes, the Asian tiger mosquito, which may carry a range of human diseases, and shrubs and grasses that are colonising forests and grasslands.

However, Brown insists that there are many plus points in the current world outlook. Spreading population stability is one; the growth of wind power is another, and indeed he says that energy in general is becoming less of a concern. It is possible that a renewable energy-based economy can emerge that will solve the big problems of oil prices and global warming. Also cheering to Brown is the way in which bicycle use is continuing to grow in towns and cities, along with public transport. In Japan and other countries, bike parking at stations and other forms of transport integration promise more rational approaches to transport problems. Even more useful, he thinks, is the emergence of the world recycling economy. The Chicago Board of Trade, one of the big world commodities exchanges, now has a futures contract in steel scrap, while minimills that use electric arc furnaces to make fresh steel from scrap have 35 per cent of the US market. Minimills are small and are fed by local collection systems. There has also been strong growth in paper recycling, where new technology and higher prices have added to its attractions.

At some point, Brown thinks, even the economic and political institutions that find it hardest to adjust to this new world will start to do so by force majeure. An example is the insurance industry. At one time, Worldwatch did large amounts of research on the possible economic effects of global warming. Now it has cut back because insurance companies, alarmed by increased storm damage and flood claims, are doing their own better-resourced work on the same subject. The "destabilising climate change" that could result from more forest destruction, says Brown, could persuade other commercial organisations to take global warming more seriously.

Despite these grace notes, the world Brown anticipates is one in which big food shortages and price rises will leave many people with too little to eat. He is the first to agree that the shock of food shortage will affect some people far more directly than others. But perhaps there is an up side: all those newspaper stories about the EU paying millions to farmers not to produce food may soon be a thing of the past.

State of the World 1996, edited by Lester Brown et al, is published by Earthscan Publications at Pounds 12.95. It appears in languages and in almost every country in the world.

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