Terra infirma

March 1, 1996

A royal commission has just concluded that we do not know much about the ground beneath our feet. Kam Patel unearths some disturbing facts about soil, and three experts explain why its degradation can no longer be ignored

Leonardo da Vinci reputedly complained that more was known about the movement of celestial bodies than about the soil under our feet. Since his day, scientists have hugely advanced our understanding of the complex processes governing soil. But the Royal Commission on Environmental Pollution, which reported yesterday, contends that there is still much more to discover.

The result of a two-year effort to draw together information from experts, the report paints a bleak picture of the health of the world's soil and the challenges that face governments in ensuring its continued use. Land worldwide is being damaged by people. Deforestation, overgrazing and poor agricultural management are the main stress factors as people struggle to meet the food requirements of a rapidly increasing world population. The 1994 population summit in Cairo suggested that by 2050 the number of people in the world could be in the region of 7.9 billion to 11.9 billion. Even the lower figure would mean a tripling of the population within a century.

The commission, chaired by the atmospheric physicist, Sir John Houghton, reports that the amount of land worldwide that has been spoilt by human activities - almost 20 million square kilometres - exceeds total farmland by around five million square kilometres. Moderate to severe erosion has damaged four fifths of the world's agricultural land.

An even more serious problem in the future may be shortages of water. "Future climate change is expected to exacerbate both problems through general warming and the more vigorous hydrological cycle this will produce," says the commission, which goes on to warn that "droughts and floods are likely to increase in frequency and intensity."

Farmland makes up around 11 per cent of the world's land. This could rise to 25 per cent if land suitable for farming but not currently being used for agriculture was brought into the picture. But in North Africa and parts of Asia where the population is already growing at an alarming rate, almost all available farmland is being used. One gloomy piece of evidence to the commission suggested that "if the loss of cultivated soils as a result of degradation continues at its present rate, reserves of agriculturally usable land will probably become scarce at the global level by 2015".

Even in the United Kingdom, which has soil that is fairly fertile because of its relatively young age, the commission acknowledges that there are worries about intensive farming and the exposure of rivers to contamination because of the massive increase in the use of fertilisers over the past 50 years.

The spread of cities and towns is also placing the UK's countryside under pressure. Nearly 10 per cent of Britain and 13 per cent of England is urban or suburban. The UK population is expected to stabilise at around 62 million by 2030 and the demand for houses is projected to rise by 14 per cent between 1992 and 2012. This will create a need for some three million new dwellings in England alone. The report says that if the average rate of transfer of land to urban use between 1945 and 1990 were to continue for the next 100 years, it would result in a doubling of the urban area of England and reduce the areas of land cultivated or used for pasture by as much as a sixth. This would represent a "significant reduction" in the UK's capacity to produce food.

In considering how such risks might be reduced, the commission strongly urges that more should be done to boost the recycling of land. A major obstacle to this is the presence of derelict or contaminated land with the attendant financial and even psychological implications of cleaning up and building on such areas. As well as recommending financial and regulatory measures to allow the market in contaminated land redevelopment to work more effectively, the report suggests that more attention should be paid to ways of making better use of micro-organisms to remove soil pollution.

One of the report's major recommendations is that the Government should have a policy on soil of equal importance to those already drawn up for water and air. In order to support such a policy scientists need to fill in the "considerable gaps" in our knowledge of geochemical cycles such as those of carbon and nitrogen and their relationship to the activities of micro-organisms in the soil.

The Royal Commission on Environmental Pollution report "Sustainable Use of Soil" was published yesterday.

John Lawton

Soil is one of the last great frontiers for biologists. A teaspoon-full of ordinary garden soil contains millions of micro-organisms, particularly bacteria, fungi and protozoa, together with hundreds of small animals with vaguely familiar names - nematode worms, mites etc.

The amazing thing is that fewer than 10 per cent of the bacteria can be identified and given a scientific name; indeed, it is only relatively recently that biologists have realised that many of these bugs are there at all. Soil fungi are also scarcely known taxonomically; the small animals rather better so, but by no means perfectly. There is, literally, an unexplored world beneath our feet.

Does it matter? Yes. Until biologists can identify and name species, we cannot study them properly, because it is impossible for different laboratories to study common problems unless they can be sure that the same organisms are involved. From this first concern follows the second - we have only the haziest notion what all these organisms do in soil; we cannot predict what would happen if they were not there. What part do they play in maintaining healthy soil, cleaning up pollutants, making vital nutrients available for plant growth, or in producing "greenhouse gases" that may contribute to global climate change? We know that some species, such as earthworms, are very important. But we are profoundly ignorant about what role most of the others play.

The commission's report draws attention to this gaping hole in biological knowledge. Better understanding would, among other things, help us to restore polluted soils. The world's soils hold a vast amount of carbon; global climate change will certainly lead to changes in this pool of carbon, with the potential either to make climate change worse (by increasing the production of greenhouse gases from soil) or better (by increasing carbon storage in soil). But we cannot at present predict which way the pendulum will swing, not least because we know so little about the organisms involved.

John Lawton is professor of community ecology, Imperial College of Science, Technology and Medicine, and director of the Natural Environment Research Council centre for population biology.

J. Gareth Morris

As a microbiologist, I find it somewhat shaming to have to concede that we know far too little about the micro-organisms that are the basis of any soil's natural fertility. John Lawton does well to remind us that relatively few of these microbes have been isolated and cultured.

Over 60 years ago the Russian soil microbiologist S. Winogradsky emphasised the importance of "making a special point of studying the reactions of the soil population as a whole, since the competition between its components is the principal determinant of their individual functions". The complexity of such heterogeneous ecosystems has frustrated generations of investigators. Yet this situation could now change with the availability of novel techniques of specific biomolecular tagging, which enable microbial populations to be analysed, and changes therein to be monitored, even when the majority of their component organisms remain uncharacterised.

The commission identifies the desirability of including biological measures of soil quality in future national soil survey data. Two questions arise: are there reliable microbial indicators of soil quality? Is it true that microbial diversity lies at the heart of the "good health" of a fertile soil and its resilience to abuse?

Microbiologists should be able to provide crucial advice in these areas.

J. Gareth Morris is professor of microbiology at the Institute of biological sciences, University of Wales, Aberystwyth.

Richard Macrory

The underlying message of the report is that soil is the forgotten environmental resource. Its own research found only one piece of UK legislation with the term soil in the title, the Agricultural Land (Removal of Surface Soil) Act 1953. This creates a criminal offence of stripping soil without planning permission, but it is doubtful whether it has ever been properly enforced. One explanation for this is the perception that pollutants in soil are unlikely to migrate to the same extent as they might do in air and water. Hence, perhaps, the EU's reluctance to develop soil protection legislation. Yet it is clear that soil is as essential to life as the other basic media.

The commission concludes that UK agricultural soil is in reasonably good state. But research on the global state of soils reveals a depressing picture with worse to come. Once built over, soil is essentially nonrenewable. Considering this, we are concerned at the continuing rate of greenfield development. It is true that the rate of urbanisation has declined since the peak periods of the 1960s, but it continues at a rate of at least 5,000 hectares a year, and with the latest housing projections, pressure will increase all the more. On an annual basis, the figures may not appear too significant, but extrapolated over 50 years, the rate of what is essentially irreversible soil destruction becomes significant.

Planning controls provide the main legal bulwark against such development, but they do not provide absolute protection, and we are not convinced that the true environmental value of soil is as significant a factor as it should be.

This led the commission to consider the extent to which existing laws on derelict and contaminated land really helped to secure development there in preference to greenfield sites. We are not convinced that policies which, to date, have relied on the market are sufficient to attract developers. Developing more environmentally friendly policies will cost public money. Whether the Government is prepared to make such an investment ultimately depends on the value it prepared to give soil as a national resource.

Richard Macrory is a member of the royal commission and professor of environmental law at Imperial College.

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