Mellanby versus theory and fact

Edward Goldsmith replies:

I must thank you for taking the trouble to answer my criticisms, nevertheless more criticisms must follow for I do not find your arguments at all convincing.

You say that you have done research yourself and directed further research on the subject of energy and agriculture, pesticides, hedgerows etc, and that the results have been unexpected and, by implication, not in keeping with what one would have expected on the basis of what you call "dogmas" and I refer to as "basic ecological principles".

First of all, I am not at all sure that it is by means of "research", as it is currently understood, that the accuracy of many of your statements can be verified. What sort of research, for instance, is going to tell you that the Australians should not set aside large areas of wilderness unless, as you told them "they have first established that there is a demand for it"? This statement merely expresses your belief in the virtues of the market economy to which, you imply, any ecological considerations should be subordinated - a belief that no amount of scientific research is likely to dispel.

What sort of research can justify your view that burning straw and spraying Paraquat over our crops are justified because they save labour? Again these statements surely reflect your belief that our energy-intensive agricultural system is here to stay, a belief that cannot be confirmed or invalidated by conducting scientific research in a laboratory. It must be examined by considering energy-intensive agriculture in the light of a holistic model of the biosphere, and this would undoubtedly reveal that few of the conditions required to sustain this type of agriculture are likely to obtain in the next decades. With regard to the other statements that I have criticised, research carried out by you that might appear to confirm their validity can be presumed to be wrong, because they conflict

1. with the basic ecological principles that you refer to as "dogmas"
2. with all the mutually consistent empirical evidence that has been acquired over the last few decades on these subjects and which confirm the validity of these principles.

Let us first consider this notion of basic ecological principles which you refer to as "dogmas". (I shall deal with the relativity between diversity and stability at a later date). Are basic physical laws dogmas too? Is the law of gravity a dogma? Is the second law of thermodynamics a dogma? Do you suggest that we should not have any laws and that every situation should be judged entirely on its own merits?

This would certainly create a paradise for scientists. Think of all the experiments that would be required if each one were only regarded as providing information on the specific white mouse it was carried out on, rather than on all white mice and perhaps even on other mammals such as man. Yet this is what you are suggesting.

As knowledge builds up and we learn how things work, it becomes possible to predict behaviour without having to carry out so many experiments and observations. If you put an earthworm in a maze it will take a long time to find its way out, a rat will get out more quickly, a man quicker still. The reason is that as we move from simple to more complex forms of life, learning ability increases and fewer experiments are required for finding out how things work. In fact one can formulate a basic principle or "dogma" to the effect that the number of observations required to understand how something works is inversely proportionate to one's knowledge of it. Otherwise there would be no reason for acquiring any knowledge.

This knowledge, like all information used in nature, is organised hierarchically to constitute a model on the basis of which responses are mediated and monitored. A model is, of necessity, hierarchically organised, being made up of basic principles that are differentiated into less and less basic ones, dealing with increasingly less general and more specific things. The most basic principles tend to be treated as a prioris.

A primitive tribe, for instance, will not question the basic principles underlying its world view which provides it with a model on the basis of which its behaviour is mediated. We do not behave any differently, and the basic principles of the world-view of industrialism, which has been swallowed hook, line and sinker by most of our scientists, are also regarded by us as a prioris - that all considerations must be subordinated to economic ones, for instance.

Epistemologically speaking, no basic principles, not even the law of gravity nor the second law of thermo-dynamics are a prioris. Each is simply the best hypothesis that we can formulated for explaining important observable patterns on this planet. A hypothesis can of course be wrong. Without being wrong, a hypothesis can sometimes be advantageously replaced by another that takes into account certain factors that the previous one did not. In this way, Newton's physics were replaced by Einstein's.

Nevertheless if a single piece of research yields a result that is not in accord with basic principles that have been found to hold good over a long period of time, it must be regarded as exceedingly likely to be wrong. All the more likely, as observations, even in controlled laboratory conditions, are notoriously unreliable.

First of all, as Heraclitus said, "You cannot step into the same river twice", the reason being that it is always changing. So too are the white mice that you study in your laboratory and the conditions in which you examine them. No two experiments can ever be carried out in identical conditions. Nor do experiments on things carried out in isolation from other things, provide very much knowledge about the real world, because things in the real World do not occur in isolation.

That is why the possibility of Minamata disease was not predicted. It was not then known that organic mercury would be changed, by the marine ecosystem, into the terribly toxic di-methyl mercury, because this did not happen in test tubes. The things that you study in your laboratory do not in fact exist outside laboratories any more than do phoenixes and unicorns.

This is one of the basic lessons of ecology. The biosphere is an organisation and as such is not just made up of the sum of its parts. How these parts are organised is equally important and this your laboratory research will never tell you, because it is designed precisely so as to isolate the thing you are studying from all other things with which they are normally interrelated and which are wrongly regarded as irrelevant for the purposes of the study.

What is more scientists often make mistakes. Que Choisir?, the French consumerist magazine, recently provided 32 laboratories with a specimen of human faeces, into which they had introduced various micro-organisms of a kind that are not commonly found in human faeces. Thirty-one of the laboratories failed to identify them and provided totally false analyses.

Scientists also cheat, as was revealed by a series of articles published last year by the New Scientist. Even if they do not falsify the results of experiments, these are often set up in such a way that they will yield the desired results. It was in this way that Dr Dolphin attempted to demonstrate that workers at Windscale had a lower cancer rate than anyone else in the country, in defiance of known principles of cancer induction by low levels of radiation.

What he did was conveniently avoid including in his study, workers who had left Windscale to work elsewhere, who had retired or who had died, (possibly of radiation-induced cancer). The same was true of the famous experiments invariably quoted by Shell Chemicals to demonstrate the harmlessness of DDT. I shall quote Wurster on this subject.

"Several studies of the physiological effects of DDT, Aldrin, Dieldrin and Endrin, have involved human subjects [Jager, 1970; Hayes et al., 1971]. These studies were deficient in experimental design, failed to consider the most relevant parameters and were more concerned with levels of CH storage than with physiological or biochemical effects. They establish only that under current environmental conditions, excluding accidents and suicides, members of the general population are not dying of acute CH insecticide poisoning, nor are they suffering overt toxic symptoms. Long-term, chronic effects were inadequately studied.

"To be more specific, the investigations by Hayes et al. [1971] and those conducted in the Shell laboratories [Jager, 1970] had only men in their samples; women, children, infants and foetuses, were not studied. The small numbers of men involved were completely inadequate to evaluate biological events (such as carcinogenesis or mutagenesis) that may occur once in many thousands of individuals. Periods of exposure were too short to detect biological effects involving induction periods that may be many years or decades. Emphasis was given to reviewing the men's attendance records at work and many of the other simple blood and other routine tests performed were largely irrelevant. When two of 22 men who were being fed high dosages of DDT became severely ill after months on this diet, they were dropped from the experiment and excluded from the data, with the conclusion that 'at no time was there any objective finding to indicate a relationship between illness and DDT storage'. [Hayes et al., 1971]

"It is unlikely that these tests on men could have detected behavioural changes, hepatic enzyme induction, carcinogenesis, mutagenesis or other effects that might be anticipated in man because they occurred in experiments with laboratory animals. The authors concluded, nevertheless, that exposure to these CH insecticides involved no ilI-effects on human health - a conclusion that has been widely quoted by the pesticide industry. It seems remarkable that although hundreds of millions of people have been exposed to these substances for more than two decades, their effects have been so inadequately tested by such primitive studies on such a small number of men!"

The fact is that observation and measurements that conflict with our knowledge of a particular subject are usually wrong, as our everyday behaviour should make clear. If you put a stick into the petrol tank of your car and it reveals it to be empty, and you then get into your car and drive off quite happily for a couple of hundred miles or so, do you assume that your car has learnt to function without petrol? Of course not. You know damned well that the measurement you made was wrong.

In just the same way, if you met a man who tells you that he has built a perpetual motion machine, you know that he is either lying or that he has failed to identify some external form of energy which is in fact responsible for the motion in question. In the same way if a BNFL scientist tells you that the cancer rate is lower at Windscale than anywhere else, and if scientists working for Shell Chemicals tell you that they have carried out experiments that have proved that DDT has no ill effects, you know that they have either made a mistake or their experiments have been wrongly carried out.

The same must be true of your particular research and that of your assistants. If it proves that modern agricultural practices do not cause erosion; that one does not encounter diminishing returns on fertilisers; that soil treated with Paraquat is an ideal habitat for wildlife; that hedges are of no ecological value; that low levels of pesticides are harmless; that we should go on using DDT and that millions of people in the Third World will die of malaria if we do not; and that growing exotic trees and clear-felling them at regular intervals is good conservation practice, then there must clearly he something wrong with it. To prove it right, you would have to reconcile your findings with the following recent theoretical and empirical material.

Why DDT must be bad

There are good, in fact unanswerable theoretical reasons why highly biologically active, synthetic substances such as DDT should not be introduced into our environment. Consider that it has taken several billion years of evolution for the biosphere or world of living things, of which we are an integral part, to take on the shape that industrial man found it in and thereby provide an ideal habitat for man and the myriads of other forms of life that compose it.

During the course of this evolution, as Commoner puts it:

"The chemical, physical and biological properties of the earth's surface gradually achieved a state of dynamic equilibrium, characterised by processes which link together the living and non-living constituents of the environment. Thus were formed the great elementary cycles which govern the movement of carbon, oxygen and nitrogen in the environment, each cycle being elaborately branched to form an intricate fabric of ecological interactions. In this dynamic balance, the chemical capabilities of living things are crucial, for they provide the driving force for the ecological cycles; it is the chemistry of photosynthesis in green plants, for example, which converts the sun's energy to food, fibre and fuel."

In other words the biosphere, or world of living things of which we are an integral part, can function as a self-regulating natural system and maintain its basic structure, on which the very survival of its living components depend, only if the critical interrelationships between all its components - at all levels of organisation, including that of the atom or the molecule - are maintained.

Now to say that the biosphere has a structure means that it displays order, organisation or negative entropy, and that the parts are subject to the influence of the whole, and hence can contribute to overall stability.

Another way of looking at this is to say that constraints limit their range of possible responses. The only situation in which there are no such constraints is that of total disorder, disorganisation or entropy. Thus as the primaeval dust began to organise itself into ever more complex forms, so has there been a corresponding increase in constraints. The evolutionary process can in fact be regarded as the development (or more precisely the accumulation) of constraints.

As Commoner points out

" ... the chemical processes which are mediated by the biochemical system represent an exceedingly small fraction of the reactions that are possible among the chemical constituents of living cells. This principle explains the frequency with which synthetic substances that do not occur in natural biological systems ... turn out to be toxic".

He illustrates this principle thus:

1. Of the approximately 100 chemical elements which occur in the materials of the earth's surface, less than 20 appear to participate in biochemical processes, although some of those which are excluded, such as mercury or lead, can in fact, react quite readily with natural constituents.
2. Although oxygen and nitrogen atoms are common in the organic compounds found in living systems, biochemical constituents which include chemical groupings in which - nitrogen arid oxygen atoms are linked to each other are very rare.
3. Although the numerous organic compounds which occur in bio-chemical systems are readily chlorinated by appropriate artificial reactions and the chloride ion is quite common in these systems, chlorinated derivatives are extremely rare in natural biochemical systems."

It is no coincidence that these chemicals are not found in living tissues. There is good reason for it. The organisation that is the biosphere has been able to evolve at the expense of eliminating possible reactions between these substances and living things. If any living systems once included them, then they have been eliminated by natural selection. As Commoner writes:

"the consistent absence of a chemical constituent from natural biological systems is an extraordinarily meaningful fact. It can be regarded as prima facie evidence that, with a considerable probability, the substance may be incompatible with the successful operation of the elaborately evolved, exceedingly complex network of reactions which constitutes the biochemical systems of living things.

Furthermore, such theoretical considerations are confirmed empirically. Thus mercury is one of those 80 elements not found in living tissue. There is at least one good reason for this - biochemical systems have evolved a system of enzymatic catalysis in which sulphur-containing groups play a crucial role. These react with mercury introduced into a living system and enzymes are inactivated, often with fatal results.

There is also a good reason why synthetic nitroso-compounds in which nitrogen and oxygen atoms are linked do not occur either in living tissue. They appear to interfere with the reactions involved in the orderly development of cells, and often give rise to cancer and mutations. So too, synthetic organochlorine compounds such as DDT and PCBs are excluded from living tissue. They are often very toxic or produce long term damage such as cancer.

In general, the more the environment changes as a result of man's activities, and the less it resembles that in which we evolved, the less efficiently will our normal behavioural mechanisms enable us to adapt to it. Thus, while the human liver is capable of detoxifying those chemicals that it has learnt to detoxify over millions of years of evolution, it is incapable of detoxifying chemicals to which man has not been exposed during this period and which are thereby likely to cause biological damage.

Perhaps, Professor Mellanby, you disagree with these principles? If not how do you explain that your research shows things to be otherwise?

If there are theoretical reasons why DDT and other such substances are harmful, there are also very good empirical ones. The amount of material that points to the biologically damaging effects of DDT is immense and growing the whole time. I cannot review it all here. I shall simply look at recent material - theoretical and empirical, that casts light on those aspects of the use of pesticides that you have stressed in your various statements - and that is relevant to the subject of forestry and conservation.

The effect of sub-lethal levels of pollutants

Since receiving your letter I have obtained copies of many of the papers read at the recent Royal Society meeting on the sub-lethal effects of pollutants on marine organisms. These papers all tend to confirm the increasingly accepted thesis that exposure to low levels of many pollutants over a long period can often be as harmful as high levels over a short period. Let me quote three paragraphs from Waldichuk's paper "The Assessment of Sublethal Effects of Pollutants in the Sea".

"In general, the harm in bio-accumulation of such substances as metals and organo-chlorines is usually associated with consumption of sea food by humans. Levels of mercury at 0.5 ppm and higher in the tissues of organisms that bio-accumulate this metal have not been considered seriously harmful to the organisms themselves. However, some laboratory research demonstrates that this may not be true. When fish containing as little as 0.1 ppm mercury in their muscle tissue, are subjected to a torque in a rotating cylinder, they have greater difficulty in compensating for it than the control fish [Lindahl & Schwanbom 1971]. Cadmium apparently affects calcium metabolism and this has adverse consequences on the otolith and the equilibrating mechanism of fish [Rosenthal & Alderdice 1976].

"Anderson [1971] demonstrated that concentrations as low as 20 ppb of DDT produced a condition response (propellor tail reflex) in trout. His experiments showed that the learnability of fish could be affected by very low concentrations of chlorinated hydrocarbons. This could have rather unfortunate consequences on the ability of fish to return to their home streams, if they were exposed to even low concentrations of DDT during the imprinting period in their juvenile stage. Kleerekoper [1976] has indicated how behavioural responses can be influenced by multiple types of alterations in the aquatic environment with a gradient in metal concentration superimposed on a thermal gradient. Chemo-receptors can be affected in organisms by pollutants and this could be of great significance to fish, not only in homing to their parent streams on a spawning migration, but also in searching for food and possibly in avoiding predators. Equilibrium in fish can be affected by uptake of mercury [Lindahl & Schwanbom 1971] and cadmium [Rosenthal & Alderdice 1976].

"The effect of sublethal stress on organisms may manifest itself in other ways than causing outright reproductive failure. It is known, for example, that some stocks of adult sockeye salmon migrating up the Fraser River must cover a distance of some 500 to 600 miles (900 - 960 kilometres) to the spawning grounds in the Stuart Lakes area near the middle of the province of British Columbia. These fish have a finite amount of energy stored in their system while they migrate (they do not feed at this stage), and it is known that during certain climatically unusual years, some of the migrating fish are unable to overcome natural obstacles on their route and fail to reach their spawning grounds. The question sometimes asked is: 'How many more sockeye would go unspawned if an additional pollutant stress were put in their path in the river or at its seaward approaches?' Ultimately, the sublethal stress has an impact on spawning success and the propagation of that particular stock of sockeye salmon.

"A side-effect that must be taken into account in sublethal stress of pollutants to marine organisms is the impact on the general vigour of the organisms and their ability to ward off predators, parasites and disease. It is known that sockeye smolts infected by parasites succumb to lower concentrations of metals than uninfected fish [Boyce, personal communication]. It is also known that fish exposed to a pollutant stress either become infected by disease more readily than unexposed fish, or may break out with a disease that previously existed only in a latent form. This is an extremely significant facet of pollution in intensive mariculture, where water quality can be an important factor in disease control."

Do you have evidence to show that Waldichuk and the other participants of this symposium are talking nonsense? If so what is this evidence?

DDT & malaria

What research have you carried out to show that DDT is necessary for eradicating malaria? Once more such a notion is irreconcilable with basic theoretical principles, which I went into in "What makes Kenny run?".

As could be expected on the basis of these principles malaria has staged its inevitable comeback. The anopheles mosquito is increasingly resistant to DDT and other pesticides. Malaria keeps coming back into sprayed areas from the ones that have not been recently sprayed. Money and resources are lacking and people have become far more vulnerable to this disease because their natural controls have now been seriously eroded. WHO now admit that "Malaria control is in a state of crisis".

However they have not explicitly stated that the whole enterprise was a fiasco, doomed from the very start, nor have they admitted how many people are today dying from the disease they only recently claimed to have eradicated. Perhaps this would make people look at their projected new campaigns to eradicate smallpox and leprosy in a somewhat unfavourable light. Professor Bruce Chwatt of the London School of Hygiene and Tropical Medicine has recently pointed out (Sunday Times 14 May 1978) how the incidence of malaria is increasing everywhere and how even national governments are reluctant to admit it.

Only 20 cases were reported to WHO from France last year, yet in four Paris hospitals alone there were nearly 1,000 cases. The Soviet Union has made no malaria case returns to WHO since 1972, Bruce Chwatt suggests that they are probably embarrassed by the figure. Nor have the governments of India, Pakistan and Bangladesh admitted that several million people in these countries are now dying of this disease every year.

Nevertheless this is what is happening, and had to happen, because on theoretical grounds alone insect species cannot be eliminated by waging chemical warfare against them. If you have done research in your laboratories which shows that this is a load of nonsense and that DDT will still continue to eradicate malaria I suggest that you communicate the results of this research to WHO as quickly as possible because it may be very valuable in influencing their future policies.

Pesticides and soil organisms

I would also be interested to know what research you have done to justify your claim that Paraquat-treated fields are an ideal habitat for our wildlife. To begin with what do you know about the effects or the sub-lethal effects, of Paraquat on the micro-organisms of the soil? If they destroy our soil organisms, not only is soil fertility certain to decline but also the fields are unlikely to be of much interest to the wildlife that would normally frequent them.

It is true that this important question has been scandalously neglected by researchers, nevertheless what we learn is fairly consistent. In the Proceedings of the 6th International Soil Zoology Colloquium of the International Society of Soil Science - a massive document of over 600 pages - I could only find one relevant paper out of 93. It was written by T. J. Perfect and others and refers to the effects of DDT on soil organisms. As one would expect - on the basis of ecological principles - which you refer to as "dogmas" - DDT spraying, among other things, reduced the number of ants and also changed species dominance.

Species of the genus Pheidole for instance, accounted for 37 per cent of the total ants trapped in untreated plots and only 2 per cent in treated ones. Earthworm behaviour was also affected by DDT, cast production being reduced to a very low level. Micro-arthropod populations also fell. Oribatid and prostigmatid mite populations were halved, the population of the Mesostigmata was actually reduced to 2.5 per cent of the level in unsprayed plots. Since the latter are important in regulating the population of collembolans the population of the latter considerably increased.

Recently it was reported in the New Scientist that studies conducted by M. A. Wright of Long Ashton Research Station, near Bristol, have shown that spraying with three benzimidazoles systemic fungicides caused very high mortality among earthworms.

"A soil drench, equivalent to run-off from a tree spray in an orchard of 1.5 kg per hectare, killed 60 to 70 percent of the exposed worms within 14 days. Similarly, leaves bearing a dose of 0.8 per sq. cm of benomyl inhibited worm feeding and double that prevented feeding completely."

This has been tentatively attributed to the fact that benzimidazoles interfere with mitosis and cause chromosomal damage.

In Wilhelm Kuhnelt's volume on Soil Biology, re-edited by Faber and Faber in 1976, there is again a surprising lack of material on the effect of pesticides on micro-organisms. This question is dealt with in one section of five pages. Nevertheless the conclusion is fairly explicit:

"A review of pesticides in the soil presupposes some concern about their indirect consequences on soil morphology and nutrient cycling above and beyond the possibility of obvious animal food contamination. The abundant arthropod forms are most directly affected by persistent chlorinated hydrocarbons, although the cyclodienes (heptachlor and chlordane in particular) and some carbamates are highly toxic to earthworms. Effects on the latter can cause pronounced changes in soil morphology. Soil micro-arthropods, in particular the Collembola and Acari, in combination with Enchytraeids and nematodes, have an important role in stimulating and/or inhibiting microbial activity, mycostasis and bacteriostasis. Since soil is a fabric of living and nonliving components, consequences of pesticide use may affect not only soil formation but also its physical and nutritional properties. The latter may be altered both positively and negatively by killing predators of saprophagous arthropods, or by reducing populations of the latter; thus permitting nutrients to remain bound up in detritus.

"The more subtle pesticide-induced ecosystem perturbations are poorly understood, and this may be a consequence of investigator preoccupation with readily measurable parameters. On the other hand, attempts to anticipate the effects on nutrient cycling, through litter decomposition studies [Crossley and Witkamp 1964, Barret 1968]; correlating ground beetle increase with species-selective Collembola mortality [Griffiths et al. 1967]; measuring long-terrn population studies following carbaryl treatment [Stegeman 1964] observations on soil bulk density and retardation of plant growth coupled with decrease in soil moisture absorption following isobenzan treatment [Kelsey and Arlidge 1968]; and correlation of sequential mortality effects with vertical penetration of the toxicant [Karg 1962] suggest that more subtle ecosystem changes are amenable to investigation."

Quite clearly we do not know enough about the effect of pesticides on soil-organisms to justify your views and what we do know unquestionably tends to invalidate them.

This is only one aspect of the problem. Before an ecologist can recommend the systematic spraying of our crops with a dangerous xenobiotic substance such as Paraquat, he must also know its effects on the different life processes of complex forms of life which in the long run are probably more vulnerable to it than are micro-organisms.

What research has been carried out on this? What do you know of the effects, in particular the sub-lethal effects, of Paraquat and of its decay products when used in combination with the countless other chemical substances that find their way into our soil? I think I can answer this myself. The answer is practically nothing. Your statement is purely gratuitous as are many of the statements that you are in the habit of making with so much authority.

Australian Forestry Commission as the best conservationist

I would like to know what research you have done which justifies your view that the Australian Forestry Commission is the best conservationists? Do you have the gall to tell us that replacing native trees that have been adapted by millions of years of evolution to the particular soil, climatic and general ecological conditions of the area, by exotic pines that have been adapted to growing in totally different conditions, is ecologically justifiable?

Yet this is what the Australian Forestry Commission is doing. If your researchers can show that it is, then you are being very anti-social in keeping this evidence to yourself. Such evidence in any case will be in conflict with all the other available evidence on the effect of growing exotic conifers on soil structures.

We published an excellent article on this very subject entitled "Conifer Plantations and soil Deterioration" by John Pelisek (The Ecologist November 1975) to which I refer you. The conclusions of Pelisek are entirely confirmed in Noirfelise's article "Aspects of Forest Management" published in the Council of Europe Nature and Environment Series, No. 1. Pelisek is a lecturer in the Faculty of Forestry at the Brno Institute of Pedology and Geology, Czechoslovakia. Noirfelise is Professor in the State Faculty for Agronomic Sciences, Gembloux, Belgium. I shall quote the relevant passages from Noirfelise's article:

"It is a well-established fact that the replacement of deciduous trees by conifers causes a profound change in the bio-coenosis of the soil. After a short while there is a notable fall in the number of earthworms whose incessant toil is a natural form of ploughing; they undermine the soil, enrich it in humus, break it up and ventilate it. Earthworms, which are very finicky eaters, have great difficulty in dealing with conifer needles, which are generally hard, waxy and rich in resin. Investigations by Ronde carried out in the Bavarian forests, have shown that there is a very sharp fall in the number of earth-worms under conifers with evergreen leaves, particularly pine and picea.

"This biological regression applies, however, not only to earthworms. It also affects the microfauna which live beneath the litter, break it down, digest it and prepare it for attack by microbes. The bacteria themselves which take part in the final phases of humification and release the nitrogen from the organic compounds also decrease by as much as 99 per cent under picea.

"The slowing-down of biological activities results in the accumulation on the ground surface of a thick layer of litter which is very slow to decompose. In this organic mass, which is three to five times as thick under conifers as under deciduous trees, large quantities of nutritive elements are immobilised, particularly nitrogen. It has been calculated that replacing beech by picea and oak by pine results in a loss of about 200 kg of nitrogen, 140 kg of phosphoric acid and 95 kg of potassium per hectare in the nutritive cycle of the forest, i.e. the equivalent of heavy agricultural fertilising.

"It is easy to understand the effect of this phenomenon in infertile forest soils. It results in impoverishment of the soil whose nutritive capital can only be reconstituted when the whole of the litter has totally decomposed after cutting down the existing trees. The immobilisation of the nitrogen and phosphorous explain in particular, certain mishaps in conifer-growing such as late recovery after replanting and the delay in the growth of subsequent plantations of pine or picea, or again, the failure of natural seeding of types of tree which produce large quantities of seed. As one specialist in forest pedology, Professor Duchaufour, put it so vividly, seedlings and young plantations suffer from 'nitrogen hunger'.

"The phenomenon of immobilisation is doubtless only an apparent impoverishment of the soil and not a true form of degradation. It may be compensated by application of fertilisers, although this is still not a very widespread practice because of the cost and the unreliability of results. Nevertheless the intensive growing of conifers can only continue provided fertilising is carried out and also provided no other setbacks are encountered.

"The changes induced by conifers do not, unfortunately, stop at this stage. In some circumstances they may bring about an insidious degradation of the soil, a process we are only beginning to understand.

"Because of its high content in lignine and resin, conifer forest litter is mainly attacked by mushrooms which proliferate on them. The activity of mushrooms results in the production of a layer of black humus ('mor'); the humic acids contained in it and carried off by rain are capable of podzolising the underlying layer of soil.

"Podzolisation is a slow destruction of clays which reduces their power to retain and exchange nutritive elements and releases iron and aluminium ions. The former can fix phosphorus and make it inaccessible for plants, the latter have toxic effects upon roots. These processes begin beneath the layer of black humus and advance in depth at a rate depending upon the nature of the soil. Sandy, acid soils or sandy silts are apparently highly susceptible: the growing of conifers over less than two centuries can podzolise such soils to a depth of 20 to 30 cm; it is also frequently noted that on such soil there is a drop in productivity from the second plantation onwards."

Pelisek refers to research by Meyer in Saxony, which shows that in an area where spruce monocultures were introduced in the middle of the last century, the annual increment of tree growth has steadily fallen until by 1929 it was less than half what it formerly was.

As could be predicted on the basis of theoretical considerations, growing exotic conifers in areas to which they are not adapted is non-sustainable as it must lead to serious soil deterioration. The other Forestry Commission practice of clear-felling is equally indefensible since it also leads among other things, to soil erosion which could be largely avoided if, instead, trees were thinned at regular intervals, as is being done more and more in Alsace for instance. A considerable amount of theoretical and empirical evidence is available on this subject.

Once more I would like to see the research you have done to show that this is all nonsense.

References

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Chwatt, Bruce (1978).	Sunday Times, 14 May 1978.
Crossley D. A. & Witkamp M. (1964).	The 8th International Congress on Soil Science, Bucharest, Romania.
Commoner, Barry.	Foreword to Samuel S. Epstein and Richard D. Grundy, Vol. 1 of the Legislation of Product Safety. MIT Press 1974.
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Kelsey J. M. & Arlidge E. Z. (1968).	"Effects of isobenzan on soil fauna and soil structure", New Zealand Journal of Agricultural Research 11: pp.245-59.
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Lindahl P. E. and Schwanbom, E. (1971).	"Rotary-flow technique as a means of detecting sublethal poisoning in fish populations", Oikos Vol. 22, pp.354-357.
Noirfelise A.	Council of Europe, Nature and Environment Series No. 1 "Aspects of Forest Management".
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