Mellanby versus theory and fact

“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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U. Lohm and T. Persoon (eds) (1976-77). Schutzdienstes, 21: 167-75 Berlin 1971, Acari (parasitiformes). Dahl, Die Tierwelt Deutschlands, 59: 1-512. –>

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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.
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