Ecological succession rehabilitated

An important principle of ecology is that ecosystems develop in a series of stages which must all occur in the right order - a process referred to as 'succession' which continues until a 'climax' is reached - a situation from which there is then little change, as it is the most stable one achievable in the circumstances.

The idea is an old one. In the 18th century, naturalists observed the process of succession in Scandinavian bogs. As Worster writes.

"water-loving hydrophytes would settle a pond and, by trapping mud with their roots, would eventually modify the environment to one more suited to mesophytes, or even xerophytes. The pond or lake would become a bog and then dry land covered by a dense forest." [1]

The principle of succession was clearly formulated by Warming. He considered that it proceeded in a definite direction - towards a climax formation or final community. This notion Warming regarded as central to the new discipline of ecology.

Later (1899) H. C. Cowles made his pioneer studies of succession of plants on the sand dunes of Lake Michigan, while V. E. Shelford studied succession among animal populations. Both studies showed that as the dunes became older, so were the species of plants and animals inhabiting them completely replaced by different species.

Succession was regarded by Frederick Clements as fundamental to the developing science of ecology. Nature, he considered, did not move aimlessly but as a steady flow toward stability. In a specific environment, a clear progression could be plotted by the scientist through what Clements called a "sere" that begins in the pioneering stages with an unbalanced and relatively unstable assemblage and ends with a complex and stable equilibrium community, one that is capable of sustaining itself indefinitely.

Clements accentuated the role of climate in determining the nature of the sere and also established the principle that in any given habitat the sere could only end in a single climax (monoclimax). He was later to be seriously attacked on both these counts.

As Worster notes, Clement's theory of succession and the climax undoubtedly reflected his

"underlying, almost metaphysical faith that the development of vegetation must resemble the growth process of an individual plant or animal organism." [2]

This view is unacceptable to modern science and hence to modern scientific ecology on a number of counts:

• Firstly, it tends to confirm the unacceptable idea that an ecosystem is a "superorganism" as Clements maintained, or at least that it resembles an organism in a significant way.
• Secondly, it implies that the development of an ecosystem is not the result of random changes selected by an undefined environmental 'invisible hand' in accordance with their competitive skills (as all life processes tend to be viewed today) but occurs instead according to an orderly strategy.
• Thirdly, it implies that this strategy is carefully co-ordinated by the ecosystem. This means that ecological development is at once teleological and holistic - a nightmarish thought for our scientists and hence for our scientific ecologists who are ideologically committed to a random and atomised world.

It is unacceptable for yet another closely associated reason, which is that it implies that the goal of ecological development is the achievement of stability, whereas our modern industrial society is committed to perpetual change in a single direction, which can only occur by reversing the successional process or sere, or by artificially maintaining the ecosystem at its most productive pioneering stage, which happens to be, ecologically, the least advanced - the stage most marked by discontinuities such as floods, droughts, epidemics, population explosions and wars.

To accept the principle of ecological succession to a climax is thus to accept the destructive nature of economic development which, from the ecological point of view, rather than being identified with 'progress' must, on the contrary, be classified as 'regress'.

It was mainly - though perhaps subconsciously - for these reasons that ecologists imbued with the paradigm of modernism, eventually came to reject Clement's thesis. Clements may have gone too far - for instance, climate is clearly not the only factor in determining the nature of a climax - nevertheless, his basic thesis is obviously correct.

Gleason, not surprisingly, was one of the first to reject it. In 1910 he wrote:

"it is impossible to state whether there is one definite climax association in each province: it seems probable that there are several such associations, each characteristic of a limited portion." [3]

And in 1927 he said

" ... succession is an extraordinarily mobile phenomenon whose processes are not to be stated as fixed laws, but only as general principles of exceedingly broad nature, and whose results need not, and frequently do not, ensue in any definitely predictable way." [4]

Succession, in this way, ceased to be a directive process tending towards a definite goal. Gleason tended to regard it, instead, as a random process just as he regarded the association as a random arrangement of individuals. "In the centre of an association", he wrote, "we see only the fluctuations in structure from year to year." [5] He even suggested that succession might be retrogressive.

Controversy over the dustbowl

The whole question came to a head during the debate over the great dustbowl in the late 1930s. Ecologists, at the time, showed that the crisis was a man-made one. Ploughing the southern plains, which should clearly never have been done, caused them to divert from their climax state and the dustbowl was the consequence. During the debate that followed, the very notion of a 'climax' came under attack. Tansley, the Oxford ecologist, was particularly keen to discredit the concept. He insisted that man, with his great ingenuity, was capable of creating his own climax, an "anthropogenic climax" as he called it, which was superior to the natural variety.

Tansley's motive was clear. To quote Worster, he

"did not want to accept any climax achieved by purely natural processes as an ideal for man to respect and follow. His concern was not to re-establish man as a part of nature, but to put down the threat to the legitimacy of human empire, posed by the natural climax theory. If Tansley was right and there were no meaningful differences between the balance achieved by nature and that contrived by man - if the two systems were at least equals in quality and performance - then what reasonable objection could there be to man's rule over the biological community, or to the further extension of his empire? The effect of Tansley's proposal, in other words, would be to remove ecology as a scientific check on man's aggrandising growth. The Clement's stand of the climatic climax must be replaced, he was saying, by a kind of environmental relativism: there would then be no exterior model against which the artificial environment could be evaluated scientifically. The yardstick would be tossed away, and man would again be free to design his own world." [6]

Clement's climax was also attacked very bitterly by the agricultural historian James Malin in 1956. According to Worster, it was the latter's purpose over a number of decades, to defend the battered reputation of the farmers "against the 'Evangelical conservationists' ". Malin insisted:

"No more brazen falsehood was ever perpetrated upon a more gullible public, than the allegation that the dust storms of the 1930s were caused by the 'plough that broke the plains'." [7]

On the contrary, large-scale mechanised agriculture was a step forward. The Plains had benefited from it, nature needed to be ploughed up, and

"blowing dirt around was necessary for it to remain vigorous and fertile." [8]

Frederick Clements was the bogey man. His writings provided the rationale for the "hysterical" conspiracy against progress. It had to be totally discredited. In 1953 Malin wrote,

"The conventional or traditional concept of the state of nature must be abandoned - the mythical, idealised condition, in which natural forces, biological and physical, were supposed to exist in a state of virtual equilibrium, undisturbed by man." [9]

This in fact is what scientific ecologists have since succeeded in doing.

Malin succeeded in persuading himself that dust storms were:

"natural phenomena of the great plains, they are part of the economy of nature and are not in themselves necessarily abnormal, at least, not in the sense in which the subject was exploited during the drought decade of the 1930s." [10]

It is easy to see what motivated Malin to write such nonsense. As Worster put it:

"Like Tansley in England, Malin was unhappy with what seemed, in ecology, to be a prejudice against civilisation: a belief that 'only civilised man was evil' and that he had no moral right to alter the natural order. The preservationist's oft-repeated charge of 'rape' for what modern man had done to the grassland especially enraged him, in part because it implied that nature is more than a mere thing, that it has personal character, that it is female and vulnerable. Nor would he accept any distinction between the environmental impact of the Indian and of the White man." [11]

Neither James Malin, nor his associate Carl Sauer, even bothered to disguise their motives. The idea of the climax, they asserted, "assumes the end of change" - which they had been clearly taught to see as providing a panacea to every possible problem. [12]

The position of modern scientific ecologists

Ironically, it is the anti-ecological ideas of Gleason, Tansley and Malin that have come to be regarded as the ecological orthodoxy. This is clear from the writings of Ricklefs:

"In recent years, the concept of the climax as an organism or unit, has been greatly modified to the point of outright rejection by many ecologists, with the recognition of communities as open systems whose composition varies continuously over environmental gradients." [13]

It is also clear from the writings of Simberloff:

"The deterministic path of succession, in the strictest Clementsian monoclimax formulation, is as much an ideal abstraction as is a Newtonian particle trajectory. There is a tidiness, an ease of conceptualisation, to well-defined ideals moving on perfect paths, that is as appealing, both aesthetically and functionally, in ecology as it was in genetics and evolution. Unfortunately, it is as poor a description of ecological, as of evolutionary reality." [14]

It is equally clear from the writings of Whittaker:

"The more closely vegetational dynamics are observed, the less clear-cut becomes the distinction between climax and successional communities. Vegetation does not really consist of climaxes and successions leading toward them. In a long-range perspective, the vegetation of the earth's surface is in incessant flux; what we observe in the field are not simply successions and climaxes, but only different kinds and degrees of vegetational stability and instability, different kinds and rates of population change." [15]

Elsewhere, he makes the same points somewhat differently:

"If one seeks to view this complexity in perspective in terms of species populations in space and successional and evolutionary change and without the intervention of man's ecological abstractions, then the view of the forest is not one of clear and orderly associations, successions and phylogeny. It is one of a veritable shimmer of populations in space and time." [16]

It is also clear from the writings of Pickett:

"The classical interpretation of succession as development of vegetation through discreet stages culminating in a regional climax... has been abandoned by modern ecologists." [17]

Though he has the grace to admit that "no ecological complete, contemporary model has replaced it."

In line with current scientific dogma, ecological succession tends to be explained today in terms of competition and in terms too of the properties of populations rather than of whole ecosystems. This is pointed out by Connell and Slayter for instance, [18] and also by Pickett. [19] It is also the view of Putnam and Wratten. Pioneering species, the latter tell us, are replaced

"not just because the environment does not suit them but because they are poor competitors and competition is more intense in climax ecosystems." [20]

It is difficult to see how they can really believe this. The operation of all sorts of internally generated negative-feedback mechanisms which Odum even refers to as "environmental hormones" [21] and which inhibit the growth of species that are replaced by other species in the succession towards a climax, is clearly visible to all but the most prejudiced eye.

Ricklefs alludes to the operation of such a mechanism when describing the process of succession on abandoned farmland in the Piedmont region of North Carolina. He describes how "Decaying horseweed roots stunt the growth of horseweed seedlings" and how "this self-inhibiting effect, whose function and origin is not understood, cuts short the life of horseweed in the sere".

Such growth inhibitors presumably are the by-product of other adaptations that increase the fitness of horseweed during the first year of succession:

"If horseweed plants had little chance of persisting during the second year, owing to invasion of the sere by superior competitors, self-inhibition would have little negative selective value." [22]

Putnam and Wratten also refuse to see the development of an ecosystem and the achievement of a climax as the result of a long-term strategy; indeed not even in terms of any of the intrinsic features of a developing ecosystem.

If ecosystem development is not in this way an orderly strategy, then the climax cannot be its logical outcome; instead it must be seen as 'thrust upon' the system from the outside. For this reason they suggest that we abandon the use of the term climax altogether and use instead the term "end community". [23]

How then does their version of succession occur? Putnam and Wratten offer but the most simplistic answers - the only ones, as one might have guessed, that can be quantified and modelled by systems ecologists, the only ones reconcilable too with the simplistic view of life adopted by modern science today.

What they actually suggest is that succession is simply the result of "an accumulation of biomass" which stops when there is no opportunity to accumulate any further biomass, because the process has in fact come up against gross features of the environment that are immutable - physical barriers - a shortage of resources for further growth. Alternatively they see it in purely energetic terms as

"an imbalance within the energy relations of the community resulting in the accumulation of biomass by the community." [24]

Both these explanations are based on the notion that the behaviour of an ecosystem is random, mechanistic, individualistic and hence uncoordinated, and also passive and externally controlled, as indeed must be all life processes if they are to be fitted, Procrustean-like, into the paradigm of modernism.

Putnam and Wratten then reveal their ideological bias still more clearly. Productivity, they tell us, is often low in a climax by comparison to that of earlier stages in the succession "due to the complexity of web-design, cycling of materials through the system is extremely slow." [25]

Such features of a climax have traditionally been regarded as beneficial. But Putnam and Wratten wonder if they really are. [26] They point out that there are "many examples of far more productive, indeed far more diverse communities characteristic of earlier, pre-climax seral(sic) stages." They then ask whether a climax is in fact "tantamount to over-maturity?" [27]

The argument assumes that productivity is the yardstick for judging ecosystems. This also was the argument of Tansley and Malin - of those, if we remember, who opposed the application of any constraints on man's ecologically destructive activities. It is the ultimate irony that those who advance it should call themselves 'ecologists'.

A non-biological explanation

But Putnam and Wratten, in line with other modern ecologists, go still further in their efforts to rationalise their ideological commitment to technological progress. They tell us that a biological explanation of succession towards a climax may not be necessary at all. All we are witnessing, they suggest, is an example of a "statistical process known as a 'regular Markov chain' ". [28]

A Markov chain, they tell us, is a "stochastic process in which characteristic probabilities depend only on a current state and not any previous state". As it develops it eventually settles into a pattern "in which various states occur more or less with characteristic frequency, that are independent of initial states".

It is argued that this final "stationary distribution" of states is the analogue of the climax community and that climaxes must occur by the statistical certainties that the Markov process always settles into a stable pattern. It is further suggested that

"the different climax communities imply different probabilities of transition among the states, rather than different initial communities, thus convergence too, is a necessary statistical artefact". [29]

Putnam and Wratten cite various researchers who have shown the "close fit" between Markovian processes and succession. The most "sophisticated" we are told is Horn, who insists that

"general properties of succession are direct statistical consequences of a species-by-species replacement process, and have no uniquely biological basis." [30]

Horn further tells us that

"the process of succession must stabilise by statistical necessity in a 'climax state' - the fact that different pioneer communities may converge to the same climax could also arise merely as a statistical necessity." [31]

What is more, if a community is temporarily disturbed, something like the original community returns. This too is a function of Markovian processes. Finally Markovian development, like succession, is characterised by rapid changes followed by undetectably slow changes. This means that stability, in the naive sense of "absence of change" increases "tautologically" as succession proceeds. What is important is that "none of these characteristics", as Putnam and Wratten insist, is "necessarily of biological origin". They then magnanimously admit that this

"does not mean that there is no biological reality about succession; it does however, suggest that many of its characteristics are not necessarily biologically determined".

Thus if there is an imbalance between community production and community respiration, with its resultant accumulation of biomass providing the driving force, (one of their original explanations of succession), for them the community will undergo a directional successional change as a statistical necessity.

They then tell us the biological systems are not in themselves the explanation for the process:

"The biological explanation we have presented for the mechanism of the process may prove no more than observation of how the statistical necessity is accommodated."

They then suggest that the idea of succession as a stochastic Markovian process, perhaps explains why climax seres (succession) are not always the ideal community they are supposed to be: why climax states often appear overmature, (in that they do not maximise productivity). [32]

The whole argument is an example of a fallacy we can best refer to as 'mathematical realism'. Children often think that because a word exists there must be something in the real world to correspond to the word, a notion known as 'nominal realism'. Piaget gives many examples of this. Thus he cites a child who says that "pigs are rightly named because they are so dirty", and that "the sun is rightly named because it is so hot."

Oxford linguistic philosophers are, in the same manner, guilty of what might be called, 'linguistic realism' - of assuming that there must be some intrinsic and universal wisdom in the structure of the English language, (in this case) which casts light on the workings of the biosphere, which in reality, it only represents, crudely at that, for conversational purposes.

Putnam and Wratten, like Horn and other scientific ecologists, are in fact, committing the same error. They suppose that because someone has developed a mathematical model which simulates, in a rudimentary manner, some aspects of the real world, then it must be capable of simulating, in a sophisticated manner, all aspects of the real world.

It is of course astonishing that the Markov chain can imitate, however crudely, any aspects at all of such real-world processes as succession to a climax. That one must thereby be able to derive other, apparently scientifically acceptable information about succession from the behaviour of a Markov chain is absurd; just as absurd as to suppose that because a puppet can be made to resemble a policeman, an examination of the cotton wool with which it is stuffed will enable you to understand a policeman's digestive system or the circulation of his blood.

What they are proposing is, in fact, little more than a modern form of divination - one that, because the diviners are actually scientists, performing their scientific rituals on scientifically consecrated premises, enjoys credibility among the naive and the gullible.

Eugene Odum's view of succession

Eugene Odum's view of succession reflects his very different ideological commitment. In his latest textbook, he quotes Clemerec 's description of a secondary succession of benthic animals off the coast of Brittany.

"After storms caused a redistribution of sediments and disruptions of bottom fauna, a period of relative calm followed. During this period, in the absence of outside interference a more or less directional and predictable sequence of populations established dominance. First were bivalve suspension feeders, then bivalve deposit feeders, and finally the benthos became dominated by polychaete worm detritus feeders, thus confirming the theory that uninterrupted succession converts an inorganic environment to a more organic one." [34]

In this example, the main features of succession are illustrated: its sequential or successional nature, the "more or less directional and predictable sequence of populations", its ability to correct diversions from its optimum course (Waddington's chreod) that which will lead to the requisite climax, and its achievement of an increasingly sophisticated and stable state as it reaches its climax, thereby converting "an inorganic environment to a more organic one". Odum states explicitly that he regards ecosystem development as resulting from

"(i) modification of the physical environment by the community acting as a whole and (ii) the interaction of competition and coexistence between component populations."

He regards Clements' main thesis, "that ecological succession is a developmental process and not just a succession of species each acting alone", as "one of the most important unifying theories in ecology." [35] In an earlier textbook, he is still more explicit. Succession, he tells us is

1. "The orderly process of community changes: these are directional and, therefore, predictable.
2. It results from the modification of the physical environment by the community.
3. It culminates in the establishment of as stable an ecosystem as is biologically possible on the site in question."

He also points out that ecological succession "is community controlled" and insists that

"each set of organisms changes the physical substrate and the microclimate (local conditions of temperature, light, etc.), thereby making conditions favourable for another set of organisms ... when the site has been modified as much as it can be by biological processes, a steady state develops - at least in theory." [36]

In the same book, he accentuates the similarity between the development of an organism and that of an ecosystem. He also asks us to think of the

"temporary communities as developmental stages analogous to the life-history stages through which many organisms pass before reaching adulthood."

At the same time, he notes that

"the mature community with its greater diversity, larger organic structure and balanced energy flows is often able to buffer the physical environment to a greater extent than the young community, which, however, is often the more productive. Thus, the achievement of a measure of stability or homeostasis, rather than a mere increase in productivity, in a fluctuating physical environment, may well be the primary purpose (that is, the survival value) of ecological succession when viewed from the evolutionary standpoint." [37]

It is unlikely that any other ecologist today would dare state this unfashionable principle quite so explicitly - yet if it is not faced, there is no way in which the behaviour of an ecologist can be understood.

The Climax as the adult state

I think that many of the controversies on ecological theory would be cleared up if it were accepted that ecosystems, in fact, grow as Clements always maintained, just like any other natural system until they reach their climax which must unquestionably be regarded as a state of adulthood.

The 'isomorphism' or rather 'isotelism' may be still closer. Thus it has often been argued that, like an organism and indeed like any other natural system, an ecosystem can also age. In his textbook Ecology, Odum suggests biological changes may be occurring, which, in the individual, we would call ageing. Thus, young trees may not be quite replacing the old ones as they die, or regeneration of nutrients may be lagging and the whole metabolism thus slowing down.

"There are few data at present, but one wonders if communities may not suffer gradual ageing after reaching maturity, just as do individual organisms." [38]

A useful approach is to view the main features of ecosystems such as diversity, complexity, stability etc. in their correct successional context. As Loucks points out,

"there have been few opportunities to date, to view diversity and its associated ideas - stability and productivity - as time-based functions, potentially dependent on the stage of development of the native communities." [39]

The associated changes involved

There is no doubt that as a system moves towards its climax i.e. becomes more mature, so do changes occur to all the variables in terms of which it can be described. These are not just random changes, but are all on the contrary, closely associated and all equally necessary for the ecosystem to fulfil its changing role as it nears maturity.

Margaleff describes that constellation of changes in the following way.

"Structure, in general, becomes more complex, more rich, as time passes; structure is linked to history. For a quantitative measure of structure it seems convenient to select a name that suggests this historical character, for instance, maturity. In general, we may speak of a more complex ecosystem as a more mature ecosystem. The term maturity suggests a trend, and moreover maintains a contact with the traditional dynamic approach in the study of natural communities, which has always been a source of inspiration.

"Maturity, then, is a quality that increases with time in any undisturbed ecosystem. Field ecologists use many criteria to estimate the maturity of an ecosystem, without the need of assessing its precise place in an actual succession. Empirical knowledge of succession leads one to consider as more mature the ecosystems that are more complex; that is, composed of a great number of elements, with long food chains, and with relations between species well defined or more specialised. Strictly stenophagous animals, parasites, all sorts of very precise symbiotic or defensive relations, are commoner in mature ecosystems. Furthermore, situations are more predictable, the average life of individuals is longer, the number of produced offspring lower, and internal organisation of ecosystem turns random disturbances into quasi-regular rhythms." [40]

Eugene Odum considers these changes in still greater detail in his seminal paper The Strategy of Ecosystem Development. In it he lists 24 different changes that occur as succession proceeds, under 6 different general headings. He notes, for instance, that the rate of primary production as a proportion of the rate of respiration falls, until eventually, in a mature ecosystem, they equal each other and the ecosystem ceases to grow any more.

At the same time, he notes, food chains which started off by being 'linear' become web-like, more complex and with detritus providing an increasingly important source of nutrients. For example,

"In a mature forest, less than 10 percent of annual net production is consumed (that is, grazed) in the living state: most is utilised as dead matter (detritus) through delayed and complex pathways involving as yet little understood animal-micro-organism interactions." [41]

The total organic content of an ecosystem also increases as succession proceeds. Also, inorganic nutrients, which were originally derived from outside the ecosystem, slowly become intra-biotic in that they are constantly recycled within it. Species diversity, as well as biochemical diversity increases and their organisation improves. Species become increasingly specialised and organisms become larger; life cycles longer and more complex. He notes too how mineral cycles, which were once open became closed:

"Mature systems, as compared to developing ones, have a greater capacity to entrap and hold nutrients for cycling within the system. For example, Bormann and Likens have estimated that only 8 kilograms per hectare out of a total pool of exchangeable calcium of 365 kilograms per hectare is lost per year in a stream outflow from a Northern Temperate watershed covered with a mature forest. Of this, about 3 kilograms per hectare is replaced by rainfall, leaving only 5 kilograms to be obtained from weathering of the underlying rocks in order for the system to maintain mineral balance." [42]

In addition, the nutrient cycle rate within the ecosystem becomes much slower since the process involved becomes more highly differentiated. Odum shows how the survival rate improves as organisms are better equipped for individual survival and parental care (increased K-selection replaces R-selection) which means that reproduction does not aim at maximising the quantity of offspring but rather their quality or sophistication.

Odum notes how Clements ascribed the increasing stability of successional stages in a sere to an increasingly tight organisation and to the integration of community components. The development of internal symbiosis i.e. increased co-operation or mutualism between the parts of the ecosystem he takes as being an essential aspect in this integration. Among other things, it clearly increases the ability of an ecosystem to conserve nutrients.

Stabilising mechanisms

In his Basic Ecology Odum shows how this increasing stability is achieved by the operation of "homeostatic mechanisms, which we may define as checks and balances (or forces and counter-forces) that dampen oscillations." This, he maintains, "operate all along the line", and hence not only at the level of the individual where for instance they "keep body temperature ... fairly constant despite fluctuations in the environment." [43]

They are also operative at the level of the population, the community and the ecosystem. Odum notes how

"we take for granted that the carbon dioxide content of the air remains constant, without realising, perhaps, that it is the integration of organisms and environment that maintains the steady conditions despite the large volumes of gases that continually enter and leave the air." [44]

Significantly, James Lovelock describes, in his celebrated book Gaia, a New Look at Life on Earth how similar stabilising mechanisms maintain a "steady condition" at the level of Gaia, i.e. the biosphere itself.

Margalef shows how, as an ecosystem becomes more mature, so does it develop correspondingly more effective homeostatic mechanisms. Up to a certain level, these homeostatic mechanisms, Margalef considers, can protect a system from disruption from external agents. "Maturity is self-preserving." Margalef, like Odum also compares the successional development of an ecosystem with evolution:

"Maturity is related to evolution in a way that permits generalisation concerning the type of organisms to be found in ecosystems of more or less maturity and stability. As evolution proceeds, there is a trend toward adjustment to maturity." [45]

What is important is that all these changes are closely associated, what is more, sheer common-sense explains why they must be, if the ecosystem is to achieve its goal, that of increased stability.

What is also important is that the changes brought about by industrial man are, in fact, reversing ecological succession, that is why we must consider industrial development or 'progress' as an anti-evolutionary process.

By reversing ecological succession it is giving rise to ever greater ecological instability - of which the symptoms are increasing soil erosion and desertification; growing water-shortages; population explosions of micro-organisms (often leading to epidemics affecting plants and animals and other organisms including man); the extinction of plant and animal species; climatic changes and other increasingly severe discontinuities that are rapidly making our world ever less habitable.

What remains of an ecosystem after it has been devastated by the activities of modern man, Eugene Odum refers to as a "disclimax" (a disturbance climax) or an "anthropogenic (human generated) sub-climax". It is significant that the term disclimax is not (to my knowledge) used by any other modern ecologist. Its use, would, of course, be difficult to reconcile with Tansley's notion of the superiority of the anthropogenic climax over the natural climax, incompatible too with the very notion of technological progress. [46] Margalef does not use the term, but he does point out that modern man's interference with the functioning of ecosystems must return them to a lower successional stage, one that is very much less stable.

Sequential development

The principle of succession is clearer if it is seen in the light of the general-systems approach. It then becomes apparent that it is not a unique phenomenon as modern ecologists tend to see it, but rather a specialised instance of a very much more general principle, one which is best referred to as 'sequential development'.

All life processes can be shown to be sequential. This implies that their various stages must occur in the right order, so much so that if one stage is left out, then the succeeding stages will not occur or will occur but imperfectly. It also implies that each stage must occur in the correct spatio-temporal environment, the only one to which behaviour at a given stage is adaptive. Let me make this a little clearer.

All behaviour must be seen as modifying the environment. Such modification is not random from the point of view of the strategy of which the behaviour is an integral part. On the contrary, the new environment will be that which will best serve to trigger off the next stage in the strategy. This does not mean that the whole process is predetermined in a precise way, for at each stage, there may be a large number of possible variants of a basic behavioural response, of which only one or more, are likely in given conditions to be mediated.

There is a third feature of sequential development. It is that it must occur at the appropriate rate. If it is speeded up or slowed down, the end product is unlikely to be optimum. The reason is that any behavioural process or strategy, because of the hierarchical nature of the biosphere, is likely to be part of a larger process or strategy with which it must be correctly synchronised. The inertia, caused by the need to synchronise a process with a host of others, Rupert Riedl refers to as its "burden". [47]

Piaget is struck by the "sequential character of development". He defines sequential development as

"une suite de stades dont chacun est necessaire, donc dont chacun resulte necessairement du precedent (sauf le premier), et prepare le suivant (sauf le dernier). Dans le domaine de l'embryogenese des Metazoaires il semble en etre ainsi, puisque les grands stades se retrouvent toujours et dans un ordre constant." [48]

"A succession of stages of which each is necessary, and therefore of which each inevitably follows from its predecessor (except the first) and pepares the way for its successor (except the last). In the embryogenesis of the Metazoans it appears to be so, because the major stages are always present, and follow in the same order." [48]

Indeed, because embryological development occurs within a highly protected and ordered environment and because it so obviously constitutes a planned strategy, its sequential nature is apparent to all.

Piaget notes how Waddington explains this in his famous book The Strategy of the Genes. Waddington maintains, according to Piaget, that:

"les actions polygeniques et pleiotropiques du genome ne sont pas a concevoir comme un systeme exclusivement ascendant, mais a chaque étape, de nouveaux genes jusque-la non actifs (quoique naturellement presents des le depart) sont mis en activité par les résultats des actions déjà effectuées par d'autres genes; par exemple le résultat X produit par les genes a, c, et e, active en retour le gene b qui, synergiquement avec a et d produit le résultat Y, qui va activer d'autres genes, etc. Il y a donc la un systeme à boucles, et dont les étages superieurs sont modifiés par le milieu, puisqu'il s'agit du phenotype, mais par un processus selectif 'sous controle génique' puisque relatif a ces synthèses successives dependant du genome."

"the polygenic and pleiotropic actions of the genome should not be thought of as exclusively linear: they are rather iterative, and in each iteration formerly inactive genes (while present from the beginnning) are activated by the results of actions already performed by other genes; for example, result X produced by genes a, c, et e, activates in turn gene b which, synergetically with a and d produces result Y, which goes on to activate other genes, etc. There is thus a bootstrapping process, whose final stages are modified by intermediate stages which express the phenotype, by a selective procedure 'under genetic control', because it is relative to these successive syntheses dependent upon the genome."

Cognitive development in a child also proceeds in a sequential manner. This is unquestionably the view of Piaget who writes

"le problème du caractère sequentiel des stades se retrouve en psychologie pour ce qui est du development des fonctions cognitives et il est important de noter, qu'en ce domaine les stades sont d'autant plus nets et d'autant plus sequentiels que l'on a faire à des regulations mieux differenciées et portant sur un champs plus large." [49]

"the problem of the sequential nature of stages of development arises in psychology as regards the development of cognitive functions, and it is important to note that in this field the stages are so much more distinct and sequential as to require better differentiated regulations, beaing across a broader field." [49]

Dr Inhelder, who worked with Piaget for many years, pointed out at Arthur Koestler's famous Ansbach Symposium that

"learning is definitely dependent upon the subject's development level. Generally, in all this research, it has been shown that the child never manages to accomplish more than the passage from one sub-stage to the next without ever jumping a stage."

She also noted that her research now enabled her to answer the often asked question whether it was possible to accelerate the passage from one stage to the next - the answer was clearly 'no'. Indeed

"if mechanisms in mental development can be compared to what Waddington 'in embryology' calls 'creodes' or necessary paths with a 'time tally', it appears obvious that development always has an optimum rate, neither too slow nor too fast." [50]

In summing up her views of cognitive development in a child, she stated that

"the research undertaken in Geneva over the last 40 years has brought to light the fact that development does not occur by chance through encounters with the physical and social environment but follows a certain direction. In the development of thought, particularly, there are sequences or stages of progressive structuration. We took this development to obey laws of self-regulation of endogenous origin, but to be subject to continuous modifications under the influence of the feedback resulting from exchanges with the environment." [51]

In other words, for her, cognitive development is governed by precisely the same laws that govern embryological development. This is not, after all, very surprising since the development of a foetus within the womb and that which occurs after a child is born, clearly form a single process. The notion that they should be governed by different laws is only conceivable because scientific knowledge is arbitrarily compartmentalised and those two sub-processes are thereby studied by separate disciplines.

It is for the same reason too that the idea can be seriously entertained that this wider process is itself radically different from other life processes, such for instance, as the development of an ecosystem. Indeed, at a certain level of generality all life processes must be seen as governed by the same general laws. This is the thesis of Von Bertalanffy's General Systems Theory and it is a very important one, which few scientists have been willing to face, largely because it is so difficult to reconcile with the reductionist method to which they are so committed.

One such general law is that of sequential development which is known in ecology as 'succession'. It is equally unacceptable to mainstream science and hence to modern 'scientific' ecology - because it implies that life processes are goal directed, highly integrated, indeed linked mutualistically with their environment and come to an end once their goal - the maximum stability or homeostasis possible in the circumstances - has been achieved.

Such a view is also incompatible with the reductionist approach as it is with the scientific dogma that the changes brought about to the biosphere by modern science and technology are anything but destructive and regressive - which they must clearly be seen to be when viewed in the light of holistic ecology.

Notes