The ecological movement cannot avoid politics

All is politically relevant, but not all is politics

All our actions, and all our thoughts, even the most private, are politically relevant. If I use a clipped tea leaf, some sugar, and some boiling water, and I drink the product, I am supporting the tea and sugar prices and more indirectly I interfere in the works and capital conditions of the tea and sugar plantations of the developing countries. In order to heat the water, I may have used wood or electricity or some other kind of energy, and then I take part in the great controversy concerning energy use. I may use water from a private source or a public source, and in either case I participate in a myriad of politically burning questions of water supply. I certainly have a political influence daily in innumerable ways.

If I reflect on all these things along ecological lines and make my opinions known, I contribute to the strength of the politically conscious ecological movement. If I do nothing instead of drinking the tea I normally drink I may contribute to the difficulties of the developing countries because then their export becomes smaller. But perhaps not: I may think that they should not export tea but rather produce more food and therefore I make it easier for the politicians of the developing countries to change their economic policies in the direction of self-reliance.

The competitive production principle, as elucidated in Chapter 3, in a sense needs no further explanation or mechanism to explain intercrop advantage. It is just the case that the intercrop system is advantageous over its monocultural alternatives if competition between the two crops is not very intense. But it nevertheless makes sense to ask, at a more mechanistic level, what is the mechanism whereby competition is rendered small. This is a common question in community ecology, where one uses phrases like ‘niche subdivision’, ‘habitat partitioning’, ‘niche overlap’, ‘resource partitioning (or overlap or subdivision)’, and probably others to refer to the same set of phenomena. When two species are obviously doing more or less the same thing in an environment, as described in Chapter 3, it is natural to expect one or the other to dominate, much as competition in sports results in a winner and loser. As we now know, stalemate in nature is as common as checkmate. When expectations of a winner and loser are assumed because of obvious similarities in the two species, but they nevertheless coexist in the same environment, it is most natural to ask why. Why is the expected extinction of one of the species not observed? Formally the question is usually posed as ‘what is the mechanism of coexistence?’

Given the formal similarity between the competitive exclusion principle and the competitive production principle, it makes sense to ask ‘what is the mechanism of intercrop advantage?’ even if it is known that the advantage stems only from the weakness of the competitive interaction.

This book received its original impetus from two seemingly unrelated personal prejudices with which I found myself burdened in the late 1970s. First, the basic science of ecology seemed to be suffering from a lack of solid empiricism, its major tenets stemming from a combination of theory and speculation based on observed natural patterns. Second, the applied science of intercropping appeared to be void of a systematic theoretical framework within which the voluminous and usually empirical work might be interpreted. It seemed logical that the empiricism of intercropping might be usefully put to the service of ecology, whereas the theory of ecology might similarly form the basis of a framework for intercropping.

That ecology appeared to me as an overly speculative discipline may be little more than a reflection of Mario Bunge's observation that sciences tend to oscillate between periods of excessive observation – experimentation and excessive theory – speculation. During the 1940s, 1950s, and early 1960s the field of ecology seemed to be caught in a rather dull phase of observation and data collection. In the late 1960s ecologists discovered probabilities, matrices, and differential equations, and initiated a rich phase of theory development. In the 1980s a great deal of concern seems to be developing over the lack of a solid empirical base to the theoretical explosion, perhaps a new swing of the pendulum.

While it is certainly not true that all ecology is done in an empirical void, most ecologists would probably be forced to agree that theory and speculation have come out of balance with data.

A frequently claimed advantage of intercropping is its capability of dealing with environmental variability, implicitly equivalent to the avoidance of risk (Abalu, 1977; Francis & Sanders, 1978; Reddy & Willey, 1985; Reich & Atkins, 1970). While it is common for intercropping reviews to contain sections on variability and risk (e.g. Aiyer, 1949; Kass, 1978; Mead & Riley, 1981; Norman, 1974; Willey, 1979a; Lamberts, 1980), only rarely is the subject a central focus. Three notable exceptions are contained in the work of Rao & Willey (1980), Pearce & Edmondson (1982), and Schultz (1984). The latter work specifically treats the first two, and forms the basis of the first two sections of this chapter (measurement and evaluation, and variability under competition and facilitation).

The ecological literature on variability, and/or stability, is enormous. Useful reviews can be found in several places (e.g. Goodman, 1975; May, 1972; McNaughton, 1977; Murdoch, 1975). It had generally been held that diverse systems are more stable, or less variable. When one component either flushes or comes close to extinction, it is more likely that another component will compensate for it if a number of components are available to do so, which would be more likely in a highly diverse system than in a more monotonous system. It was, and still is, a common-sense notion, which is why May's (1972) claim of the reverse was such a surprise. All things equal, a more diverse system is expected to be less stable, not more.

Is there an advantage to growing intercrops? The simplest answer to this question is the qualitative one. If so many traditional agriculturists do it, there must be some advantage to it. This attitude is fine at the most general level, and we really need go no further. But at a more specific level we wish to ask the question about particular intercropping systems. Is it or is it not true on a particular farm in northern Brazil that corn grown together with peanuts is better than corn grown alone and peanuts grown alone? That is the question on which we focus in this chapter.

The bases for comparison

The problem of population density and planting design

Whatever the method of evaluation, the underlying basis is always a comparison of the performance in intercrop to the performance in monoculture. The first complication arises when one must decide what monoculture production figures should be used in the evaluation. In Figure 2.1 several possibilities are illustrated. In Figure 2.1 (a), the polyculture is stipulated first, and we are to decide which monocultures to use for the computation of the land equivalent to ratio (LER). If we use case I, the overall population is the same in monoculture and intercrop. If we use case II, the overall population density is larger in the intercrop than it is in the monocultures. Consider the similar Figure 2.1 (b). In this case we begin with the monocultures as stipulated, and are to decide which intercrop to use.

Figure 4.1 shows a peculiar intercropping system in central Nicaragua. The trees are jocotes (a fresh fruit, Spondias purpurea) and the epiphytic cactus growing on their trunks is pitahaya (Hylocereus sp.) whose fruit is used to make a drink. At first glance we might think of this as a trivial case of the competitive production principle since neither species would seem to have much of an effect on the other and competition should be quite low.

But a more important, if obvious, observation is to be made here. The pitahaya is an epiphyte and does not grow well on the ground. Thus, the jocote brings something to the environment which benefits the pitahaya – its trunk. The jocote ‘modifies’ the environment in a positive way for the other species, and thus presents us with a simple and obvious case of facilitation.

The basic idea

This principle is presented as complementary to the competitive production principle, to account for the many cases known both in agricultural (e.g. Vandermeer et al., 1983; Singh et al., 1986; Nair et al., 1979; Osman & Osman, 1982) and in non-agricultural systems (Vandermeer, 1980b: Vandermeer et al., 1985; Rathcke, 1984; Hazlett, 1983; Room, 1972) in which one species provides some sort of benefit for another species. Probably there will be particular mechanisms which will not amenably fit into either category, but for the most part it is not difficult to put particular mechanisms in one or the other of these two categories.

It seems to be the case, as emphasized in Chapters 3 and 5, that many if not most cases of intercrop advantage are due to the competitive production principle. But many known cases, and probably many that have not yet been sufficiently studied, might very well be due to the modification of some environmental factor, in a positive way, by one of the crops. Certainly, the more spectacular cases must involve some sort of facilitation since competitive production can maximally yield an LER of 2.0, and any individual relative yield can never be greater than 1.0 (see Chapters 2 and 3). In those frequent cases where a relative yield is greater than 1.0, the facilitative production principle must be operative, in some way. This chapter discusses those environmental factors that are typically thought to be modified when facilitation is operative.

Nitrogen

Since many commonly occurring intercrop systems involve a nodulating legume, and since they frequently yield better than their monocultural components (Trenbath, 1976; Snaydon & Harris, 1979; Walker et al., 1954; Allen & Obura, 1983), it is most natural to suspect that nitrogen is somehow involved. Just examining the extensive literature on grass–clover combinations (e.g. Simpson, 1965; Stern & Donald, 1962; Ennik, 1969; Cowling & Lockyer, 1967; Camlin et al., 1983), one is left with little doubt that nitrogen must be of overwhelming importance. But nitrogen can be involved in two distinct ways.

Announce your value-priorities forcefully

A deep ecological movement envisages a shift in basic attitudes from the dominant paradigm in leading industrial societies. Norms and values again and again have to be contrasted, not with any explicit philosophy which justifies the dominant paradigm (that does not seem to exist) but with its practice.

Therefore, we need an elaboration of our norms and values which correspond to the shift of basic attitudes. This requires the tentative systematisation of those norms and values. This is the theoretical background which sets the stage for this chapter, where philosophically problematic topics will be discussed, bearing in mind their importance to practical ecological debate. I will discuss exactly the same subjects in different ways, because readers with diverse backgrounds have been found to require different approaches to the same topics.

Not everything can be proven – an old thought first emphasised by Aristotle. The string of proofs on any definite occasion must commence somewhere. The first unproven links in such chains of argument are called ‘axioms’ or ‘postulates’. Those which are proven by means of these postulates are called ‘theorems’. History of mathematics and logic shows a diversity of systems, but they all have starting points beyond which they do not penetrate. They also have rules, some deduced from other rules, but at least one must be simply postulated, without any justification whatsoever.

When value priorities are traced back to the very fundamentals, the validity of the latter can then be questioned.

In the face of increasing environmental problems, the solutions proposed during the late 60s and early 70s revealed two trends, one in which it was presumed that a piecemeal approach within the established economic, social, and technological framework is adequate, another which called for critical examination of the man–nature relation and basic changes which would affect every aspect of human life. The latter trend, that of the deep ecological movement, involves both concrete decisions in environmental conflicts and abstract guidelines of philosophical character. It is not a mere philosophy of man–nature.

In the previous chapters a large number of problem areas have been touched upon, primarily the technological, economic, and political. Ultimate foundations have also been considered, particularly the contrast between atomistic and gestalt thinking. It remains to go into a number of philosophical issues, and also to touch upon the religious background of man–nature thinking in the West. The treatment will have to be more personal in the sense of leading into particular aspects of my ecosophy, Ecosophy T. But it is not the aim to point to my own particular view in special detail. Much has been already said without explicitly connecting it to the Ecosophy T logical structure. The main goal, as announced in chapter 2, is to emphasise the responsibility of any integrated person to work out his or her reaction to contemporary environmental problems on the basis of a total view.

In previous chapters a variety of theoretical approaches, mainly borrowed from the ecological literature, have been presented. For the most part these formulations have been intended as a framework within which intercrops can be viewed, hoping that some qualitative insights of intercrop dynamics might be revealed in the process. In the present chapter and the one that follows we turn to the practical question of how to use such a theoretical framework in the context of intercrop design.

This problem can be approached in two philosophically distinct ways, as has most of the theory already presented. First is what I call the phenomenological approach, common in the ecological literature, in which the problem is formulated as the quantitative response of one species to varying quantities of a second species. Our concern is simply with the quantitative effect of one species on another, specifically ignoring what might be the underlying causes of that effect. Competition and facilitation are thought of as phenomena worthy of study in their own right, irrespective of the underlying mechanisms that produce the observable competitive or facilitative effects.

The second approach is the mechanistic approach, in which competition and/or facilitation are assumed, but the interest is in the study of the mechanisms that cause them. Thus, competition may be for nitrogen or facilitation may be a consequence of protection from herbivores. The mechanism of overyielding might be the partitioning of the nitrogen environment or the mechanism of facilitation might be disrupting oviposition behavior of a key herbivore.

Weed control is often cited as one of the benefits of intercropping (Moody, 1980; Shetty & Rao, 1979; Unamma et al., 1986; Robinson & Dunham, 1954; Ibgozurike, 1971; Liebman, 1986). The presumed mode of action is that one crop, through competition with the weed, provides an environment of reduced weed biomass for the other crop. An apparent example is presented in Figure 8.1, in which a luxuriant growth of Amaranthus sp. in corn, is dramatically suppressed by a secondary crop of beans. In effect, the beans seem to have been able to replace the Amaranthus completely, and either provide a source of valuable yield, or compete less with the corn than the Amaranthus does.

Perhaps the best-known example is the use of ‘cover crops’, between rows of a monoculture. Liebman (1986) reviewed nine studies involving 23 crop–cover-crop combinations. Of the 23 cases, all but three showed a significant weed suppressive effect.

While the literature on cover crops is impressive, and suggests considerable advantage is to be gained in weed control, the literature on combinations of two crops is less extensive and more equivocal. For example, Ayeni et al. (1984), working in Nigeria, found that a maize–cowpea intercrop failed to significantly suppress weeds in the early cropping season but had a significant effect in the late cropping season. Unamma & Ene (1983) failed to find weed suppression in a cassava–maize system in Nigeria, whereas Soria et al. (1975) found this combination successfully suppressed weeds in Costa Rica.

Introduction

While the focus of this book is on annual crop systems, some of the more common and spectacular examples of intercropping involve perennial crops. Rappaport's classic study of the Tsembaga in New Guinea shows a complex system of succession and intercropping which includes many perennials (Rappaport, 1967). The so-called village forest-gardens in West Java exhibit similar diversity (Michon et al., 1983), as do the compound farms of Nigeria (Okigbo & Lai, 1978). To this day the Maya of Mexico maintain kitchen gardens sometimes growing over 30 species of plants, including fruit trees, bananas, and other perennials, (Alcorn, 1984). In South-East Asia the use of perennials in slash and burn agriculture is well-known (Spencer, 1966).

But it is not only in traditional peasant production that perennials are integral components. Commercial plantations involving intercrops are legion. Coffee and cacao are almost always grown with shade trees (usually a legume), implicitly an intercropping situation, although the production of the shade trees is of no consequence to the producer (Aranguren et al., 1982a, b). But many examples exist of the joint production of two perennials: cacao and coconut (Aggaoili, 1961; Garot & Subadi, 1958; Jose, 1968; Leach, 1971; Traeholt, 1962), coffee and rubber (Townsend et al., 1964), a variety of examples with African oil palm (Sparnaaij, 1957; Webster, 1969; Blencowe, 1969; Soekarno, 1961; Wood, 1966), and at least seven different perennials with coconuts (Nair, 1983).

The foregoing chapters have summarized some of the research directions currently underway in intercropping research and have indicated some possible simple extensions of relatively routine ecological theory into the realm of intercropping research. The ideas expressed have ranged from the mainly intuitive to the highly quantitative engineering designs of intercropping systems, and have utilized some simple applications of set theory and some not so simple applications of partial differential equations. By and large to this point all material has been well-known on two levels, the level of the ecological theory to be applied and the level of the need for it in intercropping.

In this chapter we briefly consider several topics that are either not so well known as ecological formulations and/or not usually part of the typical research agenda of intercropping researchers. These topics are included here because of what appears to be a great need for their consideration among researchers. Because they are topics more for the future than the present, their presentation will be far more tentative and speculative than the rest of the material in the book has been.

Dynamic plant growth and interaction models

A situation in which the need for a dynamic approach is essential was presented in Chapter 10. The use of a static yield–density approach when applied to a system of tomatoes and beans resulted in excellent predictions some of the time.

The basic idea

We begin our exploration of the mechanisms of intercrop advantage by pointing out that one potential mechanism is, in a sense, no mechanism at all. While casual observation leads us to question what causes particular patterns, it is sometimes worthwhile to reflect and ask if the patterns perhaps occur because nothing much is happening. It turns out, as described below, that because of the way we define intercrop advantage, it is quite possible, even perhaps common, to observe an intercrop advantage without anything special happening.

It is easiest to understand this ‘mechanism’ by referring to a similar phenomenon, recognized for many years, in community ecology. It is generally accepted (although the details remain hotly debated) that when two species do similar things (i.e. occupy the same niche, interfere with each other's activities, compete with one another, etc.) it is unlikely that there is enough room in the environment for both. Loosely, two species cannot occupy the same niche. If their niche requirements are sufficiently similar, which is to say they compete with one another intensely, one or the other will become extinct, given a long enough time. On the other hand – and this point is often not emphasized sufficiently – if the two species have similar but distinct requirements, which is to say they compete with one another only weakly, they may both persist indefinitely in the environment.

The book before you is entitled Ecology, community, and lifestyle. It is not a direct translation of Arne Naess' 1976 work, økologi, samfunn, og livsstil, but rather a new work in English, based on the Norwegian, with many sections revised and rewritten by Professor Naess and myself, in an attempt to clarify the original work as well as bring it up to date.

But this is not as straightforward as it might sound. The project involved cornering Professor Naess in between his numerous intercontinental travels, then escaping the problems of busy Oslo to various mountain retreats scattered throughout the country. As the student, I then questioned the professor on the original manuscript, he responded, and together we reworked the manuscript to make it flow smoothly in English and in the 1980s. After being thwarted by blizzards, breaking a ski or two, locking ourselves out of the wood supply by mistake, we finally emerged with the manuscript in its final form.

But even now there is much more we would like to add! In a developing field like ecophilosophy, there can only be an introduction, not a conclusive summary. So we apologise to those who feel key issues may have been left out, and we also apologise to our editors for trying to work too much in. At Cambridge University Press, Dr Robin Pellew, Susan Sternberg, Alan Crowden, and Peter Jackson have all been especially understanding. Daniel Rothenberg provided insightful criticism of the introduction.

The gravity of the situation

Humankind is the first species on earth with the intellectual capacity to limit its numbers consciously and live in an enduring, dynamic equilibrium with other forms of life. Human beings can perceive and care for the diversity of their surroundings. Our biological heritage allows us to delight in this intricate, living diversity. This ability to delight can be further perfected, facilitating a creative interaction with the immediate surroundings.

A global culture of a primarily techno-industrial nature is now encroaching upon all the world's milieux, desecrating living conditions for future generations. We – the responsible participants in this culture – have slowly but surely begun to question whether we truly accept this unique, sinister role we have previously chosen. Our reply is almost unanimously negative.

For the first time in the history of humanity, we stand face to face with a choice imposed upon us because our lackadaisical attitude to the production of things and people has caught up with us. Will we apply a touch of self-discipline and reasonable planning to contribute to the maintenance and development of the richness of life on Earth, or will we fritter away our chances, and leave development to blind forces?

A synopsis of what it is which makes the situation so critical could read:

An exponentially increasing, and partially or totally irreversible environmental deterioration or devastation perpetuated through firmly established ways of production and consumption and a lack of adequate policies regarding human population increase.