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200 Distance from surface(m)

FIGURE 9.2 Patterns of vegetation extending out from a radiation source in the temperate forest at Brookhaven, New York. (From Woodwell, G. M. and R. A. Houghton. 1990. The Earth in Transition: Patterns and Processes of Biotic Impoverishment. G. M. Woodwell (ed.). Cambridge University Press, Cambridge, U.K. With permission.)

are, of course, many kinds of pollution that have been created by humans; many new kinds of habitats have also been created, especially in agricultural and urban landscapes. A whole new field of stress ecology has arisen to understand these systems with many interesting generalizations (Barrett and Rosenberg, 1981; Barrett et al., 1976; Lugo, 1978; E. P. Odum, 1985; Rapport and Whitford, 1999; Rapport et al., 1985). These references indicate that many changes in natural ecosystems caused by human impacts are similar and predictable, such as simplification (reductions in diversity) and shifts in metabolism (increased production or respiration). A good example is the set of experiments done in the 1960s which exposed ecosystems to chronic irradiation from a 137 Cs source, such as at Brookhaven National Laboratory in New York. These experiments were conducted to help understand the possible consequences of various uses of atomic energy by society. In these studies point sources of radiation were placed in forests for various lengths of time and ecosystem responses were studied. At Brookhaven, "the effect was a systematic dissection of the forest, strata being removed layer by layer" (Woodwell, 1970). Thus, a pattern of concentric zones of impact emerged outward from the radiation source, perhaps best characterized by these vegetation zones (Figure 9.2):

1. Central zone with no higher plants (though with some mosses and lichens)

2. Sedge zone of Carex pennsylvanica

3. Shrub zone with species of Vaccinium and Gaylussacia

4. Zone of tolerant trees (Quercus species)

5. Undisturbed forest

PrpadantpH

PrpadantpH

Distance from Source of Pollution

FIGURE 9.3 Model of longitudinal succession caused by a pollutant source, illustrating the position of preadapted species.

Distance from Source of Pollution

FIGURE 9.3 Model of longitudinal succession caused by a pollutant source, illustrating the position of preadapted species.

In this case the ecosystem had no adaptational history to the stress but self-organization took place in the different zones of exposure, resulting in viable but simpler systems based on genetic input from the surrounding undisturbed forest. It is interesting to note that Woodwell (1970) found similarities between the new stress of radiation and the "natural stress" of fire. Some species in this forest were adapted to fire, and there was a direct correspondence in species adaptation between fire frequency and radiation exposure. Thus, with high fire frequency Carex pennsylvan-ica dominates vegetation just as it does with relatively high radiation exposure. This is an example of preadaptation, which has been noted as being important in stress ecology by Rapport et al. (1985). A general model for the special case described above is shown in Figure 9.3. Concentration of the pollutant declines away from a point source along a linear transect in the model. Associated with the decline in pollutant concentration is a longitudinal succession of species, shown by the series of bell-shaped species performance curves. Each curve represents the ability of a species to exploit resources within the context of the pollution gradient (see Figure 1.8). This pattern of species is characteristic of a variety of ecological gradients and Robert Whittaker developed an analytical procedure for studying the pattern called gradient analysis (Whittaker, 1967). When there is no adaptational history for the pollutant, then the species closest to the point source can be said to be preadapted to the pollutant. In the classic river pollution model (Figure 2.3) the species closest to the sewage outfall are classified as tolerant. Using an alternative line of reasoning, these species are preadapted to the high sewage concentrations, and the proximity of the peak in their performance curves to the point source is an index of the degree of preadaptation. The decline in pollutant concentration in the model is due to various biogeochemical processes. When species have a role to play in the decline, then ecological engineering is possible to enhance treatment capacity of the pollution. To some extent the sequential design of John Todd's living machines (see Chapter 2) corresponds with the species patterns shown in Figure 9.3. Perhaps an adaptation of Whittaker's gradient analysis can be used as a tool for living machine design (see the upcoming section on a universal pollution treatment ecosystem).

The other class of unintentional system is the system dominated by exotic species. The situation here is that species with no common evolutionary history are being mixed together by enhanced human dispersal at rates faster than evolution. The results, as described in Chapter 7, are new viable communities with some exotic and some native species.

In both cases of unintentional systems then, evolution does not provide full understanding or predictive value of the new systems. There are a few examples of evolution taking place in the new systems, such as resistance to pesticides in insect pests or to antibiotics by bacteria and tolerance to heavy metals by certain plants (Antonovics et al., 1971; Bradshaw et al., 1965), but these are exceptions. Certain species with fast turnover can adapt to rapid changes caused by humans (Hoffmann and Parsons, 1997), but this is not possible for all species. Soule's (1980) discussion of "the end of vertebrate evolution in the tropics" is a dramatic commentary on the inability of some species with low reproductive rates to adapt, in this case, to loss of habitat due to tropical deforestation. The idea that Soule refers to is loss of genetic variability in vertebrate populations due to declining population sizes. Natural selection operates on genetic variability to produce evolution, so with less genetic variability there is less evolution.

Thus, the new systems are being organized at least in part by new processes. Janzen (1985) discussed this situation and proposed the term ecological fitting for these processes. Self-organization is proposed as the general process organizing new systems in this book. To address this new situation, Hutchinson's classic phrase may need to be reworded as "the ecological theater and the self-organizational play."

A key feature of the organization of new systems is preadaptation. The new systems are often dominated by preadapted species, whether they be native species that are tolerant of the new conditions or exotic species that evolved in a distant biogeographical region under conditions similar to the new system. There appear to be two avenues of preadaptation: those species that are preadapted through physiology and those that are preadapted through intelligence or the capacity to learn.

The best example of physiological preadaptation is for species that have been used as indicator organisms. These species indicate or identify particular environmental conditions by their presence or absence, or by their relative abundance. Indicator organisms can be either tolerant, (i.e., those present and/or abundant under stressful conditions) or intolerant, (i.e., those absent or with reduced abundance under stressful conditions). Only tolerant organisms are preadapted and they indicate the existence of new systems. Tolerant indicator organisms have been widely used in water quality assessments, dating back to the German Saprobien system in the early 1900s. A large literature exists in this field (Bartsch, 1948; Cairns, 1974; Ford, 1989; Gaufin, 1973; Patrick, 1949; Rosenberg and Resh, 1993; Wilhm and Dorris, 1968), and it can be an important starting point to developing an understanding of preadaptation as a phenomenon. Hart and Fuller (1974) provide a tremendous amount of information about the adaptations and preadaptations of freshwater invertebrates in relation to pollution. Another example of indicator organisms is plant species found on soils with unusual mineral conditions. Methods of biogeochemical prospecting have been developed by identifying particular indicator species of plants

(Brooks, 1972; Cannon, 1960; Kovalevsky, 1987; Malyuga, 1964); this approach could be important in selecting species for phytoremediation of waste zones in the future (Brown, 1995). The study of tolerant organisms for the purpose of understanding preadaption is similar to the approach of genetic engineers who study "super bugs" or microbes adapted to extreme environmental conditions (Horikoshi and Grant, 1991). These microbes have special physiological adaptations that the genetic engineers hope to exploit when designing microbes for new applications. Species can be found with adaptations for high (thermophilic) and low (psychrophilic) temperature, high salt concentrations (halophilic), low (acidophilic) and high (alka-liphilic) pH, and other extreme environments.

The other avenue of preadaptation involves intelligence or the capacity to learn. This is primarily found in vertebrate species with sophisticated nervous systems. Intelligence or the capacity to learn allows organisms to react to new systems. A. S. Leopold (1966) provided a discussion of this kind of preadaptation in the context of habitat change. Animals that can learn are able to adjust to new systems by avoiding stressful or dangerous conditions and by taking advantage of additional resources or habitats. Many examples exist including urban rats and suburban deer, along with a variety of bird species, which take advantage of new habitats: falcons in cities (Frank, 1994), gulls at landfills (Belant et al., 1995), terns on roof tops (Shea, 1997), and crows in a variety of situations (Savage, 1995).

Although some empirical generalities exist such as those from the field of stress ecology or from the long history of use of indicator organisms, little or no theory exists to provide an understanding of the organization of new emerging ecosystems. As mentioned earlier (see Chapter 1), preadaptation is little discussed in the conventional evolutionary biology literature, yet it is a major source of species that become established and dominate in the new systems through self-organization. More research on preadaptation is clearly needed. Can there be a predictive theory of preadaptation? Or is it simply based on chance matching of existing adaptations with new environmental conditions? Is a new evolutionary biology possible based on preadaptation?

One interesting topic from ecology that offers possibilities for an explanation of new systems is the theory of alternative stable states (see Chapter 7). This theory suggests that alternative equilibria or states, in terms of species composition, exist for ecosystems and that a system may move between these alternatives through bifurcations caused by environmental changes. Several authors have suggested possible views of alternative stable states in terms of human impact (Bendoricchio, 2000; Cairns, 1986b; Margalef, 1969; Rapport and Regier, 1995; Regier et al., 1995) and Gunderson et al. (2002) propose a theory called "panarchy" to explain how systems can shift between alternative states. This theory describes system dynamics across scales of hierarchy (hence the name panarchy) with a four-phase cycle of adaptive renewal. One view of the alternative stable state concept is shown in Figure 7.5 with a Venn diagram in which different sets represent alternative states. A system moves within a set due to normal environmental variations, but can jump to another set, representing a new system in the terminology of this chapter, due to some major environmental change (Parsons, 1990). The states differ qualitatively in their basic species compositions, but within a state a similar species composition exists, though in quantitatively different combinations. The alternative stable-state concept involves folded equilibria from dynamical systems theory, which may provide a foundation for understanding the new emerging systems of human impact and exotic species. Can we predict new alternative states that have never been recorded previously? Can we create alternative states through ecological engineering?

Ecological engineers will be interested in the new emerging systems for several reasons. First, these systems will be sources of organisms to seed into their new designs. Species from the new emerging systems will be variously preadapted to human-dominated conditions so that they may also be successful in interface ecosystems. For example, biodiversity prospecting is taking place at Chernobyl (where the nuclear reactor disaster took place in 1989) for microbes that might have special value due to mutations. Ecological engineers also can learn from the new systems as in reverse engineering. What kinds of patterns of ecological structure and function exist in communities of preadapted species? Useful design principles may arise from the study of the new emerging ecosystems, and the engineering method may be a helpful vantage point for study, as discussed in the next section.

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