Table

Classification of New Estuarine Ecosystems

Name of Type Characteristic Energy Source or Stress

Sewage waste

Organic and inorganic enrichment

Seafood wastes

Organic and inorganic enrichment

Pesticides

An organic poison

Dredging spoil

Heavy sedimentation by man

Impoundment

Blocking of current

Thermal pollution

High and variable temperature discharges

Pulp mill waste

Wastes of wood processing

Sugarcane waste

Organics, fibers, soils of sugar industry wastes

Phosphate wastes

Wastes of phosphate mining

Acid waters

Release or generation of low pH

Oil shores

Petroleum spills

Piling

Treated wood substrates

Salina

Brine complex of salt manufacture

Brine pollution

Stress of high salt wastes and odd element ratios

Petrochemicals

Refinery and petrochemical manufacturing wastes

Radioactive stress

Radioactivity

Multiple stress

Alternating stress of many kinds of wastes in drifting patches

Artificial reef

Strong currents

Source: Adapted from Odum, H. T. and B. J. Copeland. 1972. Environmental Framework of Coastal Plain Estuaries. The Geological Society of America, Boulder, CO.

Source: Adapted from Odum, H. T. and B. J. Copeland. 1972. Environmental Framework of Coastal Plain Estuaries. The Geological Society of America, Boulder, CO.

9.1B). However, is it appropriate only to think of an ecosystem as degraded when a source of pollution is added to the energy signature? What actually happens is that the ecosystem reorganizes itself in response to the new pollution source. Thus, degradation (Figure 9.1B) is really reorganization of a new ecosystem (Figure 9.1A). This seems like a contradiction because degradation carries a negative connotation while reorganization has a more positive sense. Both views in Figure 9 are valid. What is advocated here is the straightforward notion that ecosystem identity (i.e., elements of structure and function) is determined by the energy signature, and if the energy signature is changed, then a new ecosystem is created.

In another sense the concept of emergent new systems attempts to reduce value judgment in ecosystem classification. Rather than considering ecosystems with human pollution as degraded natural systems, the classification labels them as new systems. The value-free approach frees thinking so that the organization of new

FIGURE 9.1 Comparison of philosophical positions or interpretations of the effects of human influence on ecosystems. (A) View focusing on change to a new system. (B) View focusing on degradation.

systems can be more clearly understood. Of course, the trick is to not throw out the value-laden thinking. It is important to understand and account for human influences which society judges to be negative. Some new systems are "good" (cropland agriculture dominated by domesticated exotic species) and some are "bad" (forest invaded by exotic species), but this distinction is determined by human social convention, not by ecological structure or function.

Consider another application of this way of thinking. A distinction is made between native species and exotic species in ecosystems as discussed in Chapter 7. Native species are those that are found in a particular location naturally or, in other words, without recent human disturbance, while exotic species are those that evolved in a distant biogeographical region but have invaded the particular location under discussion. The reference point in the distinction between natives and exotics is location. However, in the energy theory of ecosystems the reference point is the energy signature that exists at the location, not the location itself. A causal relationship is implied which matches a set of energy sources to ecosystem components. Thus, if the energy signature of a location changes, then the species native to the location may no longer be as well adapted to it as compared with exotic species that invade. Under these circumstances nature favors the exotic species which are preadapted to the new energy signature, while human policy favors the old native species due to an inappropriate respect for location. Exotics are said to be the problem, when really the problem is that the energy signature has changed. Clear examples of this circumstance are the tree species that invade where hydrology has changed dramatically as in the southwest U.S. with salt cedar (Tamarix sp.) and in South Florida with melaleuca (Melaleuca quinquenervia). Tree-of-heaven (Ailanthus altissima) is another example of an exotic tree species which occupies urban areas and roadside edges (Parrish, 2000). These habitats have different energy signatures as compared with the surrounding forests in the eastern U.S. and tree-of-heaven can dominate under these new conditions. Humans are everywhere changing old energy signatures and creating new ones that never existed previously, and the results are changing ecosystems. The issue is how to choose reference points to interpret changes. This requires a philosophical position and the position advocated here is that new ecosystems are being created which have few or no reference points for comparison in the past. Thus, the future will require new ways of thinking about the new ecosystems that are being created as humans change the biosphere. The concept of new ecosystems may be especially useful for the ecological engineer who designs ecosystems. What criteria will be used to judge the new systems? Will new designs be limited to native species that are no longer fully adapted or can exotic species be used? Can humans allow nature to perform some of the design, even if it results in unanticipated or undesirable species compositions? What are the limits to ecological structure and function that can be achieved through design?

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