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<br />
<br />RESTORATION OF REGULATED RIVERS
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<br />of populations, species, guilds and other taxonomic and trophic categories across the landscape. It also
<br />encompasses the myriad of biophysical processes (functional attributes) that control these phenomena
<br />(Hall et ai"~ 1992; Doppelt et ai"~ 1993; Noss and Cooperrider, 1994; and many others), However, the sali-
<br />ent features of biodiversity, species numbers (alpha diversity) and distribution (beta diversity), are deter-
<br />mined by the availability of the resources that are needed by animals and plants in order to reproduce
<br />successfully (i,e, complete their life cycle) (Andrewartha and Birch, 1954) and thereby sustain ecosystem
<br />integrity (Frissell and Bayles, 1996; Ward, in press). Life history stages are determined by the genome of
<br />each species as derived from its legacy of genetic responses to changes in the availability of resources.
<br />Hence, the dynamic biophysical components of the landscape are controlled in space and time by envir-
<br />onmental changes (e,g, forest fires, spates, drought, disease, earthquakes) that vary in intensity and dura-
<br />tion,
<br />Similarly, human societies within catchments usually are derived from a mix of cultures (e.g. natives,
<br />immigrants) that use or market goods and services to produce wealth or some other measure of the quality
<br />oflife desired by individuals, Desires and perceptions that individuals have about life-style are dynamic and
<br />influenced by heritage, education, earning power, shortages and surpluses of goods such as fossil fuels, laws,
<br />taxes and natural resource management policies, among many other social and economic concerns.
<br />The point is, that both natural and cultural components of catchments are complex and highly interactive,
<br />Humans change catchment landscapes by using or extracting environmental goods and services; whereas,
<br />societies change in relation to the quality or ecological integrity of landscapes in which they reside (Blikie
<br />and Brookfield, 1987; Schinberg and Gould, 1994; and many others in the rapidly expanding environmental
<br />sociology and ecological economics literature),
<br />Within this natural-cultural framework, we recognize that river ecosystems have a certain natural capa-
<br />city to maintain biota and produce biomass (Warren et a/., 1979; Frissell et al. 1996; Ebersole et ai" in press)
<br />and that biodiversity and bioproduction are dynamic in time and space in relation to availability of resources
<br />(Benke el aI" 1988). Biotic dynamics derive from natural variation in the environmental setting; equilibrium
<br />conditions (e.g. logistic relationship~between resources and bioproduction) rarely exist for very long because
<br />environmental changes are constantly reconfiguring resource availability. Periodic constraints on species-
<br />specific productivity increases opportunities for other species to use resources, inferring that levels of ecosys-
<br />tem biodiversity and bioproduction generally are related to the intensity, frequency and duration of distur-
<br />bance events (Huston, 1979: Resh et ai"~ 1988; Pimm, 1991; Huston, 1994; Reice, 1994).
<br />Ecological capacity, therefore, varies from place to place and higher levels of biological richness (specios-
<br />ity) and bioproduction are most likely to occur in ecosystems with a long legacy of high spatial and temporal
<br />environmental heterogeneity (Connell, 1978; Ward and Stanford, 1983; Salo et ai" 1986; Poff and Ward,
<br />1990; Ward, in press). In contrast, total unit area biomass (standing crop) of a few species, while also con-
<br />strained by inherent ecosystem capacity, may be high under sustained conditions of environmental con-
<br />stancy owing to slow turnover rates. For example, a few species are often extremely abundant and
<br />persistent in spring-brooks, lake outlets and reservoir tailwaters, where disturbance events are relatively
<br />benign (e,g, scouring floods. very dynamic diel and annual temperature patterns and rapid changes in trans-
<br />port of particulate matter do not occur because of the buffering effect of the lake or reservior) (Ward and
<br />Dufford, 1979; Gislason, 1985; Perry and Sheldon, 1986; Valett and Stanford, 1987; Wooton, 1987; Shannon
<br />el a/" 1994).
<br />Humans tend to dominate ecosystems, thereby superimposing pervasive, continual perturbation on the
<br />natural disturbance regimes that sustain habitats and biotic communities, The result is suppression, and
<br />in some cases permanent loss, of environmental heterogeneity and biodiversity, fundamentally reducing
<br />the productive capacity of biotic resources (Warren and Liss, 1980; Frissell el aI., 1993; Frissel1 et ai"~ in
<br />press; Ebersole el ai"~ in press). The goal of river restoration should be to minimize human-mediated con-
<br />straints, thereby allowing natural re-expression of productive capacity, In some, if not most, intensely regu-
<br />lated rivers, human-mediated constraints may have progressed to the point that full re-expression of capacity
<br />is neither desired nor possible Nonetheless, the implication is that basic ecological principles applied to riv-
<br />ers in a natural-cultural context can lead to restoration of biodiversity and bioproduction in space and time;
<br />but, the constraints must be removed, not mitigated,
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