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<br />J, A, STANFORD ET AL.
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<br />INTRODUCTION
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<br />Flow regulation is perhaps the most pervasive change wrought by humans on rivers world-wide. Dynesius
<br />and Nilsson (1994) recently showed that all of the larger rivers in the northern third of the world are regu-
<br />lated; flow in most is totally controlled by dams and diversions, except for some free-flowing reaches and
<br />during extreme floods.
<br />Much research in stream ecology world-wide is now devoted to understanding and mitigating flow reg-
<br />ulation and the interactive effects of land and water use by humans within catchment basins. A primary
<br />goal of 'The Freshwater Imperative', a recent synthesis of research direction by limnologists in the USA,
<br />is understanding and predicting the influences of flow regulation on the integrity (e.g, long-term mainte-
<br />nance of native species diversity) and resiliency (e.g. natural recovery from human-mediated environmen-
<br />tal change) of epicontinental aquatic ecosystems (Naiman et al., 1995a; summarized in Naiman et al.,
<br />1995b).
<br />River corridors were the arteries for the development of ancient civilizations and modern societies and
<br />they remain central to local and global economies. Quality of life in all countries can be assessed in terms
<br />of quality and quantity of environmental goods (e.g. potable and irrigable water, fisheries) and services
<br />(e.g. sustained discharge and bioproduction) that humans are able to obtain from river ecosystems (sensu
<br />Lubchenco et al., 1991). Conservation and restoration of rivers clearly should be a national priority for
<br />responsible governments and a wide array of actions have been proposed or discussed (e.g. Gore, 1985;
<br />Toth et al., 1993; Gore and F. D, Shields, 1995; Shuman, 1995; Van Dijk et al., 1995).
<br />However, governments struggle with the designation of the specific elements of river environments that
<br />need to be conserved or restored, because of conflict between human use of riverine goods and services
<br />and different perceptions of how those finite resources can be sustained as human populations burgeon.
<br />Moreover, management actions targeted at a particular segment or species too often fail to meet objectives
<br />because rivers are not viewed as interconnected ecosystems from headwaters to ocean confluence.
<br />Indeed, a strong tendency has emerged to focus river conservation and restoration on charismatic or eco-
<br />nomically important fauna, such as trout and salmon, without thorough consideration of the attributes and
<br />processes of the catchment that control biodiversity and bioproduction (Sparks, 1995). In the USA, federal
<br />legislation aimed at recovery of species deemed in danger of extinction has fostered management and
<br />research emphasis on the biology of particular organisms rather than on the ecosystem processes that control
<br />their survival within diverse assemblages of native biota (Minckley and Deacon, 1991), For example, the dec-
<br />ade-old restoration programme for anadromous salmon runs in the Columbia River has cost well over $1
<br />billion dollars; yet, native populations are rapidly approaching non-viable levels (Nehlsen et ai" 1991, Hun-
<br />tington et aI., 1996) because restoration focused on hatchery production as mitigation for lost or damaged
<br />habitat (National Research Council, 1995),
<br />To be successful, river restoration plans must be based not only on the biology of organisms, but also on a
<br />thorough understanding of the biogeochemical processes that control the distribution and production of
<br />biota, and the human influences on those processes. In this paper we examine the general principles of river
<br />ecology and stream regulation in an ecosystem context and we use these principles as the basis for the pro-
<br />position of a general protocol for restoration of entire catchments,
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<br />NA TURAL-CUL TURAL ELEMENTS OF CATCHMENT ECOSYSTEMS
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<br />Rivers cannot be separated in theory or practice from the lands they drain (Hynes, 1975), Hence, the catch-
<br />ment basin (often referred to as watershed in the USA) defines the spatial dimensions of river ecosystems,
<br />Understanding the linkages between terrestrial and aquatic components and processes within the catchment
<br />is essential to river protection and restoration.
<br />The catchment landscape is composed of interactive, biophysical resources (e.g. water, minerals, nutri-
<br />ents, habitats, food-webs) that are used by the assemblage of animals and plants (biodiversity) that live
<br />within the ecosystem. Biodiversity encompasses such phenomena as genetic variation, morphological
<br />variation, life history variation within species and the richness, distributions, biomass and productivity
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