Ecosystem Perspective 



One shift in thinking that has occurred is from a focus on a given localized habitat, 

 such as a stream reach, old field, or woodlot, toward a more ecosystem-directed 

 approach (e.g., watershed perspective). ^3'^'' Experiences with air-borne radioactive 

 fallout and air pollution demonstrated the need for broader-based thinking about 

 ecosystems and stimulated environmental awareness and concern for man's impact 

 on other species. Air pollution has even been called a "blessing in disguise" because of 

 its potential to arouse man to achieve a "planned equilibrium with the ecology of 

 earth. "35 Man's impact is ubiquitous — for example, on such divergent systems as 

 climate, 3^ barrier islands, ^^ and seagrass.^^ The biosphere, i.e., land, water, and air, 

 must be viewed as a whole; solutions to many problems man faces today require this 

 holistic conception (Figure 3). 



The rate of loss of animal habitat is increasing, and, in some cases, the habitat is 

 beyond reclamation. Most recent species and population extinctions appear to have 

 resulted from alteration or elimination of habitat — often as the direct result of 

 human settlement and indirectly by species introductions or environmental 

 contamination.'"' Urbanization, wetland drainage, and water impoundments have 

 devastated fish and wildlife habitats. Road building, logging, agriculture, and mining 

 have adversely affected stream organisms, particularly via sedimentation,"" altered 

 storm water runoff, ''^'•'^ and acid mine drainage. ■♦''<''''''* Land-water interactions are 

 critical features of fish and wildlife habitat. Inputs from the streamside vegetation 

 often constitute the major organic resource for basic food chain elements that 

 support fish populations.*^ Present interest in riparian zones reflects increased 

 awareness during the 1970s of the interdependence of terrestrial and aquatic 

 systems. ''^ 



Many current land-use practices result in copious loss of water, soil, and plant 

 nutrients. ■*^ Soil type can affect nutrient concentrations in streams, 'o and fire may 

 enhance nutrient movement in forests as well as atmospheric loads of soluble 

 nutrients."'" Irrigation may result in localized water draw-downs, return-flow 

 problems, increased salinity, and changes in chemical composition. In addition, 

 growth of aquatic macrophytes, which may, among other things, destroy fisheries, 

 interfere with hydroelectric and irrigation schemes, obstruct navigation, and present 

 health hazards and recreational nuisance, is symptomatic of failure to adequately 

 manage resources." Although plant growth can serve as an early warning system for 

 eutrophication of aquatic habitats, it has been the target of widespread use of 

 herbicides. Side effects of environmental contaminants have received much needed 

 attention, but changes in natural nutrient cycles and macronutrients in the 

 atmosphere, soil, and water may have far-reaching consequences. These are due in 

 part to agricultural intensification and deforestation as a whole, as well as to the use 

 of chemicals in agriculture and forestry. '" 



Larson reviews changes in attitudes towards wetlands over the past decade, in 

 which a recognition and appreciation for wetland values has developed. Flood 

 control, storm damage, water quality, fish nurseries, plant productivity, groundwater 

 supply, visual-cultural aspects, and wildlife habitat are all associated with intact 

 wetlands. These changes in attitudes were undoubtedly facilitated by the ecosystem 

 approach. 



Man may well be the dam-building animal. Flow regulation has altered water 

 quality, 55 discharge, and thermal regimes through, for example, variations in the 

 stages and timing of flooding. ** In addition, it has impeded migrations essential for 

 survival of some of the more highly prized fish species. 5^58,59 instream flow values 

 were not included in legitimate uses of the nation's waters prior to 1968. The 1970s 

 have focused on description of stream reaches and the coupling of measurements of 

 instream flow regimes with such effects as water quality and sediment routing along 

 the stream-river system (Stalnaker). 



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