(NAS Colloquium) The Future of Evolution (2002) / Chapter Skim
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Human-modified Ecosystems and Future Evolution
Human-modified Ecosystems and Future Evolution
Pages 70-77
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From page 70... ...
As we enter the 21st century, the earth's atmosphere, waters, and soils have been altered by human activity to the point of changing biogeochemical cycles and climate on a global scale (13~. What can we say about future evolution in a human-dominated world?
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From page 71... ...
Truncated ecological gradients Reduced ecotones Low alpha diversity Loss of soil fauna Simplified predator-prey, herbivore-carnivore, and host-parasite networks Low internal regulation of ecosystems due to loss of keystone agents Side effects of fertilizers, pesticides, insecticides, and herbicides Invasive nonindigenous species, especially weeds and pests Proliferation of resistant strains of organism New and virile infectious diseases Genetic loss of wild and domestic species Overharvesting of renewable natural resources High soil surface exposure and elevated albedo Accelerated erosion Nutrient leaching and eutrophication Pollution from domestic and commercial wastes Ecological impact of toxins and carcinogenic emissions Atmospheric and water pollution Global changes in lithosphere, hydrosphere, atmosphere, and climate and sedimentation, have been extensively quantified (19, 20) and need no further elaboration.
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From page 72... ...
The evidence already underscores the need to consider functional roles in tracing the ripple effect of human activity on ecosystem properties and points to a novel experimental tool for ecologists (44~. Structural Asymmetry.
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From page 73... ...
will challenge species adaptations and Western Table 3. Some ecological consequences of human activity on ecosystem processes Ecosystem structure Loss of biodiversity Structural asymmetry and downsizing of communities Loss of keystone species and functional groups Ecosystem processes Low internal regulation H igh nutrient turnover High resilience Low resistance Low variability Low adaptability Ecosystem functions High porosity of nutrients and sediments Loss of productivity Loss of reflectance Global processes Modified biogeochemical cycles Atmospheric change Accelerated climatic change block migration, with grave implications for species extinction (61~.
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From page 74... ...
Finally, human activity will dominate biogeochemical cycles and affect major planetary processes such as climate through the greater porosity of energy flow and nutrients cycles across ecosystem boundaries and increased reflectance. One example is the impact of nitrogen overload on oceans through eutrophication and phytoplankton blooms (60)
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From page 75... ...
Ecological theory is essential in providing a robust, yet relatively simple explanation of ecosystems and their response to human activity. Community assembly rules and the relationship between ecosystem structure and process and how they vary biogeographically are basic to explaining overall diversity and ecosystem properties.
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From page 76... ...
The new conservation frame work must address the hierarchical scales linking global and ecosystem processes by using mutually reinforcing top-down and bottom-up approaches (83~. I touch briefly on both ap proaches to show the opportunity and need for science-based conservation.
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From page 77... ...
(1995) Species Diversity in Space and Time (Cambridge Univ.
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