The history of the use and effectiveness of instream structures in the United States
The use of instream structures, devices designed to improve fish habitat, began as early as 1880 in the United States and continues today. The practice of stream improvement was partially motivated by the desire to compensate for overfishing problems. Many of the practices that involve the use of instream structures emerged during a time period when scientific-management principles offered the hope that humans could eliminate perceived inefficiencies and increase biological productivity in natural systems. Decades later, modern criteria of instream structures trace many of their details of design to experimental devices employed in the 1920s and 1930s. However, problems with the use of many styles were noted soon after they were first deployed, and many of these troubles persist today. Dams can be undermined and outflanked by flows. Deflectors disrupt the bed and hamper the development of food organisms. Finally, cover structures suffer from siltation problems and long-term decay, which renders the devices useless. The best possible long-term solution to improved health of riverine fisheries may be to avoid the use of static engineering structures when possible and focus on reforestation and erosion control in the watersheds. Even this recommendation dates back over 65 years to the period when the use of instream structures first began to flourish in the United States.
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Humans as Geologic Agents
Homo sapiens is the only known species to consciously effect change to the Earth’s geologic environment. We reshape the Earth; intensify erosion; modify rivers; change local climates; pollute water resources, soils, and geologic media; and alter soils and the biosphere. We dig holes in it, remove parts of it, and bury highly toxic materials in it. In this volume, the authors explore human impact on the Earth and attempt to answer the following questions. What have we done to Terra? How fast have we effected change? Are the changes permanent? Are they good, or have we inadvertently caused more damage? Can we, should we, repair some or all of these changes? These are important questions for the geoscience community because, as those most knowledgeable about the Earth and its resources, geologists play a major role in sustaining and preserving the Earth.