Environmental Problems, Their Causes, and Sustainability 1

SolutionsRebuilding Salmon PopulationsBuilding upstream hatcheriesReleasing juvenile salmon from hatcheries tounderpopulated streamsReleasing extra water from dams to wash juvenilesalmon downstreamBuilding fish ladders so adult salmon can bypass damsduring upstream migrationUsing trucks and barges to transport salmon around damsReducing silt runoff from logging roads above salmonspawning streamsBanning dams from some stream areasFigure 13-15 Solutions: Some strategies used to rebuildsalmon populations in the Columbia River basin.How Can Freshwater Fisheries Be Managedand Sustained? Encourage Some Speciesand Discourage OthersFreshwater fisheries can be sustained by buildingand protecting populations of desirable species,preventing overfishing, and decreasing populationsof less desirable species.Sustainable management of freshwater fish involvesencouraging populations of commercial and sport fishspecies, preventing such species from being overfished,and reducing or eliminating populations of lessdesirable species. Ways to do this include regulatingthe time and length of fishing seasons and the numberand size of fish that can be taken.Other techniques include building reservoirs andfarm ponds and stocking them with fish, fertilizing nutrient-poorlakes and ponds, and protecting and creatingfish spawning sites. In addition, fishery managerscan protect fish habitats from sediment buildup andother forms of pollution, prevent excessive growth ofaquatic plants from large inputs of plant nutrients, andbuild small dams to control water flow.Improving habitats, breeding genetically resistantfish varieties, and using antibiotics and disinfectantscan control predators, parasites, and diseases. Hatcheriescan be used to restock ponds, lakes, and streamswith prized species such as trout and salmon, and entireriver basins can be managed to protect valuedspecies such as salmon. Some individuals haveworked to help restore degraded streams.How Can Wild and Scenic Rivers BeProtected and Restored? Let More of ThemRun FreeA federal law helps protect a tiny fraction ofU.S. wild and scenic rivers from dams and otherforms of development.In 1968, the U.S. Congress passed the National Wildand Scenic Rivers Act. It established the NationalWild and Scenic Rivers System to protect rivers andriver segments with outstanding scenic, recreational,geological, wildlife, historical, or cultural values.Congress established a three-tiered classificationscheme. Wild rivers are rivers or segments of rivers thatare relatively inaccessible and untamed and that arenot permitted to be widened, straightened, dredged,filled, or dammed. The only activities allowed arecamping, swimming, nonmotorized boating, sporthunting, and sport and commercial fishing.Scenic rivers are free of dams, mostly undeveloped,accessible in some places by roads, and of great scenicvalue. Recreational rivers are rivers or sections of riversthat are readily accessible by roads and that may havesome dams or development along their shores.Currently only 0.2% of the country’s 6 millionkilometers (3.5 million miles) are protected by theWild and Scenic Rivers System. In contrast, dams andreservoirs are found on 17% of the country’s total riverlength.Environmentalists urge Congress to add 1,500additional river segments to the system, a goal vigorouslyopposed by some local communities and antienvironmentalgroups. Achieving this goal wouldprotect about 2% of the country’s river systems. Thatis still 98% for us and only 2% for the wild rivers andtheir species.In this chapter we have seen that threats to aquaticbiodiversity are real and growing and are even greaterthan threats to terrestrial biodiversity. Keys to sustaininglife in the earth’s aquatic systems include greatly increasingresearch to learn more about aquatic life,greatly expanding efforts to protect and restore aquaticbiodiversity, and promoting integrated ecological managementof connected terrestrial and aquatic systems.These things can be done if enough people insist on it.To promote conservation, fishers and officials need to viewfish as a part of a larger ecological system, rather than simplyas a commodity to extract.ANNE PLATT MCGINNCRITICAL THINKING1. What three actions would you take to deal with theecological and economic problems of Africa’s LakeVictoria?http://biology.brookscole.com/miller14271