Environmental Problems, Their Causes, and Sustainability 1

estuaries. Then the fish are released, and adults areharvested when they return to spawn (Figure 13-14,right, p. 269).Figure 14-27 lists the major advantages and disadvantagesof aquaculture. Some analysts project thatfreshwater and saltwater aquaculture productioncould provide at least half of the world’s seafood by2020. Some also propose increased use of aquacultureto grow single-cell algae such as Spirulina, which is70% protein.But other analysts warn that the harmful environmentaleffects of aquaculture (Figure 14-27, right)could limit future production. Also, some trends inaquaculture could harm ocean fisheries. For example,intensive farming of large carnivorous fish like salmonand trout is replacing traditional aquaculture in whichfarmed fish such as carp and tilapia eat plants anddetritus. This increases overfishing of smaller marinespecies used to feed farmed carnivorous species. Ifkept up, this depletion of the seas to feed aquaculturefarms could cause the collapse of both marine fisheriesand carnivorous aquaculture. Figure 14-28 lists someways to make aquaculture more sustainable and to reduceits environmental effects.AdvantagesHighly efficientHigh yield insmall volumeof waterIncreased yieldsthrough crossbreedingand geneticengineeringCan reduceoverharvestingof conventionalfisheriesLittle use of fuelProfits not tied toprice of oilHigh profitsT rade-OffsAquacultureDisadvantagesLarge inputs ofland, feed, andwater neededProduces largeand concentratedoutputs of wasteDestroysmangrove forestsIncreased grainproduction neededto feed some speciesFish can be killedby pesticide runofffrom nearby croplandDense populationsvulnerable to diseaseTanks toocontaminated to useafter about 5 yearsFigure 14-27 Trade-offs: advantages and disadvantages ofaquaculture. Pick the single advantage and disadvantage thatyou think are the most important.SolutionsMore Sustainable Aquaculture• Reduce use of fishmeal as a feed to reducedepletion of other fish• Improve pollution management of aquaculturewastes• Reduce escape of aquaculture species into the wild• Restrict location of fish farms to reduce loss ofmangrove forests and other threatened areas• Farm some aquaculture species (such as salmonand cobia) in deeply submerged cages to protectthem from wave action and predators and allowdilution of wastes into the ocean• Set up a system for certifying sustainable forms ofaquacultureFigure 14-28 Solutions: Ways to make aquaculture moresustainable and reduce its harmful environmental effects.However, even under the most optimistic projections,increasing both the wild catch and aquaculturewill not increase world food supplies significantly. Thereason is that currently fish and shellfish supply onlyabout 1% of the energy and 6% of the total protein inthe human diet.xHOW WOULD YOU VOTE? Do the advantages of aquacultureoutweigh its disadvantages? Cast your vote online athttp://biology.brookscole.com/miller14.14-9 GOVERNMENT AGRICULTURALPOLICYHow Do Government Agricultural PoliciesAffect Food Production? To Interfere orNot to InterfereGovernments can use price controls to keep foodprices artificially low, give farmers subsidies toencourage food production, or eliminate food pricecontrols and subsidies and let farmers respond tomarket demand.Agriculture is a financially risky business. Whetherfarmers have a good year or a bad year depends onfactors over which they have little control: weather,crop prices, crop pests and diseases, interest rates, andthe global market. Because of the need for reliable foodsupplies despite fluctuations in these factors, mostgovernments provide various forms of assistance tofarmers and consumers.Governments use three main approaches to do this.One is to use price controls to keep food prices artificiallyhttp://biology.brookscole.com/miller14301