Environmental Problems, Their Causes, and Sustainability 1

A more expensive and less widely used method ofrangeland management is to suppress the growth ofunwanted invader plants by herbicide spraying, mechanicalremoval, or controlled burning. A cheaperway to discourage unwanted vegetation is controlled,short-term trampling by large numbers of livestock.Replanting barren areas with native grass seedsand applying fertilizer can increase growth of desirablevegetation and reduce soil erosion. But this is an expensiveway to restore severely degraded rangeland.Kilograms of grain needed per kilogram of body weightBeef cattlePigsChickenFish (catfishor carp)22.247How Can We Produce Meat More Sustainably?Shifting Our Meat PrioritiesWe can reduce the environmental impacts of meatproduction by relying more on fish and chicken andless on beef and pork.Livestock and fish vary widely in the efficiency withwhich they convert grain into animal protein (Figure14-22). A more sustainable form of meat productionand consumption would involve shifting from lessgrain-efficient forms of animal protein, such as beefand pork, to more grain-efficient ones, such as poultryand farmed fish (Figure 14-22).Some environmentalists have called for reducinglivestock production (especially cattle) to decrease itsenvironmental effects and to feed more people. Thiswould decrease the environmental impact of livestockproduction, but it would not free up much land orgrain to feed more of the world’s hungry people.Cattle and sheep that graze on rangeland use a resource(grass) that humans cannot eat, and most of thisland is not suitable for growing crops. Moreover, becauseof poverty, insufficient economic aid, and the natureof global economic and food distribution systems,very little if any additional grain grown on land onceused to raise livestock or livestock feed would reachthe world’s hungry people.14-8 CATCHING AND RAISINGMORE FISH AND SHELLFISHWhere Do We Get the Fish and Shellfish WeEat? Oceans and Fish FarmsAbout 88% of the fish and shellfish we eat comes fromthe ocean or is produced by aquaculture in aquaticfeedlots.The world’s third major food-producing system consistsof fisheries: concentrations of particular aquaticspecies suitable for commercial harvesting in a givenocean area or inland body of water.About 55% of the annualcommercial catch of fish and shellfish comes fromthe ocean, mostly from plankton-rich coastal waters.Figure 14-22 Efficiency of converting grain into animal protein.Data in kilograms of grain per kilogram of body weight added.(U.S. Department of Agriculture)The rest of the catch comes from using aquacultureto raise marine and freshwater fish like livestock animalsin feedlots in ponds and underwater cages andfrom inland freshwater fishing from lakes, rivers,reservoirs, and ponds. About one-third of the world’smarine fish harvest is used as animal feed, fishmeal,and oils.Some commercially important marine species offish and shellfish are shown in Figure 14-23 (p. 298).Fish and shellfish supply about 7% of the global foodsupply and are the primary source of animal protein forabout 1 billion people, mostly in developing countries.How Are Fish and Shellfish Harvested?Hunt and Gather As Much As You CanHigh-tech global fishing fleets roam the world’soceans to find and harvest most of the fish andshellfish we eat.The world’s commercial marine fishing industry isdominated by industrial fishing fleets using globalsatellite positioning equipment, sonar, huge nets andlong fishing lines, spotter planes, and large factory shipsthat can process and freeze their catches. Figure 14-24(p. 299) shows the major methods used for the commercialharvesting of various marine fish and shellfish.Let us look at a few of these methods. Trawler fishingis used to catch fish and shellfish—especiallyshrimp, cod, flounder, and scallops—that live on ornear the ocean floor. It involves dragging a funnelshapednet held open at the neck along the ocean bottomand weighed down with chains or metal plates.This scrapes up almost everything that lies on theocean floor and often destroys bottom habitats—somewhat like clear-cutting the ocean floor. Newertrawling nets are large enough to swallow 12 jumbojets and even larger ones are on the way! The largemesh of the net allows most small fish to escape butcan capture and kill other species such as seals andhttp://biology.brookscole.com/miller14297