Environmental Problems, Their Causes, and Sustainability 1

control approach and to be sure the introduced speciesthemselves do not become pests.13-3 PROTECTING AND SUSTAININGMARINE BIODIVERSITYWhy Is It Difficult to Protect MarineBiodiversity? Out of Sight, Out of MindCoastal development, the invisibility and vastnessof the world’s oceans, and lack of legal jurisdictionhinder protection of marine biodiversity.There are several reasons why protecting marine biodiversityis difficult. One is rapidly growing coastaldevelopment and the accompanying massive inputs ofsediment and other wastes from land into coastal waters.This harms shore-hugging species and threatensbiologically diverse and highly productive coastalecosystems such as coral reefs, marshes, and mangroveforest swamps.Another factor is that much of the damage to theoceans and other bodies of water is not visible to mostpeople. And many people incorrectly view the seas asan inexhaustible resource that can absorb an almost infiniteamount of waste and pollution.In addition, most of the world’s ocean area liesoutside the legal jurisdiction of any country. Thus it isan open-access resource, subject to overexploitationbecause of the tragedy of the commons.How Can We Protect Endangered andThreatened Marine Species? LegalAgreements and AwarenessWe can use laws, international treaties, and educationto help reduce the premature extinction of marinespecies.One widely used method for protecting biodiversity isidentifying and protecting endangered, threatened,and rare species, as has been done to help save a numberof endangered terrestrial species (Chapter 12).This strategy has also been used to protect a numberof endangered and threatened marine reptiles (turtles)and mammals (especially whales, seals, and sea lions;Figure 13-6, p. 258). Each year plastic itemsdumped from ships and left as litter on beaches threatenthe lives of millions of marine mammals, turtles, andseabirds that ingest, become entangled in, choke on, orare poisoned by such debris (see photo on p. viii).Three of eight major sea turtle species (Figure 13-7,p. 258) are endangered (Kemp’s ridley, leatherbacks,and hawksbills), and the rest are threatened, mostlybecause of four factors. First is loss or degradation ofbeach habitat where they come ashore to lay eggs. Secondis the legal and illegal taking of eggs. Third is theincreased use of turtles as sources of food, medicinalINDIVIDUALSMATTERKilling Invader Speciesand Saving ShippingCompanies MoneyA large cargo ship typically has adozen or more ballast tanks belowdeck. Each tank is the size of ahigh school gymnasium andholds millions of gallons of water.When a ship takes on cargo and leaves port itpumps water into the ballast tanks to keep it low inthe water, submerge its rudder, and help maintainstability. This water also contains large numbers offish, crabs, clams, and other species (many of themmicroscopic) found in the port’s local waters.When the ship’s cargo is removed at its destinationits ballast water is released until the shipis loaded again. This dumps millions of foreignorganisms into rivers and bays. Thus cargo shipsmoving about 80% of the goods traded internationallyplay the primary role in the release of nonnativeaquatic organisms into various parts of theworld.In 2002, researchers Mario Tamburri andKerstin Wasson found that pumping nitrogengas into ballast tanks while a ship is at sea virtuallyeliminates dissolved oxygen in the ballastwater. This saves the shipping industry money byreducing corrosion of a ship’s steel compartments.In addition, within three days it kills most fish,crabs, clams, and other potential invader specieslurking in the ballast tanks.ingredients, tortoiseshell (for jewelry), and leatherfrom their flippers. Fourth, many turtles are unintentionallycaptured and drowned by commercial fishingboats—especially shrimp trawlers and those usinglong lines of hooks. Conservationists estimate thateach year the global longline fishing industry unintentionallyhooks and kills as many as 40,000 sea turtles asbycatch. In 2004 the United States banned long-lineswordfish fishing off the Pacific coast to save dwindlingsea turtle populations.Until recently, U.S. shrimp trawling boats killed asmany as 55,000 sea turtles (mostly endangered loggerheadsand Kemp’s ridleys) each year. To reduce thisslaughter, since 1989 the U.S. government has requiredoffshore shrimp trawlers to use turtle exclusion devices(TEDs). In 2004 researchers at the NationalMarine Fisheries Service reported that longline fishingboats using a rounder hook with a smaller openingand baited with mackerel instead of squid could reducethe sea turtle bycatch by 65–90%.National and international laws and treaties tohelp protect marine species include the 1975 Conventionon International Trade in Endangered Specieshttp://biology.brookscole.com/miller14257