A Short History of Nearly Everything-第60章

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at　they　have　arrived　at　a　foodopportunity　and　fall　onto　it。

so　why；　if　the　seas　are　so　vast；　do　we　so　easily　overtax　them？　well；　to　begin　with；　theworld’s　seas　are　not　uniformly　bounteous。　altogether　less　than　a　tenth　of　the　ocean　isconsidered　naturally　productive。　most　aquatic　species　like　to　be　in　shallow　waters　where　thereis　warmth　and　light　and　an　abundance　of　organic　matter　to　prime　the　food　chain。　coral　reefs；for　instance；　constitute　well　under　1　percent　of　the　ocean’s　space　but　are　home　to　about　25percent　of　its　fish。

elsewhere；　the　oceans　aren’t　nearly　so　rich。　take　australia。　with　over　20；000　miles　ofcoastline　and　almost　nine　million　square　miles　of　territorial　waters；　it　has　more　sea　lapping　itsshores　than　any　other　country；　yet；　as　tim　flannery　notes；　it　doesn’t　even　make　it　into　the　topfifty　among　fishing　nations。　indeed；　australia　is　a　large　net　importer　of　seafood。　this　isbecause　much　of　australia’s　waters　are；　like　much　of　australia　itself；　essentially　desert。　（anotable　exception　is　the　great　barrier　reef　off　queensland；　which　is　sumptuously　fecund。）because　the　soil　is　poor；　it　produces　little　in　the　way　of　nutrient…rich　runoff。

even　where　life　thrives；　it　is　often　extremely　sensitive　to　disturbance。　in　the　1970s；　fishermenfrom　australia　and；　to　a　lesser　extent；　new　zealand　discovered　shoals　of　a　little…known　fishliving　at　a　depth　of　about　half　a　mile　on　their　continental　shelves。　they　were　known　as　orange1the　indigestible　parts　of　giant　squid；　in　particular　their　beaks；　accumulate　in　sperm　whales　stomachs　into　thesubstance　known　as　ambergris；　which　is　used　as　a　fixative　in　perfumes。　the　next　time　you　spray　on　chanel　no。　5（assuming　you　do）；　you　may　wish　to　reflect　that　you　are　dousing　yourself　in　distillate　of　unseen　sea　monster。

roughy；　they　were　delicious；　and　they　existed　in　huge　numbers。　in　no　time　at　all；　fishing　fleetswere　hauling　in　forty　thousand　metric　tons　of　roughy　a　year。　then　marine　biologists　madesome　alarming　discoveries。　roughy　are　extremely　long　lived　and　slow　maturing。　some　maybe　150　years　old；　any　roughy　you　have　eaten　may　well　have　been　born　when　victoria　wasqueen。　roughy　have　adopted　this　exceedingly　unhurried　lifestyle　because　the　waters　they　livein　are　so　resource…poor。　in　such　waters；　some　fish　spawn　just　once　in　a　lifetime。　clearly　theseare　populations　that　cannot　stand　a　great　deal　of　disturbance。　unfortunately；　by　the　time　thiswas　realized　the　stocks　had　been　severely　depleted。　even　with　careful　management　it　will　bedecades　before　the　populations　recover；　if　they　ever　do。

elsewhere；　however；　the　misuse　of　the　oceans　has　been　more　wanton　than　inadvertent。

many　fishermen　“fin”　sharks—that　is；　slice　their　fins　off；　then　dump　them　back　into　the　waterto　die。　in　1998；　shark　fins　sold　in　the　far　east　for　over　250　a　pound。　a　bowl　of　shark　finsoup　retailed　in　tokyo　for　100。　the　world　wildlife　fund　estimated　in　1994　that　the　numberof　sharks　killed　each　year　was　between　40　million　and　70　million。

as　of　1995；　some　37；000　industrial…sized　fishing　ships；　plus　about　a　million　smaller　boats；were　between　them　taking　twice　as　many　fish　from　the　sea　as　they　had　just　twenty…five　yearsearlier。　trawlers　are　sometimes　now　as　big　as　cruise　ships　and　haul　behind　them　nets　bigenough　to　hold　a　dozen　jumbo　jets。　some　even　use　spotter　planes　to　locate　shoals　of　fish　fromthe　air。

it　is　estimated　that　about　a　quarter　of　every　fishing　net　hauled　up　contains　“by…catch”—fishthat　can’t　be　landed　because　they　are　too　small　or　of　the　wrong　type　or　caught　in　the　wrongseason。　as　one　observer　told　the　economist：　“we’re　still　in　the　dark　ages。　we　just　drop　a　netdown　and　see　what　es　up。”　perhaps　as　much　as　twenty…two　million　metric　tons　of　suchunwanted　fish　are　dumped　back　in　the　sea　each　year；　mostly　in　the　form　of　corpses。　for　everypound　of　shrimp　harvested；　about　four　pounds　of　fish　and　other　marine　creatures　aredestroyed。

large　areas　of　the　north　sea　floor　are　dragged　clean　by　beam　trawlers　as　many　as　seventimes　a　year；　a　degree　of　disturbance　that　no　ecosystem　can　withstand。　at　least　two…thirds　ofspecies　in　the　north　sea；　by　many　estimates；　are　being　overfished。　across　the　atlantic　thingsare　no　better。　halibut　once　abounded　in　such　numbers　off　new　england　that　individual　boatscould　land　twenty　thousand　pounds　of　it　in　a　day。　now　halibut　is　all　but　extinct　off　thenortheast　coast　of　north　america。

nothing；　however；　pares　with　the　fate　of　cod。　in　the　late　fifteenth　century；　the　explorerjohn　cabot　found　cod　in　incredible　numbers　on　the　eastern　banks　of　north　america—shallowareas　of　water　popular　with　bottom…feeding　fish　like　cod。　some　of　these　banks　were　vast。

georges　banks　off　massachusetts　is　bigger　than　the　state　it　abuts。　the　grand　banks　offnewfoundland　is　bigger　still　and　for　centuries　was　always　dense　with　cod。　they　were　thoughtto　be　inexhaustible。　of　course　they　were　anything　but。

by　1960；　the　number　of　spawning　cod　in　the　north　atlantic　had　fallen　to　an　estimated　1。6million　metric　tons。　by　1990　this　had　sunk　to　22；000　metric　tons。　in　mercial　terms；　thecod　were　extinct。　“fishermen；”　wrote　mark　kurlansky　in　his　fascinating　history；　cod；　“hadcaught　them　all。”　the　cod　may　have　lost　the　western　atlantic　forever。　in　1992；　cod　fishingwas　stopped　altogether　on　the　grand　banks；　but　as　of　last　autumn；　according　to　a　report　innature；　stocks　had　not　staged　a　eback。　kurlansky　notes　that　the　fish　of　fish　fillets　and　fishsticks　was　originally　cod；　but　then　was　replaced　by　haddock；　then　by　redfish；　and　lately　bypacific　pollock。　these　days；　he　notes　drily；　“fish”　is　“whatever　is　left。”

much　the　same　can　be　said　of　many　other　seafoods。　in　the　new　england　fisheries　offrhode　island；　it　was　once　routine　to　haul　in　lobsters　weighing　twenty　pounds。　sometimes　theyreached　thirty　pounds。　left　unmolested；　lobsters　can　live　for　decades—as　much　as　seventyyears；　it　is　thought—and　they　never　stop　growing。　nowadays　few　lobsters　weigh　more　thantwo　pounds　on　capture。　“biologists；”　according　to　the　new　york　times；　“estimate　that　90percent　of　lobsters　are　caught　within　a　year　after　they　reach　the　legal　minimum　size　at　aboutage　six。”　despite　declining　catches；　new　england　fishermen　continue　to　receive　state　andfederal　tax　incentives　that　encourage　them—in　some　cases　all　but　pel　them—to　acquirebigger　boats　and　to　harvest　the　seas　more　intensively。　today　fishermen　of　massachusetts　arereduced　to　fishing　the　hideous　hagfish；　for　which　there　is　a　slight　market　in　the　far　east；　buteven　their　numbers　are　now　falling。

we　are　remarkably　ignorant　of　the　dynamics　that　rule　life　in　the　sea。　while　marine　life　ispoorer　than　it　ought　to　be　in　areas　that　have　been　overfished；　in　some　naturally　impoverishedwaters　there　is　far　more　life　than　there　ought　to　be。　the　southern　oceans　around　antarcticaproduce　only　about　3　percent　of　the　world’s　phytoplankton—far　too　little；　it　would　seem；　tosupport　a　plex　ecosystem；　and　yet　it　does。　crab…eater　seals　are　not　a　species　of　animal　thatmost　of　us　have　heard　of；　but　they　may　actually　be　the　second　most　numerous　large　species　ofanimal　on　earth；　after　humans。　as　many　as　fifteen　million　of　them　may　live　on　the　pack　icearound　antarctica。　there　are　also　perhaps　two　million　weddel　seals；　at　least　half　a　millionemperor　penguins；　and　maybe　as　many　as　four　million　adélie　penguins。　the　food　chain　isthus　hopelessly　top　heavy；　but　somehow　it　works。　remarkably　no　one　knows　how。

all　this　is　a　very　roundabout　way　of　making　the　point　that　we　know　very　little　about　earth’sbiggest　system。　but　then；　as　we　shall　see　in　the　pages　remaining　to　us；　once　you　start　talkingabout　life；　there　is　a　great　deal　we　don’t　know；　not　least　how　it　got　going　in　the　first　place。

。。！



19THE　RISE　OF　LIFE

，小，说，网
in　1953；　stanley　miller；　a　graduate　student　at　the　university　of　chicago；　took　twoflasks—one　containing　a　little　water　to　represent　a　primeval　ocean；　the　other　holding　amixture　of　methane；　ammonia；　and　hydrogen　sulphide　gases　to　represent　earth’s　earlyatmosphere—connected　them　with　rubber　tubes；　and　introduced　some　electrical　sparks　as　astand…in　for　lightning。　after　a　few　days；　the　water　in　the　flasks　had　turned　green　and　yellow　ina　hearty　broth　of　amino　acids；　fatty　acids；　sugars；　and　other　organic　pounds。　“if　goddidn’t　do　it　this　way；”　observed　miller’s　delighted　supervisor；　the　nobel　laureate　haroldurey；　“he　missed　a　good　bet。”

press　reports　of　the　time　made　it　sound　as　if　about　all　that　was　needed　now　was　forsomebody　to　give　the　whole　a　good　shake　and　life　would　crawl　out。　as　time　has　shown；　itwasn’t　nearly　so　simple。　despite　half　a　century　of　further　study；　we　are　no　nearer　tosynthesizing　life　today　than　we　were　in　1953　and　much　further　away　from　thinking　we　can。

scientists　are　now　pretty　certain　that　the　early　atmosphere　was　nothing　like　as　primed　fordevelopment　as　miller　and　urey’s　gaseous　stew；　but　rather　was　a　much　less　reactive　blend　ofnitrogen　and　carbon　dioxide。　repeating　miller’s　experiments　with　these　more　challenginginputs　has　so　far　produced　only　one　fairly　primitive　amino　acid。　at　all　events；　creating　aminoacids　is　not　really　the　problem。　the　problem　is　proteins。

proteins　are　what　you　get　when　you　string　amino　acids　together；　and　we　ne