首页
登录
职称英语
When prehistoric man arrived in new parts of the world, something strange hap
When prehistoric man arrived in new parts of the world, something strange hap
游客
2023-12-24
60
管理
问题
When prehistoric man arrived in new parts of the world, something strange happened to the large animals: they suddenly became extinct. Smaller species survived. The large, slow-growing animals were easy game, and were quickly hunted to extinction. Now something similar could be happening in the oceans.
That the seas are being overfished has been known for years. What researchers such as Ransom Myers and Boris Worm have shown is just how fast things are changing. They have looked at half a century of data from fisheries around the world. Their methods do not attempt to estimate the actual biomass (the amount of living biological matter) of fish species in particular parts of the ocean, but rather changes in that biomass over time. According to their latest paper published in Nature, the biomass of large predators (animals that kill and eat other animals) in a new fishery is reduced on average by 80% within 15 years of the start of exploitation. In some long-fished areas, it has halved again since then.
Dr. Worm acknowledges that these figures are conservative. One mason for this is that fishing technology has improved. Today’s vessels can find their prey using satellites and sonar, which were not available 50 years ago. That means a higher proportion of what is in the sea is being caught, so the real difference between present and past is likely to be worse than the one recorded by changes in catch sizes. In the early days, too, longlines would have been more saturated with fish. Some individuals would therefore not have been caught, since no baited hooks would have been available to trap them, leading to an underestimate of fish stocks in the past. Furthermore, in the early days of longline fishing, a lot of fish were lost to sharks after they had been hooked. That is no longer a problem, because there are fewer sharks around now.
Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account. They believe the data support an idea current among marine biologists, that of the "shifting baseline". The notion is that people have failed to detect the massive changes which have happened in the ocean because they have been looking back only a relatively short time into the past. That matters because theory suggests that the maximum sustainable yield that can be cropped from a fishery comes when the biomass of a target species is about 50% of its original levels. Most fisheries are well below that, which is a bad way to do business. [br] Dr Myers and other researchers hold that ______.
选项
A、people should look for a baseline that can’t work for a longer time
B、fisheries should keep the yield below 50% of the biomass
C、the ocean biomass should be restored to its original level
D、people should adjust the fishing baseline to changing situation
答案
D
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3300001.html
相关试题推荐
Allofthepeopleinthelabwere______bythestrangeresultsoftheexperiment.
Shesearchedthefacesfortwobelovedones,butsomethingtoldhersoftlythat
Ifyoudemandsomething________,youmakealotofnoise.A、vocallyB、vociferousl
Thenursegavemesomethingto________thepain.A、aggravateB、increaseC、augment
Whentheybrokeopenthedoor,theyfoundastrangemanliedontheflooruncons
Shesearchedthefacesfortwobelovedones,butsomethingtoldhersoftlythat
Thegoodthingwasthateverytimehecanceledhepromisedsomethingelse,somet
Allofthepeopleinthelabwere________bythestrangeresultsoftheexperimen
Whatsocialfunctionmaythestrangelyshapedtailfeathershave?[originaltext]
[originaltext]Whenshefirstarrivedinthiscity,Ms.Allansharedaroomwith
随机试题
Inregardtotheproductionofgoodsingreaterquantities,theauthorstatesth
TheGameoftheNameHerecomesJohnSmithwalkingt
Comparedwith"paperbacks",asissuggestedinthispassage,"proper"booksare
OnJuly20,1969,NeilArmstrongbecamethefirstpersontowalkonthe
属于专性需氧菌的是A.破伤风梭菌B.脑膜炎奈瑟C.铜绿假单胞菌D.伤寒沙门菌E.
银行确立贷款意向后,业务人员向客户索取的贷款申请资料中必须包括财务报表,下列有关
下列关于《选举法》的说法哪(一)些是错误的?A.由于某地行政区划变动,某地人大代
长期税务顾问项目一般()项目启动会。A.召开 B.不召开 C.酌情召开
对工程造成特大经济损失或长时间延误工期,经处理仍对正常使用和工程使用寿命有较大影
盖挖法施工缝施工方法中传统的方法是()。A.注入法 B.充填法 C.直
最新回复
(
0
)