首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
When prehistoric man arrived in new parts of the world, something strange happened to the large animals: they suddenly became ex
When prehistoric man arrived in new parts of the world, something strange happened to the large animals: they suddenly became ex
admin
2011-01-10
36
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.
By saying "these figures are conservative" (para. 3), Dr Worm means that ______.
选项
A、fishing technology has improved rapidly
B、then catch-sizes are actually smaller then recorded
C、the marine biomass has suffered a greater loss
D、the data collected so far are out of date
答案
C
解析
转载请注明原文地址:https://kaotiyun.com/show/tncO777K
本试题收录于:
NAETI中级口译笔试题库外语翻译证书(NAETI)分类
0
NAETI中级口译笔试
外语翻译证书(NAETI)
相关试题推荐
ThepeopleofChinaareworkingveryhardtomakeconcertedeffortstoinvigoratethecountry.
Thefeelingofcompetitionamongthestudentsinalltheclassroomswherethetestwasgoingonwasnoticeabletoeveryone.
Thehistoryteachertoldustheringwasapieceof______treasurebecauseithadbeenhandeddownfromanancientking.
Nowwhicharetheanimalsreallytobepitiedincaptivity?First,thosecleverbeingswhoselivelyurgeforactivitycanfindn
Ifyouareanenergeticpersonwithstrongviewsastotherightwayofdoingthings,youfindyourself______underpressures.
Differencesinpositionsadoptedbyoxygenandhydrogenatomsaccountforvariationsinthecrystallinestructureofdifferentf
AlphaZeroseemstoexpressinsight.Itplayslikenocomputereverhas,intuitivelyandbeautifully,witharomantic,attacking
信息通讯技术进步带来无限机遇,推动商务和生产走向高增值,并改善了香港公民的生活质量。同时,这一进步也在多方面带来了新挑战,例如信息安全、数码环境中知识产权及私稳保护、媒体交汇趋势下的适当监管模式方面。领先的数码经济体系需抓住机遇,接受挑战,才能稳居世界前列
A、Itisprosperousandstable.B、Ithasvastexpansesofdesertedcanefields.C、Itusescanefieldsastouristattractions.D、I
IntheUnitedStates,olderpeoplerarelylivewiththeiradultchildren.Butinmanyothercultureschildrenareexpectedtoca
随机试题
属于神经毒类毒蛇的是
张力性气胸的表现是()
A.葱皮状骨膜反应B.花边状骨膜反应C.放射状骨膜反应D.垂直状骨膜反应E.平行状骨膜反应骨膜下出血易出现
预防焊接变形的合理的装配工艺措施包括()。
“限额领料单”按其填制方法属于()。
发审委委员审核股票发行申请文件时,有( )情形之一的,应及时提出回避。
在信用活动中发挥主要作用的金融机构是()。
某公司在按照GB/T19001—2000建立质量体系并实施、运行,现为验证质量管理体系是否运行有效,需组织一次内审。为了组织并实施这次内审,公司必须先解决下列问题:若该公司要编制审核报告,则应由()对审核报告负责。
国家建立统一的义务教育教师职务制度。教师职务分为()职务、中级职务和高级职务。
清朝设置了哪些特别行政区?采取了哪些不同于内地的管理方法?
最新回复
(
0
)