四级作文素材

《四级作文素材》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、第五节写作内容储备　　从上表可以看出，四级题目涉及到社会生活的各个方面，但可大体归纳为几个方面，下面就是对各个主要方面常见的内容的介绍。　　一、环境(Environment)　　Likeallotherlivingbeings,humanshaveclearlychangedtheirenvironment,buttheyhavedonesogenerallyonagranderscalethanhaveotherspecies.Someofthesechanges—suchasthedestructionoftheworld’stropicalrainforest

2、stocreategrazinglandforcattleorthedryingupofalmostthree-quartersoftheAralSea,oncetheworld’sfourth-largestfreshwaterlake,forirrigationpurposes—haveledtoalteredclimatepatterns,whichinturnhavechangedthedistributionofspeciesofanimalsandplants.Scientistsareworkingtounderstandthelong-termcon

3、sequencesthathumanactionshaveonecosystems,whileenvironmentalists—professionalsinvariousfields,aswellasconcernedcitizensintheUnitedStatesandothercountries—arestrugglingtolessentheimpactofhumanactivityonthenaturalworld.PopulationGrowth(人口增长)　　Humanpopulationgrowthmaybeseentobeattherootof

4、virtuallyalloftheworld’senvironmentalproblems.Increasinglylargenumbersofpeoplearebeingaddedtotheworldeveryyear.Asthenumberofpeopleincreases,morepollutionisgenerated,morehabitatsaredestroyed,andmorenaturalresourcesareusedup.Evenifnewtechnologicaladvanceswereabletocutinhalftheenvironment

5、alimpactthateachpersonhad,assoonastheworld’spopulationsizedoubled,theearthwouldbenobetteroffthanbefore.　　ThePopulationDivisionoftheUnitedNationspredictsthatthe5.63billionhumansalivein1994willincreaseto6.23billionintheyear2000,8.47billionin2025,and10.02billionin2050.TheUN’sestimateassum

6、esthatpopulationwillpeakandstabilizeat11.6billionin2200.　　Althoughitistruethatratesofpopulationincreasearenowmuchslowerinthedevelopedworldthaninthedevelopingworld,itwouldbeamistaketoassumethatthepopulationgrowthproblemisprimarilyaproblemofdevelopingcountries.Infact,becauselargeramounts

7、ofresourcesperpersonareusedinthedevelopednations,eachcitizenfromthedevelopedworldhasamuchgreaterenvironmentalimpactthandoesacitizenfromadevelopingcountry.　　Evidencenowexistssuggestingthatthemostimportantfactorsnecessarytolowerpopulationgrowthratesinthedevelopingworldaredemocracyandso