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1、智课网托福备考资料托福阅读――指代题（十八）MayaWaterProblemsTounderstandtheancientMayanpeoplewholivedintheareathatistodaysouthernMexicoandCentralAmericaandtheecologicaldifficultiestheyfaced,onemustfirstconsidertheirenvironment,whichwethinkofas"jungle"or"tropicalrainforest
2、."Thisviewisinaccurate,andthereasonprovestobeimportant.Properlyspeaking,tropicalrainforestsgrowinhigh-rainfallequatorialareasthatremainwetorhumidallyearround.ButtheMayahomelandliesmorethansixteenhundredkilometersfromtheequator,atlatitudes17to22degrees
3、north,inahabitattermeda"seasonaltropicalforest."Thatis,whiletheredoestendtobearainyseasonfromMaytoOctober,thereisalsoadryseasonfromJanuarythroughApril.Ifonefocusesonthewetmonths,onecallstheMayahomelanda"seasonaltropicalforest";ifonefocusesonthedrymont
4、hs,onecouldinsteaddescribeitasa"seasonaldesert."FromnorthtosouthintheYucatanPeninsula,wheretheMayalived,rainfallrangesfrom18to100inches(457to2,540millimeters)peryear,andthesoilsbecomethicker,sothatthesouthernpeninsulawasagriculturallymoreproductiveand
5、supporteddenserpopulations.ButrainfallintheMayahomelandisunpredictablyvariablebetweenyears;somerecentyearshavehadthreeorfourtimesmorerainthanotheryears.Asaresult,modernfarmersattemptingtogrowcornintheancientMayahomelandshavefacedfrequentcropfailures,e
6、speciallyinthenorth.TheancientMayawerepresumablymoreexperiencedanddidbetter,butneverthelesstheytoomusthavefacedrisksofcropfailuresfromdroughtsandhurricanes.AlthoughsouthernMayaareasreceivedmorerainfallthannorthernareas,problemsofwaterwereparadoxically
7、moresevereinthewetsouth.WhilethatmadethingshardforancientMayalivinginthesouth,ithasalsomadethingshardformodernarchaeologistswhohavedifficultyunderstandingwhyancientdroughtscausedbiggerproblemsinthewetsouththaninthedrynorth.Thelikelyexplanationisthatan
8、areaofundergroundfreshwaterunderliestheYucatanPeninsula,butsurfaceelevationincreasesfromnorthtosouth,sothatasonemovessouththelandsurfaceliesincreasinglyhigherabovethewatertable.InthenorthernpeninsulatheelevationissufficientlylowthattheancientM
