Australia:Anintroduction

　　Inlandarea,AustraliaisthesixthlargestnationafterRussia,Canada,China,theUnitedStatesofAmericaandBrazil.Ithas,however,arelativelysmallpopulation.

　　Australiaistheonlynationtogovernanentirecontinentanditsoutlyingislands.Themainlandisthelargestislandandthesmallest,flattestcontinentonEarth.Itliesbetween10掳and39掳Southlatitude.

　　Thehighestpointonthemainland,MountKosciuszko,isonly2228metres.ApartfromAntarctica,Australiaisthedriestcontinent.

　　Australiaisthedriestinhabitedcontinentonearth.Itsinteriorhasoneofthelowestrainfallsintheworldandaboutthree-quartersofthelandisaridorsemi-arid.Itsfertileareasarewell-watered,however,andtheseareusedveryeffectivelytohelpfeedtheworld.Sheepandcattlegrazeindrycountry,butcaremustbetakenwiththesoil.SomegrazinglandbecamedesertwhenthelongcyclesthatinfluencerainfallinAustraliaturnedtodrought.

　　TheAustralianfederationconsistsofsixStatesandtwoTerritories.Mostinlandbordersfollowlinesoflongitudeandlatitude.ThelargestState,WesternAustralia,isaboutthesamesizeasWesternEurope.

　　Naturalenvironment

　　Australiahasaremarkablediversityoflifeformsseennowhereelseintheworld.Australianplantsandanimalsevolvedinisolationfromotherpartsoftheworld.Whenthesuper-continentofGondwanalandsplitupabout160millionyearsago,AustraliajoinedAntarcticaanddriftedtowardstheSouthPole,whereglaciersformedabarrierbetweenitandotherlandmasses.

　　Overthepast45millionyears,AustraliahasmovedawayfromAntarcticatowardstheequatorandbecomewarmerandmorearid.About35millionyearsago,eucalyptsbegantodisplacethedenseforestsofthecool,dampTertiaryera.

　　TodayAustralianeucalyptsaccountformorethanhalfofalleucalyptsfoundthroughouttheworld.

　　ThemarsupialsnativetoAustraliahaveadifferentchromosomestructurethanmammalsinotherpartsoftheworld.Typically,theysuckletheiryounginapouch.

　　Liketheeucalypts,marsupialsoccupiedawiderangeofecologicalnichesinAustralia.Thefirstkangaroomarsupialsseemtohaveappearedabout15millionyearsago.Theyvaryenormouslyinsizeandadaptation.Aspeciesoftropicalkangaroolivesintrees,butmostkangaroosaretough,efficientusersofdrybush.

　　Astheworldclimatewarmedandglaciersmelted,oceansgraduallyrosetotheircurrentlevelandthelandbridgestoNewGuineaandTasmaniawerecut.Coralscolonisedafloodedcoastalplain,formingtheGreatBarrierReefofQueensland.

　　Ancientplantsstillgrowinthewild.Large'Antarctic'treefernsarecommonindamp,shadedgulliesonthesouthsidesofridges.Cycadpalmsformanunderstoreytotall,silveryspottedgums(eucalypts)alongthesouth-eastcoast.Rarerelicsfromearliergeologicalerasarefoundinsmall,specialhabitats,suchasdesertcanyons.

　　Pressureonnativehabitatsfromagricultureandintroducedpestslikethefoxandrabbithaveresultedinextinctionsofsomenativespeciesinthepast200years.Australianowhasastrongscientificandlegalframeworktodealwiththeseissues.Australianscareabouttheiruniqueenvironment.

　　History

　　Morethan60000yearsbeforethearrivalofEuropeansettlers,Aborigi