ThehugeFloridawetlandknownastheEvergladesisaslow-movingriver80kilometerswidebutonlyafewcentimetersdeep.PeoplecalltheEvergladesa“riverofgrass”becausesawgrasscoversmostofit.Sawgrassisnotreallygrass.

　　ThehugeFloridawetlandknownastheEvergladesisaslow-movingriver80kilometerswidebutonlyafewcentimetersdeep.PeoplecalltheEvergladesa“riverofgrass”becausesawgrasscoversmostofit.Sawgrassisnotreallygrass.Itisaplantthathasleavesedgedwithtinysharpteeththatcaneasilycutthroughclothes--andskin!

　　TravelintheEvergladesisdifficult.Youcannotwalkthroughshallowwaterbecausethesawgrasswillcutyou.Thewateristooshallowforregularboats.Soweuseanairboat.Anairboatisaflatopenboat.Likeanairplaneithasabigpropellertomoveit.Thepropellerisfixedontherearoftheboat.Itmakesatremendousnoisebutitdoesthejob.Thebeatskimsalongthewater'ssurface.Althoughwecanstillgetlostinanairboatatleastweareabovethealligators（短嘴鳄）.

　　WhilehundredsofdifferentkindsofanimalsliveintheEvergladesthemostfamousissurelythealligator.OnceendangeredalligatorsarenowprotectedwithinEvergladesNationalPark.Visitorsarelikelytoseethembothonlandandinwater.

　　ForalongtimedangershavethreatenedtheEverglades.Around1900somepeoplefeltthispreciouswetlandshouldbedrained（排干）.Theysaiditwasjustabigswampandnotgoodforanything.Inthe1920stherewasalandboominFlorida.PeoplewantedtobuildhomeseverywhereincludingintheEverglades.TheybuiltcanalsleveesandotherwatersystemsthatstoppedtheriversflowingintotheEverglades.Factorieswerebuiltnearriversthatflowedintothewetland.ThesefactoriesdumpedpoisonouswastethatdamagedtheEvergladesecosystem.

　　PeoplearenowworkingtopreservetheEvergladesNationalParkforthefuture.Rightnowonebigproblemisthepaperbarkme.ThistreeisaninvaderfromAustralia.

　　Paperbarktreessoakupalotofwater.Intheearly1900speoplebroughtthemtoFloridabecausetheythoughttheywouldhelpdraintheEverglades.Howevertheinvadersadaptedtoowell.PaperbarktreeshavetakenoverhundredsofthousandsofacresoftheEvergladesandkilledothertrees.Scientistsarecuttingdowntheseinvadersorsprayingthemwithherbicidestokillthem.

　　1．WhyisitdifficulttotravelinEverglades?

　　A．Airboatsmaymakeaverybignoise.

　　B．Youmaygetlostwhenpassingthrough.