土地沙漠化英文介绍-Desertification.doc

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1、Desertificationisatypeoflanddegradationinwhicharelativelydrylandregionbecomesincreasinglyarid,typicallylosingitsbodiesofwateraswellasvegetationandwildlife.Itiscausedbyavarietyoffactors,suchasclimatechangeandhumanactivities.Desertificationisasignificantglobalecologicalande

2、nvironmentalproblem.Let’sbeginwiththeareasaffectedbythedesertificationDrylandsoccupyapproximately40–41%ofEarth’slandareaandarehometomorethan2billionpeople.Ithasbeenestimatedthatsome10–20%ofdrylandsarealreadydegraded,thetotalareaaffectedbydesertificationbeingbetween6and12m

3、illionsquarekilometres,andthatabillionpeopleareunderthreatfromfurtherdesertification.TheSaharaiscurrentlyexpandingsouthatarateofupto48kilometersperyear.Buthowisthedesertificationcomingintobeing?HerearesomeCauses.Desertificationiscausedbytwomaincategoriesoffactors:naturalf

4、actorsand,moreimportantly,humanactivities.Thenaturalfactorscausingdesertificationincludethefollowing:1.Theclimatehasamajorinfluencethroughrainfall,solarradiationandwind,whichaffecttheratesofphysicalandmechanicalerosionaswellaschemicalandbiologicaldegradationofsoil.2.There

5、liefofalandaffectstherateofsoilerosionbywater.3.Thetextile,structure,andchemicalandbiologicalstatusofsoilarefactorsdeterminingthesoilpropertiesindrysub-humidzones.Humanactivitiesplayacrucialroleindesertification.Thereasonsbehindtheseactivitiesaretheincreasingdemandforfood

6、duetotherapidpopulationgrowth,andinappropriateagriculturalpractices.Thefollowingaresomeofthehumanactivitiesthatcausedesertification:1.Uncontrolleduseoffireforhuntingorforagriculturalclearing.2.Over-exploitationofwoodyresources,particularlyforfuelwood.3.Over-grazingofselec

7、tivevegetation4.Over-harvestingwhichresultsinabandonedfields5.Agriculturalpracticesthatdestroythesoilstructure.6.Inappropriateirrigationofsoil,leadingtowaterloggingandabandonedfieldseventually.Basedontheabovefactors,wecanseethatthesoilbecomesunsuitableforvegetationgrowtha

8、ndisturnedeventuallyintoadesert.Herearesomeenvironmentalimpactsofdesertification1.Thelossoffarml