土地荒漠化ppt培训讲学.ppt

土地沙漠化,荒漠,一种残缺的美,荒漠,美丽背后的忧患,狭义的荒漠化（即：沙漠化）在脆弱的生态系统下，由于人为过度的经济活动，破坏其平衡，使原非沙漠的地区出现了类似沙漠景观的环境变化过程。DesertificationinanarrowsenseUnderthefragileecosystem,theenvironmentchangeprocesssimilartothedesertlandscapeintheformernon-desertareasisoccurredbecauseoftheartificialexcessiveeconomicactivities,whichdestroysthebalance.,1992年联合国环境与发展大会对荒漠化的概念作了这样的定义：荒漠化是由于气候变化和人类不合理的经济活动等因素，使干旱、半干旱和具有干旱灾害的半湿润地区的土地发生了退化。TheconceptofdesertificationwasdefinedbytheUnitedNationsconferenceonenvironmentanddevelopmentin1992asthedegradationoflandinarid,semi-aridandsemi-humidareas,duetofactorssuchasclimatechangeandirrationalhumaneconomicactivities.,成因,人为破坏说：认为过度放牧开垦，砍伐森林和破坏地表植被，以及水土流失是主要原因。Humandestruction:overgrazing,deforestationanddestructionoflandcover,andsoilerosionarecitedasmajorcauses,变暖说：认为在地质时期低纬度沙漠区的雨期、少雨期与高纬度冰期、间冰期的关系模式是，低纬度少雨-高纬度间冰期，低纬度多雨-高纬度冰期。在变暖的间冰期，低纬度地区少雨干燥，沙漠扩展。近年来，国外一些气候数值模拟结果，认为CO2的温室效应在未来几十年内将使全球气候变暖，导致中纬度地区干旱，其它地区变湿。Itisbelievedthattherelationshipbetweentherainperiodandthelowlatitudeglacialperiodandthehighlatitudeglacialperiodandthelowlatitudeinterglacialperiodandthelowlatitudepluvialperiodandthehighlatitudeinterglacialperiodinthegeologicalperiod.Duringthewarmerinterglacialperiods,thelowerlatitudesweredrierandthedesertexpanded.Inrecentyears,someclimatenumericalsimulationsabroadbelievethatthegreenhouseeffectofCO2willcauseglobalwarminginthecomingdecades,resultingindroughtinthemid-latituderegionandwetinotherregions.,海气相互作用说：认为是热带海温异常导致低纬度大气环流异常所引起。Air-seainteractiontheory:itisbelievedthattropicalSSTanomaliesleadtoatmosphericcirculationanomaliesatlowerlatitudes.反馈说：认为干旱开始后，由于植物枯死，土壤水分减少，蒸发大为减少，形成对流性降水的可能性减少；半干旱地区过量放牧使地面反射率增加，改变地面能量平衡，导致下沉运动，造成持久干旱；雨云中的生物源材料的消失，使降水减少等等。Accordingtothefeedback,thepossibilityofconvectiveprecipitationisreducedasthesoilmoisturedecreasesandevaporationdecreasesafterthedroughtbegins.Overgrazinginsemi-aridregionsincreasesgroundreflectivity,changesgroundenergybalance,andleadstosubsidencemovement,resultinginprolongeddrought.Thedisappearanceofbiologicalsourcematerialinraincloudscausesthereductionofprecipitation,etc.,天文说：认为由于地球轨道参数变化，使中高纬度夏季辐射量减少，导致冰期的发生和沙漠区的扩大。变冷说：认为气候变冷导致降水能源减少，蒸发量减少，干旱使沙漠扩大。Astronomicaltheory:itisbelievedthatduetochangesinearthorbitparameters,summerradiationinthemiddleandhighlatitudesisreduced,resultingintheoccurrenceoficeageandexpansionofdesertareas.Cooling:climatecoolingleadstolessprecipitation,lessenergy,lessevaporationandmoredesertexpansion.,产生沙漠化的自然因素主要是干旱、地表为松散砂质沉积物和大风的吹扬等；人为因素主要是过度放牧、过度垦殖、过度樵柴和不合理地利用水资源等。Thenaturalfactorsofdesertificationaredrought,loosesandysedimentonthesurfaceandwindblowing.Humanfactorsmainlyincludeovergrazing,overreclamation,excessivefirewoodandunreasonableutilizationofwaterresources.,举例：文明发祥地,中东的美索不达米亚（今伊拉克）地区是世上最早发展农业的地域之一，从而发展成世上最早的文明发祥地之一。美索不达米亚的土壤本来甚为肥沃，不过由于过度的农业活动、人们不理会土地长期枯渴，更开发河段上流、采伐森林，上流土地从而不能吸收降雨，雨水一气流入河中造成水土流失以及洪水。Mesopotamia(nowIraq)intheMiddleEastwasoneofthefirstregionsintheworldtodevelopagriculture,andthusbecameoneoftheearliestcradlesofcivilizationintheworld.ThesoilofMesopotamiawasoriginallyveryfertile.However,duetoexcessiveagriculturalactivities,peopleignoredthelong-termthirstoftheland,anddevelopedtheupperreachesoftheriverandharvestedforests,whichcouldnotabsorbtherainfall.Therainwaterflowingintotherivercausedsoilerosionandflood.,形成阶段,发生阶段（初期阶段）：潜在性沙漠化，仅存在发生沙漠化的基本条件，如气候干燥、地表植被开始被破坏，并形成小面积松散的流沙等；发展阶段：地面植被开始被破坏，出现风蚀，地表粗化、斑点状流沙和低矮灌丛沙堆，随着风沙活动的加剧，进一步出现流动沙丘或吹扬的灌丛沙堆Occurrencestage(initialstage):thereareonlybasicconditionsfortheoccurrenceofdesertification,suchasdryclimate,thedestructionofvegetationonthesurface,andtheformationofloosefluvialsand.Developmentstage:vegetationonthegroundstartstobedamaged,andwinderosionoccurs.Surfacecoarsening,mottledquicksandandlowshrubsandpilesoccur.Alongwiththeintensificationofwind-sandactivities,flowsanddunesorblownshrubsandpilesfurtherappear,形成阶段：地表广泛分布着密集的流动沙丘或吹扬的灌丛沙堆，其面积占土地面积50以上。Formationstage:thegroundiswidelydistributedwithdenseflowingsanddunesorblowingsandpiles,whoseareaaccountsformorethan50%ofthelandarea.,中国是世界上荒漠化严重的国家之一,中国荒漠化土地面积为262.2万平方公里，占国土面积的27.4，近4亿人口受到荒漠化的影响。中国荒漠化土地中，以大风造成的风蚀荒漠化面积最大，占了160.7万平方公里。土地的沙化给大风起沙制造了物质源泉。因此中国北方地区沙尘暴（强沙尘暴俗称“黑风”。因为进入沙尘暴之中常伸手不见五指）发生越来越频繁，且强度大，范围广。Chinasdesertificationlandcovers2.622millionsquarekilometers,accountingfor27.4percentofitslandarea,andnearly400millionpeopleareaffectedbydesertification.OfChinasdesertificationlands,winderosiondesertificationcausedbyhighwindsisthelargest,accountingfor160.7millionsquarekilometers.Thedesertificationofthelandcreatesamaterialsourceforthehighwind.HencetheduststormsinnorthernChina.Becauseenteringintotheduststormfrequentlycannotseefivefingers)occursmoreandmorefrequently,andtheintensityisbig,thescopeiswide.,沙漠化的危害,破坏土地资源，使可供农牧的土地面积减少，土地滋生能力退化，植物量减少，土地载畜力下降，作物的单位面积产量降低，给许多国家和地区的农业、牧业和人民生活财产造成严重损失。恶化生态环境，破坏生存条件，加剧自然灾害发生，制约经济发展，加深了贫困程度，严重影响社会稳定。Thedestructionoflandresources,resultinginthereductionoflandavailableforagricultureandanimalhusbandry,thedegradationoflandbreedingcapacity,thereductionofplantbiomass,thereductionoflandloadandlivestockcapacity,andthereductionofcropyieldperunitareahavecausedseriouslossestoagriculture,animalhusbandryandpeopleslivelihoodandpropertyinmanycountriesandregions.Thedeteriorationoftheecologicalenvironment,thedestructionoflivingconditions,theexacerbationofnaturaldisasters,therestrictionofeconomicdevelopment,thedeepeningofpovertyandtheseriousimpactonsocialstability.,沙漠化的防治,合理利用水资源利用生物和工程措施构筑防护林体系调节农林木牧渔的关系采取综合措施，多途径解决当地能源问题控制人口增长推广作物的轮休制度推进土壤保护制度多种植树木,RationaluseofwaterresourcesUsebiologicalandengineeringmeasurestobuildashelterbeltsystemAdjusttherelationshipbetweenagriculture,forestry,husbandryandfishingWewilltakecomprehensivemeasurestosolvelocalenergyproblemsinmultiplewaysControlpopulationgrow