土地荒漠化ppt

• 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-sea interaction theory: it is believed that tropical SST anomalies lead to atmospheric circulation anomalies at lower latitudes. • 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。 • According to the feedback, the possibility of convective precipitation is reduced as the soil moisture decreases and evaporation decreases after the drought begins. Overgrazing in semi-arid regions increases ground reflectivity, changes ground energy balance, and leads to subsidence movement, resulting in prolonged drought. The disappearance of biological source material in rain clouds causes the reduction of precipitation, etc.
• 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、半干旱和具源自文库干旱灾害的半湿润地 区的土地发生了退化。
• The concept of desertification was defined by the United Nations conference on environment and development in 1992 as the degradation of land in arid, semi-arid and semi-humid areas, due to factors such as climate change and irrational human economic activities.
• 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。 • The natural factors of desertification are drought, loose sandy sediment on the surface and wind blowing. Human factors mainly include overgrazing, overreclamation, excessive firewood and unreasonable utilization of water resources.
• Mesopotamia (now Iraq) in the Middle East was one of the first regions in the world to develop agriculture, and thus became one of the earliest cradles of civilization in the world. The soil of Mesopotamia was originally very fertile. However, due to excessive agricultural activities, people ignored the long-term thirst of the land, and developed the upper reaches of the river and harvested forests, which could not absorb the rainfall. The rain water flowing into the river caused soil erosion and flood.
• 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。 • Formation stage: the ground is widely distributed with dense flowing sand dunes or blowing sand piles, whose area accounts for more than 50% of the land area.
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。
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。
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 • Occurrence stage (initial stage) : there are only basic conditions for the occurrence of desertification, such as dry climate, the destruction of vegetation on the surface, and the formation of loose fluvial sand. • Development stage: vegetation on the ground starts to be damaged, and wind erosion occurs. Surface coarsening, mottled quicksand and low shrub sand piles occur. Along with the intensification of wind-sand activities, flow sand dunes or blown shrub sand piles further appear
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 。
• Human destruction: overgrazing, deforestation and destruction of land cover, and soil erosion are cited as major causes
• It is believed that the relationship between the rain period and the low latitude glacial period and the high latitude glacial period and the low latitude interglacial period and the low latitude pluvial period and the high latitude interglacial period in the geological period. During the warmer interglacial periods, the lower latitudes were drier and the desert expanded. In recent years, some climate numerical simulations abroad believe that the greenhouse effect of CO2 will cause global warming in the coming decades, resulting in drought in the mid-latitude region and wet in other regions.
• 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。 • Astronomical theory: it is believed that due to changes in earth orbit parameters, summer radiation in the middle and high latitudes is reduced, resulting in the occurrence of ice age and expansion of desert areas. • Cooling: climate cooling leads to less precipitation, less energy, less evaporation and more desert expansion.
• 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。
• China's desertification land covers 2.622 million square kilometers, accounting for 27.4 percent of its land area, and nearly 400 million people are affected by desertification. • Of China's desertification lands, wind erosion desertification caused by high winds is the largest, accounting for 160.7 million square kilometers. • The desertification of the land creates a material source for the high wind. Hence the dust storms in northern China. Because entering into the dust storm frequently cannot see five fingers) occurs more and more frequently, and the intensity is big, the scope is wide.
• 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。
• Desertification in a narrow sense • Under the fragile ecosystem, the environment change process similar to the desert landscape in the former non-desert areas is occurred because of the artificial excessive economic activities, which destroys the balance.