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The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The210Pb and137Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 1400 years. The ostracoda and their assemblages under the level of 1 cm samples’ cutting interval were finished for this core to reveal the past environmental changes in the lake area. A total of 15 species of ostracods belonging to 7 genera in the core sediments had been identified. According to the ostracod distributions, abundances and preservations in the core, seven ostracod assemblages had been distinguished. The ostracod assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes of the Chen Co environmental evolutions in three stages, which had responded to the Medieval Ages Warm-period (MAW), the Little Ice Age (LIA) and modern warm period. The results show that the changes of the Chen Co environment had been mainly influenced by the climatic variations. The trend of the lake level fluctuations had been accorded with that of climatic variation during the past 1400 years.

The “greatest lake period” means that the lakes are in the stage of their maximum areas. As the paleo lake shorelines are widely distributed in the lake basins on the Tibetan Plateau, the lake areas during the “greatest lake period” may be inferred by the last highest lake shorelines. They are several, even tens times larger than that at present. According to the analyses of tens of lakes on the Plateau, most dating data fell into the range of 40-25 ka BP, some lasted to 20 ka BP. It was corresponded to the stage 3 of marine isotope and interstitial of last glaciation. The occurrence of maximum areas of lakes marked the very humid period on the Plateau and was also related to the stronger summer monsoon during that period.

Have been being intensively uplifted since 3.4 Ma BP, the Tibetan Plateau, with the elevation of 4000–5000 m asl,is the youngest and highest plateau on the earth. Extremely high elevation makes the plateau as the largest high-cold area in middle latitude zone. The cold climate causes permafrost to be widely distributed in most part of the Plateau while modern glaciers are developed on the high mountains above 5000–6000 m asl.Violent uplifting also causes intensive cutting which results in the formation of high mountains and deep valleys, steep slopes and higher relative relief on peripheries of the Plateau. However,it is relatively warmer and drier in dry valleys of southeastern part of the Plateau. Due to the influence of monsoon and landforms, precipitationis gradually decreasedfrom southeasttonorthwest and vegetation appearssuccession from forest todesert. Under the background of intensive tectonic movement, multiple climatic types and active landform processes, many kinds of natural hazards frequently occur in certain areas. With increasing of human activities, they also bring a series of issues to the fragile environment.

Qiangtang, which means ‘Bare land in north’ in Tibetan language, is situated in the north of Tibet, and also called as North Tibetan Plateau. From 82.5°E to 90.7°E and from 31°N to 36°N, this land extends 750–800 km along E-W direction and crosses 450 km along S-N direction. It covers an area of over 400,000 km2 that is from the Kandese-Nyqintanggula Mountains in north to the Kunlun Mountains in south and from Mt. Aludadang of the Karakorum Mountains in west to the Mt. Gar Kangri of Tanggula Mountains in east. Situated in hinterland of the Tibetan Plateau, Qiangtang is characterized with high altitude and extremely adverse climatic environment. Except for fewer herding activities, there is no permanent resident in this area. Scientific survey in this area is very weak in researches of the total Tibetan Plateau due to difficult traffic conditions for entering this area. Under this kind of background, this area is well conserved as its original situations and less disturbed by human activities (Figure 16-1).