Loess Plateau

There are three types of gullies in the Loess Plateau, including floor gullies, hill slope gullies and valley bank gullies. The thickness of the loess is the thickest in the Loess Plateau than the loess in other areas in China. From the scale, you can see the respected thickness of the loess in different colors. Adapted from Geomap. Loess deposits Formation of loess Loess does not necessarily mean the same as silt. Loess is yellow eolian sediments that were transported by wind from an arid or semi-arid region during the Quaternary period. Around 6% of the land in the world is covered with loess. Loess records the past climate and environment. The Chinese Loess Plateau is one of the largest sinks of loess in the world. The figure shows the topography of the Chinese Loess Plateau. The loess near the Liu-p'an Mts is the thickest which is around while the loess near the Yellow River is around thick. This may also be associated with the transporting winds. During glacial periods, the Siberian High is enhanced, and the winter monsoon become drier and stronger. Therefore, the amount and grain size of the sediments will increase. Origin of the loess Although the source of loess materials is from the Gobi Desert and the sand deserts, they are not produced by those deserts. The three mountains, including the Gobi Altay Mountains, the Hangayn Mountains and the Qilian Mountains are responsible for making loess materials for the desert and plateau. However, these are not the major sources of loess. Therefore, the loess in the Chinese Loess Plateau is mainly produced by the three mountain ranges and deposited in the deserts. Through monsoon wind and dust storms, the loess is transported to the Loess Plateau. == Climate and environment ==

Climate and environmental changes The population of the Loess Plateau has been increasing since the 1600s. In 2000, the population has increased to 104 million. This is because the increase in drought indicates that the weather has become more extreme. The number of floods will also increase. The frequency of floods and droughts is increasing abnormally. The Loess Plateau becomes more vulnerable to locust swarms because the climate becomes cooler and more humid. They will destroy the farmland and reduce crop yield. From 1965 to 1979, more than 1000 landslides that happened in the Loess Plateau were triggered by earthquake shocks and monsoonal summer rainfall. == Sustainable development ==

Background The Loess Plateau suffers from one of the world's most severe soil erosion. Soil erosion in the region is affected by many factors, including vegetation cover, precipitation, strength of winds, climate etc. However, human activities contribute the most to soil erosion in the Loess Plateau in recent years. It is estimated from historical records that forest cover on the Loess Plateau declined by a factor of eight during the last three millennia, reaching a low in 1949 leading to yearly soil erosion of 3700 tons of soil per km2. Especially the northern and eastern parts of the region were once covered in forests. The population in the Chinese Loess Plateau has tripled from 1949 to 2000. It has reached 104 million people in 2000. The farming activities on the steep slopes exposed the loess materials on the slope. When there is heavy rainfall and storms, the loess are easily washed away, which cause serious soil erosion. In 1999 it was found that most of the grassland is overgrazed and facing land degradation problem. The first Loess Plateau restoration project cost US$252 million, as of 2007. From 1975 to 2015, restoration projects in the Beiluo River Basin, southwestern part of the Loess Plateau, restored cropland into grassland and forest, boosting forest cover by about 18% and raising the basin's overall ecosystem service value by roughly 54% (about US$3.2 billion). From the program beginning to 2020, the Jinghe River watershed area observed reclaimed forest and grassland on the hills, which improved soil and water conservation and ecosystem services. Overall, it is estimated that forest cover increased by 15,000 km2 from 2007 to 2017 on the plateau. Between 2000 and 2024, the Loess Plateau changed to a warming, slightly wetter climate. ==Notes==