China is one of the countries with the most serious soil erosion in the world. Due to the special physical geography and socio-economic conditions, soil erosion has become a major environmental problem. Today I will introduce the causes of soil erosion to you, hoping to help you!
China is a mountainous country, and the mountainous area accounts for 2 / 3 of the land area; China is also the most widely distributed loess in the world. The terrain of mountainous and hilly areas and loess areas fluctuates. Loess or loose weathering crust is prone to erosion in the absence of vegetation protection. Most parts of China belong to monsoon climate with concentrated precipitation. The precipitation in rainy season often reaches 60% ~ 80% of the annual precipitation, and there are many rainstorms. The geological and geomorphic conditions and climatic conditions prone to soil and water loss are the main causes of soil and water loss in China.
China has a large population and great pressure on the demand for food and civil fuel. Under the condition of low productivity, China implements predatory reclamation of land, unilaterally emphasizes food production, ignores the comprehensive development of agriculture, forestry and animal husbandry according to local conditions, and turns the land only suitable for forestry and animal husbandry into farmland. A large number of reclamation of steep slopes, so that the more the steep slopes are opened, the poorer the reclamation, and the vicious cycle of the ecosystem; Indiscriminate deforestation, even random digging of tree roots and lawns, sharp reduction of trees and exposure of the earth's surface have exacerbated soil erosion. In addition, some basic constructions do not meet the requirements of water and soil conservation. For example, unreasonable construction of roads, factories, coal mining, quarrying, etc. destroy vegetation, reduce slope stability, and cause more serious geological disasters such as landslide, landslide, debris flow and so on.
(1) natural factors. It mainly includes terrain, rainfall, soil (ground material composition) and vegetation.
① terrain. The steeper the ground slope is, the faster the velocity of surface runoff is, and the stronger the scouring and erosivity of soil is. The longer the slope, the more surface runoff collected and the stronger the scouring force.
② rainfall. Rainfall causing water and soil loss is generally heavy rain with high intensity. Only when the rainfall intensity exceeds the soil infiltration intensity can surface (super infiltration) runoff be generated, resulting in scouring and erosion of the surface.
③ ground material composition.
④ vegetation. The forest and grass vegetation with a certain canopy density can protect the soil from erosion. The higher the canopy density, the stronger the of soil and water conservation.
(2) human factors. The unreasonable use of land by human beings has destroyed the ground vegetation and stable terrain, resulting in serious soil erosion.
① destruction of vegetation
② unreasonable farming system
③ mining
1. Hydraulic erosion is most widely distributed. In mountainous areas, hilly areas and all sloping ground, hydraulic erosion will occur during rainstorm. It is characterized by taking the water on the ground as the power to wash away the soil. For example: the Yellow River Basin.
2. Gravity erosion is mainly distributed on gullies and steep slopes in mountainous and hilly areas. On both banks of steep slopes and gullies, part of the lower part is washed away by water. Due to the gravity of soil and its parent material, it can not continue to remain in its original position and collapse in scattered or patches.
3. Wind erosion is mainly distributed in the desert, sandy land and hilly sand covered areas in northwest, North and Northeast China, followed by the sandy land in the southeast coast, and then the "yellow flood area" in Henan, Anhui and Jiangsu provinces (historically, it was formed due to the sediment brought out by the breach and diversion of the Yellow River). Its characteristic is that the sand particles are lifted up by the wind, leave their original position, float with the wind and land in another place. For example: Hexi Corridor, Loess Plateau.
Loess Plateau:
1. Natural causes: loose soil and concentrated precipitation;
2. Human causes: human overexploitation (overgrazing, mining, deforestation and wasteland) [mainly water erosion].
Remediation measures: the Loess Plateau is not as good as the hydrothermal conditions in the South and is in a transitional zone. Biological measures such as planting trees and grass and returning farmland to forest and grassland need to be implemented; Engineering measures such as building reservoirs, damming and silting up land and building horizontal terraces are comprehensively managed in small watersheds, so as to improve the ecological environment of the Loess Plateau and develop the regional economy.
Southern Hills:
1. Natural causes: the fluctuation of the ground surface is conducive to water scouring, with large precipitation and long time;
2. Human causes: human over exploitation (over exploitation, woodcutting) [mainly precipitation erosion].
Rectification measures: due to the good water and heat conditions in the low mountain and hilly areas of South China, the effective measures are closing the mountains for afforestation, restoring vegetation, emerging small hydropower, and large-scale biogas (the basic guarantee for closing the mountains and forests is to effectively solve the problem of rural domestic energy consumption).
The impact of soil erosion in low mountain and hilly areas in the south is far more serious than that in the North:
I. from an economic perspective
The low mountain and hilly areas in the South have better hydrothermal conditions, higher biomass and output value per unit of land, and greater losses caused by soil and water loss per inch of land.
II. From an ecological perspective
The low mountain and hilly areas in the south are mostly Rocky Mountains with thin soil layer. Once the topsoil is eroded, it is easy to form rocky desertification, and it is more difficult to recover.
III. from a social perspective
Low mountain and hilly areas in the south are densely populated, and most of them are important industrial and agricultural production bases and economic centers in the lower reaches of rivers. Soil erosion has a greater impact on society and greater losses.
1. Reduce or even lose land productivity: the area of soil erosion in China has expanded to 1.5 million square kilometers, accounting for about 1 / 6 of China, and 5 billion tons of soil are lost every year. The loss of nitrogen, phosphorus and potassium fertilizer in the soil is estimated to reach 40 million tons, which is equivalent to China's current annual application of chemical fertilizer, equivalent to an economic loss of 2.4 billion yuan. The two major water systems of the Yangtze River and the Yellow River lose 2.6 billion tons of sediment every year. The organic fertilizer contained therein is equivalent to the total amount of 50 fertilizer plants with an annual output of 500000 tons. No wonder some people say that what the Yellow River flows away is not sediment, but the blood of the Chinese nation. Such a large area of fertile soil and nitrogen, phosphorus and potassium fertilizers have been washed away, which will inevitably lead to the decline or even complete loss of land productivity.
2. Silted rivers, lakes and reservoirs: Although the soil erosion in Zhejiang Province is relatively light, the riverbed of eight water systems in the province has generally increased by 0.2-0.1m, and the inland river navigation mileage has been reduced by 1000 km compared with that in the 1960s. For example, before 1958, wooden boats with a load of 10 tons could pass from Shengcheng county to Cao'e River. Due to too much silting in the riverbed, navigation has been forced to stop. The surface water resources have become sand, and the navigation construction company has been changed into "yellow sand" company.
Due to too much wind and sand in Dongting Lake, Hunan Province, more than 1400 hectares of sandbars emerge from the water every year. The lake area has been reduced from 3915 square kilometers in 1954 to 2740 square kilometers in 1978. What is more serious is that the water surface of Dongting Lake has been 3 meters higher than the land around the lake, which has lost its flood diversion function of the Yangtze River. This is a very serious problem.
The water and soil loss of Jialing River, Fujiang River, Tuojiang River and other basins in Sichuan Province is also very serious, and more than 20% of the sediment is deposited in the reservoir. According to the prediction of relevant experts, in another 50 years, some reservoirs in the Yangtze River Basin will be silted or become silt reservoirs.
3. Polluted water quality affects the ecological balance: at present, a prominent problem in China is the serious pollution of water quality in rivers, lakes (reservoirs). Soil erosion is an important cause of water pollution. The water quality of the Yangtze River is being polluted, which is a typical example.
Guess you're interested:
1. Causes of water and soil loss
2. What is the antonym of loss
3. Causes of soil erosion in the Yellow River
4. On water and soil conservation and ecological environment protection in Water Conservancy Scenic Spots