In China (or foreign countries), where rivers or reservoirs have dried up or the water volume has decreased (by how much)? Specific place and time!

In some provinces and cities in the west of China, such as Gansu, Xinjiang, Qinghai, Ningxia, Inner Mongolia, Shaanxi, Tibet, Sichuan, Chongqing, Guizhou, Yunnan and Guangxi, there is now a large area of desertified land (654.38+0.743 million square kilometers, accounting for 654.38+08% of the total land area). Moreover, with the continuous expansion (1995- 1999, the national net increase of desertified land 17200 square kilometers), and with the implementation of key ecological construction projects such as "Three North" shelterbelt construction, returning farmland to forests, sandstorm source control in Beijing and Tianjin, and natural forest protection, although desertification has been contained, it is still "partial". Desertification has involved 84 1 county (city, flag) and 7534 townships (town, Sumu) in 30 provinces and regions in China, resulting in direct economic losses of 54 billion yuan every year. Therefore, land desertification is the biggest obstacle to the sustainable development of resources, society and economy in western China, especially in arid and semi-arid areas in northwest China, which should be highly valued and strengthened.

2. Causes of desertification

The factors that cause land desertification in some parts of western China include natural factors and human factors, among which natural factors are the objective internal causes of the occurrence and development of desertification, and human factors are the social inducing factors of the occurrence and development of land desertification.

2. 1 Natural factors of desertification

Natural factors are mainly the degraded land, inferior soil and desert left over from history caused by natural conditions such as less precipitation, water shortage and uneven distribution, strong sunshine evaporation, windy weather at high altitude, drought, sparse vegetation, soil erosion and wind erosion in the western part of China, especially in the inland areas of northwest China.

China is a country with serious water shortage, and its per capita fresh water resources are about 1/5 of the world's, and the distribution of floods in the south and droughts in the north is uneven, especially in the northwest, and the per capita water resources decrease obviously with the population growth. With the warming and drying of the climate, the annual precipitation of 265,438+in western China in the early 20th century was significantly lower than that in the 1970s, and the Yellow River has been cut off frequently since the 1990s. In recent years, the water volume of Yili River, Tarim River, Shule River, Heihe River and other rivers has decreased year by year, and the water crisis in the basin has become more and more serious. Most parts of western China, especially the northwest provinces, live in the inland far from the sea, with high altitude and mountainous barriers, which reduces the ways and quantities of water vapor entering this area with the wind and increases the difficulty, so there is less precipitation (mostly below 400mm, even below 200mm in many places, and the least is only 65,438+). In addition, the sunshine evaporates strongly (from east to west, 800 mm to 3,000 mm) This makes the natural water supply of land in most parts of the west unable to make ends meet, the drought intensifies, and the climate is dry, thus forming a continental dry climate, which seriously affects the development and reproduction of local forest and grass vegetation, causes scarce ground vegetation, and makes the land vulnerable to external damage, even degradation and desertification.

The dry soil formed by the arid and windy climate in the northwest plateau of China is eroded by strong winds, and the organic matter and minerals are blown away and lost by the wind. In the past, the land gradually became barren, degraded and even desertification, and many desert lands gradually formed, migrated and expanded under the conditions of drought and windy.

2.2 Human factors of desertification

The human factors that cause land desertification mainly include the following aspects:

2.2. 1 Deforestation and excessive excavation of forest and grass vegetation resources lead to vegetation destruction and extinction, bare land degradation and even desertification. For example, in the tropical rain forest area of the Hani River basin in Brazil, 450 plants were wiped out, 204 species of birds were completely extinct, the inland river was blocked by quicksand, and the ecosystem was unbalanced, which made people want to cry. Most parts of northern China, especially northwest China, belong to arid and semi-arid areas, with backward social economy and large population. For the basic survival and development, people here have relaxed the management and protection of forest and grass vegetation resources in the already fragile ecosystem, allowing them to cut down trees and dig grass vegetation at will to meet the needs of production and life consumption. It leads to serious damage to the ecological environment, and the vegetation gradually dies from point to surface, from near to far. For example, Hotan area in Xinjiang neglected to manage firewood. In many places in northwest China, natural Chinese herbal medicines and economic plants such as Lycium barbarum, licorice, ephedra and Nostoc flagelliforme are also dug and scraped down at will, which destroys vegetation, even reduces or even loses the functions of forest and grass vegetation in preventing wind and fixing sand, maintaining water and soil and conserving water resources, and worsens the land ecological environment.

2.2.2 Blind reclamation and overgrazing have caused soil erosion, degradation and desertification of farmland and grassland. China has a large population and a long-term shortage of food. In this case, people exploit the land for survival and use land reclamation to increase food production, which has seriously damaged the original vegetation, degraded the land and made the soil desertification. In the grassland pastoral areas in the arid areas of northern China, the carrying capacity of grassland is limited and grazing can only be limited. But in fact, almost all pastoral areas have exceeded the reasonable livestock carrying capacity allowed by ecological security (according to the survey, the livestock overload rate of grassland in sandy areas in China is above 50%, and even as high as 100% in some areas). In many areas, grasslands have been seriously degraded due to overgrazing, and cattle and sheep in some places even eat grass roots. Therefore, ecologists believe that grazing cattle and sheep are the "first killer" of grassland plants.

2.2.3 Excessive and unreasonable development and utilization of water resources have caused drought, desertification and salinization of land. Due to the shortage of water resources in the northwest inland, underground mining has been carried out under the condition of no water on the ground. Long-term over-exploitation has led to a sharp drop in groundwater level, and rivers and lakes have dried up. The vegetation that had grown well has died in a large area because of the lack of support from shallow groundwater, which inevitably turns the bustling place of "seeing cattle and sheep in the wind" into "blowing dust in the wind". However, in some places, irrigation land is developed in the upper reaches of the water source, but the water is not drained, which makes the saline-alkali land accumulate continuously in the low-lying areas, causing serious secondary salinization of the land, causing the vegetation in the low-lying areas to die due to the harm of saline-alkali, forcing farmland to abandon farming, thus forming an abandoned saline-alkali desert and becoming a pair of "twin brothers" with the desert with poor ecological environment.

2.2.4 Excessive use of pesticides, indiscriminate hunting, poisoning beneficial insects and wild animals, so that pests and rodents parasitic on forest and grass vegetation are rampant due to the loss of natural enemies. Random use of toxic and harmful pesticides and indiscriminate hunting of wild protected animals seriously endanger the natural enemies of pest pikas in the ecological food chain, leading to the rampant occurrence of harmful pests and pikas and seriously endangering forest and grass vegetation. In the grassland, forest and farmland ecosystem in arid and semi-arid areas of northern China, the harmful pest pika and its predatory natural enemies, insects and animals, are interdependent in the food chain and are in a state of dynamic balance and mutual restriction. However, due to the abuse of pesticides to kill insects and wild animals, the number of natural enemies of the pest pika decreased sharply, which broke the natural ecological balance and made the harmful pest pika rampant. The grassland trees were seriously damaged. The forest and grass vegetation resources in Inner Mongolia steppe and the Three Rivers source area of Qinghai Province were particularly damaged by pika pests, which not only reduced the functions of forest and grass vegetation in preventing wind and fixing sand and maintaining national security, but also significantly reduced its carrying capacity. In order to change this situation, the state has to take corresponding preventive and protective measures and invest a lot of manpower, financial resources and material resources in prevention and protection.

2.2.5 Industrial traffic construction and production contributed to desertification. Modern industry, traffic production, living construction, the development and utilization of land resources and the emission of waste gas have produced the greenhouse effect, resulting in soil erosion, land waste, high temperature and drought. , and contributed to the abuse of land desertification. The modern industrial revolution has greatly promoted the development and progress of human society and brought vital interests to mankind. It also makes modern people miserable. In the construction of industrial and mining enterprises, traffic road construction, production and life, not only the original landscape vegetation is destroyed, but also a large number of toxic and harmful solid waste pollutants and high-temperature gaseous CO2 are produced and discharged, which leads to the collapse and subsidence of landslides and the desertification of the destroyed land after long-term soil erosion, drought and exposed wind erosion. The land polluted by waste has thus become barren wasteland; In the process of production and life, a lot of hot smoke, such as CO2, is emitted, which makes the global climate warm and the greenhouse effect more and more prominent, and the resulting drought is more and more obvious, and the world loses hundreds of billions of dollars every year. Especially today, individual countries refuse to sign the Kyoto Protocol to control CO2 emissions out of their own economic interests, which directly affects the control of industrial waste gas emissions, which is disturbing.

2.2.6 Insufficient understanding, imperfect legal system, lax law enforcement, poor management, rampant bureaucratic corruption, disputes and wars, man-made fires, etc. It is also an important factor leading to land desertification. In the forestry industry, there are all kinds of corruption phenomena, which have caused great losses to forestry, but they have not attracted enough attention. We know that the fourth phase of the "Three North" shelterbelt project has started construction. What is particularly abhorrent is that many bureaucrats find excuses to put national debt into their own pockets, thus making ecological construction such as desertification control an illusory thing, thus undermining the impact and weakening and delaying the efforts and progress of land desertification control.

3. Countermeasures for desertification control

Desertification control can hardly be achieved by one method of one place, one department or even several people. It must be the action of the whole society, and comprehensive measures such as law, administration, economy and technology should be taken in forestry, agriculture and animal husbandry, water conservancy, environmental protection, economy, science and technology, justice, publicity and education. Specifically, the following measures should be taken:

3. 1 Vigorously plant trees and grass, reduce population pressure, improve energy utilization rate, organize protection by legislation, strengthen law enforcement, and reduce, curb and prohibit all acts that damage the natural ecological environment. The CPC Central Committee and the State Council made the strategic decision of "giving priority to the development of the western region" and began to implement a series of ecological environment protection and construction projects, such as returning farmland to forests, grazing and grassland, and protecting natural forests. It has created a good opportunity for people to retreat and prevent land desertification, thus creating a new situation of national defense and sand control and safeguarding national security, and effectively curbing the development trend of land desertification. Attach importance to ecological construction and protection in the north, and implement ecological migration in ecologically fragile areas in a planned and step-by-step manner; In areas where conditions permit, promote the application of biogas, wind energy and solar energy technologies and resources to reduce the damage of wood burning energy consumption to forest vegetation; At the same time, a legal system for the construction and protection of the ecological environment in the western region should be established, a one-vote veto system for ecological damage should be implemented, law enforcement efforts to prevent and protect the ecological environment should be intensified, and all kinds of illegal and criminal acts such as deforestation and bureaucratic officials who are irresponsible for the prevention and control of desertification should be severely cracked down.

3.2 Implement the statutory land reclamation system, develop eco-intensive agriculture, reasonably limit grazing, formulate plans for sand prevention and control, delimit areas where agriculture, grazing and firewood are prohibited, adopt fence and other protective measures, establish a fence grazing prohibition system, implement the project of returning grazing to grassland, vigorously cultivate artificial high-yield grassland, reduce the livestock carrying capacity of natural grassland and shorten the grazing time of natural grassland. In order to relieve the grazing pressure of natural grassland, Institute of Botany of Chinese Academy of Sciences in Hunshandake Sandy Land, Inner Mongolia, used a small area of high-efficiency land to plant high-efficiency red English corn to provide feed for a large number of captive animals, which better solved the contradiction between developing animal husbandry and protecting the environment in arid and semi-arid grassland areas, with typical representative significance and worth demonstrating and popularizing.

3.3 Management, scientific allocation and rational development and utilization of water resources according to law to ensure ecological water demand. First, establish the idea and mechanism that water resources are limited and water should be saved and recycled, and change the view that water is inexhaustible. Both urban and rural areas advocate water conservation and rational use. Focus on building large sewage treatment plants in urban industrial and mining areas to solve the problem of wastewater reuse and alleviate the shortage of water resources; Agricultural production should change backward irrigation methods and advocate water-saving irrigation. Second, establish and improve the water resource fee collection system, raise the water price of non-ecological water and excess water, and restrict urban industrial water use by economic means. Third, establish a unified dispatching compensation system for the whole basin, and take measures to discharge water from upstream reservoirs in summer peak period, especially in dry years, to ensure ecological water supply for the whole basin. At the same time, according to the principle of market economy, a cross-regional compensation mechanism should be established in the whole basin, that is, the downstream directly benefited areas should pay a certain amount of resource compensation fees through taxes or other means, and support the upstream areas to plant trees for water conservation, soil and water conservation, develop water-saving irrigation, and build sewage treatment plants. Make up for the economic losses caused by the upstream area taking care of the downstream water use and prevent drought and desertification. This investment mechanism can achieve a win-win situation for the whole upstream and downstream basin. Fourth, strengthen the management of groundwater resources, adopt policies and measures to limit the exploitation of groundwater resources, crack down on illegal exploitation of groundwater resources, and prevent the groundwater level from falling.

3.4 Combat indiscriminate catching and hunting, rationally use pesticides, advocate ecological prevention and control, realize the sustainable development of agriculture, forestry, animal husbandry and ecological economy, intensify the crackdown on indiscriminate catching and hunting of wild protected animals, and curb or reduce the behavior of indiscriminate catching and hunting of wild animals; Encourage the use of biological pesticides, restrict the use of high-residue pesticides, prohibit the use of highly toxic pesticides, protect and develop natural enemy insects and wild animals, control pests and rodents in forest and grass ecology by ecological control technology, curb the reproductive harm of pests and rodents, and naturally control pests and rodents below the economic threshold, so as to prevent the degradation and desertification of farmland in woodland and grassland, ensure the sustainable utilization of land resources, realize the coordination and unity of ecological, economic and social benefits, and realize the ecological economy of agriculture, forestry and animal husbandry.

3.5 Establish an examination and approval system for land environmental assessment of production and construction projects. Implement the system of project ecological environment evaluation and demonstration and project approval, and measure the advantages and disadvantages of all construction projects with the standards that are conducive to industrial and agricultural production, sustainable development of ecological environment and economy, and sustainable utilization of land ecological environment and resources. By evaluating and demonstrating the survival of the fittest, we can learn from each other's strengths and restrict, stop, ban, close and transfer production and construction projects with high energy consumption, high water consumption and high pollution discharge.

3.6 Take the prevention and control of corruption as a supporting measure to prevent and control desertification. Establish bidding, construction, procurement supervision and reimbursement systems for ecological construction materials such as sand prevention and control ecological projects and seedlings and seeds, curb bureaucratic corruption at the grassroots level and departments, and ensure that special funds for construction projects such as sand prevention and control are really used for sand prevention and control. The establishment and implementation of the system of bidding, procurement and supply of engineering construction, medical devices and products nationwide has stopped the corrupt practices in related links, saved expenses and done good things. National ecological construction projects such as sand prevention and control should also take this as a lesson, establish a public bidding procurement supply system, curb corruption and do a good job in sand prevention and control construction projects.

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3.7 Intensify publicity and education, and raise the people's awareness of sand prevention and control. Through all-round, multi-level and regular publicity and education work on ecological construction and protection, we will organize, plan, produce and broadcast ecological public service advertisements that can raise people's awareness of sand prevention and control, create a good atmosphere of cultural public opinion, and let everyone in the whole society and all walks of life, especially those living in arid and semi-arid areas in the west, have the awareness of water conservation, sand prevention and environmental protection from the depths of their minds, and establish the awareness of "protecting land resources"