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英国paper代写-The dangers of desertification

2018-09-10 | 来源:51due教员组 | 类别:Paper代写范文

下面为大家整理一篇优秀的paper代写范文- The dangers of desertification,供大家参考学习,这篇论文讨论了荒漠化的危害。荒漠是地球上一类非常特殊的生态地理区域,它既是地球生态灾害的源头,又是人类生存发展的潜在空间,充分展示了荒漠独特和脆弱多变的特征。荒漠化有很多危害,会导致了生态环境的恶化,生存条件丧失,并且加剧了水危机问题,造成天然植被衰退和死亡,对生物多样性构成严重威胁。

desertification,荒漠化危害,英国论文代写,论文代写,paper代写

Desert is a special ecological geographical region on the earth. It is not only the source of ecological disasters on the earth, but also the potential space for human survival and development. The desert region contains economic plants, animals and herbs of unique natural species and quality, and is a unique subsystem of the earth ecosystem. The terrestrial desert ecosystem, composed of all kinds of creatures and environments in the desert region, not only guarantees the existence of 41.3 percent of the world's land area and 2 billion people, but also preserves many unique plants, animals and microorganisms for human beings, providing them with unique rich and strange natural landscapes. Desert ecosystem is not only a vulnerable zone of global ecosystem, but also an indispensable ecological type.

According to the United Nations, desertification currently affects one-fifth of the world's population and one-third of the world's land mass, resulting in direct economic losses of up to us $42.3 billion a year. Desertification is the root of poverty and an obstacle to the sustainable development of economy and society. At the same time, the desertification area in China is also the area with the largest concentration of poverty population. It is estimated that the direct economic loss caused by desertification in China is as high as 6.5 billion us dollars annually, and the indirect economic loss is 2 to 3 times of the direct economic loss. Among all kinds of natural disasters, drought, cold wave, wind, sandstorm and rainstorm caused by the change of weather are the most serious losses.

Desertification areas are economically backward, and agriculture as a basic industry is closely related to the natural environment. Except for some irrigation areas, it basically stays at the level of "depending on the weather for food". Therefore, agriculture is the most affected by desertification and the most harmful. The occurrence and development of desertification lead directly to the decrease of soil fertility, the loss of available land resources and the decrease of agricultural production.

Soil is the natural body of history, but also the material basis of human production, life and survival. Soil fertility depends on the coordination of soil fertility factors and whether the soil can provide the conditions for plant growth and development in a stable, uniform, adequate and suitable way. Soil wind erosion is not only the main part of desertification, but also the first link. Wind erosion will cause the loss of organic matter and fine matter in the soil, resulting in soil coarsening and reducing soil fertility. According to the sampling analysis, in the maowusu sand and the hedong sand area of ningxia, the organic matter in the quicksand layer accounts for 0.12%, total nitrogen accounts for 0.26% and total phosphorus accounts for 0.057%. In the soil layer covered by quicksand, organic matter accounts for 0.28%, total nitrogen 3.0% and total phosphorus 0.073%, which is much higher than the quicksand layer. On the other hand, the dust and fine sand transported by the wind fall into the farmland, which will cause soil desertification at a light weight and cover the farmland at a heavy weight. Both the former and the latter will change the physical and chemical properties of the soil and make it barren. Wind erosion also accelerates soil moisture loss, changes soil hydrothermal conditions and decreases soil fertility.

Many people have done research on the loss of soil nutrients under wind erosion. According to the measurement, in the maowusu sandy land, the soil layer is blown away by 5 ~ 7cm per year, and the organic matter is 77,70kg, nitrogen is 387kg, phosphorus is 549kg and physical clay is 39,000 kg less than 0.01mm per hectare. Compared with the 1960s, in the 1980s, organic matter was generally reduced by 20-30% and total nitrogen by 25-46%. In the bashang area of hebei province, if the soil layer that is blown 1cm thick is calculated, the soil that is blown away every year is 5429,477t, and organic matter is lost 741,400 t, nitrogen 59,000 t, phosphor 48,0800 t and potassium 1427,000 t. According to dong's estimation, the annual loss of soil organic matter, nitrogen and phosphorus due to wind erosion is 559.068 million tons, equivalent to 268 million tons of fertilizer, worth nearly 17 billion yuan. Soil fertility is formed slowly in the process of soil development. Therefore, when soil fertility is lost under the action of external forces, it takes a long time to recover naturally. According to the observation in naiman banner of Inner Mongolia, after stopping human disturbance, the organic matter in sandy soil can only increase by 0.021% per year on average, and the content of nitrogen and phosphorus can only increase by about 0.003 ~ 0.004% per year on average. It is estimated that it will take decades, hundreds of years or more, even under the conditions of artificial measures, if the organic matter, nitrogen and phosphorus in the seriously desertification land are to be restored to the original soil condition.

Agricultural production is one of the most important production and operation activities in desertification area. The sowing, growth and maturity of crops are affected by wind and sand activities, which often result in large-scale agricultural production reduction and great harm. Wind sand activities in the north of China mostly occur in April to may, when it is the spring sowing season in rural areas in the north. Strong wind and sand seriously affect spring sowing, often blowing newly sown seeds and manure out of the surface. This phenomenon is very common in desertification areas. When the wind and sand flow is close to the surface, the rapidly moving sand grains often kill and injure the young seedlings that germinate soon. The people call it sand beating and sand cutting, which is very harmful to spring sowing.

In the spring sowing season, once wind and sand damage, farmers had to replant. Reseeding is a common phenomenon in desertification areas in north China, and it is common to reseeding two or three times a year in areas where desertification is more serious. For example, in the northern county of Shanxi Province, sandstorm hazards were particularly serious in the 1980s, sowing three to five times every spring, and planting three to five times or more every year in the ejin horo banner in ordos city of Inner Mongolia autonomous region. The replanting of farmland not only wastes seed, fertilizer and labor, but also increases the input of agricultural production. During the pollination of crops, wind and sand often blow the pollen, affecting the pollination of crops. In autumn, wind and sand often cause crop collapse and affect crop yield.

Due to the damage of wind and sand, land degradation in desertification areas is very serious, which affects agricultural production greatly. According to the survey, the annual loss of grain from degraded farmland in China's desertification areas is more than 3 billion kg, which is equivalent to about 7.5 million people's rations in a year. In the past 40 years, 6.68 million ha of arable land have been turned into sand, with an average annual loss of 167,000 ha. Affected by wind and sand hazards, the yield of crops in the desertification area is generally low, with the yield per hectare mostly around 300 ~ 750kg.

The northern grassland area of China has been dominated by animal husbandry in history. "the sky is green, the wild is wild, and the wind blows the grass low to see the cattle and sheep" is a true portrayal of the flourishing ancient grassland and fat cattle and sheep. However, it is difficult to see such a scene now. Large areas of grassland are covered by quicksand, and the degradation caused by desertification seriously restricts the development of animal husbandry.

According to desertification monitoring, there are 1.05 million km2 of degraded grassland in China, and more than 50 million sheep are fed annually due to grassland degradation. Since the founding of the People's Republic of China, 23,500 km2 of grassland has been changed into quicksand. The hulunbuir grassland and xilingol grassland, which are known for their rich water and grass, respectively take up 23% and 41% of the total grassland area, and the most seriously degraded grassland in ordos has reached 68%. On the one hand, the grassland degradation shows that the plants become low and sparse, and the grass yield decreases. On the other hand, the number of legume, gramineae and other good forage grass decreased, the number of poisonous and harmful plants with poor palatability and low nutrition value increased, and the quality of forage grass declined. Grassland desertification greatly reduces the biomass and greatly reduces the stocking capacity of grassland. Due to the decrease in the quality of forage grass, the livestock is often hungry and semi-hungry. As a result, the growth of the livestock is slow, the weight is small, the storage time is long and the stock rate is low. In regions with severe sandstorms, strong sandstorms in spring often accelerate the evaporation of water on the surface of grassland, which is not conducive to the rejuvenation of forage. The fast moving sand often kills and injures the young grass that has just returned to green, causing the grass to turn green slowly and exacerbating the harm caused to animal husbandry in the spring due to the lack of forage grass.

Desertification leads to deterioration of ecological environment and loss of living conditions. More than 24,000 villages and many towns across the country are regularly affected by desertification. Sand pressure villages, sand into people retreat, in some areas common. In the past 30 years, more than 220 houses were buried under the sand in ertok banner, Inner Mongolia autonomous region, and more than 3,300 shelters were built. The underground water level in the minqin oasis in the lower reaches of the shiyang river in gansu province has dropped by 0.5 to 1.0 meters per year, making it difficult for over 70,000 people and 120,000 livestock to drink water. Located in the southern edge of the taklamakan desert pishan, minfeng two counties, because of sand hazards, the county moved twice, zheller county moved three times. Since the 20th century, sandstorms have become more and more frequent in China. From the 1950s to now, more than 70 sandstorms have caused major losses. In the southeast of the desertification area, the number of days of annual sandstorm is more than 5 to 10 days. Over 20 days of sandstorm in ganxin gobi and desert regions; The southern xinjiang and alxa plateaus are sand-prone areas, with more than 30 days. Sandstorms are extremely harmful, causing serious damage to the ecosystem and exacerbating land desertification. The occurrence of desertification not only brings great loss to people's life and property, but also destroys the space that our descendants depend on for survival.

Desertification has exacerbated the northwest region's increasingly severe water crisis, causing natural vegetation to decay and die, groundwater levels to drop, lakes to dry up, and oasis to decline. According to reports, the area of Euphrates poplar forest in the lower tarim river has been reduced from 54,000 ha in the 1950s to 16,000 ha now, and the 180km "green corridor" from northern xinjiang into southern xinjiang is disappearing. In arid regions, many oasis subterranean water levels along inland rivers continue to fall, and groundwater mineralization increases, leading to water shortages for residents and livestock and abandoned farmland. Moreover, desertification also directly threatens the atmospheric environment and ecological environment of big cities. At present, sandstorms originated in northern China almost threaten most parts of the country and even the entire northeast Asia. Moreover, desertification directly threatens the urban security of Beijing.

Desertification reduces biological quality, decreases species abundance and increases inferior weeds, which poses a serious threat to biological diversity. Desert region, especially in arid areas to protect biodiversity is of special significance: the desert region of plants and animals in the natural conditions and long-term evolution in the extreme, successfully developed many adaptation mechanisms, many of which wild plants is one of the important germplasm resources, biological measures against desertification many animals are our ancestors, livestock in the desert plants and animals contain many kinds of high economic value. For example, many desert herbs and small semi-shrubs are nutrient-rich forages, and many species have medicinal value.

According to the survey, there are 356 species of medicinal plants in desert regions of China alone, among which 103 species are commonly used. Desert ecosystem plays an irreplaceable role in fixing quicksand, weakening wind erosion and improving environment. Due to unreasonable human activities such as excessive firewood, excessive mining, excessive reclamation and excessive hunting, as well as the rapid expansion of desertification caused by them, the biological resources in the desertification area have been severely damaged and the biological diversity has been sharply reduced. Desert plants such as licorice trifolium, salt birch have become extinct, as have desert animals such as the xinjiang tiger, Mongolian mustang, high-nosed antelope and xinjiang tilapia. In addition, dozens of species are endangered. In the grassland areas of China, due to man-made destruction and desertification, many Chinese medicinal materials once widely distributed in the past, such as ephedra, licorice, windbreak, bupleurum, polychondrium, cistanche and suiyang, have been decreasing in number, some are on the brink of extinction. Land desertification also leads to habitat destruction, biodiversity reduction, biological population, community destruction, survival capacity reduction, many species are becoming endangered or dying out, many species are facing extinction.

Most of the desertification areas in China belong to the old, young, border and poor areas and are also populated by ethnic minorities. There are 31 ethnic minorities and 220 autonomous banner counties. Most of the four autonomous regions of xinjiang, Inner Mongolia, Tibet and ningxia are located in the desertification areas. According to the statistical data analysis, in 2008, the per capita GNP of the western region was only 15,937 yuan, equivalent to only 43 percent of the eastern region. In recent years, with the implementation of the national western development strategy, although the economic growth rate of the western region is slightly higher than that of the eastern region, the gap between the rich and the poor is still large due to its poor foundation.

According to statistics, there are 101 state-level poverty-stricken counties in the desertification area of China, accounting for 21.4% of the total number of counties in the whole region. The poverty-stricken population is about 15 million, accounting for 65.2% of the total population of the whole region, accounting for about 1/4 of the whole country's poverty-stricken population. In some areas, some farmers, settlements and even counties have to be relocated as quicksand moves forward to bury buried houses and livestock roll sheds. According to desertification monitoring, more than 24,000 villages in 12 provinces and autonomous regions in north China have been affected by sandstorms.

In China, desertification areas are often one of the poorest areas, and the local economy and the living standard of local people are generally relatively low. To better promote the work of combating desertification, we must first improve the lives of the people. Only when we become rich can we be more enthusiastic about combating desertification.

To govern the desert and develop sand industry is an undertaking of merit in the contemporary era and benefit the future generations. In the face of the "cancer of the earth" that threatens the survival of human beings, we have to act, through unremitting efforts and exploration, with a long green dragon lock the ravaging desert, we can not let our future dry.

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