What are the outstanding ecological and environmental problems in Dunhuang area? Try to explain its causes from a natural point of view.

Huangshi is located at the westernmost end of Hexi Corridor, and its natural ecological environment is unique. The main problems in ecological environment are the lack of water resources, low vegetation coverage, intensified wetland degradation and expanding land desertification. The continuous deterioration of the ecological environment is the result of the joint action of natural and human factors. Natural factors are the potential conditions for the development of ecological environment deterioration, while human factors are the important external reasons for the deterioration of ecological environment. Unreasonable human activities can be summarized as "five abuses"-indiscriminate reclamation (unplanned and uncontrolled land reclamation), overgrazing (overgrazing), deforestation (trees), indiscriminate mining (Chinese herbal medicines, turf) and so on. ) and abuse of water resources (over-exploitation of groundwater, etc. ).

1 ecological environment evaluation of Dunhuang city

1. 1 characteristics of natural ecological environment

The total area of Dunhuang is 3 1.200 km2, of which the oasis area is 1.400 km2, accounting for only 4.48% of the total area. The city governs 6 towns and 3 townships with a total population of 6.5438+0.88 million, including 9.30 agricultural people. Located in the hinterland of the desert, the average annual temperature is 9.30℃, the average annual precipitation is 39.90 mm, and the evaporation is 2486 mm, which is a typical arid climate. Due to the dry climate and extreme wind erosion, the exposed rocks and gravel at the foot of the mountain and the contiguous desert have formed a typical Gobi desert landscape.

1.2 Present situation and problems of ecological environment

The surface water in Dunhuang area mainly includes Danghe River originating from Qilian Mountain Glacier and Shule River originating from Tuolai Nanshan to Shule Nanshan in the west of Qilian Mountain. Aksai Kazak Autonomous County in the upper reaches of Danghe River, due to the implementation of the "Leading the Party into the Red River" project, the annual water consumption for the treatment and recharge of Yueya Spring is 6 million m3, the population and cultivated land area have increased sharply, and Danghe River has been cut off. The completion and use of Shuangta Reservoir in Guazhou County and Changma Reservoir in Yumen City have blocked the river and caused the Shule River to cut off. Therefore, Dunhuang City has to exploit 465.438 billion cubic meters of groundwater for agriculture, industry and life every year, resulting in an average annual decline of 0.43 meters of groundwater level. The water area of Crescent Spring, a famous tourist attraction, has dropped sharply from13,000 square meters in the 1960s to more than 5,300 square meters now, and the water depth has dropped from more than 10 meters in the past to the average water depth of only 1. 10 meters now. The continuous decline of water level makes Dunhuang face a serious ecological crisis.

1.2. 1 wetland shrinkage

Wetlands have been decreasing at the rate of 0.10.3 million hm2 every year. Until 2005, the wetland area in China decreased by nearly13, leaving only10.8 million hm2. In the oasis area, 80% of the more than 0.07 million hectares of saltwater lakes and 66.67 hectares of freshwater lakes have disappeared.

1.2.2 Vegetation decreased sharply.

According to statistics, at the beginning of the founding of New China, there were natural forests146,000 hectares in the east, west, North Lake and Nanshan areas of Dunhuang, including 29,300 hectares of Populus euphratica, which was the "green barrier" of Dunhuang Oasis. In 2005, the natural forests in Dunhuang disappeared by nearly 1/2, leaving only 86,700 hm2. According to the investigation of Gansu Grassland Team, there were 384,000 hectares of grassland in Dunhuang in 1965, and the total carrying capacity was120,000 sheep units. Now it is only 90,000 hm2, down by 77%, and the stocking capacity is 50,000 sheep units, down by 57%.

1.2.3 sand enters and sand retreats

The desertification area of the city is 33,300 hm2. Since 1.994, the desertification area around the oasis area has increased by 1.300 hm2, with an average annual increase of 0. 1.300 hm2. Now there are more and more sandstorms and floating dust. The intensity of sandstorms is getting bigger and bigger. It used to be mainly concentrated in March-May, but now it appears almost every month.

The world-famous Mogao Grottoes have also been eroded by sandstorms and are facing the threat of sandstorms. The impact and abrasion of the wind-blown sand in Mingsha Mountain on the open-air murals on the cliff surface led to the fading and discoloration of the murals, which also made many cave areas and cave tops dilapidated, and a considerable number of cave tops were eroded, even causing the cliff body to collapse. The threat of floating dust weather to Mogao Grottoes is also growing. The observation shows that the annual dustfall of Mogao Grottoes has reached 65.4t·km2, of which more than 83% are angular and subangular particles with high hardness. They can not only abrade murals and statues with the rapid airflow, but also invade the gap between murals and statues, and the bacteria and chemicals they carry will also have various biological and chemical effects on the pigments of murals. They also constantly use the cracks in the murals to crack them. When the dust is deposited to a certain extent, it will produce an outward extrusion force, which will make the pigment layer and white powder layer of the mural fall off, and in serious cases, it will make the whole mural fall off in a large area. At the same time, a large amount of dust settled on the mural surface, which not only seriously affected the artistic effect, but also was difficult to remove without damaging the mural, which brought many difficulties to the restoration and dust removal of the mural.

2. Causes and trends of the continuous deterioration of the ecological environment

2. 1 natural factors

Dunhuang is located in the hinterland, and precipitation is scarce. According to the data of meteorological department, the annual precipitation in Dunhuang is 39.90mm, and the evaporation is 2486mm, which is 62 times of the precipitation.

2.2 Human factors

2.2. 1 Construction of Shuangta Reservoir and Changma Reservoir

1970, the construction of Shuangta Reservoir and Changma Reservoir caused the following 400km river sections to be cut off (300km of which is in Dunhuang); Almost at the same time, Danghe River, a tributary of Shule River, was also intercepted by Aksai County upstream, with a water volume of 5 million m3. In Dunhuang, the water conservancy department also built a dam. The disconnection of Danghe River and Shule River led to the decrease of groundwater flow to Dunhuang, the shrinkage of peripheral wetlands, the degradation of vegetation and the disappearance of animal and plant populations.

2.2.2 The water in Dunhuang reservoir area is mainly used for agricultural irrigation.

The water in Dunhuang reservoir area is mainly used for agricultural irrigation, and the seepage prevention of canal irrigation greatly reduces the recharge of groundwater. In addition, the population of Dunhuang has increased from less than 40,000 at the beginning of liberation to188,000 at present, and the irrigation area has increased from 890,000 hm2 to 25,300 hm2, receiving more than one million tourists every year. According to statistics, the annual demand for various types of water in Dunhuang City is 362 million m3, and the actual inflow of Danghe River is 260 million m3.

2.2.3 Overgrazing

Overgrazing leads to vegetation degradation and desertification.

Overexploitation of groundwater

From 1976 to 1986, more than 800 motor wells were newly dug, which is equivalent to at least one motor well per square kilometer in Dunhuang Oasis. At present, the annual groundwater exploitation in Dunhuang is 60 million m2(3 the allowable exploitation is 55 million m2), of which 2/3 is used for irrigation. The groundwater level in Dunhuang is decreasing at an average rate of 0.20m per year. By 200 1, the groundwater level had dropped by nearly 1 1 m ... This serious "imbalance between income and expenditure" directly led to the decline of the water level of Crescent Moon Spring-1986, the water level of Crescent Moon Spring was less than 2m, and only 0.90m was left in 2005.

2.2.5 Agricultural flooding increased water consumption.

According to the statistics of Dunhuang Water Affairs Bureau, Dunhuang City lacks nearly 80 million m3 of water every year, including 30 million m3 of agricultural water and 50 million m3 of ecological water. The main reasons are serious waste of water resources, low water use efficiency and extensive agricultural irrigation methods, mostly series irrigation, flood irrigation and deep irrigation. On the one hand, there is a serious shortage of water resources, on the other hand, the waste of water resources is very prominent. The main reasons are that the price of water resources is low, the water price mechanism is unreasonable, and the social cost, ecological cost and future cost are not considered in the composition of water price.

Dunhuang Municipal Party Committee and Municipal Government have formulated and implemented various policies and measures. Through the implementation of "water saving, water diversion, drainage, water seepage and water saving" measures, the four mechanisms of national participation, coordination, governance according to law and responsibility assessment have been improved, and efforts have been made to solve the problems existing in ecological protection work, and effective results have been achieved in increasing revenue and reducing expenditure and building a water-saving society. However, due to the limitation of the existing system, there are still many obstacles to solve the ecological problems in Dunhuang. First, due to the existing compartmentalization system, it is impossible to give overall consideration to the basin economy, social development and environmental protection, production, ecological and domestic water use, and the upper, middle and lower reaches of the basin. Second, local ecological protection and economic construction are fragmented, lacking coordination and restriction mechanism, and resource development causes ecosystem function degradation. Third, the local economic development mode is extensive, and the proportion of water-consuming agriculture is too large, which causes the groundwater level to drop and aggravates the deterioration of water ecology.

3 the strategic significance of ecological environment construction

Serious land desertification, shrinking wetlands and sharp decline in vegetation have destroyed the natural ecological environment on which people depend and seriously threatened the sustainable development of human economy and society. The rapid increase of population and serious overload have increased the extreme consumption of natural resources and the great pressure on the fragile ecological environment. The extremely fragile ecological environment and overloaded population have brought double pressures to this area, and the relationship among population, resources, environment and development is seriously unbalanced. Even affect the sustainable development of the economy in the northwest region. The ecological environment construction in Dunhuang area is of great strategic significance. The ecological environment of Dunhuang Oasis is not optimistic because of sandstorm, land desertification and lack of water resources. If it is not adjusted and improved in time, it will even endanger the Hexi Corridor and even the whole northwest region in the future.

4 Dunhuang ecological environment construction should start from its roots.

The relevant person in charge of the State Environmental Protection Administration also sent special personnel to inspect and investigate the continuous deterioration of Dunhuang ecology. The investigation shows that the ecological protection situation in Dunhuang is very severe, and it is urgent to establish a national ecological function protection zone, and effectively protect the fragile natural ecology of Dunhuang through comprehensive planning across river basins and regions.

First of all, it is necessary to change the way of water resources development and utilization, from "engineering water conservancy" to "ecological water conservancy", and cut off the Danghe River and Shule River through scientific regulation and control, thus fundamentally solving the problem of ecological environment deterioration; Change the concept and method of water saving and increase groundwater recharge at the same time; Change the mode of economic growth, change the planting structure, and promote the planting proportion of water-saving and efficient crops such as flowers and grapes.

Secondly, actively learn from the management experience of the Yellow River and Heihe River, and establish a unified dispatching mechanism for water resources in Shule River and Danghe River basins. The environmental protection department should make full use of the EIA system, strengthen the planning of EIA, strictly manage the development and utilization projects of resources, set the development scale according to the water supply, and carefully emigrate, so as to restrict the disorderly utilization of river basin resources and finally realize the coordinated, healthy and sustainable development of river basin economy, society and environment.

Third, comprehensively evaluate the ecology of Shule River and Danghe River as soon as possible, sum up the experience and lessons of the development and utilization of water resources in the basin, apply the concept of comprehensive ecological management, break the administrative boundaries of the basin, make overall consideration of economic, social and environmental factors, and make overall plans for production, ecology and domestic water use, so as to establish Dunhuang National Ecological Function Protection Zone. With the construction of ecological function protection zones as the carrier, it will be transformed into agriculture, forestry and forestry through large-scale ecological protection across river basins and regions.

The ecological environment of Dunhuang is related to the survival of Dunhuang, the survival of cultural and natural landscapes such as Mogao Grottoes and Crescent Springs, and the ecological security of Dunhuang and its surrounding counties and cities, Hexi Corridor and even the whole northwest region. The deteriorating ecological environment in Dunhuang has sounded the alarm for us. It is urgent to protect the ecological environment of Dunhuang.