Marx once quoted Tremaud's famous saying: "A human plan that is not based on the great laws of nature will only bring disaster."
At the seminar on "Physical Geography and Ecological Construction" held not long ago, some experts pointed out that there are obvious regional differences on the earth's surface, and the research on this difference also has different scales in the world, countries and regions. In areas of different scales, social and economic development should maintain a harmonious relationship with population, resources and environment, because resources and environment are the material basis for human survival. He emphasized that the objective law of natural zonality is independent of human will, and we must constantly deepen our understanding of the earth's natural system and improve human evaluation of natural value.
The arid areas in northwest China are vast, including semi-arid grassland areas in Inner Mongolia and northern Shaanxi, and arid desert areas in Ningxia, Gansu, Xinjiang and Qinghai. Ecological construction is an important connotation of the development strategy of arid areas in northwest China. The distribution of the main ecosystem types on the land surface depends on the combination of temperature and water conditions, forming a spatial pattern restricted by the laws of natural zones. According to the principle of respecting nature, I analyzed some problems existing in the current ecological construction in China.
Afforestation and "greening project"
For a long time, there has been a general one-sided understanding that "greening is equal to afforestation" and "ecological construction is afforestation", which is mainly due to the lack of understanding of the laws of natural zonality. Usually, humid and semi-humid areas have good natural conditions and can be used for afforestation and forest layout; In semi-arid and arid areas, trees can only be planted in local areas and forests can be distributed in suitable places in mountainous areas, but it is not suitable for large-scale afforestation. Some scholars have suggested that forest coverage rate is one of the indicators of sustainable development in various regions of China, which is debatable. Taking the arid area in northwest China as an example, the areas suitable for forest growth and distribution are limited, and the coverage rate of natural forests in some provinces and regions is mostly below 5%. If these provinces are required to plant trees on a large scale in order to achieve the same forest coverage index in humid and semi-humid areas, it is not in line with the laws of nature. Therefore, the coordination of environment and development in semi-arid and arid climates should respect nature, and neither bear the burden of low forest coverage nor unilaterally pursue unrealistic afforestation indicators.
However, in semi-arid and arid areas, we can still see the phenomenon of water diversion irrigation, afforestation and the construction of airport high-speed "green belt", or dig holes along the contour lines to plant shrubs and spray irrigation on hills on both sides of some expressways to create a "greening project". As a result, the forest belt disappeared and the already fragile environment was destroyed. The relevant departments even proposed to auction the desert hilly land in the suburbs of Urumqi and implement the "tree planting and greening" plan by contracting. Small-scale farmland shelterbelts can be built on the edge of oasis in arid areas of northwest China, but it is not suitable to build forests on a large scale, let alone exaggerate the role of shelterbelts.
According to the characteristics of natural zones in arid and semi-arid areas, some scholars suggest that we should re-examine the construction of shelterbelts in the Three North Areas. Because the large-scale construction of shelterbelts in arid and semi-arid areas is not helpful to prevent sandstorms, nor does it conform to the objective reality of water shortage, and there are still many aspects that need to be improved. The total area of the Three-North Shelterbelt Construction Project is 394.5× 104 square kilometers, of which desert accounts for 55% and grassland and desert grassland account for 20%. Large-scale afforestation under such natural conditions completely violates the law of regional differentiation. For major plans or projects to transform nature, we should conduct dynamic monitoring, constantly sum up successful experiences, draw lessons from failures, and correct and improve them in time. Just as Marx quoted Bibi Tremaud's famous saying: "A human plan that is not based on the great laws of nature will only bring disaster".
Here are some key points I have summarized:
1. Construction of nature reserves
As a natural product, desert has its natural laws of formation, evolution and development. Since the 1950s, the successful experience and failure lessons in the development of arid areas in northwest China deserve to be carefully summarized and learned. For example, Mosuowan area in Junggar basin, located in the alluvial plain at the northern foot of Tianshan Mountain, has good original natural vegetation. Due to unreasonable large-scale reclamation, intensive firewood collection and overgrazing, sand dunes have been seriously activated. The Gurbantunggut Desert in the middle of the basin is dominated by fixed and semi-fixed sand dunes, with a large area of Haloxylon ammodendron and Haloxylon ammodendron forest, as well as short-lived plants unique to spring. It is one of the regions with the richest biodiversity in temperate desert and an important genetic treasure house in temperate arid areas. Although the original vegetation has been destroyed by unreasonable human activities, as long as appropriate enclosure measures are taken, it can quickly resume succession to the corresponding climax community. Practice shows that enclosure protection is an effective way to restore degraded habitats in sandy land. It is suggested to strengthen the natural protection of the whole Gurbantunggut Desert, delimit areas with special value, and establish nature reserves or national desert park. Since 1983 established Altun Nature Reserve in the middle of Kunlun Mountain, various vegetation such as mountain grassland has been protected, and the populations of rare animals such as roe deer, Tibetan antelope and marmoset have gradually increased, and the natural restoration of vegetation has achieved remarkable results.
Development and utilization of water resources
When talking about the development and utilization of water and soil resources, some scholars pointed out that environmental improvement, ecological construction and regional development are closely related, mutually restricting and acting together. Compared with other desert areas in the world, the arid areas in northwest China have unique advantages. There are many alpine glaciers on a series of high mountains, which provide important water sources for the development of desert oases. At present, the main problems are insufficient utilization of water resources, poor management, low efficiency and great waste.
In arid areas, water is a very scarce resource. To save irrigation water in the field, scientific experiments should be carried out in combination with local conditions, and technical measures suitable for application in arid areas should be summarized. Plastic film mulching agriculture has great development prospects in arid areas. Under plastic film mulching, we can not only get enough photosynthetic effective radiation energy, eliminate the shortcoming of large daily temperature difference, but also save water consumption, which will be beneficial to expand the growth of various plants. Of course, we should also study the influence of surface conditions under plastic film mulching on soil, soil animals and soil microorganisms. The scheme of inter-basin water transfer project in northwest arid area needs to be very cautious, and the main goal should be to serve the city and industrial and mining water. It is not suitable to transfer water to cultivate and develop agriculture, otherwise it will destroy natural vegetation and aggravate the secondary salinization of soil. At present, the over-exploitation of groundwater in the piedmont plain oasis in northern Xinjiang leads to a sharp drop in groundwater level, which seriously threatens the ecological security and sustainable development of the oasis in this area.
From the point of view of humid areas, some people think that water transfer to arid areas in northwest China is a necessary prerequisite for development and regulation. They believe that as long as there is enough water, deserts and Gobi can become fertile fields, and grain, cotton and fruits are all high-quality products. So some people put forward the idea of "transferring water from the East to the West to completely transform the northern desert", while others advocated transferring 40 billion cubic meters of water from the Yarlung Zangbo River to Xinjiang, believing that they had the corresponding scientific and technological capabilities. But they don't know that the problems in arid areas can't be solved by water transfer, and the objective law of natural zonality is independent of human will.
No matter from the perspective of natural conditions or social and economic development, there are many problems in the idea of large-scale long-distance inter-basin water transfer in arid areas of northwest China, such as feasibility, market demand, investment benefit and so on, which need to be carefully analyzed and must not be acted rashly.
Reclamation of land resources
In 1950s and 1960s, the development of arid areas in northwest China was mainly based on the reclamation and utilization of land resources. Agricultural reclamation played a positive role at that time and achieved obvious results, but the negative impact of large-scale reclamation on the environment was also very prominent. Taking Xinjiang as an example, from 1950 to 1998, 392.8× 104 hectares were reclaimed, and the original cultivated land should be 5 13.8× 104 hectares. In 1998, the cultivated land area was 33 1× 104 hectares, and the lost cultivated land area was 182.8× 104 hectares, with a loss rate of 35.6%. According to the newly reclaimed land, the loss rate is as high as 46.5%, of which, except a few are occupied by construction, most of them are retreated to wasteland. From 1953 to 1965, 8.39× 104 hectares were reclaimed in Qaidam basin, and most of the reclaimed land was good grassland or woodland. Due to the secondary salinization and desertification of the land, the cultivated area actually reserved to 1995 is only 3.74× 104 hectares, and the abandonment rate is over 55%. The wind erosion of the surface soil of abandoned farmland is much greater than that of cultivated land and desert land. It can be seen that although the arid area in northwest China is vast, most of the land suitable for farming has been reclaimed and utilized. What's more, in the reserve cultivated land resources, the proportion of salinized land area is very high. In the future, we should focus on increasing the output of existing cultivated land, rather than blindly reclaiming land to expand the cultivated land area. In recent years, the relevant departments in Xinjiang have put forward a plan to reclaim10 million mu of wasteland, which has aroused people's concern and anxiety.
Oasis crisis in the lower reaches of Shiyang River
Nature is an organic whole, and the regions are interrelated and restricted, and the role and influence between upstream and downstream are more prominent. Minqin Oasis in the lower reaches of Shiyang River has a long history of development, and the land desertification was serious in the first half of the 20th century. From 1950s to early 1980s, a series of biological and engineering measures achieved good results. Since 1950s, the shelterbelt dominated by Elaeagnus angustifolia forest has been built in Minqin Basin, and it has been widely popularized. Elaeagnus angustifolia forest 199 1, 1.7× 104 hectares and shrub forest 2.7× 104 hectares have been built. Due to the rapid decline of groundwater level, it caused serious decline, with the death of Elaeagnus angustifolia forest of 0.6× 104 hectares, dead branches of 0.6× 104 hectares and artificial shrubs of 0.8× 104 hectares. It can be seen that in the oasis of arid desert area, the construction of shelterbelt should not pursue the proportion of woodland coverage unilaterally, but should be arranged appropriately. Otherwise, the regional groundwater level will drop sharply, which will not only affect the development of agriculture and animal husbandry production, but also make the forest belt decline and lose its function, and make desertification come back.
At present, the global temperature is rising, and arid areas are gradually spreading. The living environment of human beings is controlled by human beings. I was deeply shocked by this study of drought environment data and careful study of drought ecology. Our home is constantly being destroyed, so it is imperative to prevent and control it. I hope that scientists can develop more reasonable and simple methods and technologies as soon as possible, so that more people can understand the deterioration of the ecological environment and have a sense of responsibility for prevention and control.