Reasons for the difference in population distribution in China.

Natural environmental factors affecting population distribution in China

The natural environment is the sum of various natural elements around human beings, which provides basic living space for human beings and is the source for people to create all means of production and living. No matter when, the survival and development of human beings are inseparable from this natural foundation. Therefore, man is the product of the combination of labor and nature. In ancient times, when the level of productivity was still low and people had to rely on ready-made food and other means of subsistence provided by nature, the population distribution was greatly influenced by the natural environment. It is no accident that China's Lamarcosaurus and Yuanmou ape-man fossils were found in the south. Obviously, it is easier to make a living in tropical and subtropical areas in the south than in the north, where there are more natural foods and there is no threat of cold. Only when people master the skills of fire, hunting and fishing can they move to a wider area. Beijingers, Lantian people and cavemen are the representatives of this period.

With the development of productive forces, human's ability to adapt and transform nature has been strengthened, but the natural environment is still the basis of production and life. The regional differences of natural environment, the advantages and disadvantages of natural conditions and the amount of natural resources directly affect the economic development of various regions, and then affect the distribution of population. After the initial agriculture appeared in China more than/kloc-0,000 years ago, the plain and hilly areas in the middle and lower reaches of the Yellow River gradually developed into the most densely populated areas, which is obviously inseparable from the warm and semi-humid climate, loose and fertile soil and flat and well-drained terrain. In short, superior natural conditions are conducive to the growth of dry-cultivated millet and millet. Generally speaking, whenever possible, people always choose a place with good climate, reliable water sources and flat and fertile land as their residence. With the same labor force and capital, more wealth can be created here, and the population is easy to multiply. In those areas with relatively harsh natural conditions, even if people can adapt, the development of productive forces will inevitably be limited, which has a particularly significant impact on agricultural production, and it is difficult to multiply the population. There are indeed some ethnic minorities in China who have lived in a relatively harsh natural environment for a long time. The most typical is Tibetan. They have lived on the "roof of the world" at an altitude of about 4000 for generations. The climate here is dry and cold, and the air is thin. Many places have not been exploited until now. Although Tibetan compatriots have formed a unique adaptability to the plateau environment, due to various restrictions of natural conditions, it has brought many adverse effects on the development of productive forces, and the population has been stagnant and shrinking for centuries. Although there are many reasons, they are not unrelated to the natural environment. On the contrary, the vast areas in eastern and southern China are dominated by temperate and subtropical monsoon climate, with rich water and heat resources and deep and fertile soil layers. Farmers take advantage of this favorable natural condition to plant a wide range of crops such as rice, millet, wheat, millet, hemp, mulberry, melons and fruits, and the amount of cultivated land and agricultural production level have long been at the forefront of the world. This vast area has developed into a prominent densely populated area for thousands of years, and it is in the ascendant today. It is obviously unimaginable that there is no relatively superior and stable natural environment as the foundation.

In the whole natural environment, there are many factors affecting population distribution, which are interrelated. For convenience, they are described as follows:

(1) Topography As pointed out earlier in this book, most of China's population is concentrated in relatively low plains and hilly areas, and the population density drops rapidly with the elevation, which is very obvious. The fundamental reason is that the temperature and pressure field decrease with the increase of height, which directly restricts the physiological function of human body. For some people, altitude sickness may occur at an altitude of 1800 meters, and if it exceeds 4000 meters, it may lead to death due to low air pressure. Generally speaking, compared with the plains in the same area, the climate in mountainous areas and plateaus is cold and windy, and the average temperature drops by 0.5 ~ 0.6℃ per 100 meter. With the increase of height, the accumulated temperature gradually decreases and the growth period becomes shorter and shorter. The accumulated temperature ≥ 100℃ in northern China decreases 150 ~ 200℃ for every increase of 100 m, and the duration decreases for 3 ~ 6 days. Coupled with poor soil and inconvenient transportation, not only agricultural production is deeply limited, but also other economic activities have many unfavorable factors. The greater the fluctuation of altitude and terrain, the steeper the slope, and the more obvious this unfavorable factor is. Therefore, the population in mountainous areas and plateaus is not as dense as that in plain areas, which is a common phenomenon in most parts of China (Table 44).

For altitude, it should also be analyzed in combination with latitude. Generally speaking, the higher the latitude, the lower the distribution height of snow line and Rocky Mountain (referring to bare bare bare mountain and bald ridge), and the greater the restriction on the vertical distribution of population. In the west of China, the latitude of Himalayas is the lowest, and the lowest heights of Rocky Mountain and Snow Line are 5000m and 5400m, respectively, so the population distribution can reach up to 5200m. The lowest heights of Rocky Mountain and Snow Line on the northern slope of Kunlun Mountain are 3,500m and 5 100m, Tianshan Mountain is 3,500m and 3600m, Altai Mountain is 2700m and 3,000m, and the highest height of population distribution is much lower than that of Himalayan Mountain, of which the northern slope of Kunlun Mountain and the southern slope of Tianshan Mountain are 3,000m, the northern slope of Tianshan Mountain is 2500m and the southern slope of Altai Mountain is only 24000m.

Due to the different geographical conditions, the characteristics of the vertical distribution of population in various regions can be described as similarities and differences, and each has its own characteristics, which is not a simple relationship that the population decreases with the increase of height. For example, on the southern slope of Altai Mountain in Xinjiang, the population is mainly distributed in the piedmont alluvial plain, the middle part of alluvial fan and the valley plain below 1000 meters above sea level. Rich in water resources, good soil quality and high temperature, it is the main distribution area of farmland and grassland, and its population accounts for more than 80% of the whole vertical zone. The "low valley" of population distribution is located at the river outlet of1000 ~1500m and the upper part of alluvial fan. River water flows through this area, and most of it seeps into groundwater, and the surface is not covered with soil. Unable to engage in farming and animal husbandry activities, the population is very small, accounting for less than 4% of the whole vertical zone. The mountainous area of 1500 ~ 2400 meters has dense forests and open grasslands, and the population accounts for 15%, which obviously exceeds the previous "low valley". The northern slope of Tianshan Mountain is on the windward side, with more precipitation. The new oasis is densely populated below 500 meters above sea level, and the population accounts for about 60% of the whole vertical zone. The population density calculated by cultivated land can reach 250 ~ 300 people/square kilometer. 500 ~ 1000 meters is an old oasis dense area with a population of 30%. Geomorphologically, it belongs to the middle, middle and lower parts of the piedmont alluvial fan and the middle part of the alluvial plain, where most villages, counties and towns are concentrated. 1000 ~ 1250 meters is a mountain pass, with a population ratio of less than 5%, which is a very sparsely populated area. 1250 ~ 2500m, which is a farming-pastoral ecotone, accounting for about 8% of the population. The southern slope of Tianshan Mountain is located in the rain shadow area, showing desert and semi-desert landscape, and the vertical band spectrum of population is completely different from that of the northern slope. Among them, 900 ~ 980m is the densely populated area of the new oasis, and the population accounts for 10% of the vertical zone. 980 ~ 1500m is an old oasis densely populated area, accounting for 87% of the vertical zone, and the population density of cultivated land can reach 400 people /km2. 1500 ~ 3000m The mountainous area is dominated by nomadic population, and the population is extremely sparse. The climate on the northern slope of Kunlun Mountain is extremely dry and the vertical distribution of population is unique. Below the altitude of 1250 meters, it is a desert no man's land. In the range of 1250 ~ 1500m, 94% of the population in the whole vertical zone is concentrated. The population density of cultivated land is 450 people/km2. 1500 ~ 3000m, with a population of only 6%. Thus, it can reflect the general law of the vertical distribution of population in temperate regions.

However, in the tropical and marginal areas of China, the vertical distribution pattern of population is different from other areas. Some tropical valley plains, such as Nanding River and Nanka River in Yunnan, are low and flat, but they are overheated and humid, and the drainage is not smooth, so soil fertility is easy to decompose and lose. In addition, there are lush vegetation and poisonous insects, especially malaria, which pose a great threat to human health. Historically, it has been called "the hometown of boils", with a small population, and it is especially difficult for foreign residents to adapt. After the founding of New China, although the people's health level has been greatly improved, the population is still sparse. Other tropical valley plains, such as the middle reaches of Yuanjiang River in Yunnan, are located in the rain shadow area, with dry and hot climate, tropical savanna landscape and small population. On the contrary, in the mountainous areas and plateaus with moderate altitude, the population is dense, and the temperature and precipitation here are suitable for agricultural production and human health, especially higher than the upper limit of the distribution of Anopheles, thus forming a sharp contrast with the valley areas. Take Yunnan Province, where China is located on the tropical edge, as an example.

Table 45 Elevation Distribution Map of Yuanyang County 1978 Residential Area in Yunnan Province (No.)

Source: Atlas of Yunnan Province.

For example, the whole province can be divided into three levels from bottom to top: ① Low-heat layer, with the elevation below 1200m in the east and below 1500m in the west; ② Intermediate warm layer; (3) Alpine layer, more than 2,200m in the east and 2,500m in the west. The population distribution is densest in the middle-warm layer and lowest in the low-heat layer. Important towns and developed agricultural areas in the province are basically concentrated in the middle and warm layers. The distribution of this population is obviously different from that in temperate regions. Table 45 provides the residential distribution data of Yuanyang County, Yunnan Province, which is located on the south bank of the middle reaches of Yuanjiang River, and can typically reflect the above characteristics.

Even in the plains of temperate zone and subtropical zone in China, the difference of population distribution is not small. In some places, the terrain is too low and flat, and the drainage is not smooth, especially in the monsoon climate, where the rainy season is concentrated and the precipitation intensity is high, and it is often threatened by floods, floods and collapses. In some areas, marshes and salinization even occur because of the high groundwater level, too sticky soil and poor farming suitability. These areas are sparsely populated, such as Sanjiang Plain in the northeast, Songnen Plain in the middle and He Lixia Plain in Jiangsu. Generally, the fan-shaped alluvial plain at the foot of the mountain and its transition zone with depression have the best agricultural production conditions and the densest population in the plain. The terrain is gentle and has a certain slope (about 0. 1%), which is beneficial to farming and drainage. Groundwater and surface water are moderate, neither prone to drought as in mountainous areas nor waterlogging as in depressions, and the soil layer is deep and fertile. It will often develop into an agricultural elite, and the rural population density is extremely high. A typical example is the alluvial plain at the foot of Taihang Mountain in central Hebei Province, which starts from Dingxing and Xu Shui counties in the north, passes through Xinle, Zhengding and Shenze counties in the south, and reaches Luancheng and Zhaoxian counties, forming the most densely populated area in the province. The eastern Henan-northern Anhui plain, which is mainly located in Zhoukou area of Henan Province, is an extremely densely populated rural area with a large area, and the topographical conditions here are also very conducive to agricultural production. Of course, human beings are not satisfied with simply adapting to nature, but also constantly transforming nature. There are many low-lying plains and deltas. After long-term transformation, it has gradually developed into a land of fish and rice with dense population and rich economy, such as the Yangtze River Delta, Hanjiang Delta and Pearl River Delta, but their development history is indeed shorter than that of Huanghuai Plain.

China is a mountainous country, which is much wider than the plain. According to estimates, all kinds of mountains, hills and plateaus in China account for 66. 1% of the country's total area, and the population and cultivated land also account for 1/3 and 2/5 respectively. Plains and plateaus only account for 33.9% of the total area. Of the more than 2,300 cities and counties in China, 1, 600 are located in mountainous areas, including about 80 in high mountainous areas, more than 740 in Zhongshan and low mountainous areas, about 720 in hills and more than 60 in plateaus, while only 1, 20 in plateaus and 60 in plains respectively.

The altitude and topography of the hilly plateau are relatively large, and the influence of this feature on population distribution is mainly manifested in the following aspects.

First of all, less flat land and more sloping land not only limit the expansion of cultivated land, but also make it difficult to improve the production level, which is not conducive to the development of agricultural production and affects its population capacity like the plain. At present, China's population distribution is basically proportional to several indicators in agricultural production, such as reclamation index, multiple cropping index and yield level, but in these aspects, mountainous areas are not as good as plains. For example, Ankang area in Shaanxi Province is located in a mountainous area, only 3.3% of cultivated land has a slope less than 5, 46. 1% with a slope of 5-25, 34. 1% with a slope of 25-35, and 65,438+06.5% with a slope greater than 35. Although the sloping land is used to this extent, the average reclamation index is still less than 13%, and the production level is not high. 1990 The average population density is only 120.8 people/km2, and most of them are concentrated in Hanjiang River Basin and several mountain basins. On the contrary, the Guanzhong Plain, which is separated from it by a mountain (Qinling Mountains), although the climate is not as warm and humid as that in Ankang area, is superior in topography, with a reclamation index of nearly 50%, a multiple cropping index of 150 ~ 160%, a high yield per unit area, and an average population density of more than 300 people/km2, which is about twice as high as that in Ankang area. The eastern part of Sichuan Province is also very telling (see figure 15). From Huaying Mountain to the east, more than 30 anticlines of different lengths form the northeast parallel ridge and valley area. Syncline has a wide terrain, mostly valleys and plains, with an altitude of 300 ~ 500 meters, rivers running through it, fertile soil, developed agriculture and population density of more than 400 people per square kilometer. The anticline is compact, forming long and low mountains, such as Huaying Mountain, Mingyue Mountain, Tiefeng Mountain and Fangdou Mountain. The altitude is generally between 500- 1 100 meters, and the main peak is relatively high. The population density is less than 200 people per square kilometer, even less than 100 people.

Secondly, the terrain is complex, and the imbalance of population distribution greatly exceeds that of the plain. Generally speaking, mountain basins and valleys are the most densely populated. They are plains in mountainous areas, but their area is small and their distribution is not concentrated. Typical is the dam on the Yunnan-Guizhou Plateau. For example, 84% of Yunnan's products are mountains, 10% are plateaus, and 6% are bazi. The slopes of these dams are below 8, and the largest dam can reach 1000 square kilometers. According to statistics, there are 1 4,42 dams over 1 km2 in the whole province, while there are only 49 dams over 1 km2. They are like a mirror embedded in the rugged Yunnan-Guizhou Plateau. The high density of agriculture and population makes the densely populated areas appear a little messy on the population distribution map, which is completely different from the uninterrupted large densely populated areas on the eastern plain.

As can be seen from the population density profile, the population density curve in mountainous areas is always ups and downs, and the magnitude can change dozens or even hundreds of times in just a few tens or even twenty kilometers. The curve is flatter on the plateau and flatter on the plain. Figure 16 provides the population density profiles of four typical cities in Shaanxi Province, among which Hanzhong, Shangluo and Baoji are sandwiched between Daba Mountain, Hanjiang River, Qinling Mountain, Weihe River and Longshan Mountain respectively, and the curves fluctuate greatly. However, the Yulin curve on the Loess Plateau is far gentle, showing obvious differences in the balance of population distribution.