Why is the population unevenly distributed?

The main factors affecting population distribution The population distribution on the earth is the product of human transformation, utilization and interaction with nature, and it is strongly restricted by natural conditions and natural resources. Areas with suitable climate, fertile soil, abundant resources and convenient transportation often become densely populated areas. However, human beings have the dual attributes of nature and society. With the progress of society and the renewal of labor tools, the leading role of human beings in nature has been gradually strengthened, the zoological characteristics of human beings have gradually faded, the communication between people has increased, and the sociality has been continuously enhanced. Various purposeful activities of human beings are also restricted by social and economic conditions. Therefore, socio-economic conditions will inevitably affect the distribution of population. 1. Natural conditions Natural geographical environment is the natural basis of population distribution, providing human beings with living space. The influence of natural conditions on population distribution varies with different stages of historical development. In ancient times, due to the great dependence of human beings on nature, the population distribution was also greatly influenced by the natural environment. Many scholars believe that the most likely origins of human beings are East Africa, Central Asian grasslands, South Asia and southwest China, which have good living conditions, but they cannot be areas with extremely cold climate and extremely difficult living conditions. In today's highly developed science and technology, human activities can get rid of the shackles of nature to a great extent, and human footprints can be spread all over seven continents. Natural conditions affect population distribution in two different ways. First, the direct influence of natural conditions; The second is the indirect effect that affects the social and economic conditions of various places and then affects the population distribution. The influence of natural conditions on population distribution is realized by topography, climate, hydrology, soil, vegetation, natural resources and other factors. (1) The influence of climate on population distribution can be explained by two indicators: temperature and precipitation. The north and south poles of the earth and the plateau areas with high altitude are not suitable for large-scale population settlement. Those areas are too cold to grow crops and are prone to respiratory diseases. Although the tropical region is rich in water and heat resources and has a wide variety of crops, which can be harvested in more than one year, the temperature there is high, crop diseases and insect pests are serious, and infectious diseases are easy to spread, so the population in the tropical rainforest region is not as large as that in the temperate region. In arid desert areas, rainfall is extremely scarce, which is not suitable for farming and the population is very small. Only river banks and desert oases are densely populated areas. Generally speaking, except for arid areas within the mainland and temperate areas outside the mountains, hydrothermal conditions are suitable for crop growth and people's lives, so it has become the most densely populated area in the world (Table 3-5). (2) The influence of altitude on population distribution As far as the world is concerned, the population is mainly distributed in areas below the altitude of 1000 meters. According to calculations, 90% of the world's population lives in plains below 400 meters above sea level, such as the Ganges Plain in India, the mid-latitude region in Europe, the Great Lakes region in the northeastern United States, the Yangtze River Delta, the Pearl River Delta, the Northeast Plain, the North China Plain and the Sichuan Basin in China. Generally speaking, the altitude is too high, the temperature and air pressure are low, which is easy to cause mountain reaction; Cold and windy climate, barren soil, limited cultivated land, closed traffic conditions, etc. , so that the conditions for the development of production are far different from those in the plains of latitude. Therefore, the population density in temperate and frigid mountainous areas and plateau areas is lower than that in plain areas. However, the tropics are an exception. For example, in Bolivia, Ecuador, Peru and other countries in Latin America, the densely populated areas are not plains, but plateau basins above 3000 meters above sea level. This is because the temperature in mountainous areas and plateaus is moderate, unlike in plain areas, which are too hot and humid and have poor drainage. Moreover, above the upper limit of Anopheles distribution, it is less harmful to diseases, beneficial to agricultural production, and has become an important human habitation in tropical areas. The population distribution in tropical areas of southern China also conforms to the above characteristics. For example, along the Red River, Lancang River and other rivers, although the terrain is low and flat, it is too hot and humid, with lush vegetation and rampant pests, especially malaria, which is known as the "hometown of malaria", so the population is sparse and it is more difficult for foreign residents to adapt to the local natural conditions. On the contrary, in the plateau and mountainous areas with moderate altitude, the temperature and precipitation conditions are more suitable for agricultural production and human health, and the distribution of Anopheles mosquitoes is less, so the population is more dense. In addition, different terrain parts also have great influence on population distribution. Generally speaking, mountain basins, valleys, sunny slopes and foothills are suitable for living and developing agricultural production, and the population is relatively concentrated. Table 3-5 1950 Population density of different climate types (person /km2)(4) Influence of water bodies on population distribution Water is one of the most basic material conditions for human survival, development and production, so the nature and distribution of rivers, lakes, oceans and other water bodies and the degree of water resources security often become important factors limiting population distribution. The influence of water on population distribution is mainly manifested in two aspects: one is to provide water for human beings, and the other is to provide convenient transportation conditions for people. Almost all densely populated areas on the earth are distributed along rivers and coasts. Because people close to these water bodies can get close to the water source and get convenient traffic conditions. The Nile, the Euphrates, the Indus and the Yellow River became the cradles of ancient civilizations and benefited from the favorable conditions provided by rivers to mankind. (5) Influence of soil conditions on population distribution Soil is one of the most basic conditions for developing agricultural production. Different soils have different soil fertility and characteristics suitable for farming. Therefore, the influence of soil conditions on population distribution is mainly reflected by the influence of various soil fertility and suitable farming degree on agricultural production. Generally speaking, black soil, chernozem, brown forest soil and alluvial soil are the most suitable soils for cultivation. Therefore, temperate regions and deltas, such as Yangtze River Delta, Pearl River Delta, Ganges River Delta, Nile River Delta and Mekong River Delta, are densely populated areas in the world. Saline-alkali soil, swamp soil, calcareous soil, red soil and other soil types are relatively barren and the population is sparse. (6) Influence of mineral resources on population distribution With the development of industrial production, the status of mineral resources is becoming more and more important. Mining centers are very attractive to the population, and sometimes they become the decisive factor of population distribution. The representative is a large number of immigrants caused by the gold rush. One of the important reasons why the New World was able to attract a large number of European immigrants at first was that the colonists rushed for gold. In many areas where a large number of people are concentrated because of resource development, the population often drops sharply because of resource depletion. Of course, due to the modernization of mining technology, there has been a phenomenon that a large number of mining mineral resources have not caused a large number of population migration and changed the population distribution. 2. Socio-economic conditions (1) The influence of social mode of production on population distribution Although natural conditions are the basis of human existence and population distribution is more or less branded with natural factors, nature only provides the possibility for population distribution on the earth, and social mode of production is the decisive factor to realize this possibility. The influence of natural conditions on population distribution changes with the development of social productive forces. For example, in the early stage of the development of human society, the level of productivity was extremely low. Humans mainly made a living by gathering and hunting, and the population distribution depended largely on the distribution of edible animals and plants. After human tamed wild animals and plants, agriculture and animal husbandry developed, human's ability to control nature was greatly enhanced, the cultivated land area was continuously expanded, and the distribution range of human beings was also expanded. For example, due to the development of water conservancy and the improvement of irrigation level, deserts and arid areas that were originally considered unable to develop agriculture began to be inhabited with the development of agriculture. Today, with the high development of modern industry, the industrial structure has undergone tremendous changes. The number of employees in agriculture and extractive industries has decreased, urban manufacturing and various service industries have flourished, the degree of urbanization has increased, and the population has increasingly concentrated in cities. The industrial and commercial centers of various countries are often the areas with the most concentrated population distribution. (2) Influence of production development and layout on population distribution Agriculture is the foundation of national economic and social development. Historically, the distribution of agricultural production is closely related to the distribution of population. Developed agricultural areas are often both the birthplace of ancient civilization and densely populated areas. In the farming era, the level of agricultural production and agricultural layout are the basic factors that determine the population density of a region. In areas with developed agricultural production, the population per unit area of land can support a large number, so it is densely populated; On the contrary, in areas with backward farming technology, people use the natural fertility of the land for extensive management, with low output and few people to feed, so the population is sparse. Since the 20th century, especially after the Second World War, the world agricultural productivity has undergone drastic changes. Agriculture in developed countries has been modernized, agricultural labor productivity has been unprecedentedly improved, and the required agricultural labor force has been greatly reduced. The population originally scattered in rural areas gradually concentrated in cities and industrial and mining areas. For example, the agricultural labor force in the United States only accounts for 2-3% of the total labor force in the country, but it produces 120% of the grain needed by the whole country. The imbalance of production layout and economic development level often leads to the imbalance of population distribution. For example, the population of the former Soviet Union is mainly concentrated in Europe, and the population of the United States is concentrated in the northeast, which are all manifestations of unbalanced production layout. In addition, the development of traffic has expanded the spatial scope of human activities and promoted the continuous increase of population density along the traffic. For example, the excavation of the Grand Canal in Sui and Tang Dynasties led to the emergence of a number of prosperous port cities along the canal and became a densely populated area in the country. (3) Influence of other socio-economic factors on population distribution Other socio-economic factors, such as changes in major population and economic policies, wars, famines, epidemics, traditional concepts, etc., all have an impact on population distribution. Political factors sometimes have a great influence on population distribution, which will change the population distribution in a short time. For example, during World War II, the population moved from Eastern Europe to Germany reached 6 million. After the founding of New China, in order to balance the distribution of productive forces and support the construction of inland and frontier areas, the state has planned to transport workers, veterans and technicians from the eastern coastal areas to the inland and frontier areas.