The relationship between humans and environment has varied from the early periods of human settlement on the earth to the present day. The relationship between environment and human beings has also being varying from place to place at any given period of time. For example, early humans considered the environment to be dominant. They were afraid of lightning and thunder, dense forests, wild animals, vast oceans and large rivers, to name a few.
The environment has considerably affected human beings right from his evolution. The environment affects humans in many ways. Population on the earth varies due to variation in the environment. The main factors which affect the distribution of population and human settlement are:
1) Relief of Land
The populations in the high mountainous areas, such as the Himalayas in India, Andes in South America, Rocky in North America, etc., have very low settlement level. This is because the relief is rugged here which represents obstacles in the construction of roads, railways and communication. Due to steep slopes, agriculture is done with a great difficulty and industries also could not be established. These places having very less economic activity have less population and hence have small isolated settlements.
Whereas the plain areas of the world are most suitable for human settlement. Fertile plains of Ganga in India, Indus in Pakistan, Hwang-Ho in China and plains of Europe have huge population concentration having compact or huge semi-compact type of settlement.
Most of the areas of the earth having density less than two persons/sq. km are not favorable for settlement because of their unfavorable climate.
Areas of cold climate-North Siberia, North Canada, Alaska etc. have low density of population. Hot and arid regions of -Sahara, Kalahari Desert in Africa, Great Australian Desert etc are not suitable for human settlement. In tropical regions due to heavy rain and temperature, the density of population is very low, example in Amazon basin population density is less than two persons/sq. km. But places with favorable climate and favorable terrain, have dense population and hence have compact settlement.
Fertile alluvial soils encourage dense population which in turn gives rise to compact type of settlement. This is so because alluvial soils give rise to agricultural activities. Java Islands of Indonesia has fertile soil of young volcanic material and agriculture is an important activity, hence dense and compact settlements are found here. Whereas in Sumatra, due to infertile soil, the population density is very low.
4) Mineral Deposits
Mineral wealth is yet another factor responsible for population distribution and density. The presence of coal and iron-ore in different parts of the world has attracted huge population. Coal mining regions have become regions of dense population for example, Jharkhand in India and gold mines in Australian desert.
5) Water supply
Population distribution is very much affected by water supply. The earliest settlements or civilizations developed on the banks of major rivers, example-Nile, Indus, etc. Adequate water supply provides irrigation facilities to farmers and hence population increases due to increase in primary activities. In dry regions, population is concentrated in those areas where there is water, hence nucleated- circular settlements are found.
Thus it can be said that the environment plays an important role in deciding population distribution, density, settlement type and pattern.
The Industrial Revolution which provided mechanical power, invention of steam engine and other machinery, greater use of metals etc gave them opportunities to modify the environment. At the same time agriculture provided abundant food so that they could settle down permanently. The family grew in size and people migrated to different parts, via rail, road and sea, because of improvement in transport system, example the new lands in America and Australia were settled by people from Europe.
Another development which enabled humans to survive was the use of preventive and cumulative steps taken to protect them from epidemics and diseases-it increased the span of human life and reduced death rate.
With increase in the knowledge and skill and development of human economy there was a gradual increase in carbon dioxide content. It is estimated that carbon dioxide content has increased by 25% in last 100yrs and the global temperatures have risen between 0.3 degree Celsius to 0.7 degree Celsius. Increase in carbon dioxide is attributed to large scale deforestation and will lead to increase in sea level causing submergence of coastal regions.
Burning of coal, oil and petroleum adds sulphur dioxide to the atmosphere. Lead, carbon monoxide and nitrogen dioxide are added to the atmosphere from automobile exhaust. These gases result in acid rain which affects aquatic life, example acid rain in industrial regions of Europe and North America.
Even now substances which were not present previously, are introduced into the air, water and soils. The most dangerous one is radioactive substance spewed into the atmosphere by nuclear explosions. They have adverse effects on organisms including man and cause death, impairment of limbs, diseases and psychological disorders.
The catastrophe of nuclear disaster at Chernobyl in Ukraine (1988) is a burning example of adverse environmental effects of use of minerals like uranium, thorium etc. through most advanced and sophisticated technology.
The environment has already been degraded to such an extent in certain areas that people are forced to migrate. They are facing scarcity of resources like food and energy.
Man’s impact on environment has resulted in pollution of environment which not only affects air, water and land but also organisms of biosphere. The main points summing up the impact of man on environment are:
Air pollution-burning of fossil fuels in large quantities from jet aircraft, CFCs used in aerosol spray cans, refrigerators and farm blowing are responsible for depletion of ozone to 3-4% in last 100 years.
Water pollution-leakage of petroleum from huge ships and oil tankers into the sea, causes oil slicks which spread rapidly over water and spell disaster to marine life and to human depending on marine resources. The leakage of 100000tons of crude oil near Spanish coast in 1976, leakage of crude oil off Alaskan coast in 1989 are a few examples of the many such incidents which tell the impact of negligence and failure of technology on environment.
The most widespread source of water pollution is disposal of sewage of urban centers into rivers. The Ganga and Yamuna are polluted in this way and the same rivers provide domestic water supply as well. Ocean waters are polluted by discharge of sewage from cities located along the coast.
Land degradation-dumping of solid waste from urban centers and waste materials from mining centers renders the land unsuitable for any use. Surface run-off from such areas pollutes streams and ground water seepage. Saline encrustation of irrigated lands is another example of land degradation. In the semi-arid region, wind action causes deposition of sand on a large scale over cultivated land rendering them unfit for cultivation. This marks the beginning of the process of desertification.
Depletion of resources-population growth in the recent past has resulted in rapid depletion of all kinds of resources. The most striking example of such resource depletion is the food deficit faced by about 100 countries of the world.
Forest and soil resources are getting depleted at a fast rate owing to population pressure. Tropical forests are depleting at a rate of 2% per annum. It is estimated that the world is losing 7% of top soil per decade.
Depletion of resources is most significant in respect of non renewable mineral and power resources. The world is facing energy crisis as existing oil resources may last for a few decades. Though coal reserves are adequate for a few centuries but it cannot replace oil, especially for transport.
Humans have come to realize that their economic activities are threatening their survival on earth. Their survival depends on their realization that they have to live in harmony with the various elements of environment which are interconnected. An understanding of the components and processes which take place in environment, the relationship between biotic and abiotic components, and the assessment of resources with reference to need of people in a region is essential for their survival.