In 1800 only about 2 percent of the world's population lived in urban areas. That was a small wonder: Until a century ago, urban areas were some of the unhealthiest places for people to live.
According to The Department of Economic and Social Affairs, half of the global population already lives in cities, and by 2050 two-thirds of the world's people are expected to live in urban areas. But in cities two of the most pressing problems facing the world today also come together: poverty and environmental degradation.
The majority of people move to cities and towns because they view rural areas as places with hardship and backward/primitive lifestyle. Therefore, as populations move to more developed areas (towns and cities) the immediate outcome is urbanization. This normally contributes to the development of land for use in commercial properties; social and economic support institutions, transportation, and residential buildings. Eventually, these activities raise several urbanization issues.
Poor air and water quality, insufficient water availability, waste-disposal problems, andon density and demands of urban environments. Strong city planning will be essential in managing these and other difficulties as the world's urban areas swell.
Urban populations interact with their environment. Urban people change their environment through their consumption of food, energy, water, and land. And in turn, the polluted urban environment affects the health and quality of life of the urban population.
As cities grow in number, spatial extent and density, their environmental and ecological footprints increase. Urban expansion that takes place in forests, wetlands and agricultural systems leads to habitat clearing; degradation and fragmentation of the landscapes. Urban lifestyles, which tend to be consumptive, requiring great natural resources and generating increasing amounts of waste also lead to increased levels of air, water and soil pollution.
A paper published in the PNAS states that unsustainable urbanization will have disastrous effects on global ecosystems. The areas of Asia, Africa and South America that are rapidly growing will overlap with biodiversity hotspots. The aftermath? Urban expansion will lead to the demise of 139 amphibian species, 41 mammalian species and 25 bird species. All of these are endangered or critically endangered.
Approximately 97% of the earth’s water is stored in the oceans, and only a fraction of the remaining portion is usable freshwater. When precipitation falls over the land, it follows various routes. Some of it evaporates, returning to the atmosphere, some seeps into the ground, and the remainder becomes surface water, traveling to oceans and lakes by way of rivers and streams.
Impervious surfaces associated with urbanization alter the natural amount of water that takes each route. The consequences of this change are a decrease in the volume of water that percolates into the ground; and a resulting increase in volume and decrease in quality of surface water. These hydrological changes have significant implications for the quantity of fresh; clean water that is available for use by humans, fish and wildlife.
Air pollution often plagues industrialized cities, particularly during their early development. Episodes of high levels of sulfurous smog killed or sickened thousands in Donora in 1948, as well as in London in 1952. Other cities—primarily in the industrialized regions of the United States and Europe—also suffered from notoriously bad air quality. These events were the result of very high emissions of sulfur dioxide, smoke, and other particles during stagnant, foggy weather conditions.
Urbanization has led to reduced physical activity and unhealthy nutrition. The World Health Organization predicts that by 2020, non-communicable diseases such as heart disease will account for 69 percent of all deaths in developing countries. Another urbanization-related threat is infectious diseases. Air travel carries bacteria and viruses from one country to the next. In addition, people relocating from rural areas are not immune to the same diseases as long-time city residents, which puts them at a greater risk of contracting a disease.
This is a consequence of urban industry, emissions from cars, and the electricity demand. Around the world, companies use fossil fuels such as coal and petrol to generate electricity. Burning these compounds leads to an increase in air pollutant and greenhouse gas emissions. They represent a health and environmental hazard, for they contribute to the formation of smog and the precipitation of acid rain. Urban GHG emissions are largely responsible for global warming and climate change.
The cost of living in urban areas is very high. When this is combined with random and unexpected growth as well as unemployment, there is the spread of unlawful resident settlements represented by slums and squatters. The growth of slums and squatters in urban areas is even further exacerbated by fast-paced industrialization, lack of developed land for housing, large influx of rural immigrants to the cities in search of better life, and the elevated prices of land beyond the reach of the urban poor.
Although urbanization is a necessary condition for modernization, we can mitigate the effect of it. We just need to learn how to save the planet and conserve our natural resources, through recycling water and the use of renewable energy.
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