The urban environment is largely artificial, that is, a cultural (or humanized) landscape, built by man and not in balance with the natural environment.
As cities grow, there are changes in the natural landscape that generate serious environmental problems. The lack of urban planning in most cities shows the dominance of the economic factor on the environmental and human factor.
Floods and landslides
One of the main alterations that occurs in the urban environment is the waterproofing of the soil due to the removal of the vegetation landscape and its replacement by asphalt, concrete and urban works, which prevent the infiltration (water percolation) and increase the surface runoff.
In cities where underground water galleries are not sufficient, in addition to silting rivers, serious problems with flooding occur. In areas with slope occupancies, that is, with constructions located in areas of high slope, slope slides may occur.
In addition, there are problems of urban microclimate caused by the formation of heat islands and acid rain.
Pollution and heat islands
Heavy traffic and coal heating pollute the atmosphere of many cities, especially in China. This causes smog , a kind of fog that, in turn, is the source of rising temperatures in urban areas. They create a kind of heat island, or urban microclimate.
The heat islands correspond to the rising temperatures in the more urbanized areas, the central region of a large city presents higher temperatures than the peripheral regions.
The concentration of pollutants increases the volume of particulate matter in suspension, giving rise to hygroscopic cores that generate condensation and, therefore, increase the precipitation in the urban areas generating the floods.
The phenomenon of acid rain is related to the concentration of gases, such as sulfur dioxides and nitrogen oxides, which, when reacted with water suspended in the atmosphere, form acids, such as sulfuric acid and nitric acid, which increase the acidity the rains.
When these rains occur in the urban environment, the consequences are the degradation of buildings and monuments, but if the winds carry them to distant places, they can affect lakes, plantations and soils, causing the death of vegetation and animals.
In large cities, where there is a greater concentration of polluting gases in the atmosphere, possible changes in the circulation of air layers close to the surface can further aggravate pollution.
Usually hot air rises to the upper layers of the atmosphere and cools. On colder days, notably in winter, when atmospheric air has lower temperatures near the surface, atmospheric stagnation occurs – the layers of hot and cold air can not circulate. Thus, there is no dispersion of pollutants, becoming more common cases of eye and throat irritation, respiratory diseases like asthma and bronchitis.
Another urban environmental problem in the agenda of environmental discussions is the collection and final destination of urban waste . Uncontrolled consumption of industrial products generates large amounts of solid waste.
In most cities in developing countries, garbage is deposited in open pit soils. This action causes great damage to public health, contaminates the water table with slurry, generates bad smell, transmits disease and promotes the attraction of people in search of products for recycling or food.
Better solutions could be made through landfills, composting plants (organic waste), recycling and incineration. Improper disposal of e -waste, which causes the contamination of people who handle it, soil and water by chemical substances (eg lead, cadmium, mercury, beryllium, etc.), is made every year a serious socio-environmental problem.
According to the United Nations Environment Program (UNEP), the world’s cities produce annually around 1.3 billion tons of solid waste, approximately 1.2 kg per capita daily. However, the estimates for 2025 are worrisome given the possibility of garbage production jumping to 2.2 billion tonnes per year.