Today, more than half of the world's population lives in cities. By 2050, according to the UN, two-thirds of humanity will live in cities. Meanwhile, all cities in the world occupy less than 2% of the Earth's surface. City dwellers consume much more food, household goods, and natural resources than rural residents. Thus, megacities make a significant contribution to air, water, and soil pollution, and exacerbate the waste problem. In addition, the expansion of urban areas reduces the area of agricultural land and harms biodiversity, leading to changes in natural zones.

UN experts call human activity the main cause of global warming. "The city, being a point of high concentration of people, disrupts the processes that have developed in nature. Given current urbanization trends, human impact will only grow," admits urban planner and urbanist Grigory Solomin.

Climate change and the consequences of environmental problems

Densely populated residential areas, industrial enterprises, and road networks create a huge burden on the environment, exacerbating urban environmental problems. According to the UN, cities consume 78% of the world's energy and are the source of more than 60% of all greenhouse gas emissions.

Modern cities are heat islands, where the air temperature is higher than in the surrounding areas. The phenomenon is explained by the fact that large settlements are densely built up, they have a large accumulation of vehicles, asphalted and waterproof surfaces, such as roads, parking lots, dark roofs, can absorb solar radiation, releasing a large amount of heat afterwards. In addition, tall buildings block air flows, which prevents the city from cooling down. Due to the lack of space for the construction of new buildings, green spaces and water bodies are often reduced in megacities, although it is vegetation and water that cool the air.

In 2019, American and Chinese scientists came to the conclusion that by the middle of the 21st century, the heat island effect will enhance the effect of climate change in many megacities of the world. So, an increase in air temperature by 2°C means for a city a warming of 3-4°C.

Deterioration of air quality

Polluted air is the main threat to human health, according to the World Health Organization (WHO). According to scientists, 80% of residents of megacities breathe polluted air, and 7 million people die from this every year.

According to the IQAir ranking of cities by air quality, the most polluted city in the world in 2020 was Hotan, China. It is followed by 13 Indian cities, including Delhi. In the Russian Federation, the dirtiest air is in Kamensk-Shakhtinsky in the Rostov Region, Krasnoyarsk, Magnitogorsk, Tolyatti, and Moscow. In the ranking of countries with the most polluted air, Russia in 2020 ranked 86th (Bangladesh, Pakistan, and India lead).

Impact on water resources

The rapid growth of the urban population requires the construction of housing and infrastructure, and accelerates industrial development. According to experts, the need of cities for water has increased tenfold over the past 100 years, and in large megacities such as Paris, Rome, Moscow, Berlin, and New York, by more than 100 times. For the needs of cities, the course of rivers and streams is changed using collectors, dams, and artificial reservoirs. This disrupts the regime of surface and groundwater exchange and can lead to the drying up or disappearance of reservoirs. In addition, their pollution and disappearance are facilitated by the discharge of untreated wastewater and waste disposal.

According to hydrologists, in Russia, the Volga is experiencing the greatest load: more than 35% of all untreated wastewater in the country is discharged into its basin annually. Violations in water management and disregard for sanitary norms create risks to human health. According to WHO data, contaminated water can be a source of diseases such as dysentery, typhoid fever, hepatitis A, diarrhea, cholera, and polio.