**2.2. Urban areas and environmental impact**

According to Demographia World Urban Areas 13th Annual Edition 2017, a slight majority (51.4%) of the large urban area population lives in built-up urban areas between 4000 and 10,000 persons per square kilometre. Approximately one-quarter (0.9%: 40,000 and over; 4.8%: 20,000–40,000; 18.3%: 10,000–20,000) lives at higher densities and one-quarter (15.2%: 2000–4000; 9.4% under 2000) lives at lower urban area densities.

There are 37 megacities in the world (urban areas over 10 million population). A total of 84 urban areas are indicated with 5,000,000 or more population [11].

the peaks of city skylines. Their construction had a little weight and provided with none or small usable space. At the same time, the tallest office or residential buildings reached heights of only a few dozen metres. Steel-framed construction and reinforced concrete increased heights for residential and office buildings tenfold and exceeded 300 m. This building struc-

In the first half of the twentieth century, labour-saving innovation slowed down the growth of employment in manufacturing. Jobs were created in the service sector and in knowledge-intensive professions. Although expected, the shift away from manufacturing did not entail de-urbanisation trends. The urbanisation continued and reasons for that can be found in the amenities that cities offer, such as various types of entertainment places (pub concert rooms, cinemas, theatres, restaurants and concert halls), better healthcare, education facilities and specialised shopping opportunities. Agglomeration effects ensured advantage for businesses located in cities.

New technological innovation played a crucial role in shaping post-industrial urbanisation: electric trolley line (1888, Richmond, Virginia), automobile (1890s European and North

From the 1920s onwards, automobiles became more common due to lower prices made possible by Henry Ford's revolutionary assembly-line production techniques. The affordable automobile price, city trolley line network and high-quality sub-urban and inter-urban roads allowed the increase of distance between working and place of residence for the majority of

It is important to emphasise that in 1800 only 3% of the world's population lived in cities. For example, the three largest cities in population size were Boston (18,230 citizens), Philadelphia

Since the 1800s, the process of urbanisation has moved rapidly in the entire world. In 1950, about two-third of the population worldwide lived in rural settlements and one-third in

Today, more than half of the world's population lives in urban areas, and the number of cities over 1 million stands at more than 400. By 2030, almost two-thirds of the world's population is projected to live in urban areas. The number of megacities (cities with populations over 10

According to the Sustainable Urbanisation Policy Brief, urban centres currently occupy less than 5% of the world's landmass. Nevertheless, they account for around 70% of both global

According to Demographia World Urban Areas 13th Annual Edition 2017, a slight majority (51.4%) of the large urban area population lives in built-up urban areas between 4000 and 10,000 persons per square kilometre. Approximately one-quarter (0.9%: 40,000 and over; 4.8%: 20,000–40,000; 18.3%: 10,000–20,000) lives at higher densities and one-quarter (15.2%:

million) rose from 3 in 1975 to 16 in 2000 and is expected to reach 27 by 2025 [9].

ture technological innovation contributed to increased population density.

224 Mobilities, Tourism and Travel Behavior - Contexts and Boundaries

American cities) and construction of freeways or highways (1950s onward).

(28,522 citizens) and New York (33,131 citizens) [7].

energy consumption and greenhouse gas emission [10].

2000–4000; 9.4% under 2000) lives at lower urban area densities.

**2.2. Urban areas and environmental impact**

the population.

urban settlements [8].

Urban population accounted for 34% in 1960 will continue to grow approximately 1.84% per year between 2015 and 2020, 1.63% per year between 2020 and 2025, and 1.44% per year between 2025 and 2030 [12].

The World Cities Report 2016, Urbanization and Development: Emerging Futures, projects that by 2030, the urban population of developing countries will double, while the area covered by cites could triple [13].

Such concentration of people and their activity creates increased demands on the environment. In order to reduce the effects of the urban areas to an ecologically acceptable level, planning and design processes should take into consideration the assessment of the ecological footprint and ecological deficit, urban heat islands, construction activities' impact, urban aerodynamic influence, the land use, traffic, **w**aste management, urban dust and air quality and clear water demand.

**Ecological footprint** is the sustainability indicator that measures the impact of the population on the planet. An urban "ecological footprint" is the total amount of the earth's surface needed to support a given city's level of resource consumption and absorption of its waste products [14].

The surface area that makes up a footprint is a sum of all land required to supply resources and absorb wastes, wherever that land may be on earth. Throughout history, areas with rich agricultural hinterlands have enabled the growth of cities. Nowadays, cities may draw on resources travelling great distances from where they are located. When urban areas use resources above their regeneration boundaries, an ecological deficit occurs. This situation can be improved with importing bio-capacity through trade or liquidating regional ecological assets.

Today, among first 20 built-up urban areas, with 500,000 and over population and with occupied land area from 11,875 to 3212 square kilometres, 11 cities are from the United States, 3 from Japan, 3 from China, 1 from Russia, 1 from Indonesia and 1 from Argentina. When we increase the number analysing the top 50 urban areas with occupied land from 11,875 to 1917 square miles, we have again United States on the 1st place with 22 cities, followed by China with 5 cities, Japan and Australia sharing the 3rd place with 3 cities and all other countries with 1 city. Those countries are Russia, Indonesia, Argentina, Brazil, Thailand, France, South Korea, Germany, South Africa, Mexico, Canada, US Puerto Rico, India, Malaysia, Nigeria and Egypt [15].

Above-mentioned data underline that the wealthier the cities are, the greater the ecological footprint they create.

**Urban heat islands** are built-up areas of higher temperature than those in the natural environment caused by increased sunlight absorption of materials with higher thermal capacity, such as asphalt and concrete, air pollution, air flow reduction, air humidity increase, etc. The density of population in cities is proportional to the intensity of the influence of thermal islands. High temperatures in urban areas during the warmer months of the year increase the need for electricity needed for cooling and air conditioning, which results in increased carbon dioxide production and other pollutants. Urban heat island effect raises the temperature by 1–3°C [16].

**Construction activities**, in course of the development life cycle, create impact during initial on-site work, throughout the construction and operational period up to final demolition. Potential impacts of construction activities are noise and vibration generation; atmospheric emissions; impacts to cultural resources; transport issues; solid, industrial and hazardous waste generation; potential impacts to workers' and public health and safety like earthmoving, large equipment transportation, the danger of potential accidents and incidents, geological hazard activation (earthquakes and landslides) by excavation, altering natural drainage patterns, etc.; soil alternation and other land use impacts; impact to paleontological resources, such as complete destruction of the resources if present in areas undergoing surface or excavation; water consumption and quality; flow alternation of surface and groundwater systems; increased energy consumption and dust generation.

Additional impacts include short-term increased transportation density; road and bridge modification due to shipments of heavy, oversized and hazardous loads; new roads or expansion of existing roads and parking area development; limited access to the urban area of significant interest to residents and tourists and potential urban visual identity deterioration.

The complex **aerodynamic** interaction within the built environment will continue to influence sustainable urban development significantly, today and in the future.

In the cities, the wind speeds are generally lower compared to those in the natural environment because of the buildings obstructing the airflow. This urban aerodynamics influences the temperature and evaporation processes and is therefore an important factor at the microclimatic level. High-rise buildings can cause complex streams of airflow, which often result in wind turbulence in some areas or concentric pollution due to impending airflow in other areas. "With the change in urban topology, an individual building immersed in a complex surrounding can experience different flow mechanisms, such as wake effects and channelling. These flow mechanisms depend on the shape, height and location of the surrounding structures, which alter with the city development." [17].

The **land used** for built-up area construction is a scarce, limited resource that is often used improperly and harshly. Urban form, urban development density and characteristics of land use in general, all undoubtedly strongly influence the urban environment. Low-density cities use significantly more energy compared to high-density cities. Changes such as of city shape, layout, size, residential density and location of city attractiveness could yield energy savings up to 150% [18].

The urban land use is interrelated with transport, CO<sup>2</sup> emissions, etc. It could be said that the city is an organism in which population density, transport organisation, both public and individual, air pollution and the health and safety of citizens interact with one another. Therefore, the organisation of life in the city and the possible problem resolution should take this into account.

**Traffic** congestion decreases the quality of life in cities, consumes energy and increases environmental degradation. Excessive amount of land used for traffic circulation, inadequately functioning public transportation and lack of walkways and cycle paths, in addition to other poorly functioning solutions, can create pollution, problems with drainage, limited absorption and flooding. Urban concepts and design largely determine traffic solutions.

islands. High temperatures in urban areas during the warmer months of the year increase the need for electricity needed for cooling and air conditioning, which results in increased carbon dioxide production and other pollutants. Urban heat island effect raises the temperature by

**Construction activities**, in course of the development life cycle, create impact during initial on-site work, throughout the construction and operational period up to final demolition. Potential impacts of construction activities are noise and vibration generation; atmospheric emissions; impacts to cultural resources; transport issues; solid, industrial and hazardous waste generation; potential impacts to workers' and public health and safety like earthmoving, large equipment transportation, the danger of potential accidents and incidents, geological hazard activation (earthquakes and landslides) by excavation, altering natural drainage patterns, etc.; soil alternation and other land use impacts; impact to paleontological resources, such as complete destruction of the resources if present in areas undergoing surface or excavation; water consumption and quality; flow alternation of surface and groundwater systems;

Additional impacts include short-term increased transportation density; road and bridge modification due to shipments of heavy, oversized and hazardous loads; new roads or expansion of existing roads and parking area development; limited access to the urban area of significant interest to residents and tourists and potential urban visual identity deterioration.

The complex **aerodynamic** interaction within the built environment will continue to influence

In the cities, the wind speeds are generally lower compared to those in the natural environment because of the buildings obstructing the airflow. This urban aerodynamics influences the temperature and evaporation processes and is therefore an important factor at the microclimatic level. High-rise buildings can cause complex streams of airflow, which often result in wind turbulence in some areas or concentric pollution due to impending airflow in other areas. "With the change in urban topology, an individual building immersed in a complex surrounding can experience different flow mechanisms, such as wake effects and channelling. These flow mechanisms depend on the shape, height and location of the surrounding struc-

The **land used** for built-up area construction is a scarce, limited resource that is often used improperly and harshly. Urban form, urban development density and characteristics of land use in general, all undoubtedly strongly influence the urban environment. Low-density cities use significantly more energy compared to high-density cities. Changes such as of city shape, layout, size, residential density and location of city attractiveness could yield energy savings

city is an organism in which population density, transport organisation, both public and individual, air pollution and the health and safety of citizens interact with one another. Therefore, the organisation of life in the city and the possible problem resolution should take this into

emissions, etc. It could be said that the

sustainable urban development significantly, today and in the future.

increased energy consumption and dust generation.

226 Mobilities, Tourism and Travel Behavior - Contexts and Boundaries

tures, which alter with the city development." [17].

The urban land use is interrelated with transport, CO<sup>2</sup>

up to 150% [18].

account.

1–3°C [16].

**Waste management** of household, industrial or commercial waste produces valuable raw materials, but also a major source of environmental pollution. Waste, resulting from an urban lifestyle and all other activities taking place in the city, should be at the centre of attention of local authorities and urban residents. Waste reduction, separation, recycling and reuse are feasible, low-cost alternatives to open incineration of solid waste commonly used in developing cities. Sustainable urban waste management strategies can result in multiple improvements of both climate and health. Anaerobic bio-solid digestion systems can produce gas composed of up to 70% methane, a fuel for cooking, heating or other power needs, making an added value in the form of alternative energy source.

Human activity, especially in more developed economies, is increasingly leading to endangered **air quality**, ozone depletion, increase of greenhouse gas emissions and reduction of positive effects of sunlight, especially during the colder days, generally changing dynamic processes in the atmosphere. Furthermore, indoor air pollution is of particular concern in developing cities, possibly contributing to respiratory infections and other serious human health conditions.

In addition to all these, there is the so-called **urban dust** phenomenon. The airborne dust particles in the cities are by-products of construction works, exhaust gases from buildings, street traffic, production and other processes. The particles cling to porous surfaces such as stone, brick or concrete.

Air pollution in cities can be reduced and combined solutions should be applied simultaneously. To improve air quality, the city administrations should be working actively on reducing traffic by promoting walking and cycling, eliminating polluting vehicles with limited access zones, issuing permits exclusively to developers and contractors of building planed and design according to the sustainable architecture principles, decreasing unnecessary road building and freeing up city surface capacity, as well as improving air quality and reclaiming space for public parks, pedestrians and cyclists. Additionally, the city administration should introduce incentives to retrofit polluting vehicles and green the city by maintaining and increasing green urban areas that could enhance air quality.

Unsustainable city lifestyle and conventional urban water management create increasing barriers for efficient management, faced by the city's administration and residents, of scarcer and less reliable water resources. To minimise environmental degradation, the sustainable city development plans and design integrate the urban water cycle, including storm water, groundwater and wastewater management and water supply. For example, very often dust, dirt and other solid waste go into drains with rainwater or other unregulated watercourses. By increasing the area of hard, impermeable surfaces in cities, appropriate and more efficient collection and drainage of rainwater are possible.

**Sustainable water management** develops effective storm water management options, provides effective water supply services for all at minimum impact on water resources and the environment at large, develops effective sanitation and waste management options and integrates urban water systems into ecological and other productive functions of water at city level [19].
