Google Earth Engine-Based Visual/Qualitative Investigation on Urbanization: Quick Urban Sprawl Visualization in Beijing, China

a. Introduction to Urbanization

What urbanization stands for? Generally, it is defined as the locomotion of the population from rural areas to urban areas (Hussain & Imitiyaz, 2018). However, the definition of urbanization is still controversial since it is varied concerning the country under discussion. For instance, in the case of Argentina if an area has inhabitants ³ 2000 it is referred to as “urban”. However, in Sweden if inhabitants are ³ 200 and houses in that specific area are 200m apart it is called an urban area. In Japan to be denoted as an “urban” that area should fulfill three conditions (1) it should contain ³ 50,000 residents (2) ³ 60% of the houses should be in core built-up area (3) ³ 60% of the area’s population should be involved in the urban-type of businesses. On the other hand, in the case of India urban areas should contain (1) residents ³ 5000 (2) 75% of the male workers should be involved in pursuits other than agriculture (3) minimum 400 residents per square km (Ritchie & Roser, 2020).

In 2018 a report published by The United Nations about the world’s urbanization prospects collected the data of 233 countries including their urban and rural population. Some of the key facts mentioned by this report were as follows (1) worldwide more people dwell in urban areas compared to rural areas (2) >55% people were residing in urban areas in 2018, this figure was 30% in 1950 and is expected to increase up to 68% in 2050 (3) in 1950 the urban population was 751 million which increased dramatically and turned into 4.2 billion in 2018 (4) in 2018 the most urbanized regions of the world were North America, Latin America & Caribbean, Europe, Oceania, Asia and Africa with a population of 82%, 81%, 74%, 68%, 50%, and 43% respectively. Conversely, since 1950 a slower growth trend was observed in the world’s rural population which was 3.4 billion in 2018 and it is expected to decrease to approximately 3.1 billion in the year 2050 (United Nations, 2018).

b. Urban Extent Worldwide

In 2018 data for the degree of urbanization was comprehensively compiled in the form of a report by the United Nations department of economic and social affairs, population division. In this report data of 233 countries/areas were assembled from 1950 until the present even anticipated future trends up to the year 2050. The World’s urbanized areas are increasing with time. For instance, in 1950 only 3 countries (Singapore, Macao & Belgium) out of 201 countries had an urban population ³ 90%. By 2018 this figure increased to 20 countries/areas having > 90% urban inhabitants including China, Kuwait, Singapore, Hong Kong, Réunion, Qatar, Guadeloupe, Belgium, United States Virgin Island, Uruguay, Guam, Malta, Iceland, Puerto Rico, Israel, Argentina, Japan, Netherland, Luxembourg, and Jordan. However, in 2050 more than 42 countries/areas are anticipated to have > 90% of their population in urban areas with Kuwait leading the list (United Nations, 2019). Migration to the metropolitan areas happened very recently, according to UN estimates more people migrated from rural to urban areas in the year 2007(Ritchie & Roser, 2020). Nevertheless, by careful observation of urbanization statics, it was found that 90% of the global population used to live in the rural areas until 1800 however from 1900 urbanization increased gradually with the United States at top of the list with 40% of its population living in urban areas followed by India and China with 10% and 7% respectively. In 1950 US urban share reached 64% followed by Japan, India, and China with 53%, 17%, and 11% respectively. However, in 2001 Japan Overtook United states with 80% of urban share followed by China and India with 37% and 27% respectively. Until 2016 Japan remained at the top with 91.30% urban inhabitants placing the United States, China, and India on 2^nd, 3^rd, and 4^th rank (Kuroda, 1990; Bairoch, 1991; Forstall, 1996; Ritchie & Roser, 2020). Nevertheless in 2018 China with 837 million urban inhabitants headed the list followed by India and the United States (United Nations, 2019).