Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform

Dramatic urban land expansion and its internal sub-fraction change during 2000–2020 have taken place in Africa; however, the investigation of their spatial heterogeneity and dynamic change monitoring at the continental scale are rarely reported. Taking the whole of Africa as a study area, the synerg...

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Autores principales:	Zherui Yin, Wenhui Kuang, Yuhai Bao, Yinyin Dou, Wenfeng Chi, Friday Uchenna Ochege, Tao Pan
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	urban land mapping remotely sensed images impervious surface area fraction vegetation space fraction the whole Africa Science Q
Acceso en línea:	https://doaj.org/article/ecc125d654da4a4eb338bfef6a4b7b3b
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spelling	oai:doaj.org-article:ecc125d654da4a4eb338bfef6a4b7b3b2021-11-11T18:53:00ZEvaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform10.3390/rs132142882072-4292https://doaj.org/article/ecc125d654da4a4eb338bfef6a4b7b3b2021-10-01T00:00:00Zhttps://www.mdpi.com/2072-4292/13/21/4288https://doaj.org/toc/2072-4292Dramatic urban land expansion and its internal sub-fraction change during 2000–2020 have taken place in Africa; however, the investigation of their spatial heterogeneity and dynamic change monitoring at the continental scale are rarely reported. Taking the whole of Africa as a study area, the synergic approach of normalized settlement density index and random forest was applied to assess urban land and its sub-land fractions (i.e., impervious surface area and vegetation space) in Africa, through time series of remotely sensed images on a cloud computing platform. The generated 30-m resolution urban land/sub-land products displayed good accuracy, with comprehensive accuracy of over 90%. During 2000–2020, the evaluated urban land throughout Africa increased from 1.93 × 10<sup>4</sup> km<sup>2</sup> to 4.18 × 10<sup>4</sup> km<sup>2</sup>, with a total expansion rate of 116.49%, and the expanded urban area of the top six countries accounted for more than half of the total increments, meaning that the urban expansion was concentrated in several major countries. A turning green Africa was observed, with a continuously increasing ratio of vegetation space to built-up area and a faster increment of vegetation space than impervious surface area (i.e., 134.43% vs., 108.88%) within urban regions. A better living environment was also found in different urbanized regions, as the newly expanded urban area was characterized by lower impervious surface area fraction and higher vegetation fraction compared with the original urban area. Similarly, the humid/semi-humid regions also displayed a better living environment than arid/semi-arid regions. The relationship between socioeconomic development factors (i.e., gross domestic product and urban population) and impervious surface area was investigated and both passed the significance test (<i>p</i> < 0.05), with a higher fit value in the former than the latter. Overall, urban land and its fractional land cover change in Africa during 2000–2020 promoted the well-being of human settlements, indicating the positive effect on environments.Zherui YinWenhui KuangYuhai BaoYinyin DouWenfeng ChiFriday Uchenna OchegeTao PanMDPI AGarticleurban land mappingremotely sensed imagesimpervious surface area fractionvegetation space fractionthe whole AfricaScienceQENRemote Sensing, Vol 13, Iss 4288, p 4288 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	urban land mapping remotely sensed images impervious surface area fraction vegetation space fraction the whole Africa Science Q
spellingShingle	urban land mapping remotely sensed images impervious surface area fraction vegetation space fraction the whole Africa Science Q Zherui Yin Wenhui Kuang Yuhai Bao Yinyin Dou Wenfeng Chi Friday Uchenna Ochege Tao Pan Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform
description	Dramatic urban land expansion and its internal sub-fraction change during 2000–2020 have taken place in Africa; however, the investigation of their spatial heterogeneity and dynamic change monitoring at the continental scale are rarely reported. Taking the whole of Africa as a study area, the synergic approach of normalized settlement density index and random forest was applied to assess urban land and its sub-land fractions (i.e., impervious surface area and vegetation space) in Africa, through time series of remotely sensed images on a cloud computing platform. The generated 30-m resolution urban land/sub-land products displayed good accuracy, with comprehensive accuracy of over 90%. During 2000–2020, the evaluated urban land throughout Africa increased from 1.93 × 10<sup>4</sup> km<sup>2</sup> to 4.18 × 10<sup>4</sup> km<sup>2</sup>, with a total expansion rate of 116.49%, and the expanded urban area of the top six countries accounted for more than half of the total increments, meaning that the urban expansion was concentrated in several major countries. A turning green Africa was observed, with a continuously increasing ratio of vegetation space to built-up area and a faster increment of vegetation space than impervious surface area (i.e., 134.43% vs., 108.88%) within urban regions. A better living environment was also found in different urbanized regions, as the newly expanded urban area was characterized by lower impervious surface area fraction and higher vegetation fraction compared with the original urban area. Similarly, the humid/semi-humid regions also displayed a better living environment than arid/semi-arid regions. The relationship between socioeconomic development factors (i.e., gross domestic product and urban population) and impervious surface area was investigated and both passed the significance test (<i>p</i> < 0.05), with a higher fit value in the former than the latter. Overall, urban land and its fractional land cover change in Africa during 2000–2020 promoted the well-being of human settlements, indicating the positive effect on environments.
format	article
author	Zherui Yin Wenhui Kuang Yuhai Bao Yinyin Dou Wenfeng Chi Friday Uchenna Ochege Tao Pan
author_facet	Zherui Yin Wenhui Kuang Yuhai Bao Yinyin Dou Wenfeng Chi Friday Uchenna Ochege Tao Pan
author_sort	Zherui Yin
title	Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform
title_short	Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform
title_full	Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform
title_fullStr	Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform
title_full_unstemmed	Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform
title_sort	evaluating the dynamic changes of urban land and its fractional covers in africa from 2000–2020 using time series of remotely sensed images on the big data platform
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/ecc125d654da4a4eb338bfef6a4b7b3b
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Evaluating the Dynamic Changes of Urban Land and Its Fractional Covers in Africa from 2000–2020 Using Time Series of Remotely Sensed Images on the Big Data Platform

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