Monitoring Urban Expansion and Urban Green Spaces Change in Addis Ababa: Directional and Zonal Analysis Integrated with Landscape Expansion Index

Eyasu Markos Woldesemayat,Paolo Vincenzo Genovese

doi:10.3390/f12040389

Abstract

Addis Ababa, the capital of Ethiopia, is urbanizing very fast. This study aimed to assess urban expansion and Urban Green Spaces (UGS) change in the city from 1989 to 2019. Remote Sensing and Geographical Information System (GIS) and Landscape Expansion Index (LEI) were used to extract Land Use Land Cover (LULC) data, measure urban expansion and UGS change and analyze urban growth pattern in inner zone, outer zone and eight quadrants. The results showed that urban area in the inner zone increased from 3712 ha to 3716 ha (0.1%), and from 3716 ha to 3874 ha (4.2%) and in the first (1989–1999) and second periods (1999–2009), while it decreased from 3874 ha to 3733 ha (3.6%) in the third period (2009–2019), portraying a non-unidirectional trend of change. Conversely, the UGS in the inner zone decreased from 60 ha to 54 ha (10%), and from 54 ha to 38 ha (29.6%) in the first and second periods, while it increased from 38 ha to 53 ha (39.4%) in the third period, reporting spatial tradeoff between the two land cover types. Meanwhile, urban areas in the outer zone increased from 10,729 ha to 15,112 ha (40%), from 15,112 ha to 21,377 ha (41.4%) and from 21,377 ha to 28,176 ha (31.8%) in the first, second and third periods, respectively, representing frontiers of suburbanization. On the other hand, the UGS in the outer zone decreased from 3624 ha to 3171 ha, from 3127 ha to 2555 ha and from 2555 ha to 1879 ha, with an annual rate of decline of 1.25%, 1.8% and 2.6%, respectively, showing increasing trend of UGS destruction for urban construction. Furthermore, the LEI analysis result showed that urban expansion pattern demonstrated largely an outlying growth characterized by differentiation and isolation of patches, whereas the infill and edge expansion pattern were insignificant and fluctuated over 30 years. Furthermore, the directional analysis showed that urban area predominately expanded in SEE,> SSE,> SSW,> SWW,> and NEE directions with varying magnitude in the first, second and third period, but decreased in third period in NWW, < NNW< and NNE directions. In response to such urban growth pattern, the center of gravity of urban area shifted from north to south during the study period, displaying main direction urbanization in recent years. Conclusively, zonal and directional studies are more effective in characterizing the Spatio-temporal dynamics variabilities of urban expansion and UGS change for informed urban planning towards sustainable urban development.

Highlights

Urbanization, which is commonly described as social and political changes that result from economic development and industrialization [1], is occurring at an unprecedented rate across the world
The analysis revealed that urbanization in the North North East (NNE), NEE and North North West (NNW) directions was low compared to other directions
The establishment of the National Urban Planning Institute in 1987, post-1991 decentralization of urban governance and spatial planning and the subsequent implementation of the UDP are some of major policy approaches that have been came into effect over the past decades

Summary

Introduction

Urbanization, which is commonly described as social and political changes that result from economic development and industrialization [1], is occurring at an unprecedented rate across the world. According to the United Nations [2], 55% of the total the human population currently lives in an urban area and this figure is projected to surge to 70% by. Of this growth, 90% of the urban population increase will take place in Africa and Asia, the two largest continents on our planet [4,5]. The accelerated urbanization has been consuming natural resources at alarming rate and subsequently has led to many intertwined social, economic, and environmental challenges, i.e., shortage of housing, lack of employment, congestion, lack of basic amenities and mounting environmental challenges. Loss of ecological resources, decline of the proportion of the UGS, increases in the urban thermal environment, increases in impervious surfaces and high building density [6], Urban Heat Island (UHI)

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