Study of the Urban Environment and Ecosystem Services of Addis Ababa: Implications for Urban Greenspace Planning
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Date
2016-06
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Addis Ababauniversity
Abstract
Study of the Urban Environment and Ecosystem Services of Addis Ababa: Implications for Urban Greenspace Planning
Tekle Woldegerima Kahsay
Addis Ababa University, 2016
Urban green spaces serve as repository of biodiversity and source of ecosystem services which influence the quality of life the urban dwellers. To understand how these ecosystem services are provided one must understand the "ecological" and "cultural" driving forces that explain how the green spaces in any particular urban morphology are structured or created. The aims of this study were to: (i) characterize the urban environment of Addis Ababa through UMTs mapping and application of UMT based land surface cover assessment and (ii) analyze ecosystem services provided by the urban green spaces of Addis Ababa such as regulating and supportive functions which may help to suggest planning scenarios for the sustainable management of green spaces in the city of Addis Ababa.
UMTs maps of 2006 and 2011 were produced by digitizing ortho-rectified aerial photographs and verified with field assessment. These UMTs maps served as a base for surface cover analysis. Changes in UMTs and land surface cover between 2006 and 2011 have been detected, mapped and analyzed using various GIS techniques. Based on the UMTs and land surface cover types as well as selected ecosystem services were analyzed and used as input for urban green space planning.
The result showed the spatio-temporal structure of UMTs that provides urban ecosystem services in the selected study areas. Accordingly, a total of 11 higher level and 35 detailed urban morphology types (UMTs) have been identified and mapped for both 2006 and 2011 covering the entire urban and peri-urban areas of Addis Ababa. Within the defined higher levels UMTs in 2006, the most dominant one was agriculture covering 38%; of the total area while in 2011 residential UMTs stand out with the highest land coverage (33.3%) of the total UMTs indicating rapid conversion of other land uses to residential category. Results of land surface cover analysis showed 12 surface cover
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categories. The change analysis between 2006 and 2011 revealed that the surface cover types of built structure type I, non-eucalyptus trees, dark bare-ground, light bare ground and vegetable farm have shown a positive change whereas, built structure type II, eucalyptus trees, shrub/bush vegetation, grassland and field crop cover have shown a negative change.
Results of ecosystem service analysis have shown that carbon density in the study area varied with forest categories viz. 293tonns/ha, 142tonns/ha and 132tonns/ha in the dense, medium and open forest strata respectively. The Shannon-Wiener diversity index reported as 3.24 for Junipers dominated forest, 2.98 for mixed forest and 2.76 for Eucalyptus dominated forest. Furthermore, the formation of soil erosion features are significantly different (p<0.001) among the three forest categories including Eucalyptus forest, Juniperus forest and Mixed forest where high incidence of soil erosion was recorded in the Eucalyptus forest. Therefore, irrespective of the environmental factors such as slop, aspect and elevating differences, there is a positive association between Eucalyptus forest and high soil erosion features. To ensure sustainable supply of ecosystem services and to maintain a balanced urban environment, all green spaces in the city should be networked as functional ecosystem units with diverse components. Therefore, characterizing the urban environment through UMTs and land surface cover analysis would provide essential information for an effective planning of green space.
Key words: ecosystem service, greenspaces, land surface cover, planning, urban morphology types
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Keywords
ecosystem service, greenspaces, land surface cover, planning, urban morphology types