Urban Heat Island Effect of Addis Ababa City: Implications of Urban Green Spaces for Climate Change Adaptation

Abstract

Land use and land cover (LULC) change is one of the most visible results of human’s modification of the terrestrial ecosystem, and it has a significant impact on climate. Urbanization has been a major force of LULC throughout human history that has had a great impact on climate change. Urban areas generally have higher absorption of solar radiation and greater thermal capacity and conductivity, leading to a relatively higher temperature in the urban areas compared with the surrounding rural areas. Studies related to the impact of land use and land cover changes in Addis Ababa are few. This study therefore examined the influence of LULC change on urban climate in Addis Ababa city from 1986 to 2011 by retrieving land surface temperature (LST) from thermal infrared (TIR) data of Landsat TM satellite data. The results show that in Addis Ababa, the area for grass land, agricultural land, forest land and bare land declined by 43.32, 16.03, 9.74, and 9.65 km2, respectively, on the other hand, built-up areas was dramatically expanded from 100.13 km2 in 1986 to 180.13 km2 in 2011 that is almost two times from the base year. Changes in LULC were accompanied by changes in LST. The average LST in 1986 was 302 K (28.88 °C) and it increased to 304 K (30.88 °C) in 2011. The change in LST is mainly associated with changes in impervious surface. The urban-rural temperature differences between the urban core and its surrounding areas show a maximum difference of 15 K. This could lead to an intensified urban heat island effect in the urban areas. The relationship between LST and Normalized Difference Vegetation Index (NDVI) clearly shows that vegetation has great impact on reducing UHI effect. Thus, development of urban green spaces is one of the most promising climate change adaptation response in order to minimize the impact of elevated temperatures on human health and comfort.