Ecological risk resonance of urbanization and its effect on geohazard disaster: the case of Freetown, Sierra Leone
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Ecological risk resonance of urbanization and its effect on geohazard disaster: the case of Freetown, Sierra Leone Wen Jin 1,2,3
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Yifei Cui 4
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Shengnan Wu 3,5
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Deqiang Cheng 1,3
# Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Land use changes associated with urbanization may increase ecological risk and subsequent geohazard risk. Africa is particularly vulnerable at preset as, since 2005, the highest rates of rapid urbanization-associated forest degradation have occurred there. On August 14, 2017, a compound geohazard in Freetown, Sierra Leone, caused thousands of fatalities and destroyed hundreds of houses. Land use change is considered the main factor contributing to geohazard initiation. Here, we use Freetown as a case study to quantitatively assess the magnitude of the increase in ecological risk associated with land use changes. To achieve the aim, satellite images are used in the case study area from 2007 to 2017, the data are integrated into a geographic information system. A series of indices are then used based on the processed images to describe land use and ecological risk, including dynamic index, trend and state index, and ecological risk index. The results show that Freetown experienced a rapid urbanization process, together with an unbalanced increase in urban land and complex conversion of bare and grass land, from 2007 to 2017. Significantly degenerated forest was converted into urban land (2.77%), bare land (6.47%), and grassland (10.27%), while the ecological risk level increased from low to high. The ecological risk in the affected area of geohazard is found higher than that of the surrounding mountainous area. It indicates that vegetation may reduce the risk of disaster. This result is helpful for the tradeoff between urban development and ecological protection and rational urban planning. For disaster resilience and sustainable development of Freetown, and also other rapidly urbanizing cities in mountainous areas, ecological protection must be incorporated into development planning. Keywords Ecological risk . Urban expansion . Forest degeneration . Trend analysis . Mountain area . Freetown
Introduction * Yifei Cui [email protected] Wen Jin [email protected] Shengnan Wu [email protected] Deqiang Cheng [email protected] 1
Key Laboratory of Mountain Hazards and Earth Surface Process, Chinese Academy of Sciences, Chengdu 610041, China
2
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
4
State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
5
Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
Land use change is a key research issue in many different fields as it reflects the dynamic processes of human–nature interactions (Li 1996; Eric et al. 2001; Costa et al. 2003; Folega et al. 2015; Li et al. 2017; Locatelli et al. 2017). Previous
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