Evaluation of urban greenspace vulnerability to typhoon in Taiwan

Urban greenspace (UGS) represents an essential component of city ecosystems. It plays a critical role for various purposes, such as reducing urban heat island effect and air pollution, regulating torrential run-off and offering joyful routes for walking, jogging and cycling based on personal interest as well as a platform for social networking. It is especially important in a populated country like Taiwan with population highly concentrated in cities. It is rather vulnerable to strong winds and heavy precipitation brought up by typhoons, while there are no existing frameworks to access its vulnerability to typhoons in Taiwan. Here, we examine the vulnerability of UGS to typhoons in Taiwan by a novel assessment framework considering 21 indicators organized into three dimensions, including hazard, exposure/sensitivity and adaptive capacity. The 21 indicators are derived from the Sentinel-2 MSI data obtained from European Space Agency (ESA), typhoon data acquired from Japan Meteorology Agency (JMA), and census data achieved by the government official sites of Taiwan. Google Earth Engine and GIS are used to analyze the deviation of UGS variables. Five major metropolitan areas of Taiwan are selected as the study sites, consisting of Taipei, New Taipei, Taoyuan, Taichung, and Kaohsiung cities. Interestingly, it is found that (i) There exists a great spatial gap between hazard levels and the top-priority regions to enhance the strategies and adaptive capacity in order to better respond to typhoons in Taiwan; (ii) The Northern and middle parts of Taiwan exhibit high and very high hazard levels since the occurrence frequency and wind speed of typhoons are higher. In contrast, the Southern Taiwan is characterized by low and very low hazard levels occupying over approximately half of the study sites; (iii) Exposure and sensitivity of the UGS in Taiwan vary greatly from very low to very high levels over the study sites with 43 % attributed to high and very high levels; and (iv) 22 % of the metropolitan areas are classified as high and very high vulnerable, mainly distributed over the Taoyuan, Taichung, Taipei, and New Taipei cities. Results suggest that the presented framework is useful in evaluating the vulnerability of UGS to typhoons and implicates proper management of urban trees as a nature-based solution to mitigate the impacts of climate change.