Cities and Urban Green

Cities are known to induce so called "urban heat island" effects. Therefore climate change will have a significant impact in urban environments upon thermal comfort. As urban green can mitigate local temperature peaks, green space is an essential feature in cities and one option to prevent decline of thermal comfort and related effects. Direct climate induced damages on urban green overlap with urban environmental stressors which are judged currently to be more critical than climate damages. Indirect climate induced damages of urban green will enforce subsequent negative effects of local temperature increase in cities: e.g. on health, tourism and urban economy which are difficult to delimit and quantify. The one robust option to quantify climate change damages used in this chapter is the preventative cost approach, i.e. damages are monetized by the level of costs that measures would imply to prevent increasing urban heat islands (here focusing on construction and maintenance of additional urban green). Expansion of urban green is triggered by settlement growth that preserves appropriate urban green shares and-potentially-by explicit policy to counter local temperature increase in urban environments in the future. Both issues are considered here. Green space expansion because of urban growth in Austria´s six larger cities is assumed to reach 144 ha (4.7 %) from 2011 till 2030 and 62 ha (2 %) from 2031 till 2050. Adapting additionally to climate change would result in more expansion: 195 ha (6.4 %) between 2011 and 2030 and 143 ha (4.7 %) between 2031 and 2050 reaching a total of 11 % urban green growth by 2051. Annual investment costs for new parks are estimated at 119 million euros for the period 2011-2030, and 93 million euros for 2031-2050 respectively. Annual costs for maintaining these additional parks are estimated at 7.6 million euros till 2030 and 13.4 million euros till 2050. Such preventative costs are an approximation that can be considered as lower bound of thermal discomfort due to climate change in the six larger Austrian cities.