2.1.3. Economic benefits
The economic benefits of blue-green spaces are introduced in two aspects. Firstly, a blue-green space can provide a good landscape for a city, increase the attractiveness of the city, promote the development of tourism, and increase the value of real estate in the city. It promotes the productivity of citizens and the growth of urban economy. The beautiful landscape of Singapore and Kuala Lumpur, Malaysia is one of the factors that attract a lot of foreign investment, enhance the property value and increase the financial return of land developers by 5% to 15% depending on the type of a project (Heidt and Neef, 2002). Secondly, green buildings or infrastructure in blue-green spaces, mainly including GI, provides better facilities and entertainment opportunities for human beings in addition to habitats (Ashley, 2017).With vegetation features on the ground, such as swamps, cisterns and rain gardens, based on natural drainage processes SuDS/GI facilities fully integrate the ecological benefits of water bodies and green spaces, promote ecosystem services and improve the efficiency of urban drainage systems and the economic development (van den Berg et al. , 2015). In addition, the blue-green space has the benefit of UHI reduction and can reduce energy consumption. A Chicago study showed that increasing tree coverage by 10% in a city could reduce total energy required for heating and cooling by 5% to 10% (Sorensen et al. , 1997). Therefore, the development of urban blue-green spaces may be a better solution than cool materials (Carvalho et al. , 2017).