Abstract: Urban green space is an important green infrastructure in cities, providing various ecological services. However, unlike natural green space, there will be a lot of energy and resource inputs during the construction and maintenance of urban green space, which will result in negative environmental impacts. These negative environmental impacts are often ignored. Based on field surveys, the negative environmental impact of urban green space in Tianjin was analyzed using life cycle assessment method. The results showed that during the 50-year life cycle, the environmental impact index of tree layer, shrub layer, and herb layer per unit area was 5.51×10³, 8.75×10³, and 1.60×10³ respectively. Freshwater toxicity and soil toxicity were the main environmental impact types of urban green space, accounting for 73.12% and 26.65% of the total, respectively. According to our calculation, pest control was the main contributing factor of environmental impacts of urban green space, accounting for 99.33%. Compared with agriculture and forestry, the environmental impact index of urban green space was relatively high. Therefore, the negative environmental impact of urban green space should be paid more attention. Our results can provide support for urban green space management in a more low-carbon and sustainable way.

Key words: urban green space, life cycle assessment, environmental impact, maintenance.