Life cycle cost analysis of urban trees: a case study of five cities in Germany

Trees in urban sites are a nature-based solution for mitigating local heat stress due to the tree's ability to provide shading, enhance evaporation, and increase biodiversity. In supporting well-being in the built environment, the goal of the European Green Deal emphasizes planting new trees; it does not address the protection of existing trees nor the quality of new plantings in response to climate change. Additionally, the economic benefits of urban tree protection have received less attention in research than new plantings. Hence, in several planning competitions, we developed cost benchmarks for six urban tree scenarios, focusing on realistic planning scenarios. We compared the life cycle costs, analyzing construction, maintenance, and end-of-life costs based on the German building cost index and variations in discount rates. Our 50-year life cycle cost assessment shows that preserving existing trees, including implementing tree protection measures, is more cost-effective than tree removal and replacement planting during the cycle. Furthermore, if new tree planting is required, planting in a green space is more than twice as cost-effective as planting in partially sealed areas. Planting in partially sealed areas is up to five times more expensive than preserving existing trees. When planting in sealed sites is unavoidable, the payback period of an optimized tree pit is after approximately 34 years, considering no discount rate. If a discount rate is included, a lower rate of 1.5 % encourages planting in an optimized tree pit. Our benchmarks provide valuable insights for decision-makers to optimize tree management strategies for urban areas. This study encourages preserving urban trees and non-sealed locations to maximize long-term cost efficiency.