A multiple criteria decision-making approach to put forward tree species in urban environment

• A decision-making scheme for benchmarking/prioritizing tree species is presented.
• Combined employment of two multicriteria techniques is adopted in the analysis.
• ELECTRE III and PROMETHEE/GAIA are incorporated.
• Sensitivity analysis demonstrates the robustness of the final optimal ranking.
• Mulberry, sweetgum, scholar tree and hackberry are highly ranked.

Trees are vital for improving urban climate in many aspects and dimensions, especially for densely populated environments characterized by high levels of air pollution. This paper presents a decision-making scheme for benchmarking and prioritizing tree species in urban environments. Public authorities in real-life cases put forward trees species based mainly on cost or aesthetics criteria. In contrast to most-real life cases, the proposed approach facilitates the inclusion of multiple criteria to support decision-making i.e. life span, required growth space, planting capability in built environment, aesthetics, tolerance, pollution attenuation, adaptation to local climate, crown density, cost, and potential allergenicity of species. The framework combines two multi-criteria methods to provide an optimal ranking and enhance the robustness of decision-support. The approach is implemented for the center of Thessaloniki, Greece. Mulberry, sweetgum, scholar tree and hackberry are highly ranked and can be considered as excellent alternatives considering their combined performances to all criteria. A thorough sensitivity analysis by varying parameter values demonstrates the robustness of the corresponding ranking. Although there are gaps of knowledge and uncertainties, especially in the quantification of air pollution attenuation, the proposed approach provides a roadmap for decision-makers to put forward tree species in an organized manner.