Selection of the most suitable tree species in urban areas based on their capability of capturing heavy metals: a forest policy approach

The aim of this paper is to select the most suitable tree species in urban areas, taking into consideration their capability of capturing heavy metals. Five of the most common tree species for urban green in Greece were examined with the use of the PROMETHEE method, considering as criteria the captivity of seven heavy metals: manganese, zinc, copper, lead, cadmium, chromium and nickel. The best choice among the alternatives is the Arizona cypress; a reasonable outcome, because as an evergreen species it absorbs heavy metals during the whole year, contrary to deciduous tree species. Broadleaves species with compound leaves could also capture high quantities of heavy metals. The selection of these species would have important benefits for the citizens of Thessaloniki, a city characterised by lack of urban green. Forest policy can play an important role in planning the green spaces in cities in an attempt to increase urban green.