Weed dynamics in the Mediterranean urban ecosystem: ecology, biodiversity and management

Summary This paper presents a review of weed dynamics in the Mediterranean urban ecosystem, seen both in an ecological and biological perspective and also in relation to the interaction between human activity and the survival strategies of the various phytocoenoses. Although generalizations on urban weeds cannot easily be drawn on account of the wide range of microenvironments, anemochoric dissemination mechanisms (Asteraceae), resilience (grasses) and perennation are of particular importance. The reasons underlying the undesirability of weeds in the urban environment are investigated. Not only are weeds considered unsightly, but they may also give rise to ‘functional’ obstacles, damaging sidewalks or clogging storm drains. Furthermore, they may adversely affect human health by releasing allergenic pollen into the atmosphere. Management of urban weeds is based almost exclusively on mechanical control, as chemical measures may involve a toxicity risk for man. Paradoxically, certain weeds species may however have a positive effect if they are linked to fauna (butterflies, birds, etc.) considered to give a favourable impression in the cityscape. Finally, the possibility of favouring the biodiversity of the urban ecosystem by introducing some wildflowers typically associated with the degree of biodiversity of the surrounding environment is discussed.