Diversification of tree species planted along roadsides

Climate change threatens mono-specific tree species with three types of risk : the limited adaptability of certain species to new levels of heat and moisture conditions, the proliferation of diseases and pests in areas conducive to their expansion and a significant loss in the event of a health or climatic problem due to the excessive concentration of a single species of tree in an urban environment. Comparing the situations of Paris and Barcelona enables a better understanding and puts future challenges into perspective. This is all the more pertinent because the climatic conditions in Barcelona represent those that Paris is likely to experience in the medium term.

Since the 19th century these two metropolises have undergone enormous urban reconfiguration and development. These transformations have led to roadside trees becoming a defining feature of street landscapes, whether they be Haussmann's strategies in Paris or those of Cerdà in Barcelona. Today these cities have put in place specific diversification policies, which need to be presented and analysed in order to draw conclusions in terms of landscaping, heritage, ecology and management of the tree stock.

The study, carried out in collaboration with the City of Paris Department of Green Spaces (DEVE)  and particularly the Tree and Woods Division (SAB) and the Vegetation and Agriculture Technical Division (STAV), has also been the subject of discussions with the City of Barcelona Direcció de Serveis de Planificació Estratègica Parcs i Jardins.

It opens up the possible options for the future diversification of species for the street-lining trees of tomorrow.