Article

Mediterranean urban areas house substantial amounts of biodiversity – both plant and animal. Urban green spaces include (a) areas of natural or semi-natural vegetation such as ecosystem fragments, reserves, nature parks, forests, and river banks, which house varying amounts of native species; (b) urban agriculture and horticulture; (c) managed spaces with cultivated vegetation such as parks and gardens; and (d) informal urban green spaces such as wastelands or brown field sites which are largely colonized by weeds, ruderal plants and invasive species. Considerable attention has been paid to the biodiversity values of the first two categories but the last category which includes areas such as industrial wastelands, roadside verges, river and canal banks, railway line embankments, has been largely neglected. The benign climate of the Mediterranean region has permitted the cultivation of a wide range of both temperate and semitropical trees, shrubs and herbaceous plants in parks, gardens and other urban settings. The main managed elements are public parks, private and domestic gardens, botanic gardens, zoological parks, glasshouses and shade houses, planted urban forests, street trees, landscaping of office blocks, residential apartment blocks, public buildings, university and college campuses, business parks, golf courses, nurseries, garden centres, and more recently green roofs and living walls. While the diversity of species grown in urban botanic gardens is usually well documented, we have little detailed information on the overall range of species grown in public parks and gardens and, with some exceptions, even less of those grown in private gardens. Street trees are an important component of urban diversity with more than 55% of streets in a city like Madrid populated with trees, totalling altogether 300,000 specimens. Many cities have published guides to their urban street trees but there is no overall compilation. Overall, it is likely that altogether several tens of thousands of plant species are grown in Mediterranean urban areas, representing a very substantial source of biodiversity. The inventory of urban plant diversity is very uneven: for some cities such as Ioannina, Jerusalem, Montpellier, Naples, Patras, Rome, Sousse, fairly comprehensive inventories have been compiled but for most our knowledge is incomplete. Given the large growing percentage of city dwellers in the Mediterranean, it is important that much more attention should be paid to understanding and maintaining urban plant diversity which contributes substantially to human health and wellbeing.