An Indicator-Based Approach to Assess the Readiness of Urban Forests for Future Challenges: Case Study of a Mediterranean Compact City

Urban Forests (UFs) are key elements in Mediterranean compact cities, as they provide numerous ecosystem benefits and increase the resilience of cities against the anticipated impacts of climate change. It is, thus, necessary to review all the aspects that may have a negative effect on their ecosystem functions and the services that they provide. In this paper, a set of indicators is proposed that allow for a preliminary evaluation of some of the main disservices and factors that Mediterranean UFs present and the ways to maximize their benefits for users. For this purpose, 20 indicators, divided into three categories—Biodiversity, Accessibility/Facilities, and Infrastructure—were selected. Within these three categories, a range of values was established, from low to high or absence/presence. The indicators were tested in 24 urban forests of different types, all of which are representative of a medium-sized compact Mediterranean city. The results highlight that the UFs have adequate species richness and diversity, but among the species present are quite a few that emit BVOCs and allergens, as well as some that have invasive behavior. Poor cleaning, absence of night lightning, and scarcity of water points are aspects to improve in a good number of UFs; while a high surface area of impermeable soil, low tree cover, and extensive areas of grass that require large amounts of water for maintenance are the main issues of the infrastructure block that need medium-term planning to be addressed. It can be concluded that the proposed set of indicators allows for a general assessment of the readiness of UFTs in Mediterranean cities for the upcoming climatic, social, and ecological challenges.