Urban plants are important components of the landscape and provide numerous benefits and services. In particular, urban vegetation covering parks, gardens, tree-lined avenues, sport fields and hedges is an important sinks for atmospheric carbon dioxide (CO2) through photosynthesis, storing the excess carbon (C) as biomass in plant tissues. Urban greening also contributes to mitigate air temperature by shading and transpiration, and reduce noise level. Moreover, plants accumulate pollutants through their roots and leaf surfaces. Besides this, green spaces provide health, physical and psychological benefits of people living in cities increasing the attractiveness of communities. Among green areas, Botanical Gardens have a key role in plant conservation, taxonomic research, horticultural and economic Botany, and public education. In such context, we shall analyze an additional role for Botanical Gardens that should be considered, namely the contribution of plant collections in improving environmental quality by reducing CO2 concentration, metal and noise pollution and mitigating air temperature. In particular, the research will be carried out in the Botanical Garden of Rome in order to analyze and quantify its contribute in improving the air quality. At the present, there is not data on the potential role of the Botanical Gardens in environmental quality amelioration, which is related to species, plant age and growing conditions. Thus, it is important to survey data on species presence, distribution and size as well as understanding their contribution in improving the environmental quality. The results may suggest appropriate policy interventions in order to facilitate future urban designs enhancing the environmental and social benefits from green areas that should also include Botanical Gardens.
Despite CO2 sequestration by vegetation is a well-known example of the global market for ecosystem services, the relationship between vegetated urban areas and CO2 emission reduction has not been well clarified at the present time. Moreover, the exact magnitude and spatial distribution of emissions in urban areas remains poorly quantified (Kordowski and Kuttler, 2010. Atmos. Environ. 44: 2722-2730). Only recently, the use of plants to ameliorate urban air quality has become a focus of research (Novak et al., 2006. Environ. Pollut. 116: 381-389; Gratani and Varone, 2007. Landsc. Urban Plann. 81: 282-286; Gratani and Varone, 2014. Urban Ecosyst. 17: 501-511; Yin et al., 2011. Environ. Monit. Assess.177: 609-621). A better knowledge on the contribution of urban vegetation to reduce atmospheric CO2 in urban areas is important to improve our understanding about the offset potential of different urban tree species (Peters and Fadden, 2012. Geophys. Res. Biogeosci. 117:1-16). Moreover, the novelty of this research is the selected site. In fact, at the present, there are not studies about the role of the Botanical Garden in environmental quality amelioration. Our results could facilitate the spread of information about the meaning of the Botanical Gardens, not only for ex situ plants conservation, but also for their role in biophysical benefits (i.e. reducing CO2 atmospheric concentration, mitigating air temperature, decreasing noise and metal pollution). Moreover, the obtained results might be used to suggest appropriate policy interventions in order to facilitate future urban designs enhancing the environmental and social benefits from green areas that should also include Botanical Gardens. In addition, improving knowledge on plant species capability to environmental quality amelioration could facilitate the choice of the most suitable species in an urban context.