Quantifying intangible values of wetlands as instrument for conservation in the Po delta park (Italy).

Wetlands possess intangible values that are usually overlooked in decision-making processes. Based on questionnaire surveys, this work aims to quantify both the non-use and cultural values provided by the different wetlands of the Po Delta Park (Northern Italy), selected as ideal case study, using willingness to pay (WTP) for wetland conservation and travel cost methods, respectively. Their relationships with socio-economic variables and respondents' preferences for current and future use were also analysed. The 61.39% of participants were willing to pay a mean amount of 95.8 € (±40). The average travel cost was 38.68 € (±6.24), with higher values observed for environmental experts than for other citizens. Wetlands differ significantly in travel costs, current and future use, but not in WTP. Poisson regressions showed that non-use and cultural values were significantly dependent on personal information, preference variables and travel distance. Intangible dimensions, such as bequest and existence values, showed higher valuations/rates than option and direct use values. The results highlight that perceptions of the intrinsic value of nature are influenced by demographic characteristics, distance from the area and desired future uses. Non-use values seem abstract and generalised to the whole area, regardless of the ecological characteristics of the wetland, even though a significant relation to wetland uses was observed. In contrast, cultural values are tied to specific wetlands, as indication of the importance of historical relationships between people and nature. Such findings underline that the different dimensions of intrinsic value of nature may act at different scales and help decision-makers to incorporate such values into environmental accounting.

Species-specific efficiency in PM2.5 removal by urban trees: From leaf measurements to improved modeling estimates.

The growing population in cities is causing a deterioration of air quality due to the emission of pollutants, causing serious health impacts. Trees and urban forests can contribute through the interception and removal of air pollutants such as particulate matter (PM). The dry deposition of PM by vegetation depends on air pollutant concentration, meteorological conditions, and specific leaf traits. Several studies explored the ability of different plant species to accumulate PM on leaf structures leading to the development of models to quantify the PM removal. The i-Tree Eco is the most used model to evaluate ecosystem services provided by urban trees. However, fine particulate matter (PM2.5) removal is still calculated with a poorly evaluated function of deposition velocity (which depends on wind speed and leaf area) without differentiating between tree species. Therefore, we present an improvement of the standard model calculation introducing a leaf trait index to distinguish the species effect on PM net removal. We also compared model results with measurements of deposited leaf PM by vacuum filtration. The index includes the effect of morphological and functional leaf characteristics of tree species using four parameters: leaf water storage, deposition velocity, resuspension rate and leaf washing capacity. Leaves of 11 common urban tree species were sampled in representative areas of the city of Ferrara (Italy) and at different times of the year from 2018 to 2021. This includes four deciduous broadleaf trees (Tilia cordata, Platanus acerifolia, Acer platanoides, Celtis australis), three evergreen broadleaf trees (Quercus ilex, Magnolia grandiflora, Nerium oleander), and four conifers (Thuja orientalis, Cedrus libani, Pinus pinaster, Picea abies). The results provide significant advancement in assessing PM removal using decision support tools such as models to properly select tree species for future urban tree planting programs aimed at improving air quality.