Fire represents a major threat to Mediterranean terrestrial ecosystems because of the high temperatures reached during summer. While massive loads of organic, inorganic compounds and particulate matter are known to be emitted into the atmosphere from forest wildfires, less is known about the emission from vegetation surrounding fires where air temperatures higher than 100 °C can be reached. Little information exists on the emission from dead vegetation accumulated as litter over forest soils, from which fires often starts. In this study, the response of litter to heatwaves generated by nearby fires was investigated under controlled conditions. Litter samples collected in a Mediterranean maquis and a Holm oak stand during summer were placed in an enclosure flushed with a continuous flow of air, the temperature of the enclosure was progressively risen to 125 °C, until some smog developed but no flaming occurred. The gas from the enclosure was analysed for the content of CO2, H2O, and volatile organic compounds (VOC) to assess the dependence of emission from the air temperature. VOC emission was continuously determined by Proton-Transfer-Reaction mass spectrometry with time of flight (PTR-TOF-MS). Data obtained were complemented with those obtained by collecting VOC on traps that were later analysed by Gas chromatography-mass spectrometry (GC-MS). Results provided useful information to understand the emission mechanism of VOC and other gases from dead vegetation present in the litter of two Mediterranean ecosystems, both dominated by evergreen vegetation species. The study demonstrated that low molecular weight VOC and aromatic hydrocarbons (arenes) produced mostly by thermal oxidation of the wood biopolymers are emitted in addition to isoprenoids typically associated to storage organs and photosynthetic pathway. Moreover, our results support parameterization of litter VOC emission processes in air quality models.

Simulating the carbon-water fluxes at more widely distributed meteorological stations based on the sparsely and unevenly distributed eddy covariance flux stations is needed to accurately understand the carbon-water cycle of terrestrial ecosystems. We established a new framework consisting of machine learning, determination coefficient (R2), Euclidean distance, and remote sensing (RS), to simulate the daily net ecosystem carbon dioxide exchange (NEE) and water flux (WF) of the Eurasian meteorological stations using a random forest model or/and RS. The daily NEE and WF datasets with RS-based information (NEE-RS and WF-RS) for 3774 and 4427 meteorological stations during 2002-2020 were produced, respectively. And the daily NEE and WF datasets without RS-based information (NEE-WRS and WF-WRS) for 4667 and 6763 meteorological stations during 1983-2018 were generated, respectively. For each meteorological station, the carbon-water fluxes meet accuracy requirements and have quasi-observational properties. These four carbon-water flux datasets have great potential to improve the assessments of the ecosystem carbon-water dynamics.

Cities are nowadays facing compelling environmental and climatic challenges that threaten human health and well-being; for this reason, enhancing their sustainability and resilience has rapidly ascended to the top of the global and regional political Agenda. The Urban Green Infrastructure represents a key factor in enhancing the environmental quality of cities, and its planning should be steered by a scientifically-sound operationalisation of the Ecosystem Services concept. In this work, we assess the Ecosystem Services mismatch for air quality regulation in four Italian Municipalities (Milan, Bologna, Rome, and Bari), considering the O3 and PM10 pollution; the study frames a geographical gradient (North-South) and has been conducted on a seasonal basis. We propose a composite-indicatorbased approach for estimating the supply and demand of said Ecosystem Services, including the dimensions of air quality and human health, using both geospatial and tabular data. The spatial and temporal features of mismatch allow distinguishing concerns depending on vegetation quantity (green space areas) and quality (functional diversity), structure of urban settlements and cross-cutting criticalities among cities, and to highlight common indicators of mismatch and priority areas for upcoming interventions. We found that northern cities (Milan and Bologna) suffer a high mismatch, as a result of poor air quality and limited vegetation abundance and functional diversity; southern cities experienced lower demand related to air quality; however, the high mismatch is driven by urban settlement structure and population vulnerability. We also found that compact urbanisation, namely dense urban fabric and the increasing buildings' height, is linked to a marked mismatch regardless of the city's dimension and geographical location. We believe such an effort is a fundamental step for translating the Ecosystem Services conceptual framework into the development plans of cities, and thus into concrete actions. Plus, as far as we know, this is one of the first studies explicitly linking urban structure indicators (e.g. building heights and compactness of the urban settlements) to the Ecosystem Services' mismatch.

Carbon dioxide (CO2) uptake by plant photosynthesis, referred to as gross primary production (GPP) at the ecosystem level, is sensitive to environmental factors, including pollutant exposure, pollutant uptake, and changes in the scattering of solar shortwave irradiance (SWin) - the energy source for photosynthesis. The 2020 spring lockdown due to COVID-19 resulted in improved air quality and atmospheric transparency, providing a unique opportunity to assess the impact of air pollutants on terrestrial ecosystem functioning. However, detecting these effects can be challenging as GPP is influenced by other meteorological drivers and management practices. Based on data collected from 44 European ecosystem-scale CO2 flux monitoring stations, we observed significant changes in spring GPP at 34 sites during 2020 compared to 2015-2019. Among these, 14 sites showed an increase in GPP associated with higher SWin, 10 sites had lower GPP linked to atmospheric and soil dryness, and seven sites were subjected to management practices. The remaining three sites exhibited varying dynamics, with one experiencing colder and rainier weather resulting in lower GPP, and two showing higher GPP associated with earlier spring melts. Analysis using the regional atmospheric chemical transport model (LOTOS-EUROS) indicated that the ozone (O3) concentration remained relatively unchanged at the research sites, making it unlikely that O3 exposure was the dominant factor driving the primary production anomaly. In contrast, SWin increased by 9.4 % at 36 sites, suggesting enhanced GPP possibly due to reduced aerosol optical depth and cloudiness. Our findings indicate that air pollution and cloudiness may weaken the terrestrial carbon sink by up to 16 %. Accurate and continuous ground-based observations are crucial for detecting and attributing subtle changes in terrestrial ecosystem functioning in response to environmental and anthropogenic drivers.

In this chapter, we analyse the current state of the art on how green infrastructures mitigate and adapt to climate changes and pollution, how they may improve urban air quality, increase green mobility, and can promote other important ecosystem benefits as water cycle regulation and supply. Relevant case studies will be also described, as gaps and future perspectives will be analyzed towards reaching the full potential of urban forests and other green spaces, for Biocities in Europe and beyond.

This introductory chapter will evaluate how we have reached the current point in the history of world urbanity, its relationship with nature, and why a fusion between the two is now necessary. In order to define BioCities as cities which follow the principles of natural ecosystems to promote life, we will refer to the extensive knowledge of the history of urban science, the need for cities to be reinvented based on ecological principles, and new methods of analysing and measuring reality through digital systems. This vision of the main functions and traits of BioCities will also serve as a thread and reference for the subsequent chapters which will highlight and elaborate on the different properties of the BioCity vision. The final chapter will draw from this vision the constituting principles of the BioCity and will outline possible pathways of transition towards BioCities.

Fundamental axes of variation in plant traits result from trade-offs between costs and benefits of resource-use strategies at the leaf scale. However, it is unclear whether similar trade-offs propagate to the ecosystem level. Here, we test whether trait correlation patterns predicted by three well-known leaf- and plant-level coordination theories - the leaf economics spectrum, the global spectrum of plant form and function, and the least-cost hypothesis - are also observed between community mean traits and ecosystem processes. We combined ecosystem functional properties from FLUXNET sites, vegetation properties, and community mean plant traits into three corresponding principal component analyses. We find that the leaf economics spectrum (90 sites), the global spectrum of plant form and function (89 sites), and the least-cost hypothesis (82 sites) all propagate at the ecosystem level. However, we also find evidence of additional scale-emergent properties. Evaluating the coordination of ecosystem functional properties may aid the development of more realistic global dynamic vegetation models with critical empirical data, reducing the uncertainty of climate change projections.

LINEE GUIDA: Il presente documento sintetizza i contenuti e gli orientamenti essenziali del progetto di ricerca EUFORICC per proporre modelli, programmi, metodi e protocolli metodologici volti a sostenere la pianificazione, la gestione e la progettazione del verde urbano, mediante l'adozione di soluzioni basate sulla natura, con particolare riferimento agli alberi e alle aree boscate. L'approccio ecosistemico ha lo scopo di favorire o migliorare l'efficienza funzionale e la sostenibilità delle infrastrutture verdi. Lo scopo è di contribuire alla crescita di consapevolezza e capacità di attori e portatori di interesse, a una governance condivisa del verde pubblico, al miglioramento del benessere ambientale, fisico e sociale di chi vive in città. Per ottenere questo si pone in evidenza la necessità di ridurre impatti fisici, bioecologici, culturali e comportamentali per superare elementi critici che possono modificare in entità e durata i servizi ecosistemici prodotti dalle aree verdi. Le Linee Guida si fondano su un'esperienza pluriennale degli enti di ricerca che le presentano, arricchito da un successivo processo di approfondimento di oltre tre anni di consultazione e dialogo con attori internazionali, nazionali e locali, mondo accademico, settore privato, iniziative, associazioni e comitati locali. Il documento individua le principali sfide ambientali e le possibili soluzioni basate sulla natura per le città contemporanee e future con un focus sugli elementi emersi dai percorsi di ricerca del progetto. Questo volume è collegato alle due pubblicazioni "Indicatori" e "Protocolli e Modelli", output del progetto. INDICATORI: Durante lo svolgimento del progetto PRIN EUFORICC (Establishing Urban FORest based solutions In Changing Cities), le numerose ricerche compiute in concerto tra le sei unità di ricerca afferenti al progetto hanno contribuito ad individuare una lista di indicatori per il monitoraggio e la gestione delle foreste urbane. Il monitoraggio delle sfide socio-ambientali e la gestione delle foreste urbane passano per l'uso di strumenti qualitativi/quantitativi in grado di valutare l'impatto di una determinata struttura: ovvero degli indicatori, sia di influenza che di performance. Questo tipo di strumento permette di stimare il progresso di un progetto di verde urbano, intrapreso con l'intento di raggiungere obiettivi specifici. Inoltre, può guidare chi si occupa di verde urbano nella scelta di specifici interventi sulla foresta urbana esistente. Questo volume è collegato alle due pubblicazioni "Linee Guida" e "Protocolli e Modelli". Il primo fornisce indicazioni generali per la pianificazione e la gestione delle foreste urbane, il secondo permette un approfondimento metodologico per il monitoraggio degli indicatori stessi qui elencati. PROTOCOLLI E MODELLI: Compendio di metodologie pratiche e modelli per il supporto nel monitoraggio degli indicatori e nella gestione e pianificazione del verde urbano

In order to maximize ecosystem services (ES), a proper planning of urban green areas is needed. In this study, the urban greenery of two Italian cities (Milan and Bologna) exposed to high levels of atmospheric pollutants was examined. Vegetation maps were developed through a supervised classification algorithm, trained over remote sensing images, integrated by local trees inventory, and used as input for the AIRTREE multi-layer canopy model. In both cities, a large presence of deciduous broadleaves was found, which showed a higher capacity to sequestrate CO2 (3,953,280 g m2 y -1 ), O3 (5677.76 g m2 y -1 ), and NO2 (2358.30 g m2 y -1 ) when compared to evergreen needle leaves that, on the other hand, showed higher performances in particulate matter removal (14,711.29 g m2 y -1 and 1964.91 g m2 y -1 for PM10 and PM2,5, respectively). We identified tree species with the highest carbon uptake capacity with values up to 1025.47 g CO2 m2 y -1 for Celtis australis, Platanus x acerifolia, Ulmus pumila, and Quercus rubra. In light of forthcoming and unprecedent policy measures to plant millions of trees in the urban areas, our study highlights the importance of developing an integrated approach that combines modelling and satellite data to link air qual

Ecosystem services delivered by natural ecosystems are increasingly important for climate change adaptation and mitigation and play a huge role in biodiversity conservation. For this reason, the EU has the ambitious goal of protecting at least 30% of land by 2030. Member states are called to improve and expand the network of protected areas within the next few years; to do so, scientific studies aimed at identifying areas with high ecological value, as well as at defining best management practices, are highly needed. In this study, we used the InVEST suite of models to spatially assess three regulating ecosystem services, that is, carbon storage, seasonal water yield, and urban flood risk mitigation in three administrative regions of central Italy. Using overlay analysis, we found areas with the highest delivery in each of the considered ESs; based on these findings, we eventually proposed four new protected areas, which combine for 888 km2 , that is, 2.73% of the study area. Interestingly, each of the newly proposed protected areas has somehow been discussed and hypothesized by stakeholders, but only one is presumably going to be part of the national network of protected areas within the next years. Hopefully, by prioritizing areas according to the production of ecosystem services, this study can be intended as a step towards the systematic inclusion of ecosystem services studies for enhancing the network of areas under national protection schemes and achieving the goal of protecting at least 30% of land in Europe by 2030

Biogenic Volatile Organic Compounds (BVOCs) emitted from vegetation are precursors of ozone (O3), photochemical oxidants and secondary organic aerosols (SOA) in the lower troposphere. The interaction between urban polluted air plumes originated along the coasts of the Mediterranean basin with biogenic emission occurring inland contributes to the occurrence of exceedances of the air quality standards for O3 and fine suspended particles (PM10, PM2.5). This interaction is favoured by prevailing sea-land breeze circulation during persistent high-pressure conditions. The actual contribution of BVOC to photochemical pollution is still uncertain because the approaches used to assess the emissions from terrestrial vegetation are quite different. There is some evidence in literature that BVOC emissions from Mediterranean vegetation is not accurately estimated by models based on the plant functional types (PFT) approach. To investigate these issues, a Plant Specific Emission Model (PSEM) was developed and applied to the Campania region in Southern Italy, for which a detailed vegetation inventory has been built. BVOC emission maps estimated by PSEM were compared with those generated using a PFT methodology, evidencing significant differences. BVOC emissions from the two models were then used to predict the concentrations of precursors and products of photochemical smog pollution over the Gulf of Naples (Italy) using a chemical-transport model. Simulations were performed during a period characterised by high pressure conditions that favour an enhanced O3 production under a sea-breeze circulation regime. VOCs concentration profiles predicted by the two models were compared with field data collected over Mount Vesuvius using a tethered balloon coupled with a PTR-MS. The results proved the better capability of PSEM to predict the concentrations of many BVOCs, including isoprene and some of its primary oxidation products over the measuring site, and suggested the significant potential of BVOC emission to produce SOA over the gulf of Naples.

Mediterranean coastal areas are among the most threated forest ecosystems in the northern hemisphere due to concurrent biotic and abiotic stresses. These may affect plants functionality and, consequently, their capacity to provide ecosystem services. In this study, we integrated ground-level and satellite-level measurements to estimate the capacity of a 46.3 km Estate to se-questrate air pollutants from the atmosphere, transported to the study site from the city of Rome. By means of a multi-layer canopy model, we also evaluated forest capacity to provide regulatory ecosystem services. Due to a significant loss in forest cover, estimated by satellite data as -6.8% between 2014 and 2020, we found that the carbon sink capacity decreased by 34% during the consid-ered period. Furthermore, pollutant deposition on tree crowns has reduced by 39%, 46% and 35% for PM, NO2 and O3, respectively. Our results highlight the importance of developing an integrated approach combining ground measurements, modelling and satellite data to link air quality and plant functionality as key elements to improve the effectiveness of estimate of ecosystem services.

Nature-based solutions and green urban infrastructures are becoming common measures in local air quality and climate strategies. However, there is a lack of analytical frameworks to anticipate the effect of such interventions on urban meteorology and air quality at a city scale. We present a modelling methodology that relies on the weather research and forecasting model (WRF) with the building effect parameterization (BEP) and the community multiscale air quality (CMAQ) model and apply it to assess envisaged plans involving vegetation in the Madrid (Spain) region. The study, developed within the VEGGAP Life project, includes the development of two detailed vegetation scenarios making use of Madrid's municipality tree inventory (current situation) and future vegetation-related interventions. An annual simulation was performed for both scenarios (considering constant anthropogenic emissions) to identify (i) variations in surface temperature and the reasons for such changes, and (ii) implications on air-quality standards according to EU legislation for the main pollutants (PM10, PM2.5, NO2 and O3). Our results suggest that vegetation may have significant effects on urban meteorology due to changes induced in relevant surface properties such as albedo, roughness length or emissivity. We found a net-heating effect of around +0.18 C when trees are introduced in dry, scarcely vegetated surfaces in the city outskirts. In turn, this enhances the planetary boundary layer height (PBLH), which brings about reductions in ambient concentrations of relevant pollutants such as NO2 (in the range of 0.5-0.8 g m?3 for the annual mean, and 2-4 g m?3 for the 19th highest 1 h value). Conversely, planting new trees in consolidated urban areas causes a cooling effect (up to ?0.15 C as an annual mean) that may slightly increase concentration levels due to less-effective vertical mixing and wind-speed reduction caused by increased roughness. This highlights the need to combine nature-based solutions with emission-reduction measures in Madrid.

Dry deposition could partially explain the observed response in ambient ozone to extreme hot and dry episodes. We examine the response of ozone deposition to heat and dry anomalies using three long-term co-located ecosystem-scale carbon dioxide, water vapor and ozone flux measurement records. We find that, as expected, canopy stomatal conductance generally decreases during days with dry air or soil. However, during hot days, concurrent increases in non-stomatal conductance are inferred at all three sites, which may be related to several temperature-sensitive processes not represented in the current generation of big-leaf models. This may offset the reduction in stomatal conductance, leading to smaller net reduction, or even net increase, in total deposition velocity. We find the response of deposition velocity to soil dryness may be related to its impact on photosynthetic activity, though considerable variability exists. Our findings emphasize the need for better understanding and representation of non-stomatal ozone deposition.

Soil organic carbon (SOC) is essential for ensuring soil health and fertility, supporting key soil functions and related ecosystem services such as stabilization of soil structure and regulation of nutrient and water cycles. Moreover, SOC represents the largest terrestrial organic C reservoir but remains the largest source of uncertainty in future C cycle projections. In this context, Mediterranean areas show a high potential for C sequestration, but strictly dependent by anthropogenic pressure and changes in land use and climate. The amount, the spatial distribution, and the quality of soil organic matter, also evaluated through C and N stable isotopes, depend on transformation processes due to microbial activity. We applied a multidisciplinary approach to study C and N pools in the peri-urban Mediterranean forest of Castelporziano (Rome, Italy), a class 1 ecosystem station of the ICOS network (IT-Cp2) equipped with an eddy covariance tower measuring net ecosystem C fluxes. In the main site, several ecosystem types (e.g., holm oak, stone pine, Mediterranean scrub) and 14 soil profiles have been characterized and collected from a physical, chemical, isotopic, and spectroscopic point of view. Data will be discussed through an integrated approach to clarify the SOC dynamics in soil profile to deeper insight the processes of C stock and resilience of Mediterranean forest ecosystems. Results showing soil spatial heterogeneity may also help refining ICOS protocols for soil CO2 flux measurements which are very sensitive to the displacement of soil automatic chambers within each control point surrounding the eddy covariance tower.

I cambiamenti climatici rappresentano una seria minaccia per le foreste mediterranee. In particolare, la frequenza, intensità, durata e tempistica di eventi meteoclimatici hanno un impatto negativo nei confronti della produttività e capacità di stoccaggio di carbonio. Inoltre le foreste, soprattutto in ambiente urbano e periurbano, sono soggette a un ulteriore elemento di stress ambientale rappresentato dagli inquinanti gassosi (NOx, VOC, particolato, ozono tra tutti) prodotti da attività antropica. Per queste motivazioni, un team di scienziati coinvolti in diverse reti di monitoraggio ecologico ed esperti nella valutazione delle risorse forestali collaborerà nell'ambito del progetto multi-obiettivo MULTIFOR adottando metodologie innovative per meglio comprendere gli effetti specifici dell'inquinamento e dei cambiamenti climatici sulla crescita e la produttività delle foreste attraverso quattro Work Packages (WP) interconnessi: gestione e disseminazione dei risultati del progetto (WP1); risposta degli ecosistemi agli stress ambientali (WP2) con campagne di misura "ad hoc" per misurare flussi di gas serra, VOC e particolato e valorizzazione dei dati di flussi misurati con tecnica Eddy Covariance presso siti appartenenti alla rete ICOS (Integrated Carbon Observation System); Applicazioni di "Precision Forestry" per la caratterizzazione dei popolamenti forestali e valutazione statistica avanzata del footprint nelle misure Eddy Covariance (WP3); assimilazione di big data per prevedere la risposta delle foreste ai disturbi ambientali e ai cambiamenti climatici unendo un set di dati multivariati di osservazioni a livello di singolo sito e a livello regionale proponendo innovativi disegni di campionamento statistico; applicazione di modelli forestali avanzati per prevedere la crescita e gli impatti di cambiamenti climatici ed inquinamento secondo scenari di riferimento (WP4). Attraverso un approccio che copre più scale spaziali e temporali, MULTIFOR contribuirà a migliorare le attuali conoscenze sui meccanismi che regolano gli scambi di gas serra e inquinanti tra ecosistemi forestali ed atmosfera e supporterà la realizzazione di un nuovo sistema informativo delle risorse forestali a livello regionale/nazionale.

The following authors were omitted from the original version of this Data Descriptor: Markus Reichstein and Nicolas Vuichard. Both contributed to the code development and N. Vuichard contributed to the processing of the ERA-Interim data downscaling. Furthermore, the contribution of the co-author Frank Tiedemann was re-evaluated relative to the colleague Corinna Rebmann, both working at the same sites, and based on this re-evaluation a substitution in the co-author list is implemented (with Rebmann replacing Tiedemann). Finally, two affiliations were listed incorrectly and are corrected here (entries 190 and 193). The author list and affiliations have been amended to address these omissions in both the HTML and PDF versions.

The role of stomata in regulating photosynthesis and transpiration, and hence governing global biogeochemical cycles and climate, is well-known. Less well-understood, however, is the importance of stomatal control to the exchange of other trace gases between terrestrial vegetation and the atmosphere. Yet these gases determine atmospheric composition, and hence air quality and climate, on scales ranging from local to global, and seconds to decades. Vegetation is a major sink for ground-level ozone via the process of dry deposition and the primary source of many biogenic volatile organic compounds (BVOCs). The rate of dry deposition is largely controlled by the rate of diffusion of a gas through the stomata, and this also governs the emission rate of some key BVOCs. It is critical therefore that canopy-atmosphere exchange models capture the physiological processes controlling stomatal conductance and the transfer of trace gases other than carbon dioxide and water vapor. We incorporate three of the most widely used coupled stomatal conductance-photosynthesis models into the one-dimensional multi-layer FORest Canopy-Atmosphere Transfer (FORCAsT1.0) model to assess the importance of choice of parameterization on simulated ozone deposition rates. Modeled GPP and stomatal conductance across a broad range of ecosystems differ by up to a factor of two between the best and worst performing model configurations. This leads to divergences in seasonal and diel profiles of ozone deposition velocity of up to 30% and deposition rate of up to 13%, demonstrating that the choice of stomatal conductance parameterization is critical in accurate quantification of ozone deposition.

Tropospheric ozone is a dangerous atmospheric pollutant for forest ecosystems when it penetrates stomata.Thresholds for ozone-risk assessment are based on accumulated stomatal ozone fluxes such as the Phytotoxic Ozone Dose (POD). In order to identify the effect of ozone on a Holm oak forest in central Italy, four flux-based ozone impact response functions were implemented and tested in a multi-layer canopy model AIRTREE and evaluated against Gross Primary Productivity (GPP) obtained from observations of Eddy Covariance fluxes of CO2. To evaluate if a clear phytotoxic threshold exists and if it changes during the year, six different detoxifying thresholds ranging between 0 and 5 nmol O3 m- 2 s - 1 were tested. The use of species-specific rather than more general response functions based on plant functional types (PFT) increased model accuracy (RMSE reduced by up to 8.5%). In the case of linear response functions, a threshold of 1 nmol m- 2 s - 2 produced the best results for simulations of the whole year, although the tolerance to ozone changed seasonally, with higher tolerance (5 nmol m- 2 s - 1 or no ozone impact) for Winter and Spring and lower thresholds in Summer and Fall (0-1 nmol m- 2 s - 1). A "dynamic threshold" obtained by extracting the best daily threshold values from a range of different simulations helped reduce model overestimation of GPP by 213 g C m- 2 y- 1 and reduce RMSE up to 7.7%. Finally, a nonlinear ozone correction based on manipulative experiments produced the best results when no detoxifying threshold was applied (0 nmol O3 m- 2 s - 1), suggesting that nonlinear functions fully account for ozone detoxification. The evidence of seasonal changes in ozone tolerance points to the need for seasonal thresholds to predict ozone damage and highlights the importance of performing more species-specific manipulative experiments to derive response functions for a broad range of plant species.

At forest sites, phytotoxic tropospheric ozone (O ) can be monitored with continuously operating, active monitors (AM) or passive, cumulative samplers (PM). For the first time, we present evidence that the sustainability of active monitoring is better than that of passive sensors, as the environmental, economic, and social costs are usually lower in the former than in the latter. By using data collected in the field, environmental, social, and economic costs were analyzed. The study considered monitoring sites at three distances from a control station in Italy (30, 400, and 750 km), two forest types (deciduous and Mediterranean evergreen), and three time windows (5, 10, and 20 years of monitoring). AM resulted in more convenience than PM, even after 5 years, in terms of O depletion, global warming, and photochemical O creation potential, suggesting that passive monitoring of ozone is not environmentally sustainable, especially for long time periods. AM led to savings ranging from a minimum of EUR 9650 in 5 years up to EUR 94,796 in 20 years in evergreen forests. The resulting social cost of PM was always higher than that of AM. The present evaluation will help in the decision process for the set-up of long-term forest monitoring sites dedicated to the protection of forests from O .