Designing vegetation barriers for urban air pollution abatement: a practical review for appropriate plant species selection

Abstract

Vegetation can form a barrier between traffic emissions and adjacent areas, but the optimal configuration and plant composition of such green infrastructure (GI) are currently unclear. We examined the literature on aspects of GI that influence ambient air quality, with a particular focus on vegetation barriers in open-road environments. Findings were critically evaluated in order to identify principles for effective barrier design, and recommendations regarding plant selection were established with reference to relevant spatial scales. As an initial investigation into viable species for UK urban GI, we compiled data on 12 influential traits for 61 tree species, and created a supplementary plant selection framework. We found that if the scale of the intervention, the context and conditions of the site and the target air pollutant type are appreciated, the selection of plants that exhibit certain biophysical traits can enhance air pollution mitigation. For super-micrometre particles, advantageous leaf micromorphological traits include the presence of trichomes and ridges or grooves. Stomatal characteristics are more significant for sub-micrometre particle and gaseous pollutant uptake, although we found a comparative dearth of studies into such pollutants. Generally advantageous macromorphological traits include small leaf size and high leaf complexity, but optimal vegetation height, form and density depend on planting configuration with respect to the immediate physical environment. Biogenic volatile organic compound and pollen emissions can be minimised by appropriate species selection, although their significance varies with scale and context. While this review assembled evidence-based recommendations for practitioners, several important areas for future research were identified.

Vegetation ecology with anthropic drivers and consequences

“…However, its global extent and consequences at this scale are yet to be fully explored. Exploration of interventions to manage or mitigate the impacts of nitrogen flux or other pollutants can start with principles of vegetation ecology (Barwise and Kumar, 2020).…”

“…Vegetation ecology can also contribute to responses to these problems. Establishing standards for critical loads is an important frontier for communicating vegetation ecology to decision makers (Symstad et al, 2019) and to extend efforts to mitigate impacts (Barwise and Kumar, 2020; Clark et al, 2019). Vegetation ecology can also inform efforts at phytoremediation of excess nitrogen in terms of ecosystem services (Zalesny et al, 2019).…”

Urban forests at the time of COVID-19 protect us from fine dust

“…Come osservato da Baró et al (2014), le foreste urbane abbattono il particolato di pochi punti percentuali se si confronta il livello di background con la quantità di particolato effettivamente rimosso dalle foglie, tuttavia dobbiamo considerare che i parchi urbani riescono a veicolare la dispersione del particolato lungo strade e margini dei parchi. L'effetto di dispersione del particolato alcuni giorni fa è stato trattato da Barwise & Kumar (2020), che hanno messo in luce come una sapiente distribuzione del verde (ad esempio prevedendo una barriera verde alta almeno due metri composta da specie arboree e arbustive piantate ad elevata densità) riesce a creare ambienti a ridotta concentrazione di inquinanti a beneficio dei cittadini che vi transitano. Occorre dunque una adeguata progettazione ad opera di esperti di diverse discipline, come dimostrano recenti esperienze di ricerca, dalla COST Action Greeninurbs (http://www.greeninurbs.com/), ai progetti europei del programma LIFE come VEG-GAP (https://www.lifeveggap.eu/) che offrono ai cittadini strumenti di valutazione dei servizi ecosistemici, fino al recente progetto nazionale PRIN EUFORICC focalizzato sullo studio dei servizi ecosistemici forniti dal verde urbano.…”

A new landscape architecture : The living fences experience in Buenos Aires

“…green barriers are increasingly used in the UK and elsewhere as a response to growing concern with air quality and its implications for health and wellbeing (Barwise and Kumar, 2020). In Buenos Aires, the city's overall levels of contamination exceed WHO air quality guidelines, and in some neighbourhoods they are three times acceptable levels (Greenpeace Argentina, 2018).…”