Green spaces are not all the same for the provision of air purification and climate regulation services: The case of urban parks

Abstract

The growing human population concentrated in urban areas lead to the increase of road traffic and artificial areas, consequently enhancing air pollution and urban heat island effects, among others. These environmental changes affect citizen's health, causing a high number of premature deaths, with considerable social and economic costs. Nature-based solutions are essential to ameliorate those impacts in urban areas. While the mere presence of urban green spaces is pointed as an overarching solution, the relative importance of specific vegetation structure, composition and management to improve the ecosystem services of air purification and climate regulation are overlooked. This avoids the establishment of optimized planning and management procedures for urban green spaces with high spatial resolution and detail. Our aim was to understand the relative contribution of vegetation structure, composition and management for the provision of ecosystem services of air purification and climate regulation in urban green spaces, in particular the case of urban parks. This work was done in a large urban park with different types of vegetation surrounded by urban areas. As indicators of microclimatic effects and of air pollution levels we selected different metrics: lichen diversity and pollutants accumulation in lichens. Among lichen diversity, functional traits related to nutrient and water requirements were used as surrogates of the capacity of vegetation to filter air pollution and to regulate climate, and provide air purification and climate regulation ecosystem services, respectively. This was also obtained with very high spatial resolution which allows detailed spatial planning for optimization of ecosystem services. We found that vegetation type characterized by a more complex structure (trees, shrubs and herbaceous layers) and by the absence of management (pruning, irrigation and fertilization) had a higher capacity to provide the ecosystems services of air purification and climate regulation. By contrast, lawns, which have a less complex structure and are highly managed, were associated to a lower capacity to provide these services. Tree plantations showed an intermediate effect between the other two types of vegetation. Thus, vegetation structure, composition and management are important to optimize green spaces capacity to purify air and regulate climate. Taking this into account green spaces can be managed at high spatial resolutions to optimize these ecosystem services in urban areas and contribute to improve human well-being.

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

“…Improving plant diversity in urban areas is imperative for increased urban ecosystem resilience to environmental hazards including and beyond air pollution 7,11,68 . Furthermore, several studies have demonstrated that diversity not only in species but in vegetation type and structure is important for air quality, carbon sequestration and the sustainable provision of diverse ecosystem services 128,130,148 . Discouragement of monoculture planting is another reason for which it was decided that the species in Tables 3 and 4 would not be ranked.…”

Global Changes in Urban Vegetation Cover

“…Furthermore, suburban vegetation may not be equitably available to all urban residents [76]. Green intensification of existing urban areas could help to accommodate growing populations while adding new vegetated cover [36], but it is important to consider the types of vegetation that are added to a city, because different types of vegetation have different abilities to provide ecological functions and services [77]. For example, highly manicured parks and vegetated buildings may be added to increase the aesthetic value of dense cities during green intensification, but these vegetation types can have high associated maintenance costs [78,79] and perform only a limited role in providing other ecosystem services such as supporting biodiversity [80,81].…”

Defining and assessing urban forests to inform management and policy

“…Forested natural areas are primarily sustained though natural regeneration, are influenced by successional dynamics, and on death trees often decompose in place. Forested natural areas can support habitat for native plants and animals that require larger patches (Nielsen et al 2013, Soga et al 2014, Salvati et al 2017, offer human health benefits related to nature-based experiences (Müller et al 2018), and have disproportionately high measures of some ecosystem services compared to other types of urban greenspace (Vieira et al 2018). Separate assessments of street trees and forested natural areas have been developed in local municipalities to inform management (Chacalo et al 1994, Galvin 1999), yet are not commonly put into the context of assessments or policy needs of the entire urban forest (Nowak and Greenfield 2018b).…”