The Urban Forest and Ecosystem Services: Impacts on Urban Water, Heat, and Pollution Cycles at the Tree, Street, and City Scale

Abstract

Many environmental challenges are exacerbated within the urban landscape, such as stormwater runoff and flood risk, chemical and particulate pollution of urban air, soil and water, the urban heat island, and summer heat waves. Urban trees, and the urban forest as a whole, can be managed to have an impact on the urban water, heat, carbon and pollution cycles. However, there is an increasing need for empirical evidence as to the magnitude of the impacts, both beneficial and adverse, that urban trees can provide and the role that climatic region and built landscape circumstance play in modifying those impacts. This special section presents new research that advances our knowledge of the ecological and environmental services provided by the urban forest. The 14 studies included provide a global perspective on the role of trees in towns and cities from five continents. Some studies provide evidence for the cooling benefit of the local microclimate in urban green space with and without trees. Other studies focus solely on the cooling benefit of urban tree transpiration at a mesoscale or on cooling from canopy shade at a street and pedestrian scale. Other studies are concerned with tree species differences in canopy interception of rainfall, water uptake from biofilter systems, and water quality improvements through nutrient uptake from stormwater runoff. Research reported here also considers both the positive and the negative impacts of trees on air quality, through the role of trees in removing air pollutants such as ozone as well as in releasing potentially harmful volatile organic compounds and allergenic particulates. A transdisciplinary framework to support future urban forest research is proposed to better understand and communicate the role of urban trees in urban biogeochemical cycles that are highly disturbed, highly managed, and of paramount importance to human health and well-being.

Combining the Conservation of Biodiversity with the Provision of Ecosystem Services in Urban Green Infrastructure Planning: Critical Features Arising from a Case Study in the Metropolitan Area of Rome

“…On the one hand, the selection of estimates that prevalently refer to the regional, metropolitan, municipal or strictly urban area of the case study allows the widely acknowledged limitations of information transfer from different climatic, socio-economic and biogeographic contexts to be overcome [83][84][85]. This approach is in keeping with the urban ecology principle that is based on an integrated vision of cities and surrounding landscapes [86].…”

Do Indigenous Street Trees Promote More Biodiversity than Alien Ones? Evidence Using Mistletoes and Birds in South Africa

“…Consequently, there is a growing emphasis on the greening of urban environments to maximise the provision of such ecosystem services [3]. Street trees are a particularly important component of urban greening because (i) they are located throughout the urban matrix; (ii) although streets are narrow, their combined area is often much larger than that of formal parks and green spaces; and (iii) a considerable proportion of the time that urban residents spend outdoors is spent on the streets, according to Todorova et al [4] a considerable proportion of the time that urban residents spend out of doors in spent on the streets.…”

Double Insurance in Dealing with Extremes: Ecological and Social Factors for Making Nature-Based Solutions Last

“…However, despite this wide recognition of value, the fact that urban forests themselves may be vulnerable to the same disturbances is less recognised. Most studies that have looked at the benefits of such forests are based upon the species, number and size of trees in the urban landscape and how these shape effect (Nowak et al 2013;Farrugia et al 2013;Livesley et al 2016). Less attention has been dedicated to the benefits of diversity and species specific traits in the composition of the forests, and when discussed it is usually along broad theoretical reasons for why diversity is important (Muller and Bornstein 2010).…”