Urban Greening

Urban greening is a general term used to describe efforts to renature urban areas by installing various types of green infrastructure. These revegetation strategies are often implemented with climate resilience goals in mind, but are also often cited as a way to increase local residents’ mental and physical health (García-Lamarca et al. 2022). This strategy focuses on three different forms of urban greening: urban forestry, green roofs, and pollinator gardens.

Urban forestry is an “integrated concept defined as the art, science, and technology of managing trees and forest resources in and around community ecosystems for the psychological, sociological, aesthetic, economic, and environmental benefits trees provide society” (Konijnendjik and Randrup 2004). Reforestation refers to reestablishing trees on lands that were recently covered by forest but experienced a disturbance, such as wildfire, timber harvest, or wind effects. Afforestation refers to the establishment of trees in areas that have not recently been covered in forests. Since there is no agreed-upon timeline when referring to reforestation versus afforestation and they are often used interchangeably, the term urban reforestation is used here to refer to both reforestation and afforestation, (IPCC 1998). Urban reforestation is a nature-based solution in which trees are planted in urban areas to subdue the effects of climate change and provide cobenefits to the environment and people (Ogunbode and Asifat 2021).

Green roofs, also known as vegetated roofs or living roofs, are defined by the vegetated layer growing on top of a rooftop (Figure 1; GSA 2021; EPA 2014). There are two different types of green roofs: extensive, in which lighter plants are planted and little maintenance is required; and intensive, which are similar to traditional gardens or parks and can handle most plant types, but need more structural support, higher initial investment, irrigation, and continued maintenance compared to extensive green roofs (EPA 2008). Semi-intensive green roofs represent a hybrid of both types (EPA 2021). Green roofs have layers that each perform different purposes, including plant growth, waterproofing, and structural support (EPA 2014).

Pollinator gardens are efforts to create green spaces filled with native plants that are attractive to pollinators. These gardens are typically installed to help support local pollinators, which globally have been declining due to pesticides, disease, and habitat loss. These gardens are designed to provide resources that pollinators need, including food sources (nectar and pollen), nesting sites, and larval host plants (Majewska and Altizer 2018).