Next Generation Urban Greening

Next Generation Urban Greening helps the region meet water quality, biodiversity, and resiliency goals through the implementation of effective green infrastructure. This project is developing the tools needed to catalyze significant multi-objective, watershed-scale outcomes that can be difficult to implement in urban spaces due to competing priorities and limited space. This project brings together a diverse set of regional partners to develop a Regional Framework that reflects collective vision, iterative learning, and rigorous review, and will guide the next generation of urban greening efforts that promote resilient urban ecosystems and communities across the Bay Area.

About Next Generation Urban Greening

Next Generation Urban Greening is a broad partnership to help cities achieve more benefits through green infrastructure. In collaboration with partners, SFEI is developing new information and tools that municipalities, regulators, NGOs, and other stakeholders need to simultaneously address multiple management challenges, including improving water quality, flood risk reduction, habitat provision, and heat resilience.

Throughout the project, concepts and frameworks are being iteratively developed, refined, and adjusted to meet the needs of practitioners in the region. City agencies, regulators, and practitioners are invited to participate through annual Regional Forums and provide input and feedback as SFEI develops guidance and tools.

The project includes a focused case study in the Islais Creek watershed in San Francisco to showcase benefit quantification and spatial prioritization tools. Three green stormwater infrastructure (GSI) features in San Francisco are being monitored during storm events to evaluate the removal of PCBs, mercury, microplastics, and contaminants of emerging concern. The lessons learned from the case study and monitoring are being applied through a set of implementation projects in southeast San Francisco.

The Regional Framework will integrate the quantitative methods and qualitative guidance that are advanced through this project with applied implementation project examples. This framework and shared learning process will support rapid adoption by regional stakeholders, leading to improved environmental outcomes in numerous cities over the coming decade.

What is urban greening?

Urban greening is a broad term encompassing a wide range of strategies that promote ecological health and functioning, and provide ecosystem services within city environments.

Urban greening activities include any number of interventions that introduce vegetation and natural features into the urban realm. They include creating and restoring parks and green space, building greenways along pedestrian and bicycle routes, planting street trees, and installing green walls and green roofs.

“Urban greening elements,” a term we use often in this project, is another way of framing urban greening. Urban greening elements, as the name implies, relates to developing green features that generate specific public services or benefits. Urban greening elements range from highly engineered features (e.g., bioretention features, street trees in structural cells) to more natural, less designed green spaces and landscaped areas (e.g., trees in parks; open, plantable areas).

Multiple benefits

Green infrastructure in cities provides innumerable benefits for both people and ecosystems. These ecosystem services can include improving water quality, mitigating flooding, cooling the urban environment, supporting biodiversity, and providing benefits for human health and wellbeing.

Considering the many benefits of urban greening helps make a strong case for building, planting, and installing urban greening elements in cities. However, some of the greatest challenges of promoting urban greening continue to be accounting for, planning for, designing for, and measuring the disparate types of benefits that green features provide.

Through Next Generation Urban Greening, we developed a Regional Framework for the San Francisco Bay Area that can help cities and practitioners make the case for urban greening, and design features that will optimize the benefits that are most important to their communities.

Water quality

Contaminants that accumulate on impervious surfaces during dry weather are transported across the landscape, into the stormwater system, and ultimately into San Francisco Bay. Green infrastructure can provide water quality benefits by intercepting and soaking up rainfall, thereby reducing urban runoff. Certain types of green infrastructure can also filter contaminants in urban runoff, reducing pollutant loading to streams and the Bay.

Heat

Urban environments experience extreme heat conditions in areas with limited vegetation and canopy cover, a phenomenon known as the urban heat island effect. Trees and other vegetation provide cooling by reflecting and absorbing radiation and cooling the surrounding air through evapotranspiration (similar to how sweat cools our skin). Maximum air temperatures in the Bay Area have already increased by nearly 2o F since 1950 and more and longer duration extreme heat events are predicted for the future. Understanding how urban greening strategies can mitigate urban heat and the priority locations for mitigation is an important benefit to consider when planning green infrastructure projects.

Biodiversity

Increased canopy cover and overall vegetation cover constitute a substantial habitat improvement, conferring numerous ecological benefits to humans and wildlife. Increased urban green space can provide increased habitat for plants and wildlife and connect nearby habitats, improving the ability of insects, wildlife, and plants to move across the urban landscape.

Equity and human health

Urban greening, and especially planting trees, is linked to improved public health outcomes in cities, ranging from decreased co-morbidities to improved mental health and social cohesion. However, urban trees and greenery are often distributed inequitably across cities. Socioeconomically disadvantaged communities tend to have lower tree canopy cover than more affluent areas. Prioritizing urban greening in underserved and tree-deficient communities not only closes the “green gap” in cities, but can also help ameliorate other environmental justice burdens that trees and green spaces can mitigate, such as disproportionate exposure to extreme heat, air pollutants, and flooding.

Project update: Benefit quantification

For more information about this project, please contact [email protected]