[Planning] Green Urban Fabric - Making Nature's City

Green Urban Fabric

Image credits: Zanck FL, Unsplash

Urban Greening Goals and Targets

Green urban fabric is the term we use to represent the potential for the urban matrix to have vegetation and greenness woven throughout. In ecology, the matrix is the area in which habitat patches are embedded. In an urban context, this is typically everything outside of formal park spaces and green corridors. Opportunities include vegetated street buffers, green vacant lots, green stormwater infrastructure, parking lot trees, office parks, campuses, gardens, and private yards

Biodiversity role:

A robust green matrix can provide added connectivity for species moving between park patches and provide habitat and food resources for smaller urban-adapted fauna such as pollinator insects, small mammals, and birds. A greener urban fabric can increase the effective size of patches, so that they can support more species.

Human health role:

Non-park components of an urban landscape can significantly increase greenness. Living and working in areas with higher overall greenness have been associated with positive health outcomes, including greater physical activity, lower obesity rates, and better mental health. A green matrix can also mitigate the urban heat island effect.

Key tensions and tradeoffs:

Small greenspaces within the urban matrix may not be able to support both human and biodiversity uses. For example, a greenspace may support human health without supporting biodiversity if plantings are non-native and lack complex structure. Small greenspaces that are not well-connected to habitat patches also have the potential to function as ecological traps.

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Integrate private
spaces with public
greenspace networks

Privately owned, publicly accessible greenspaces play an increasing role in the greenspace networks of many cities. Including these spaces in local plans such as specific and area plans can help ensure that these private spaces are connected with public greenspaces.

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Prioritize connections

For biodiversity, a green urban fabric is most helpful when it connects patches of habitat and makes it safer to move across the landscape. Non-park greenspaces can serve as stepping stones for dispersal or can augment the functional value of adjacent parkland.

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Increase tree canopy cover

Programs to both maintain existing street trees and encourage additional tree planting can help increase the urban tree canopy. The Tree Equity Score tool can be used to set achievable targets based on biome and urban density in U.S. cities.

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Use native plants

Connect habitats with native plantings to allow wildlife to move through and access different resources. Widespread use of common non-native plants exacerbates fragmentation. Native plants often also can better support native insects and wildlife, due to their coevolutionary relationships.

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Engage homeowners

In cities with many single-family homes and suburban development, privately owned yards present an opportunity to create additional habitat. Educational campaigns and resources for homeowners can help create understanding of the potential benefits of these spaces and encourage participation.

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Convert vacant lots

Vacant lots provide an opportunity for cities to create small greenspaces with benefits for biodiversity and people. One study in Philadelphia found vacant lot conversion resulted in a 76% increase in time spent outdoors and a 29% decline in local shootings. Vacant lots contribute to urban avian diversity.

Relevant Site Design Strategies

Different types of urban sites present their own opportunities to support health and biodiversity based on their spatial configuration, design, site programming (or intended uses), and management decisions. Typical contexts and documents in which these strategies may be relevant include: (1) Community-led visioning for urban greenspaces; (2) Project development and planning (ex. conceptual and schematic site plans); (3) Project design (ex. detailed construction drawings and site plans).