Playbook for Urban Biodiversity

3. Green infrastructure will solve the biodiversity crisis in cities

Myth

Most urban green infrastructure projects are not designed to provide habitat as a primary purpose. Yet high level policies and reviews continually lump green infrastructure into solutions to the biodiversity crisis in cities. Green infrastructure such as green roofs, street trees, rain gardens, street gardens and urban parks come in many forms and can create habitat for target species if done deliberately, thoughtfully, and using an evidence-based approach. We need to have a better understanding of the resources required for the species we seek to support, as well as the spatial and temporal scale they operate in, to inform plant selection, design and maintenance of green infrastructure projects.

Counter arguments

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) conceptual framework recognises that relationships between people and nature exists within three dimensions – “nature, the benefits that people derive from nature and a good quality of life”. Whilst green infrastructure (GI) is designed to provide multiple benefits, the latter two of the three dimensions are often prioritised, with nature’s intrinsic value being overlooked in policies, strategies and implementation.

Green infrastructure must specifically address biodiversity

An understanding of how ecosystems function is crucial for the appropriate implementation of biodiversity friendly GI design. Scalability is often prioritised in GI projects at the expense of design elements that target local species. Ecosystems and the species they support possess unique qualities and traits. GI projects must therefore incorporate these distinct requirements into designs over broad-brush approaches3.

Failure to consider local ecosystems in GI design can result in unintended consequences, wasted resources and creation of ecological traps. Ill-informed projects can be disruptive to ecosystems and threaten ecosystem health, where for example the Victorian Volcanic Plains grasslands have different requirements from other urban ecosystems and therefore require appropriate knowledge to care for.

Green infrastructure: A balancing act

Balancing GI’s capacity to sustain vegetation with its ability to support biodiversity is crucial if GI is to solve the biodiversity crisis in cities. While green roofs offer numerous benefits, they are incomparable to ground level vegetation. Green roofs support species that are mobile, have small body sizes and can complete their life-cycle within the green roof environment. In comparison, species with low dispersal rates that are unable to access the roofs and require deep soils will not benefit from green roofs.

In similar capacity, residential gardens are more conducive as habitats for small bee species than large bee species as there may be greater overlaps in resources and similar foraging niches available. Larger and more formal forms of urban green space including parks and golf courses can provide ample habitat for birds, bats and bee species, although this is dependent on the quality and appropriateness of such habitat being provided.

A tinted image of four houses in a neighbourhood.

Case Study

Floral resources to encourage colonisation and use of green roofs by invertebrates