Planetary positive on-site

The impacts of urban development on healthy ecosystems can be split into local impacts occurring on and around the development site, and remote impacts occurring throughout the global supply chain, linked for instance with the production of construction materials. Local impacts are easier to understand and measure, because they can be made visible to the developer, project teams and stakeholders. Because of the local scale and smaller geographical distribution, on-site impacts can often be measured directly by surveys and mapping of projected ecosystem change, freshwater use etc. However, some of the control variables mentioned above are difficult to scale down, and other indicators might be more appropriate for decision support at the local level.

To assess impacts on biodiversity loss and land use change a dedicated biodiversity metric developed for the UK planning legislation can be used (Natural England, 2023). The tool has been integrated into BREEAM Schemes for sustainability assessment, and in Denmark the methodology is currently being developed as a national survey method for urban nature. The ‘Biodiversity Net Gain’ approach compares the types of land and habitats in the area before the project, in the project plans, and after the project is realised. See “How do you define a project’s biodiversity baseline?” on the next spread.

Different areas are attributed different values representing their importance for biodiversity, based on the type of habitat (woodland, grassland, bare ground, etc.), its distinguishing features, its condition (quality and health of the habitat), and its strategic significance for biodiversity in the surrounding area. Based on these values, each area is attributed a score representing its importance for biodiversity. The tool calculates the total biodiversity impact of the project and of any regenerative measure by comparing the biodiversity values of all areas before and after development. The results can be used to document the project’s impact on biodiversity loss and land use change on-site, and find ways of reducing negative impacts. It can also help identify opportunities to regenerate biodiversity in vulnerable areas, with the aim to provide a positive value that outweighs the project’s residual negative impacts in vulnerable areas off-site. More details are provided in the Appendix Chapter 4 and Chapter 7.

To assess impacts on freshwater and the release of pollutants, multiple indicators should be reported. This includes indicators for freshwater use and amount of infiltration (which affects groundwater levels as well as lakes and rivers). Pollutants can be tracked via indicators for the number of pollutants used in the development and potentially leaching from the development site, as well as indicators related to waste handling (to minimise the risk of pollutants such as plastics spreading to the environment). Protocols and detailed criteria to monitor these aspects are already implemented in sustainability assessments for certifications such as DGNB or BREEAM.

Figure 29: In business-as-usual scenarios biodiversity is considered an on-site (local) issue, but if we’re to truly apply Doughnut principles in urban development we must apply a life-cycle perspective which includes the quantification of off-site (global) biodiversity impacts that happen across the supply chain. We can measure biodiversity on-site (locally) with the ‘Biodiversity Net Gain’ method and biodiversity impact off-site (globally) can be done using the ‘Off-site Biodiversity Tool’.

How do you define a project’s biodiversity baseline?

The Planetary Boundaries framework assesses the state of boundaries compared to a baseline, set either at pre-industrial times or at the start of the Holocene (roughly 9,000 years BCE). The point is to show the impacts caused by human activity on the various boundaries.

For climate change, it is possible to define and aim for a boundary based on atmospheric concentration of carbon to preserve the climate conditions of the Holocene. However, ecosystems are fundamentally different: it is nearly impossible to revert to a Holocene-like state, since lost species cannot be brought back and converted ecosystems cannot be restored back to pristine conditions. Therefore, to document the effects of human activity for a specific development, the chosen baseline is often the state of the development area prior to the development. In most cases, that implies considering previous land use, which may be urban, industrial, agricultural or natural ecosystems. The baseline is thereby not determined by the ownership or planning status of an area, but by the physical and ecological quality.