Our partner Carbone 4 has published a position paper on "grey" (embodied) biodiversity in buildings, written with the support of Nexity and Altarea. Darwin took part as study partner: the biodiversity footprint of the building was modelled on the Darwin platform. Here is a short summary. The full paper, in French, is available on the Carbone 4 website.
A blind spot for the building sector
The construction sector mostly manages its biodiversity impact on the plot itself, through land take. Yet most of the damage happens upstream, in the extraction and processing of materials: this is "grey" biodiversity. Construction accounts for around 50% of global raw material extraction, but no building standard (RE2020, labels) covers this impact today, and no measurement tool exists for the sector.
Over 4 months, Carbone 4, Nexity and Altarea framed a first method to measure it. They modelled a typical 50-unit residential building with a concrete structure, using the INIES life-cycle data already collected for RE2020, and calculated its biodiversity footprint on the Darwin platform (IMPACT World+ method, in PDF.m².yr).
Key findings
- Materials outweigh the site by 5 to 10 times. The embodied impact of the building reaches 272,000 PDF.m².yr, the equivalent of 12,500 m² of deforestation, nearly 10 times its footprint on the ground. Materials account for more than 80% of the project's total impact, and can exceed 90% depending on the assumptions.
- Pollution and climate change are the main pressures, driven by concrete. The superstructure alone accounts for more than a quarter of the impact. Aluminium and steel also weigh through the pollution they generate during extraction and processing.
- Bio-based materials need traceability. Replacing concrete with wood lowers the carbon footprint but, if the origin is not controlled, it can triple the land use change pressure and raise the overall biodiversity impact by about 15%.
- Climate and biodiversity are largely, but not always, aligned. Using less material and reuse benefit both; bio-based materials call for vigilance.
What to do now
Grey biodiversity is where embodied carbon was 15 years ago: the impact is documented, but shared tools and standards are still to be built. The paper recommends acting now: calculate the footprint of a few flagship projects to engage project and procurement teams, and secure the traceability of bio-based and other high-impact materials with suppliers. In the medium term, the sector should build a common measurement standard and responsible sourcing guidelines by material type.
The full paper, with the methodology and detailed results, is available in French on the Carbone 4 website. To measure the biodiversity footprint of your own projects or portfolio, use the Book a demo button below.