Inputs of land for raw material production and fabric manufacturing. Such land use has significant implications for biodiversity—the diversity of Earth’s species, which provide critical services such as pollination, water purification, and climate regulation.

Although land use is a major driver of biodiversity loss, there is no easily applicable method for incorporating land use impacts on biodiversity into life cycle assessment (LCA)—a widelyused tool for evaluating potential environmental impacts of a product system.

The characterization factors used in this study are based on the spatial classification ecoregion, a large area with distinct species and environmental conditions. Ecoregions provide more ecologically-relevant characterization factors than those calculated at larger spatial scales. For all 867 ecoregions, de Baan et al. provide a characterization factor for every combination of 4 broad land use types (agriculture, pasture, managed forest, and urban) and 5 taxa (birds, mammals, reptiles, plants, and amphibians). We used aggregated characterization factors, which are a weighted average of the taxon-specific characterization factors.

Raw material production contributes more than 99% of the total biodiversity impact and land occupation for the cotton and wool t-shirts, and 92% of the lyocell t-shirt. These textiles require agriculture- and pasture-based land use, which have significantly lower yields, and thus require more land per functional unit, than the urban manufacturing processes.