A road toward nature neutrality? Incorporating biodiversity restoration into life cycle assessment of road construction

Abstract Road construction irreversibly alters landscapes, fragments ecosystems, and reduces local biodiversity. The sector increasingly intends to mitigate these impacts, aiming for nature neutrality, i.e. full compensation for both the area and quality of ecosystems lost through restoration. Local soils are often reused for restoration after road construction, yet it remains unclear to what extent this practice helps achieve nature neutrality. We assessed the potential consequences of four scenarios in a planned road project through a natural area in Norway: no road construction (reference) and three levels of soil reuse—low, medium, and total reuse, the latter including off-site restoration. Plant species responses to soil management were tested through a soil translocation experiment. We evaluated full and poor recovery trajectories of plant species diversity at the road site, biogenic carbon stock change, and machinery emissions over 75 years. We applied a site-specific life cycle impact assessment method using the potentially disappeared fraction of plant species and developed a complementary metric, the potentially restored fraction. Species loss fractions were used to estimate the off-site restoration area required to reach nature neutrality. Total soil reuse reduced plant species loss by 70% and CO₂-equivalent emissions by 45% compared to low reuse. However, even in this scenario at least 26% of the reference plant species richness was lost and 1180 t CO 2eq emitted. Machine use emissions contributed <2% of total CO 2eq emissions. Achieving nature neutrality in terms of plant species richness would require restoration of areas 26%–41%, 39%–54%, and 123% the size of the road construction site under total, medium, and low soil reuse, respectively, with greater needs under poor recovery. Our results show that reusing natural soils can jointly reduce biodiversity loss and emissions, but attaining nature neutrality demands large off-site restoration areas that may not always be available.