Linear Transport Infrastructures (LTI) contributes to the land use changes underpinning the 6th extinction. However, as the term LTI covers several types of infrastructure, the link between the presence of an LTI and the extinction increase is not always straight forward and depends on the nature of the LTI and its surrounding landscape. To limit the impact of LTI on biodiversity, the mitigation hierarchy aims at balancing biodiversity losses and gains to achieve the No Net Loss goals. Based on a scenario comparison of expected losses and gains during the conception to exploitation sequence of a gas pipeline on the protected butterfly P. alcon, we showed that the evaluation's spatial range of impacts and offsets is crucial to design the compensation measures. Indeed, using individual-based spatially-explicit model of P. alcon metapopulation functioning, we showed that at the locale scale (environmental impact assessment scope), the equivalence (population size, global flow of in-dividuals and connectivity) is not reached after the project development. The forest opening due to the pipeline building contributes to reaching the equivalency of flow of individuals but changes in the population functioning leads to a loss of individuals. At the sub-regional scale, simulation results highlight unexpected negative effects up to 3 km from the infrastructure. The changes in the population functioning at the locale scale influence the sub-regional population functioning leading to a loss of population size, global flow of individuals and con-nectivity. Considering our results, we illustrate the crucial role of spatial scales to implement the mitigation hierarchy in environmental assessment. Practitioners should ensure that impacts and offset range of expected effect overlap at any impacted spatial scales. We argue that ecological modelling should be a relevant approach to test scenarios even at larger scales than current practices that can be monitored on operative environmental impact assessment.