Talk A method to assess impacts of LTI projects on a territory and its biodiversity stakes

Local and national administrations commonly make environmental impact assessment (EIA) on infrastructure projects like Linear Transport Infrastructure (LTI) to evaluate their potential impacts on biodiversity. This assessment hypothetically needs: i) a standardised and spatialised knowledge of biodiversity on their administrative area (depending on census effort on all the area) and ii) a good knowledge of impacts intensity of the different infrastructure types on all main taxonomic groups. Finally, iii) the main objective of this EIA is to assess the potential impacts of infrastructure projects against biodiversity. From knowledge about biodiversity stake of a study area, the goal is to obtain a threat index compared to a threat level of biodiversity sensitivity to the project.

Such standardisation can limit heterogeneity in analysis and help instructors to carry out EIA.

Study area and method

In the Midi-Pyrénées region, we developed a new method for regional administration (DREAL) from 2012 to 2015.

i) A grid of 2.5 km square units is applied on the regional area. Each square unit contains a list of (censused) flora and fauna species and natural habitats (DREAL, CBNPMP and CEN MP databases). This species (and habitats) list allows calculation in a square unit of a regional Stake index which is a sum of 3 indexes applied on each species: Responsibility, Rarity and Vulnerability indexes.

ii) For each type of linear infrastructure (LTI, power lines, pipelines, but also wind plant and solar plant, urban project, dam, quarry...), the sum of sensitivity of the main natural habitats and taxonomic groups (Mammals, Birds, Reptiles, Amphibians, Fishes and Crustaceans, Molluscs, nocturnal Lepidopters, Odonates, other Arthropods, aquatic - semi-aquatic and other Flora and natural habitats) are detailed, towards all impacts that can potentially occur during construction and exploitation periods (= Sensitivity index). This analysis depends on literature review and on joint expertise.

iii) To obtain a Threat index, a crossing analysis is made, in a square unit impacted by a linear infrastructure project, using comparison between the sum of Stake indexes of all species in the square unit multiplied by the taxonomic Sensitivity indexes towards this kind of project, and a regional Threat level towards an infrastructure project type. This Threat level has been defined as the interaction between the quartiles 3 of all Stake index (per square unit) in the region, of the species number of all square units in the region and of all taxonomic groups Sensitivity index towards linear infrastructure projects.


Our work provides a normalised tool which can be a common basis for stakeholders, instructors and biodiversity administrative departments or offices, in biodiversity (environmental) impacts assessment of infrastructure (LTI) projects in a regional or national area ; this has been improved with real projects. We will discuss the strengths and weaknesses of this method and its future development.

EIA, Method, Threat level, LTI, Impacts, Biodiversity stakes, species, habitats, Midi-Pyrénées region