Maximizing habitat connectivity in the mitigation hierarchy. A case study on three terrestrial mammals in an urban environment

Abstract

Environmental policies and the objective of no net loss highlight the importance of preserving ecological networks to limit the fragmentation of natural habitats and biodiversity loss, especially due to urbanization. In the environmental impact assessment context, habitat connectivity and the spatio-temporal dynamics of biodiversity are crucial to obtaining reliable predictions that can support decision-making. We propose a methodological framework 1) to quantify the overall impact of a development project on the functioning of an ecological network, and 2) to select the best locations for implanting new habitat patches intended to enhance landscape connectivity. The amount of reachable habitat concept was applied to three representative terrestrial mammal species: the red squirrel, the Eurasian badger and the European hedgehog. All three species are recognized as vulnerable to human pressures and potentially affected by the construction of a new stadium in our study site, Lyon (Southern France). The method combines the species distribution model Maxent with the landscape functional connectivity model Graphab. The results showed that using any one of the avoidance and reduction measures on its own was unsuccessful in achieving the objective of no net loss when habitat connectivity is considered. However, the combination of new habitat patches and corridors offered a higher gain than distinct measures. This is especially important in the short term, when new hedgerow plantations have not yet developed enough to be used by the target species. Our findings indicate, first, the need to take the temporal scale into account in environmental impact assessment. We also show that applying the optimal scenario, constructed using a cumulative patch addition followed by a similar process testing a set of potential land-use changes, maximizes habitat connectivity. Our methodology provides a useful tool to increase target species' habitat connectivity within the mitigation hierarchy and to enhance development project design for increased environmental efficiency.

Quantifying the impact of vegetation‐based metrics on species persistence when choosing offsets for habitat destruction

“…Our results showed that the negative impacts of using only habitat-based metrics and ignoring species-specific connectivity may be significant, vary greatly among metrics, and, most alarmingly, are likely to go unnoticed unless changes in population dynamics are tested explicitly. These findings provide strong support for earlier calls that both structural (e.g., patch size and distance) and functional connectivity metrics (e.g., metapopulation connectivity and capacity [Moilanen et al 2005;Bojkovic et al 2015]) should be accounted for in early stages of impact assessment and offset planning to avoid unexpected declines in populations and species (Tarabon et al 2019).…”

“…2015]) should be accounted for in early stages of impact assessment and offset planning to avoid unexpected declines in populations and species (Tarabon et al. 2019).…”

Integrating a landscape connectivity approach into mitigation hierarchy planning by anticipating urban dynamics

“…Thus, our models could be improved by incorporating more qualitative developments, such as wildlife crossings. Wildlife crossings lead to landscape defragmentation and reconnect environments with each other, thereby enhancing the overall connectivity of ecological networks (Bergès et al, 2020;Mimet et al, 2016;Tarabon, Bergès, Dutoit, & Isselin-Nondedeu, 2019b).…”

Pooling biodiversity offsets to improve habitat connectivity and species conservation

“…In the light of recurrent failures in biodiversity offsetting implementation (see Bezombes et al, 2019;May et al, 2017;Weissgerber et al, 2019), there is growing evidence of the benefits of including landscape connectivity into the mitigation hierarchy (Dalang and Hersperger, 2012;Tarabon et al, 2019bTarabon et al, , 2020. A territorial-scale conservation strategy seems to further increase these benefits.…”