Pooling biodiversity offsets to improve habitat connectivity and species conservation.

Land developers can apply biodiversity offsetting in different ways, from a project-by-project approach to a pooled and proactive approach, this latter appearing to provide greater advantages both in terms of implementation and of the No Net Loss objective. Incorporating landscape connectivity into the mitigation hierarchy is commonly recommended, but the benefits of pooling and anticipating offsets have never really been demonstrated from modeling approaches. Here, we compare connectivity gains from two different offsetting scenarios, when interconnections at offset sites are taken and not taken into account. Assuming that gains can be increased by optimizing the location of offsets, we identified sites where biodiversity offsetting generates the greatest ecological gains in habitat connectivity. The method was applied to a study case in the suburbs of Lyon (Southern France) using several representative species and the landscape functional connectivity model Graphab. Pooling biodiversity offsets led to additional gains in overall habitat connectivity of +103% on average, which we show can be further improved (+8%) by using a patch addition process available in Graphab to plan spatially and ecologically coherent offsetting areas. Pooling and anticipating biodiversity offsets in this way can help preserve the biodiversity and the functionality of natural environments at the territorial scale.

Habitat patches for newts in the face of climate change: local scale assessment combining niche modelling and graph theory.

Triturus cristatus and Triturus marmoratus are two protected and declining newts occurring in the administrative department of Vienne, in France. They have limited dispersal abilities and rely on the connectivity between habitats and their suitability. In a warming climate, the locations of suitable habitats are expected to change, as is the connectivity. Here, we wondered how climate change might affect shifts in habitat suitability and connectivity of habitat patches, as connectivity is a key element enabling species to realize a potential range shift. We used ecological niche modelling (ENM), combining large-scale climate suitability with local scale, high-resolution habitat features, to identify suitable areas for the two species, under low and high warming scenarios (RCP 2.6 and RCP 8.5). We associated it with connectivity assessment through graph theory. The variable 'small ponds' contributed most to land cover-only ENMs for both species. Projections with climate change scenarios revealed a potential impact of warming on suitable habitat patches for newts, especially for T. cristatus. We observed a decrease in connectivity following a decrease in patch suitability. Our results highlight the important areas for newt habitat connectivity within the study area, and define those potentially threatened by climate warming. We provide information for prioritizing sites for acquisition, protection or restoration, and to advise landscape policies. Our framework is a useful and easily reproducible way to combine global climate requirements of the species with detailed information on species habitats and occurrence when available.

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

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.

Environmental impact assessment of development projects improved by merging species distribution and habitat connectivity modelling.

Environmental impact assessment (EIA) is performed to limit potential impacts of development projects on species and ecosystem functions. However, the methods related to EIA actually pay little attention to the landscape-scale effects of development projects on biodiversity. In this study we proposed a methodological framework to more properly address the landscape-scale impacts of a new stadium project in Lyon (France) on two representative mammal species exemplary for the endemic fauna, the red squirrel and the Eurasian badger. Our approach combined species distribution model using Maxent and landscape functional connectivity model using Graphab at two spatial scales to assess habitat connectivity before and after development project implementation. The development project had a negative impact on landscape connectivity: overall habitat connectivity (PC index) decreased by -6.8% and -1.8% and the number of graph components increased by +60.0% and +17.6% for the red squirrel and the European badger respectively, because some links that formerly connected habitat patches were cut by the development project. Changes affecting landscape structure and composition emphasized the need to implement appropriate avoidance and reduction measures. Our methodology provides a useful tool both for EIA studies at each step of the way to support decision-making in landscape conservation planning. The method could be also developed in the design phase to compare the effectiveness of different avoidance or mitigation measures and resize them if necessary to maximize habitat connectivity.

Author Correction: Agricultural landscapes and the Loire River influence the genetic structure of the marbled newt in Western France.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Agricultural landscapes and the Loire River influence the genetic structure of the marbled newt in Western France.

Amphibians are particularly sensitive to landscape fragmentation. Potential barriers between breeding sites can negatively influence the dispersal of individuals and increase genetic structure between populations. In this study, we genotyped 10 microsatellites for 334 marbled newts (Triturus marmoratus) at 11 different locations in Western France. Samples were collected in different regions with contrasting agricultural landscapes (low and high proportion of arable land in the north and south, respectively). We found a strong genetic structure between the northern and southern sampling sites. Isolation by distance was recorded after 62 km, but within the northern region, little or no genetic structure was detected over large distances (up to 114 km). Genetic structure at shorter distance (43 km) was found between sites situated in landscapes with larger amounts of arable lands. A significant positive relationship was found between the pairwise genetic distance (Fst) between sites and the amount of arable land together with the distance between sites. Our results suggest that the Loire River might act as a corridor for the marbled newt, while arable land might act as a barrier. Finally, although a large city is located between sampling sites, no effect was detected on population structure.

Epizoochorous dispersal by ungulates depends on fur, grooming and social interactions.

The transport phase of the animal-mediated plant dispersal process is critical to dispersal effectiveness as it determines the spatial distribution of the diaspores released and their chance for further recruitment. Assessing this specific phase of the dispersal process generally requires combining diaspore retention times with the associated distances covered. Here, we specifically tested the effect of grooming behavior, interindividual contacts and ungulate fur on diaspore retention times and associated dispersal distances for the hooked diaspores of Xanthium strumarium L. experimentally attached to tamed individuals of three ungulate species. We used a comparative approach based on differing fur quality on different body zones of these three ungulates. During 6-hr sessions, we monitored for grooming and social interactions that may induce intended or inadvertent diaspore detachment. Additionally, we proposed innovative approaches to directly assessing diaspore dispersal distances by red deer in situ. Fat-tailed functions fitted diaspore retention time, highlighting the potential for long-distance dispersal events. The longer the hair, the higher the retention capacity of diaspores in the animal's fur. As predicted, donkey retained diaspores longer than red deer and dwarf goat; and we also confirmed that diaspores attached to the short hair of the head fell off more quickly than did those on the other body zones. Dwarf goat groomed more often than both red deer and donkey, but also when it carried diaspores. Up to 14% of the diaspores detached from animal fur after specific grooming behavior. We observed, in controlled conditions, for the first time and for each ungulate species, interindividual transfers of diaspores, representing 5% of the diaspores attached to animals' fur. Our results militate for incorporating animal behavior into plant dispersal modeling approaches.