International audienceLand-cover changes (LCCs) could impact wildlife populations through gains or losses of natural habitats and changes in the landscape mosaic. To assess such impacts, we need to focus on landscape connectivity from a diachronic perspective.We propose a method for assessing the impact of LCCs on landscape connectivity through a multi-species approach based on graph theory. To do this, we combine two approaches devised to spatialize the variation of multi-species connectivity and to quantify the importance of types of LCCs for single-species connectivity by highlighting the possible contradictory effects.We begin with a list of landscape species and create virtual species with similar ecological requirements. We model the ecological network of these virtual species at two dates and compute the variation of a local and global connectivity metric to assess the impacts of the LCCs on their dispersal capacities.The spatial variation of multi-species connectivity showed that local impacts range from −6.4% to +3.2%. The assessment of the impacts of types of LCCs showed a variation in global connectivity ranging from −45.1% for open-area reptiles to +170.2% for natural open-area birds with low-dispersion capacities.This generic approach can be reproduced in a large variety of spatial contexts by adapting the selection of the initial species. The proposed method could inform and guide conservation actions and landscape management strategies so as to enhance or maintain connectivity for species at a landscape scale
ContextLandscape graphs are widely used to model networks of habitat patches. As they require little input data, they are particularly suitable for supporting conservation decisions (and decisions about other issues as e.g. disease spread) taken by land planners. However, it may be problematic to use these methods in operational contexts without validating them with empirical data on species or communities.
ObjectivesSince little is known about methodological alternatives for coupling landscape graphs with biological data, we have made an exhaustive review of these methods to analyze links between the main purposes of the studies, the way landscape graphs are constructed and used, the type of field data, and the way these data are integrated into the analysis.
MethodsWe systematically describe a corpus of 71 scientific papers dealing with terrestrial species, with particular emphasis on methodological choices and contexts of the studies.
ResultsDespite a great variability of types of biological data and coupling strategies, our analyses reveal a dichotomy according to the objective of the studies, between (i) approaches aimed at improving ecological knowledge, mainly based on land-cover maps and using biological data to test the influence of landscape connectivity on biological responses, and (ii) approaches with an operational aim, in which biological data are directly integrated into the graph construction and assuming a positive effect of connectivity.
ConclusionsBeyond these main contrasts, the review shows that landscape graphs can benefit from field data of different types at varying scales. The great variability of approaches adopted reveals the flexible nature of these tools.
As an important component of the quality of the living environment, landscape is increasingly addressed in terms of its visual dimension. In contrast to the point‐like character of in situ observations and photographic analyses, the modeling of landscape visibility from digital data has the advantage of scanning geographical space in a systematic way. However, the tools currently available for visibility modeling are limited to the mapping of viewsheds. They require complementary operations for a complete landscape assessment, including direct and easy computation of landscape metrics. Furthermore, none of those tools integrates recent technical advances to better characterize the visible landscape by tangential vision (i.e., from ground level as opposed to vision by viewshed from above). Starting from this, PixScape software proposes to integrate a large set of functions for modeling landscape visibility while remaining interfaced with GIS software. This software can be used to perform a complete landscape assessment by computing a wide range of original landscape metrics. It performs tangential analysis in addition to viewshed analysis, which can produce more realistic outcomes. Because landscape visibility analysis over large areas implies significant computation time, the software also integrates a multi‐resolution process intended to speed up calculations while also taking into account the cognitive abilities of human vision.
Landscape graphs are increasingly used in ecology, conservation, and landscape planning for modeling habitat connectivity of wildlife species. We present here the follow-up of Graphab, a software application for modeling habitat networks. This application has been recently enhanced by advanced functions of spatial analysis, command-line facilities, and connections with other software applications. It has been used in many studies, first in ecological studies for analyzing the role of landscape connectivity on biological responses measured in the field, second for supporting decisions concerning biodiversity preservation. Future improvements could be made to make the links more realistic with respect to ecological processes.
Habitat loss and fragmentation remain major threats in estuaries, particularly with respect to the erosion of intertidal areas that provide shelter and food resources for numerous fish species. Improving our understanding of the fauna–intertidal seascape relationship is thus of critical importance. Here, the seascapes of 24 tidal estuaries were compared at multiple spatial scales (from estuary to local) to determine how the spatial structure of intertidal patches affects the abundance of several fish functional groups.
For the majority of fish groups, our results support the statement that a large intertidal area can support high fish abundance at both of the studied scales; however, the spatial distribution of patches within estuaries, and especially the presence of large intertidal patches close to the estuary mouth, appeared to be an important feature for both marine and estuarine‐resident fish.
It was also shown that habitat fragmentation at the estuary scale is associated with a decline in the abundance of several fish groups, probably as a result of reduced intertidal suitability and accessibility. At the local scale, the area of intertidal–subtidal interface was positively related to fish densities, emphasizing the importance of fish having permanently flooded refuges close to feeding grounds.
This study provides essential insights to guide conservation and restoration actions for intertidal areas at both estuary and local scales (10–100 m2), by stressing differences in species sensitivity to seascape modification.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.