Invisible barriers: anthropogenic impacts on inter- and intra-specific interactions as drivers of landscape-independent fragmentation

Abstract

Anthropogenically induced fragmentation constitutes a major threat to biodiversity. Presently, conservation research and actions focus predominantly on fragmentation caused directly by physical transformation of the landscape (e.g. deforestation, agriculture, urbanization, roads, etc.). While there is no doubt that landscape features play a key role in fragmenting populations or enhancing connectivity, fragmentation may also come about by processes other than the transformation of the landscape and which may not be readily visible. Such landscape-independent fragmentation (LIF) usually comes about when anthropogenic disturbance alters the inter- and intra-specific interactions among and within species. LIF and its drivers have received little attention in the scientific literature and in the management of wildlife populations. We discuss three major classes of LIF processes and their relevance for the conservation and management of species and habitats: (i) interspecific dispersal dependency, in which populations of species that rely on other species for transport and propagation become fragmented as the transporting species declines; (ii) interspecific avoidance induction, where species are excluded from habitats and corridors owing to interspecific interactions resulting from anthropogenically induced changes in community structure (e.g. exclusions by increased predation pressure); and (iii) intraspecific behavioural divergence, where populations become segregated owing to anthropogenically induced behavioural differentiation among them. This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation'.

Urban specialization reduces habitat connectivity by a highly mobile wading bird

“…This reduced movement stems in part from the presence of reliable resources in urban landscapes [20]; for instance, migratory white storks that feed on landfills have recently established resident populations [21] and brown bears revisit known feeding sites in winter when resources are otherwise scarce [22]. These less-frequent or shorter-distance movements can limit connectivity to the extent of creating apparent landscape fragmentation, even when it is not present structurally (i.e., habitat-independent fragmentation: [23]). Highly mobile species can be particularly important for connectivity because they transport propagules over long distances [24], so understanding their movement responses to urbanization is important for understanding both population and ecosystem processes.…”

Behavioral Causes, Ecological Consequences, and Management Challenges Associated with Wildlife Foraging in Human-Modified Landscapes

“…For example, reduced movement through natural landscapes can reduce the dissemination of seeds (Chapman and Onderdonk 1998 , Naoe et al 2016 , Sebastián-González et al 2019 ) or the maintenance of open habitats or corridors (Cumming et al 1997 ). Decreased interactions between species is then likely to increase fragmentation of resources and habitats (Berger-Tal and Saltz 2019 ). In human-altered landscapes, the presence and increased movement of wild species can increase the spread of exotic and invasive species (Mellado and Zamora 2014 ) or diseases to humans or domestic species (Daszak et al 2000 , Donnelly et al 2006 , Flint et al 2016 ).…”

Behavioural valuation of landscapes using movement data

“…The definition of patches and resistant surfaces can then be used to estimate optimal linkages (corridors) among patches using least-cost path, circuit theory and ‘hybrid’ approaches such as randomized shortest path [69]. Pros and cons of the different algorithms and how to best use these approaches have been the subject of extensive discussion, including that such optimality approaches may be misleading given wildlife often traverse unsuitable habitat or avoid apparently suitable habitat for alternate reasons [68,70,71].…”

“…Validation of movement networks is rarely done but is important for ensuring usefulness for conservation [72,73], as there is a potential risk that areas identified as potential movement corridors or important patches from a connectivity point of view are not actually used by individuals [66,68]. As with all extrapolative modelling, this is particularly the case when predicting beyond the area where data were captured.…”