Shifting landscape: forest fragmentation in the Polish Carpathians over last 150 years
New approach in landscape and habitat fragmentation assessment: landscape hypsometric curve
Effects of different matrix representations and connectivity measures on habitat network assessments
Assessing landscape connectivity is important to understand the ecology of landscapes and to evaluate alternative conservation strategies. The question is though, how to quantify connectivity appropriately, especially when the information available about the suitability of the matrix surrounding habitat is limited. Our goal here was to investigate the effects of matrix representation on assessments of the connectivity among habitat patches and of the relative importance of individual patches for the connectivity within a habitat network. We evaluated a set of 50 × 50 km2 test areas in the Carpathian Mountains and considered three different matrix representations (binary, categorical and continuous) using two types of connections among habitat patches (shortest lines and least-cost paths). We compared connections, and the importance of patches, based on (1) isolation, (2) incidence-functional, and (3) graph measures. Our results showed that matrix representation can greatly affect assessments of connections (i.e., connection length, effective distance, and spatial location), but not patch prioritization. Although patch importance was not much affected by matrix representation, it was influenced by the connectivity measure and its parameterization. We found the biggest differences in the case of the integral index of connectivity and equally weighted patches, but no consistent pattern in response to changing dispersal distance. Connectivity assessments in more fragmented landscapes were more sensitive to the selection of matrix representation. Although we recommend using continuous matrix representation whenever possible, our results indicated that simpler matrix representations can be also used as a proxy to delineate those patches that are important for overall connectivity, but not to identify connections among habitat patches.
Ziółkowska E., Ostapowicz K., Radeloff V.C., Kuemmerle T. (2014) Effects of different matrix representations and connectivity measures on habitat network assessments. Landscape Ecology, 29, 1551-1570, DOI: 10.1007/s10980-014-0075-2 http://link.springer.com/article/10.1007%2Fs10980-014-0075-2
What hampers wisents’ movements? – a case study from the northwestern Carpathians
Reintroductions are an important tool for re-establishing or reinforcing populations of threatened species, and thus to restore ecosystems. However, predicting how reintroduced populations will spread is difficult, and past reintroductions often lacked a thorough assessment of habitat availability and connectivity. Using the case of reintroduced European bison (Bison bonasus L.) in the northern Carpathians, we show how habitat suitability models in combination with connectivity assessments based on circuit theory can remedy such shortcomings, and identify potential habitat patches and corridors between these. European bison were reintroduced in our study area in the 1960s, and against prior expectation, have not spread along the Carpathian ridge, but instead expanded their range towards human settlements. Our analyses provide an explanation for this pattern. Although we identified a network of suitable habitat patches along the Carpathian ridge, the functional connections between them were limited due to a number of major barriers to movement. To avoid future conflicts between European bison and people, and to achieve the long-term goal of a viable bison metapopulation in this region, conservation action should focus on establishing connectivity between habitat patches through the creation and legal protection of corridors and wildlife passages, which would benefit Carpathian wildlife in general. Our study emphasizes the importance of landscape-scale connectivity analyses to guide restoration efforts, and of adaptive management to ensure the success of reintroduction projects.
Ziółkowska E., Perzanowski K., Bleyhl B., Ostapowicz K., Kuemmerle T., 2016, Understanding unexpected reintroduction outcomes: Why aren't European bison colonizing suitable habitat in the Carpathians?, Biological Conservation, 195, 106-117, doi:10.1016/j.biocon.2015.12.032
Assessing diffrences in connectivity based on habitat versus movement models for brown bears in the Carpathians
Connectivity assessments typically rely on resistance surfaces derived from habitat models, assuming that higher-quality habitat facilitates movement. This assumption remains largely untested though, and it is unlikely that the same environmental factors determine both animal movements and habitat selection, potentially biasing connectivity assessments. We evaluated how much connectivity assessments differ 5 when based on resistance surfaces from habitat versus movement models. In addition, we tested how sensitive connectivity assessments are with respect to the parameterization of the movement models. We parameterized maximum entropy models to predict habitat suitability, and step 10 selection functions to derive movement models for brown bear (Ursus arctos) in the northeastern Carpathians. We compared spatial patterns and distributions of resistance values derived from those models, and locations and characteristics of potential movement corridors. Brown bears preferred areas with high forest cover, close to forest edges, high topographic complexity, and with low human pressure in both habitat and movement models. However, resistance surfaces derived from the habitat models based on predictors measured at broad and medium scales tended to underestimate connectivity, as they predicted substantially higher resistance values for most of the study area, including corridors. Our findings highlighted that connectivity assessments should be based on movement information if available, rather than generic habitat models. However, the 20 parameterization of movement models is important, because the type of movement events considered, and the sampling method of environmental covariates can greatly affect connectivity assessments, and hence the predicted corridors.
Ziółkowska E., Ostapowicz K., Radeloff V.C., Kuemmerle T., Sergiel A., Zwijacz-Kozica T., Zięba F., Śmietana W., Selva N., Assessing diffrences in connectivity based on habitat versus movement models for brown bears in the Carpathians, Landscape Ecology (accepted)
Implication of future land cover change on the brown bear habitat suitability in the northern part of the Carpathians
Large carnivores and herbivores often require large, undisturbed habitats, and can become in conflict with people and land use, which makes their conservation in humandominated landscapes highly challenging. Distribution range and population size of brown bear (Ursus arctos) populations in Europe have changed significantly in the past and the
long-term persistence of the species is threatened by habitat loss and fragmentation due to infrastructure development. In this study, we aim to model future land cover change and their influence on the brown bear habitat suitability in the Carpathians, one of the largest strongholds of brown bears in Europe and where this population has been fragmented since the early 20th century. In particular, we focus on possible changes in brown bear habitat fragmentation caused by road networks development and growth of built-up areas in the study region. We use the Dyna-CLUE land use modelling framework to create land cover change scenarios up to year 2065, and maximum entropy modelling approach to assess changes in brown bear habitat suitability. We assume that the future increase of infrastructure density will affect significantly an increase of brown brear habitat fragmentation in the study region.
Project supported by a grant from the National Science Centre