TY - JOUR A1 - Kärcher, Oskar A1 - Filstrup, Christopher T. A1 - Brauns, Mario A1 - Tasevska, Orhideja A1 - Patceva, Suzana A1 - Hellwig, Niels A1 - Walz, Ariane A1 - Frank, Karin A1 - Markovic, Danijela T1 - Chlorophyll a relationships with nutrients and temperature, and predictions for lakes across perialpine and Balkan mountain regions JF - Inland Waters N2 - Model-derived relationships between chlorophyll a (Chl-a) and nutrients and temperature have fundamental implications for understanding complex interactions among water quality measures used for lake classification, yet accuracy comparisons of different approaches are scarce. Here, we (1) compared Chl-a model performances across linear and nonlinear statistical approaches; (2) evaluated single and combined effects of nutrients, depth, and temperature as lake surface water temperature (LSWT) or altitude on Chl-a; and (3) investigated the reliability of the best water quality model across 13 lakes from perialpine and central Balkan mountain regions. Chl-a was modelled using in situ water quality data from 157 European lakes; elevation data and LSWT in situ data were complemented by remote sensing measurements. Nonlinear approaches performed better, implying complex relationships between Chl-a and the explanatory variables. Boosted regression trees, as the best performing approach, accommodated interactions among predictor variables. Chl-a-nutrient relationships were characterized by sigmoidal curves, with total phosphorus having the largest explanatory power for our study region. In comparison with LSWT, utilization of altitude, the often-used temperature surrogate, led to different influence directions but similar predictive performances. These results support utilizing altitude in models for Chl-a predictions. Compared to Chl-a observations, Chl-a predictions of the best performing approach for mountain lakes (oligotrophic-eutrophic) led to minor differences in trophic state categorizations. Our findings suggest that both models with LSWT and altitude are appropriate for water quality predictions of lakes in mountain regions and emphasize the importance of incorporating interactions among variables when facing lake management challenges. KW - chlorophyll a KW - nutrients KW - Ohrid-Prespa region KW - perialpine lakes KW - water temperature Y1 - 2020 U6 - https://doi.org/10.1080/20442041.2019.1689768 SN - 2044-2041 SN - 2044-205X VL - 10 IS - 1 SP - 29 EP - 41 PB - Taylor & Francis CY - London ER - TY - GEN A1 - Kärcher, Oskar A1 - Filstrup, Christopher T. A1 - Brauns, Mario A1 - Tasevska, Orhideja A1 - Patceva, Suzana A1 - Hellwig, Niels A1 - Walz, Ariane A1 - Frank, Karin A1 - Markovic, Danijela T1 - Chlorophyll a relationships with nutrients and temperature, and predictions for lakes across perialpine and Balkan mountain regions T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Model-derived relationships between chlorophyll a (Chl-a) and nutrients and temperature have fundamental implications for understanding complex interactions among water quality measures used for lake classification, yet accuracy comparisons of different approaches are scarce. Here, we (1) compared Chl-a model performances across linear and nonlinear statistical approaches; (2) evaluated single and combined effects of nutrients, depth, and temperature as lake surface water temperature (LSWT) or altitude on Chl-a; and (3) investigated the reliability of the best water quality model across 13 lakes from perialpine and central Balkan mountain regions. Chl-a was modelled using in situ water quality data from 157 European lakes; elevation data and LSWT in situ data were complemented by remote sensing measurements. Nonlinear approaches performed better, implying complex relationships between Chl-a and the explanatory variables. Boosted regression trees, as the best performing approach, accommodated interactions among predictor variables. Chl-a-nutrient relationships were characterized by sigmoidal curves, with total phosphorus having the largest explanatory power for our study region. In comparison with LSWT, utilization of altitude, the often-used temperature surrogate, led to different influence directions but similar predictive performances. These results support utilizing altitude in models for Chl-a predictions. Compared to Chl-a observations, Chl-a predictions of the best performing approach for mountain lakes (oligotrophic-eutrophic) led to minor differences in trophic state categorizations. Our findings suggest that both models with LSWT and altitude are appropriate for water quality predictions of lakes in mountain regions and emphasize the importance of incorporating interactions among variables when facing lake management challenges. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1443 KW - chlorophyll a KW - nutrients KW - Ohrid-Prespa region KW - perialpine lakes KW - water temperature Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-515271 SN - 1866-8372 IS - 1 ER - TY - JOUR A1 - Markovic, Danijela A1 - Walz, Ariane A1 - Kärcher, Oskar T1 - Scale effects on the performance of niche-based models of freshwater fish distributions: Local vs. upstream area influences JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Niche-based species distribution models (SDMs) play a central role in studying species response to environmental change. Effective management and conservation plans for freshwater ecosystems require SDMs that accommodate hierarchical catchment ordering and provide clarity on the performance of such models across multiple scales. The scale-dependence components considered here are: (a) environment spatial structure, represented by hierarchical catchment ordering following the Strahler system; (b) analysis grain, that included 1st to 5th order catchments; and (c) response grain, the grain at which species respond most, represented by local and upstream catchment area effects. We used fish occurrence data from the Danube River Basin and various factors representing climate, land cover and anthropogenic pressures. Our results indicate that the choice of response grain local vs. upstream area effects and the choice of analysis grain, only marginally influence the performance of SDMs. Upstream effects tend to better predict fish distributions than corresponding local effects for anthropogenic and land cover factors, in particular for species sensitive to pollution. Key predictors and their relative importance are scale and species dependent. Consequently, choosing proper species dependent spatial scales and factors is imperative for effective river rehabilitation measures. KW - Catchment order KW - Conservation planning KW - Danube KW - Freshwater fish KW - Species distribution modelling KW - Upstream area Y1 - 2019 U6 - https://doi.org/10.1016/j.ecolmodel.2019.108818 SN - 0304-3800 SN - 1872-7026 VL - 411 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kärcher, Oskar A1 - Frank, Karin A1 - Walz, Ariane A1 - Markovic, Danijela T1 - Scale effects on the performance of niche-based models of freshwater fish distributions JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Niche-based species distribution models (SDMs) have become an essential tool in conservation and restoration planning. Given the current threats to freshwater biodiversity, it is of fundamental importance to address scale effects on the performance of niche-based SDMs of freshwater species’ distributions. The scale effects are addressed here in the context of hierarchical catchment ordering, considered as counterpart to coarsening grain-size by increasing grid-cell size. We combine fish occurrence data from the Danube River Basin, the hierarchical catchment ordering and multiple environmental factors representing topographic, climatic and anthropogenic effects to model fish occurrence probability across multiple scales. We focus on 1st to 5th order catchments. The spatial scale (hierarchical catchment order) only marginally influences the mean performance of SDMs, however the uncertainty of the estimates increases with scale. Key predictors and their relative importance are scale and species dependent. Our findings have useful implications for choosing proper species dependent spatial scales for river rehabilitation measures, and for conservation planning in areas where fine grain species data are unavailable. KW - Catchment order KW - Conservation planning KW - Danube KW - Generalized additive models KW - Species distribution modelling Y1 - 2019 U6 - https://doi.org/10.1016/j.ecolmodel.2019.05.006 SN - 0304-3800 SN - 1872-7026 VL - 405 SP - 33 EP - 42 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Hellwig, Niels A1 - Walz, Ariane A1 - Markovic, Danijela T1 - Climatic and socioeconomic effects on land cover changes across Europe BT - Does protected area designation matter? T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Land cover change is a dynamic phenomenon driven by synergetic biophysical and socioeconomic effects. It involves massive transitions from natural to less natural habitats and thereby threatens ecosystems and the services they provide. To retain intact ecosystems and reduce land cover change to a minimum of natural transition processes, a dense network of protected areas has been established across Europe. However, even protected areas and in particular the zones around protected areas have been shown to undergo land cover changes. The aim of our study was to compare land cover changes in protected areas, non-protected areas, and 1 km buffer zones around protected areas and analyse their relationship to climatic and socioeconomic factors across Europe between 2000 and 2012 based on earth observation data. We investigated land cover flows describing major change processes: urbanisation, afforestation, deforestation, intensification of agriculture, extensification of agriculture, and formation of water bodies. Based on boosted regression trees, we modelled correlations between land cover flows and climatic and socioeconomic factors. The results show that land cover changes were most frequent in 1 km buffer zones around protected areas (3.0% of all buffer areas affected). Overall, land cover changes within protected areas were less frequent than outside, although they still amounted to 18,800 km2 (1.5% of all protected areas) from 2000 to 2012. In some parts of Europe, urbanisation and intensification of agriculture still accounted for up to 25% of land cover changes within protected areas. Modelling revealed meaningful relationships between land cover changes and a combination of influencing factors. Demographic factors (accessibility to cities and population density) were most important for coarse-scale patterns of land cover changes, whereas fine-scale patterns were most related to longitude (representing the general east/west economic gradient) and latitude (representing the north/south climatic gradient). T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 764 KW - Species-Diversity KW - Determinants KW - Intensity KW - Patterns KW - Transformation KW - Tree KW - National-Parks KW - Biodiversity KW - Drivers KW - Abandonment Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-437885 IS - 764 ER - TY - JOUR A1 - Hellwig, Niels A1 - Walz, Ariane A1 - Markovic, Danijela T1 - Climatic and socioeconomic effects on land cover changes across Europe BT - Does protected area designation matter? JF - PloS One N2 - Land cover change is a dynamic phenomenon driven by synergetic biophysical and socioeconomic effects. It involves massive transitions from natural to less natural habitats and thereby threatens ecosystems and the services they provide. To retain intact ecosystems and reduce land cover change to a minimum of natural transition processes, a dense network of protected areas has been established across Europe. However, even protected areas and in particular the zones around protected areas have been shown to undergo land cover changes. The aim of our study was to compare land cover changes in protected areas, non-protected areas, and 1 km buffer zones around protected areas and analyse their relationship to climatic and socioeconomic factors across Europe between 2000 and 2012 based on earth observation data. We investigated land cover flows describing major change processes: urbanisation, afforestation, deforestation, intensification of agriculture, extensification of agriculture, and formation of water bodies. Based on boosted regression trees, we modelled correlations between land cover flows and climatic and socioeconomic factors. The results show that land cover changes were most frequent in 1 km buffer zones around protected areas (3.0% of all buffer areas affected). Overall, land cover changes within protected areas were less frequent than outside, although they still amounted to 18,800 km2 (1.5% of all protected areas) from 2000 to 2012. In some parts of Europe, urbanisation and intensification of agriculture still accounted for up to 25% of land cover changes within protected areas. Modelling revealed meaningful relationships between land cover changes and a combination of influencing factors. Demographic factors (accessibility to cities and population density) were most important for coarse-scale patterns of land cover changes, whereas fine-scale patterns were most related to longitude (representing the general east/west economic gradient) and latitude (representing the north/south climatic gradient). KW - Species-Diversity KW - Determinants KW - Intensity KW - Patterns KW - Transformation KW - Tree KW - National-Parks KW - Biodiversity KW - Drivers KW - Abandonment Y1 - 2019 U6 - https://doi.org/10.1371/journal.pone.0219374 SN - 1932-6203 VL - 14 IS - 7 PB - PLOS 1 CY - San Francisco ER - TY - JOUR A1 - Markovic, Danijela A1 - Carrizo, Savrina F. A1 - Kaercher, Oskar A1 - Walz, Ariane A1 - David, Jonathan N. W. T1 - Vulnerability of European freshwater catchments to climate change JF - Global change biology N2 - Climate change is expected to exacerbate the current threats to freshwater ecosystems, yet multifaceted studies on the potential impacts of climate change on freshwater biodiversity at scales that inform management planning are lacking. The aim of this study was to fill this void through the development of a novel framework for assessing climate change vulnerability tailored to freshwater ecosystems. The three dimensions of climate change vulnerability are as follows: (i) exposure to climate change, (ii) sensitivity to altered environmental conditions and (iii) resilience potential. Our vulnerability framework includes 1685 freshwater species of plants, fishes, molluscs, odonates, amphibians, crayfish and turtles alongside key features within and between catchments, such as topography and connectivity. Several methodologies were used to combine these dimensions across a variety of future climate change models and scenarios. The resulting indices were overlaid to assess the vulnerability of European freshwater ecosystems at the catchment scale (18 783 catchments). The Balkan Lakes Ohrid and Prespa and Mediterranean islands emerge as most vulnerable to climate change. For the 2030s, we showed a consensus among the applied methods whereby up to 573 lake and river catchments are highly vulnerable to climate change. The anthropogenic disruption of hydrological habitat connectivity by dams is the major factor reducing climate change resilience. A gap analysis demonstrated that the current European protected area network covers <25% of the most vulnerable catchments. Practical steps need to be taken to ensure the persistence of freshwater biodiversity under climate change. Priority should be placed on enhancing stakeholder cooperation at the major basin scale towards preventing further degradation of freshwater ecosystems and maintaining connectivity among catchments. The catchments identified as most vulnerable to climate change provide preliminary targets for development of climate change conservation management and mitigation strategies. KW - catchment connectivity KW - climate change KW - exposure KW - freshwater biodiversity KW - gap analysis KW - resilience KW - sensitivity KW - vulnerability Y1 - 2017 U6 - https://doi.org/10.1111/gcb.13657 SN - 1354-1013 SN - 1365-2486 VL - 23 SP - 3567 EP - 3580 PB - Wiley CY - Hoboken ER -