Synergistic and antagonistic interactions of future land use and climate change on river fish

Our most recent article on the synergistic and antagonistic interactions of future land use and climate change on the fish assemblages of River Elbe (GER) has been published in the upcoming issue of Global Change Biology:

GCB Radinger etal 2016

River ecosystems are threatened by future changes in land use and climatic conditions. However, little is known of the influence of interactions of these two dominant global drivers of change on ecosystems. Does the interaction amplify (synergistic interaction) or buffer (antagonistic interaction) the impacts and does their interaction effect differ in magnitude, direction and spatial extent compared to single independent pressures. In this study, we model the impact of single and interacting effects of land use and climate change on the spatial distribution of 33 fish species in the Elbe River. The varying effects were modeled using step-wise boosted regression trees based on 250 m raster grid cells. Species-specific models were built for both ‘moderate’ and ‘extreme’ future land use and climate change scenarios to assess synergistic, additive and antagonistic interaction effects on species losses, species gains and diversity indices and to quantify their spatial distribution within the Elbe River network. Our results revealed species richness is predicted to increase by 0.7–2.9 species by 2050 across the entire river network. Changes in species richness are likely to be spatially variable with significant changes predicted for 56–85% of the river network. Antagonistic interactions would dominate species losses and gains in up to 75% of the river network. In contrast, synergistic and additive effects would occur in only 20% and 16% of the river network, respectively. The magnitude of the interaction was negatively correlated with the magnitudes of the single independent effects of land use and climate change. Evidence is provided to show that future land use and climate change effects are highly interactive resulting in species range shifts that would be spatially variable in size and characteristic. These findings emphasize the importance of adaptive river management and the design of spatially connected conservation areas to compensate for these high species turnovers and range shifts.


French review of our recent article in Ecological Applications

The team of the French non-profit organization and website has reviewed our recent article:

Radinger, J. and Wolter, C. (2015) Disentangling the effects of habitat suitability, dispersal and fragmentation on the distribution of river fishes. Ecological Applications 25:914-927. DOI: 10.1890/14-0422.1

Here a short English summary on what found most interesting in our study in particularly in a French river restoration context:

River restoration is a hot topic in France. Due to the WFD 2000 implementation and French river connectivity policy (“Trame bleue”), thousands of weirs and dams are to be either partially/totally removed, either equipped with fish pass or migration devices before 2018. Theses reforms meet some opposition from mills’ owners, citizens living in the riverside areas, local authorities concerned about side-effects of dam removals, industrial hydroelectric facilities. So there is a strong attention to the debates about the efficiency and scientific accuracy of morphological restoration (e.g. Palmer et al 2005, Morandi et al 2014), the relative effect of each anthropic pressure on biological populations (e.g. Dahm et al 2013, Villeneuve et al 2015), specifically the link between flow fragmentation and fish assemblages (e.g. Branco et al 2012, Van Looy et al 2014). Johannes Radinger and Christian Wolter’s recent model of 17 common stream species’ distributions is exposed to a French general public (laypersons) and contextualized with some recent results of this field of research. Complexity of river restoration and uncertainty of its outcome is emphasized, particularly the urgent need of multivariate modeling tools for the restoration planning at the catchment level.

The whole review in French (L’introuvable influence des seuils et barrages sur les peuplements piscicoles) can be found here:

Herewith I’d like to thank for the comprehensive review and for bringing this topic to a broader, French audience.

Brief Idea: Source populations in the context of dispersal modelling

The following short article has been published on June 26, 2015 open access (CC BY):

Radinger, J. (2015) Source populations in the context of dispersal modelling. Journal of Brief Ideas. DOI: 10.5281/zenodo.19097

In conservation ecology, missing source populations are often considered the main bottleneck for the successful (re-)colonisation of (restored) habitats (e.g. Kail et al. 2015). In theoretical ecology and population biology, sources as opposed to sinks are defined as good quality habitats with a positive net difference between immigrating and emigrating individuals (demographic surplus, Dias 1996). This definition differs from source populations used for dispersal modelling (e.g. Radinger et al. 2014) that typically builds on initial starting (source) populations for e.g. diffusion processes. Here, each site with at least one specimen present that might possibly emigrate can be considered as a potential source population. The presence of species and, hence, the location of initial starting (source) populations for dispersal and (re-)colonization can be either based on (i) sampling data or on (ii) species distribution models (empirical models of species presence based on explanatory environmental variables) (Kail et al. 2015). However, while the first probably underestimates the number of sources since only a limited number of sites is typically sampled, the latter is probably overestimating the number of sources as suitable habitat might not be directly translated into species presence. Hence, future research should focus on appropriate methods to identify / locate source populations that can be used in dispersal modelling.

River habitat, fish dispersal and fragmentation

Our most recent article on the effects of habitat suitability, fish dispersal and fragmentation on river fish distribution has been published in Ecological Applications and is available online.

Habitat suitability, dispersal potential, and fragmentation influence the distribution of stream fishes; however, their relative influence and interacting effects on species distributions are poorly understood, which may result in uncertain outcomes of river rehabilitation and conservation. Using empirical data describing 17 relatively common stream f ishes, we combine (1) species habitat suitability models (MaxEnt) with a (2) species dispersal model (FIDIMO) and a (3) worst-case scenario of the influence of river fragmentation on dispersal. Using generalized linear mixed models, we aimed to uncover the role of these factors in explaining the probability of presence. Simulations over nine years allowed for assessing the relative importance of dispersal over time for structuring species occurrences vs. the importance of habitat suitability. Models combining all three structuring factors performed consistently better in predicting the spatial occurrence patterns than models including only single factors. Our results confirmed that distribution patterns of stream fishes are jointly controlled by species dispersal and habitat suitability. An increase of 0.1 habitat suitability probability more than doubled the odds of species occurrence; an increase of 0.1 dispersal probability yielded a 14-fold increase of the odds of species occurrence. Temporal simulations revealed that over short time frames (1–2 years) dispersal from nearby source populations is four times more important than habitat suitability for species presence. However, over longer time periods, the importance of habitat suitability increases relative to the importance of dispersal. Surprisingly, fragmentation by migration barriers did not appear as a significant driver of occurrence patterns. Concluding, these findings demonstrate the importance of the spatial arrangement of suitable habitats and potential source populations, as well as their relative position in relation to barriers. We emphasize considering the direction of connections within river networks and the dispersal abilities of fishes, as well as providing (access to) new, suitable habitat for successful river rehabilitation.

Johannes Radinger and Christian Wolter (2015). Disentangling the effects of habitat suitability, dispersal, and fragmentation on the distribution of river fishes. Ecological Applications 25:914–927. DOI: 10.1890/14-0422.1



I’d like to repost an announcement for a Summer school on spatio-temporal analyis and bid data processing using free and open source software taking place in Santa Barbara – USA California from July 16 to 22, 2015. The Summer school is organized by in collaboration with Department of Ecology, Evolution, and Marine Biology at University of California, Santa Barbara:

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GRASS 7.0 is out, but the development continues unabated

Try it out!


Just a thumbs-up for the developers of GRASS GIS, who evidently do not rest on their laurels since their release of GRASS GIS 7.0. Below one of those more visible new features in the GRASS GIS development version which make live just that much easier.

nice new feature A really welcome addition to the drop-down menu for selection of raster or vector layers. It now shows the open maps under a separate header.

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GRASS GIS 7.0.0 Release Candidate 1


The release candidate of GRASS GIS 7.0 has been released, with too many improvements and new features to summarize here. Go to and check out the details!

Kudos to the developers and for the users out there that are still using GRASS GIS 6.4… this is really a good time to switch to the latest and greatest!

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How will the hydropower boom affect global river ecosystems?

An interesting study of some IGB-colleagues…

The Freshwater Blog

Itaipu Hydropower Project on the Paraná River located on the border between Brazil and Paraguay. Image: Wikipedia

There are currently around 3,700 major new hydropower dam projects planned or under construction across the world, many of them in developing countries which lack widespread, reliable and affordable electricity supplies.  However, many of these same countries support biodiverse and relatively ‘natural’ large river systems, which raises questions of how to balance the potential ‘green’ energy gains from hydropower projects with the potential harm – barriers to fish migration, siltation, habitat change amongst others – they can cause to river ecosystems.

A new study ‘A global boom in hydropower dam construction‘, has been carried out by Professor Christiane Zarfl from the University of Copenhagen and colleagues at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) in Berlin, including BioFresh head Klement Tockner. The research team compiled data on future major hydropower projects to predict how much energy would…

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