Braided rivers are highly dynamic and support high levels of biodiversity. Like many ecosystems, these riverscapes are threatened by habitat loss and fragmentation. Despite supportive regulations, restoration of braided riverscapes remains difficult for key species including riparian plants. For wind-dispersed seeds to successfully colonize these riverscapes, there must be habitat available that’s not only suitable, but also reachable and connected.
Wagner, T.C. and Woellner, R. 2023. A new set of metrics and framework to assess the colonization potential of riverscapes by wind-dispersed plant species. Scientific Reports 13(1): 20097.
While there are many connectivity metrics to quantify the connectivity of river systems, most of these focus on the aquatic components, such as fish. Those that do address terrestrial species tend to focus on animals, and are often inadequate to understand connectivity for plants, whose dispersal occurs over different scales and with different connectivity needs.
To improve the ability to conserve and manage these key river species, new metrics have been developed to evaluate connectivity in dynamic river ecosystem for wind-dispersed plants. By using a combination of R packages (raster and rconnect), five metrics can be calculated across multiple scales: effective seed rain, colonization potential, number of connections, effective connectivity, and effective distance. These metrics provide a straight-forward and effective way to find out the probability that a given species will reach suitable habitat within a riverscape.
In a case study, the metrics were applied across the Tyrolean Lech River and the Isar River in western Europe, using two alpine river plants that require natural braided rivers. The results highlight how the metrics can be successfully applied to determine colonization potential across multiple species and across multiple habitat configurations.
These new methods provide a simple and realistic way to determine how likely a riverscape is to be colonized by key riparian species. They also provide a more comprehensive view of both the current ecological conditions of the riverscape, and the potential for restoration to create suitable habitat. When reintroductions are possible, they can be directly applied to determine whether or not reintroduction efforts might succeed. With them, a more accurate view of current conditions and potential restoration outcomes can lead to better decisions on how to manage riverscapes, and add one more tool to the toolbox for conservation and restoration planning.
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