River Fragmentation: Why We Should Give a Dam

Globally, built infrastructure such as dams, weirs, and roads crisscross and fragment our world’s freshwater ecosystems. Yet, our understanding of the locations and potential effects of built infrastructure on freshwater ecosystems and the species and communities that they support remains limited. In today’s guest blog by Stephanie Januchowski-Hartley, she discusses why built infrastructure are increasingly under the research lens, and highlights what a collective of European institutions are doing in their multi-nation project.

There are an estimated 6,862 large dams (1) across the earth’s surface. However, we know that these numbers are far from representative, and do not account for smaller infrastructure like weirs or culverts that are consistently shown to be higher in number than large dams. We also know that occurrence and distribution of built infrastructure are constantly changing around the world both with regards to larger dams and smaller weirs, and even roads. Why are these numbers constantly changing? Built infrastructure expansion and contraction are linked to global and local socio-economic and political situations. In some countries like the United States, and even entire regions (like western Europe), dam and weir removals have been on the rise over the last 5 years primarily because of aging infrastructure that no longer serve their original purpose, are costly to maintain, and once removed are shown to bring benefits to nature and humans. At the same time, new dams are being proposed in the same countries, or adjacent regions, as a form of ‘green’ or sustainable energy, but the implications of this rhetoric, and subsequent implementation of infrastructure, are likely to be damaging if the processes are not planned or regulated. The same goes for continued and increased dam expansion in tropical regions where there are heightened concerns about the loss of species, particularly of those of importance for subsistence fisheries.

Recently, there has been a push for dam removal in much of Europe. But do we fully understand the consequences?
Recently, there has been a push for dam removal in much of Europe. But do we fully understand the consequences? (Image Credit: Wikipedia Commons)

How can we work to better understand the potential implications of decisions about the removal and construction of built infrastructure, and guide potential solutions that return benefits for both people and nature? This is part of what we aim to address with Project Odysseus, a collaboration between researchers in Sweden, Norway, Spain, and France, which includes the NTNU Museum of Natural History. Project Odysseus is a project funded by the BiodivERsA network. Our primary goals in relation to understanding the potential implications of built infrastructure on freshwater ecosystems are to quantify the characteristics of built infrastructure, the ability of species (primarily fishes) to pass different types of built infrastructure, and to better understand the relationship between the size of fragments to species’ ranges caused by built infrastructure and extinction risk. Ultimately, in coupling our findings from achievement of these goals with data and understanding of other human stressors on freshwater ecosystems, we aim to develop and implement a decision support tool that allows decision makers to evaluate and potentially trade-off the ecological consequences of built infrastructure removals and construction in relation to the potential or perceived socio-economic gains. To ensure stakeholder input to this process there has been ongoing dialogue between researchers and government decision makers across the study areas.

Ultimately the ecological implications of built infrastructure construction are not necessarily transparent or consistent across countries or regions, and our understanding of the potential ecological benefits of removals is only beginning. Projects like those of Odysseus aim to better our understanding of the potential ecological implications of built infrastructure, and identify ways that we can ensure decisions that reduce negative impacts on both nature and people.

To read more about Steph’s work, you can visit her website here.

(1) Large dam – Dam with a reservoir and storage capacity of more than 0.1km³

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