Is it possible to put a number on and calculate the effect that dams and their removal have on biodiversity? Peter Carlson has thought about that question.
Our nature is important. That it has functioning ecosystems is ever more important considering the climate changes that are in our future. Therefore, we need sustainable water resource management and it needs to be easy to determine whether the aquatic ecosystem is in good condition or poor. Peter Carlson, researcher at the Department of Aquatic Sciences and Assessment, SLU, is looking into the question of how to evaluate effects on ecosystems from man-made infrastructures (e.g. dams) in waterways.
- Effects of dams and other man-made infrastructure on biodiversity, ecosystems, and ecological goods and services provided to people and societies are of growing concern, says Peter. An understanding of how dams affect the hydromorphology, biodiversity and functioning of river ecosystems, remains very limited, hindering effective management. In turn, discrepancies exist between the needs of conservation, restoration, and mitigation of running waters, and water management practice because lack of effective tools for predicting the impact of these activities.
To be able to determine if the aquatic biodiversity is good or bad, scientifically based tools are needed. Peter is planning a quantitative review of existing literature as well as statistical models that will facilitate the development of tools that can be used in decisions in connection to dam removal and building. The models will be built on biological indicators. Peter comments:
- Fish and macroinvertebrate communities comprise organism groups with a wide range of environmental tolerances and preferences and are routinely used in the classification of the ecological status according to the Water Framework Directive. In riverine systems, these communities are strongly influenced by flow variables such as velocity and shear stress, with the main drivers related to substratum characteristics such as particle size, texture, and heterogeneity. Hence, these organism groups are recognized as good indicators of how human activities and infrastructure alters instream hydromorphology and should be ideal indicators to quantify dam effects on riverine systems.
As Peter recently received a grant for the quantitative review and development of the models, he now starts to plan actions toward that aim. Besides searching and extracting data from the existing literature on dams and dam removal, he plans to use statistical models to be able to see relationships that exist between data on different geographical parts of watercourses, and over time. That way, the models that Peter will develop will be robust and take into account the entire watercourse and its surrounding landscape, not just a certain part.
Before making decisions about dam removal, the effects this will have on the ecosystems along the waterway and over time, needs to be properly looked into. To also have a tool that allows you to quantify the effects, facilitates decision-making.
Building a dam has an effect on nature and biodiversity in the watercourse. Dams retain water in the impoundment and often reduce water downstream resulting in conditions that are completely different from the free-flowing water that in turn affects different living conditions for plants and animals. It is surely nothing unknown, and it should be just as obvious that the ecosystem is affected when you demolish a dam.
- Discrepancies exist between case studies. This limits our ability to make general predictions on the spatial scale, magnitude, trajectory, and duration of responses. By compiling the data from individual studies in a quantitative review of the existing literature the drivers of discrepancies and consistencies among studies can be identified.
The project is financed by fisheries conservation funds through the Swedish Agency for Marine and Water Management. Peter’s project runs between March 2023 and 2025.