Effects of beaver dams on low-flow hydrology, temperature, and fish movement in Minnesota Lake Superior Tributaries

Presented by
Dr. Karen Gran
Professor, Dept. of Earth and Environmental Sciences, UMD

Josh Dumke
Senior Research Scientist, UMD NRRI (Natural Resources Research Inst.) 

Wednesday, June 1, 2022   6:30 PM
Duluth Town Hall, 6092 Homestead Road

A description of the presentation:

This presentation will cover results from a 2-year study funded by Minnesota Sea Grant in the Knife and French Rivers, providing more data to help with trout management in North Shore streams. Their research team got involved in looking at the impacts of beavers on hydrology and fish movement in the Knife River when the AKRW brought forward their concerns about potential unintended consequences of removing beaver dams for steelhead passage. 

Presentation Abstract:

Beaver dams are ubiquitous in streams in northeastern Minnesota, with fundamental impacts to the hydrology of the systems. Beaver are actively removed from mainstem channels of the Knife River to improve steelhead passage, but the potential implications of this management action on low-flow discharge and temperature are not well-known. Our study was designed to monitor 8 subbasins (4 pairs) in the Knife River watershed over the course of two years. Beaver were present in all subbasins in year 1 and were removed from one subbasin in each of the 4 pairs in year 2, setting up a short-term BACI (Before-After-Control-Impact) study to better understand the impact of beaver dam removal on low-flow hydrology. A parallel study assessed the ability of fish to swim past low-head (less than 3 ft tall) beaver dams in the Knife and the French Rivers. Fish were captured around 8 beaver dams and 4 riffles (acting as controls), marked with a visible implant elastomer tag, and recaptured several weeks later. We recaptured 20% of 1,200 marked fish and found that fish had passed up and downstream of dams. Samples sizes of moving fish were low, but we were still able to determine that fish movement was correlated to flow conditions at each dam. 

Dr. Julie Etterson Presentation: 

Minnesota Million - Planning our future forests

Monday, April 11, 2022     4-6 pm

A description of her presentation:

Coastal forests of Lake Superior have already warmed 0.6–1.7°C, which translates into a spatial climate shift of ~240 km, to conditions that formerly occurred near Minneapolis/St. Paul. This warming is causing widespread declines of common boreal tree species. Tree mortality leaves gaps that are susceptible to invasion which reduces opportunities for native trees to move to cooler refuges. Human intervention, such as “assisted migration” (intentionally moving plants north with climate change), could help smooth the transition to new resilient forest communities. In this presentation, I will describe a 10-year experiment with The Nature Conservancy (TNC) to test the efficacy of this strategy. I will also describe a major impediment to widespread implementation of assisted migration which is simply that we do not grow enough climate-appropriate seedlings. To remedy this, I collaborated with the Northeast Regional Sustainable Development Partnership and TNC to pilot a program where small-scale farmers in northeastern MN raised tree seedlings to be sold to restoration planters, benefiting local farmers now, and local ecosystems in the future. This pilot project is on a successful trajectory that will bolster the pipeline of seedling availability while also diversifying the agronomic economy in NE MN. We are now in the process of planning a similar project for all forested regions of the state which we are calling "Minnesota Million" that will pave the way to more reliance forests while also sequestering 1.5 million metric tonnes of carbon dioxide equivalents annually. 

Links to videos shown in her presentation:
Tree-planting project aims to help northern Minnesota forests adapt to climate change

Building Capacity for Reforestation

For more information, contact Dr. Julie Etterson at jetterso@d.umn.edu