By Gabrielle Gasser GUEST COLUMNIST
Each year many fish species, like salmon, make an arduous journey upstream to the headwaters of rivers to spawn, laying thousands of eggs to ensure the continuation of their species. However, not all fish are successful. Some encounter dams too high to jump over, or culverts too shallow to swim through. Others may find that the water temperature at their favorite historical spawning ground is too warm, or predators are too easily able to eat them or their eggs.
In the U.S., there are an estimated five million stream-road crossings and roughly 90,000 dams, 85% of which are over 50 years old and no longer serve a purpose. Each one of these crossings and dams presents a barrier to aquatic connectivity or the ability of fish and other aquatic organisms and processes to move freely.
“So much of our work is geared towards making rivers more resilient in the face of climate change,” said Scott Bosse, northern Rockies regional director at American Rivers, a national nonprofit dedicated to protecting and restoring river health. “The number one way to make rivers more resilient to climate change is to reconnect them by removing dams and reconnecting them to their floodplains.”
The movement of fish and other aquatic organisms is critical to biological diversity, healthy populations and accommodating shifting habitat ranges due to climate change. Without free-flowing rivers, aquatic and terrestrial organisms can’t access fragmented habitats, flooding can worsen and the impact of wildfires increases.
American Rivers is currently working towards its goal of removing 30,000 dams, or a third of the total dams in the U.S., by the year 2050. Removing these barriers will restore connectivity allowing both aquatic and terrestrial species to thrive and increasing the landscape’s resilience to climate change.
“Connectivity is about maintaining and restoring the pathways that animals need at various stages of their lives,” Bosse said. “Animals always have to move, whether it’s in the water or on land, and we need to find out where their movement occurs and preserve those corridors.”
In southwestern Montana, the U.S. 191/MT 64 Wildlife & Transportation Assessment, conducted by the Bozeman-based nonprofit Center for Large Landscape Conservation and Montana State University’s Western Transportation Institute, found that of 53 surveyed culverts underneath U.S. Highway 191 and Montana Highway 64 (Lone Mountain Trail), 40% may not allow for the unimpeded passage of fish.
“Improving culverts to ensure aquatic and riparian connectivity and aquatic organism passage can be hugely beneficial and is one of the best strategies to combat species decline and biodiversity decline based on climate change and shifting habitat needs and ranges,” said Liz Fairbank, road ecologist with CLLC.
As CLLC works with partners to make infrastructure improvements along U.S. 191 with a focus on preventing wildlife-vehicle collisions with terrestrial species, culverts will also be an important piece of the efforts to improve habitat connectivity and create more wildlife crossings.
There are some cases where a barrier is intentional to protect native species from hybridization or competition with non-native species. However, on the stretch of road between Four Corners and West Yellowstone, further evaluation is needed according to Fairbank.
“Given that the Gallatin River is a world-class fishery, and a huge amount of our Gallatin Valley recreation and tourism economy is based on it, aquatic health and connectivity is definitely critical in that corridor,” Fairbank said.
Connectivity wouldn’t just benefit fish and riparian habitats; terrestrial species also frequently use riparian areas for movement.
“When we restore aquatic connectivity, we also restore terrestrial connectivity,” Bosse said. Removing dams provides dual benefits to both the fish swimming in the river and the terrestrial species that rely on a thriving riparian habitat for food and shelter.
This August, the CLLC and American Rivers will be the beneficiaries of Wildlands, a music and charity event hosted by Outlaw Partners, the publisher of Explore Big Sky. Both organizations hope to use proceeds raised at the event, headlined by Dave Matthews, to improve habitat connectivity and riparian health in the region.
American Rivers plans to use the proceeds from Wildlands to launch a dam removal program in the Northern Rockies, including areas in Montana, with the goal of restoring aquatic connectivity and removing old dams that no longer serve a valuable purpose.
The CLLC will use the proceeds to support continued efforts to establish wildlife crossings along U.S. 191 with the goal of reconnecting fragmented habitat and improving road safety for people and wildlife alike.
Gabrielle Gasser is the communications and development coordinator for Center for Large Landscape Conservation.
