Each year many fish species, like salmon, make the 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 United States, there are an estimated 5 million stream-road crossings and roughly 90,000 dams, 85 percent 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.
In part of the Greater Yellowstone Ecosystem in Southwestern Montana, the US-191/MT-64 Wildlife & Transportation Assessment, conducted by the Center for Large Landscape Conservation and Montana State University’s Western Transportation Institute, found that of 53 surveyed culverts underneath US-191 and MT-64, 40 percent may not allow for the unimpeded passage of fish.
The Center’s work is part of a larger movement to not only connect landscapes, but also help ensure that waters are connected for fish and other aquatic species. In particular, the Gallatin River is known for healthy populations of several trout species including native Westslope cutthroat trout, which need to move be able to move freely to remain abundant and healthy.
“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 the Center.
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 Bozeman and West Yellowstone, further evaluation is needed according to Fairbank.
As the Center works with partners to make infrastructure improvements along US-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. In addition, larger culverts help communities be more resilient to climate change by preventing road flooding.
One of our partners, American Rivers, a national nonprofit dedicated to protecting and restoring river health, 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.
“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. “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.
“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.”
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 Center and American Rivers will be the beneficiaries of Wildlands, a music and charity event hosted by Outlaw Partners in Big Sky, Montana. 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 Center will use the proceeds to support continued efforts to establish wildlife crossings along US-191 with the goal of reconnecting fragmented habitat and improving road safety for people and wildlife alike.
A version of this article appeared in Explore Big Sky newspaper.
Top photo: Center for Large Landscape Conservation staff records data on two culverts as part of the 191 assessment. Credit: CLLC/Cole Oshiro-Leavitt
