GREAT SAND DUNES NATIONAL PARK, CO — In the mountains of Great Sand Dunes National Park in the San Luis Valley just north of Alamosa, Medano Creek flows down into the valley. The river helps shape the dunes.
“A key piece of this is the role of water,” said Fred Bunch, chief of resource management at the park. Without the river, the dunes would blow away.
“We had to become advocates for the land,” he said. “This is some of the best natural water anywhere.”
But water in the park is in trouble. Ranchers in the valley to the east divert flows in Medano Creek, siphoning off a fifth of the water each year. And the aquatic life is suffering.
Like most rivers, this one is a sensitive environment. The life inside of it depends on its chemistry and flow.
It is currently filled with non-native fish originally brought to stock the river for fishing. They have taken over the river and beat out the native trout.
The National Park Service rangers are now planning to kill all of the fish in the river, including the native trout and the endangered Rio Grande Suckers. The trout is already on the list to become federally protected, according to the NPS’s website.
To empty the river of its fish, they will introduce Rotenone into the water. Rotenone is a natural poison that essentially causes the fish to suffocate. It doesn’t affect animals other than fish according to the Southern Regional Aquaculture Center.
However, the poison can be harmful to humans and other wildlife if not applied properly. If the NPS does everything properly, there will be no harm to the environment except for the mass die-off of fish.
The NPS plans to restock the river with the Rio Grande Cutthroat Trout after the river has detoxified, Bunch said.
Climate change will affect the river’s temperature. By 2060, the sand dunes could be up to eight degrees warmer said Bill Battaglin, a United States Geological Survey scientist. This will make the trout’s cold water habitat recede farther and farther up the mountain leaving them with less room to live and less natural aquatic habitat.
But, having the native trout instead of the imported ones will help the river’s ecosystem greatly, Bunch said. “As natural as possible is best.”