Losing our natural landscape to invasive species

Invasive species are the second biggest threat to biodiversity, preceded only by habitat loss, according to Colorado Parks and Wildlife. Invasive plants are spread by natural forces, such as wind and wildfire, and largely by unknowing humans.

Dr. David Anderson, program director and chief scientist of the Colorado Natural Heritage Program at Colorado State University in Fort Collins, says losing natural landscapes to invasive species impacts more than just the food web.

“The value of biodiversity transcends all aspects of our life,” said Dr. Anderson. “It provides the ecosystem services we need, clean water and clean air, holds our soil together, and provides food and medicines. It provides an intrinsic joy to everybody because it’s what we need to persist on this planet.”

Colorado’s wealth of natural resources is a crucial part of the ecosystems they inhabit. One public scourge, commonly known as cheatgrass, is destroying sagebrush shrublands up and down the state. According to the Colorado Weed Management Association, Bromus tectorum first appeared in Colorado in 1892. Since then, it has spread uncontrollably, to the point where eradicating it may no longer be possible.

The native animals that call the shrublands home, including mule deer, elk, and the pygmy rabbit, all depend on the natural order for food and shelter. The delicate balance in these ecosystems, already disturbed by cheatgrass, is at greater risk when irresponsible or uninformed recreators enter the picture. A cigarette butt, a stray coal from a campfire, or a seed on the bottom of a boot can all pose a significant threat.

“The invasion of exotic annual grasses, especially cheatgrass, into those systems, has changed the fire regime dramatically. They’re causing them to burn frequently and making them very susceptible to fire,” explained Dr. Anderson. “And those systems have not evolved with fire the way that others have in Colorado so when they burn frequently, the sagebrush shrublands just can’t handle it. They don’t stick around and those landscapes might transform into a completely exotic annual grass-dominated landscape.”

One conduit for invasive species is tourism. While tourism and outdoor recreation bring in billions of dollars for Colorado each year, they also come with significant risks.

One easily recognizable example is the European zebra mussel. Originally brought to the U.S. on the hulls of transoceanic ships, these aquatic invaders have spread across the continental U.S. on recreational boats. They outcompete native species and clog pipes and dams. The problem has become so severe that Colorado Parks and Wildlife recently drained Highline Lake in an attempt to eradicate them.

Scott Woodall, Rangeland Program Manager at the White River National Forest, emphasizes it’s not just tourists who are spreading invasive species.

“I think even those of us who work in the forest have to be cognizant of where we’ve been and when we walk through a field of invasive species to make sure we brush off our clothes and boots. It’s something to always be mindful about, regardless of where you’re from or how often you’re here,” said Woodall.

The best way to combat the spread of invasive species is through a comprehensive approach to prevention. Tourists and residents alike are encouraged to take precautions by cleaning their boots, gear, pets, and tires to avoid spreading seeds.

The White River National Forest hands out noxious weed pamphlets and is looking at putting brushes at trailheads so hikers can brush off their boots in case of unwanted guests.

“We do a lot of prevention work as far as an invasive species goes, and we do a lot of preventive work to educate the public. I know we post weed information on the kiosk, at trailheads. We require weed-free hay for those using horses in the forest,” Woodall said.

The rangeland program manager said they want to set up stations at trailheads where people can brush off their boots, as invasive species can spread when seeds get caught in shoelaces, pants, legs, and boots.

Prevention also relies heavily on accurate and timely information. The Colorado Department of Agriculture and CPW provide in-depth, up-to-date data on the severity and location of invasive species across the state.