Boulder’s semi-arid climate puts it ever at risk of becoming desert. Today, some land around town — about a thousand of Boulder’s 16,000 agricultural acres — is succumbing to that risk. Unless we intervene, acres available to local farmers could drastically decrease in the coming years and decades.
Solutions, none of them easy, range from increasing biodiversity and compost application, to swapping one rodent for another.
“We might think of desertification as a challenge faced in Africa or other places,” said Brett KenCairn, Boulder’s senior policy advisor for climate and resilience. “But really it’s indicative of a pattern of human land use that has existed for thousands of years.”
Farming is to blame for much desertification around the world. Boulder is no exception. When humans set forth to farm, they clear away native vegetation to impregnate the land with their desired crops. Often, those desired crops are not native and, in dryland climates like Boulder’s, require more water than the landscape can naturally provide. This necessitates dams and ditches, hoses and sprinklers. If anything stops the flow of those ditches and hoses, problems arise. Problems are arising.
“There’s climatic change now taking place that’s going to disrupt systems that worked okay for several generations,” KenCairn said.
Boulder farmers historically enjoyed a summer monsoon rain cycle. Despite planting crops that needed more water than native plants, summer rains quenched the introduced plants’ thirst. But not including this year and part of last, these rainstorms have tapered considerably, meaning fields around Boulder could be turning to desert unless they’re transitioned to closer resemble their roots.
The demise of the Bennett property, now desert-like
Smooth Bromegrass is one of Boulder farmers’ desired crops — used for hay — facing an uncertain future. Planted because of its high yield per acre, it is a cool season grass that’s “reliant on irrigation water,” said Lauren Kolb, Boulder’s senior agricultural program manager. If the weather gets too hot in the summer, Bromegrass goes dormant.
“If we have a spring like this one where we don’t really have precipitation and then it gets really hot, we have yield decreases of 50 to 80 percent,” Kolb said. “That’s where [Open Space and Mountain Parks] is really working on diversification in those fields.”
Diversification means seeding fields with more native grasses — like Big Bluestem or Sudan Grass — that have a better chance of handling Boulder’s rising summer heat. Without such adaptation, crisis awaits.
Imagine a Boulder field of Bromegrass where all vegetation adapted to our semi-arid climate has been removed. On this field, cattle nibble the grass, dormant in the summer heat, to nubs. Seeing a field now comprised of mostly dirt, prairie dogs, whose preferred habitat is flat, dry, sparsely vegetated land, move in.
These small, chirping rodents aid cattle in their decimation of the last Bromegrass stands and soon there’s nothing holding down the soil.
Now here comes the wind.
And there goes the soil.
This is the story of the Bennett property, a 103-acre parcel north of town purchased by OSMP in 2007. In 2014, after overgrazing by cattle and prairie dogs, a wind event similar to what fanned the Marshall Fire “basically blew the entire topsoil from that property east,” KenCarin said. He added that a fence-line was completely buried “like in the Dust Bowl.”
“Once that happens,” KenCairn said, “once you lose that soil and don’t have any vegetative cover, you have desert.”
As is the case with much of the 16,000 agricultural acres of Boulder open space, the Bennett property was leased to a cattle farmer. The invasion of prairie dogs and subsequent soil loss led that farmer to quit the business.
“Most of her properties ended up getting prairie dogs on them,” Kolb said. “She ended up selling her cattle and moving out of state.”
Prairie dogs maintain a desert status quo
Winter wind events will accelerate the transition to desert on Boulder properties not held down by plants. The Bennett parcel is a warning. According to KenCairn, the property is unlikely to naturally recover unless there are several consecutive wet years, something that’s becoming more improbable with climate change.
“Now we have a big hill to climb to get that property back to a place where it’s ecologically stable and self-sustaining,” KenCairn said.
The city is trying to climb that hill, however, because as Kolb said, “we’ve been trusted to keep these sites in perpetuity.”
“It’s like ‘Oh my gosh, why spend all this time here?’” Kolb said, acknowledging the energy investment. “But we own [the property], so [the question is]: How do we best hand it forward to the next generation? I think it’s by making interventions now.”
Both Kolb and KenCairn agreed interventions are necessary, and sooner rather than later, because when land has become as barren as the Bennett property, not only will it not recover on its own but “it’s only going to get worse,” Kolb said. “And as stewards, it doesn’t feel good to throw up your hands and walk away.”
But the prairie dogs aren’t giving up their new real estate willingly. Whenever KenCairn and Kolb apply compost and reseed — in hopes of revitalizing the land and holding down what’s left of the soil — prairie dogs eat what’s been planted.
“We’ve tried to [rejuvenate the system] in the context of allowing prairie dogs to remain on the site,” KenCairn said. “But we can’t seem to get momentum reestablished in the system sufficiently to not keep losing it.”
If the property is going to step back from the brink of desert and return to a place enjoyed by cattle and wildlife — elk and raptors used to frequent the area — the dogs have to go.
“Right now, we’re discussing either removing them in 2023 or 2024,” Kolb said. “That will make things a lot easier because there won’t be that constant grazing pressure.”
Beavers to the rescue
Proactive measures should still be taken on land that hasn’t yet arrived at the dire state of the Bennett property. As Kolb said, reintroducing more native vegetation is important. For KenCairn, the priority is water, getting water back into the land.
“Part of the reason we have these increasingly volatile landscapes is that they don’t hold water anymore,” KenCairn said.
For a lesson in how to put water back in the land, look no further than a flat-tailed, waddling rodent with endlessly growing teeth.
In the 1800s, trappers killed hundreds of millions of beavers in North America, shipping furs to cities where pelt top hats were all the rage. In doing away with these natural hydrologists, trappers caused our continent to dry out.
When beavers build a dam in a waterway, water flows from the established creekbed onto the surrounding floodplain. This creates wetlands. Not only are these wetlands havens for wildlife, they also inject water into the ground below, saturating the landscape. Wet landscapes don’t blow away, or burn with any vigor.
In the time of Lewis and Clark, beavers dammed the same streams over and over, creating links of wetlands. What we think of as a picturesque mountain stream is really a post-trapper mountain stream. A healthier stream would be damned into a series of pools and marshes.
“We’re going to have to start acting like beavers,” KenCairn said. “And, where we can, reintroducing beavers.”
Cool Boulder opportunities
Acting like beavers means building beaver-like dams. Starting next spring, Boulder’s residents will have the opportunity to do just that. Through Cool Boulder‘s Absorbent Landscape campaign, those interested can help build “low tech, hand-tool based water retention structures” that are currently used on the western slope and in New Mexico.
“We’re starting to realize ‘Oh, we’re kind of living in desert conditions, we need to try that too,’” KenCairn said of looking south for water management tips. As the climate changes, Boulder’s weather will begin mimicking Albuquerque of old.
Another benefit of beavers and beaver-like dams is their fire mitigation potential – pertinent in an area where fire risk is increasing. Not only would dams restore water to the landscape, the produced wetlands would act as a fire break. And after a fire, beaver dams provide erosion control and filter sediment from water. They also slow floodwaters, an asset to Boulder, whose flood risk impresses the rest of Colorado.
Historically, however, beavers don’t have many fans. As humans encroached on their habitat, their dams created wetlands on roads and in basements. They also built in irrigation ditches.
“A lot of people don’t like beavers, ranchers specifically,” Kolb said. “Boulder County and other places that have infrastructure, for a beaver dam to work the way you want it to, it has to be in the right place.”
But where we have altered the landscape to put ourselves in a climate-changing bind, beavers could help undo some of that damage. If we let them.
In 2017, Boulder County and the City of Boulder funded a study to see if we could restore beavers to this area. We can, the authors concluded, and we should.
Some have already been reintroduced in Caribou Ranch.