Each spring the streets of Santa Fe are littered with pale, yellow pods, kicking up into the wind like a dense snow. They collect in gutters by the thousands, pool in stairwells, cling to spiderwebs and the underbelly of cars. Each tree can shed thousands of these seeds. Those that survive entrench themselves in the earth, absorbing the summer rain to sprout sturdy saplings that can grow over 70 feet tall with deep root systems that are the bane of homeowners, plumbers and city officials.
The New Mexico Department of Agriculture and U.S. Department of Agriculture have classified them as noxious weeds. The city of Santa Fe has had an active program for more than a decade to eradicate them.
But for all the hate, Santa Fe and many communities in New Mexico would have little shade without the dreaded Siberian elm. And now, as climate change increasingly makes the state hotter and drier, some researchers and arborists are rethinking the value of this hardy tree.
“It is a new world we live in, and elms are succeeding,” said Nate McDowell, a former Los Alamos National Laboratory scientist who led a Southwestern tree study that found that climate change could leave the high-desert mountains of New Mexico nearly bald, with the majority of piñon and juniper trees dying off by 2100 as a result of drought, heat and bark beetles.
“Do you really want to cut down something that is doing OK when other things are dying?” said McDowell, who is now with the Pacific Northwest National Laboratory studying the effects of climate change on tropical forests. “That’s a tough question, it’s a public question. … It is a cool question.”
It was a harsh shift of climate that brought the Siberian elm to New Mexico in the first place.
In the 1930s, the state’s eastern plains dried up and cracked, kicking up blinding, mile-wide and 1,500-foot-tall clouds of dirt. Cows died and crops refused to grow.
To ease the devastation of the Dust Bowl, former New Mexico Gov. Clyde Tingley, who later was chairman of the Albuquerque City Commission, found a solution to the shadeless, drought-prone corridors of his city in a Mongolian plant. Native to the Gobi Desert, it could thrive even when water was scarce and grow a lush canopy of foliage as a refuge to the desert sun.
He handed out the wrinkled, dime-sized seeds of Siberian elm trees to anyone who would plant them.
They grew fast and hardily, and by the 1970s, the trees had spread throughout the state, building colonies of elm forests in open spaces.
Many New Mexicans incorrectly refer to them as Chinese elms, a similar species not nearly as prevalent in the state.
Ben Wright, an arborist and chairman of the Taos Tree Board, said Siberian elms uniquely adapt to the Southwestern landscape, needing little space or water to grow, while able to withstand strong winds.
“In the West, it was introduced to solve problems,” he said. “As are many troublesome species.”
Wright has spent the last several years studying Siberian elms in New Mexico for his master’s degree at Oregon State University and has become a recognized expert on the tree. He says removing Siberian elms from Santa Fe would change the tree canopy dramatically.
“There are some places where the streets are lined with Siberian elm, and that is what is providing shade, so removing it is out of the question, not only because it is difficult, but because it is providing benefits,” he said. “You may think you don’t need it, but what nature and trees add to our lives is beyond comprehension.”
Wright began studying Siberian elms — their ecological characteristics and how they adapted to North America — because he was interested in why so many people seem to hate them. The trees make up a large portion of the overall tree canopy in the region, especially in Taos, where he lives, but people seem at odds with how to manage them.
“To me, it is the number one priority: How do we take care of the trees and the plants and the wildlife that exist alongside us in cities?” he said.
Tree studies are underway in a number of cities, including Santa Fe. But a recent survey conducted in Taos found Siberian elms make up nearly 30 percent of the tree canopy there. In Santa Fe, whole stretches of streets like Palace Avenue and Alameda Street are lined with them, turning the throughways into leafy tunnels.
Paul Bryan Jones, an arborist in Taos, said the benefits provided by the Siberian elms identified by Gov. Tingley may make them an important tree in the future as the planet continues to warm and retain higher levels of carbon dioxide. New Mexico is only expected to get hotter, drier and more prone to large-scale wildfires in the coming decades.
“I don’t tell people to get rid of them — thin them out, prune them,” Jones said. “There are a lot of environmental benefits to Siberian elm. … It’s a good tree, but it can get out of hand really fast.”
Because of their desert origins, Siberian elms also are uniquely equipped for drought. The stomata, or pores, in their leaves have evolved to close under dry conditions, allowing the trees to hold in moisture and survive when water is scarce. This water retention makes the species more resistant to forest fires, and the elms can often survive a burn. Their leaves also efficiently trap carbon dioxide and particulate matter, purifying and cooling the air around them.
“With climate change coming down the road, they may be an important tree to help with the shading and the wind breaks,” Jones said. “… Because we are going to have less and less water.”
You can even eat them.
Wright and Jones said the seeds, which when eaten raw taste sweet and a little like roasted sunflower seeds, could be harvested as a future food source. They suggest composting the seeds or using them in salads. Wright says they’re best when still green.
But for more than a decade, the city of Santa Fe Parks and Recreation Department has been working to eliminate Siberian elm trees — classified as a noxious plant — from the city landscape. And the city’s plumbers have been in a continual war removing the tree’s invasive roots from sewer pipes.
Joe Bernal, a Santa Fe plumber, says he has received calls almost every day since he started his business, Drain Surgeon, 20 years ago, about roots backing up septic systems and blocking toilets.
“Eighty percent of my calls that do involve roots, it is usually the elm,” he said.
“Sometimes the roots get so big that it punctures the line,” he said. “Some people just let it grow and let it grow. It’s just basically a big, fat branch in the sewer line.”
Most people with roots in their pipes have to have them cut back annually, but eventually the plant will stop growing back, he said. These problems are concentrated in the older part of the Santa Fe, according to Bernal, who said the aging pipe systems were sealed with lead or concrete and are easier for the elm roots to penetrate. In the newer parts of town, sewage lines are made from plastic and don’t cause as many issues, he said.
Richard Thompson, Santa Fe Parks and Recreation Division director, said the trees suck water out of the soil, outcompete native species, produce large amounts of pollen and seeds, obscure visibility on road medians and destroy infrastructure like sidewalks and waterlines.
“What I would like to see is eradication of the species within the city limits and replacement with native and adaptive trees that don’t escape cultivation,” he said.
He said the trees are “better suited to take on the changes in climate, i.e. drought, extreme freezing temps, extreme hot,” but said this doesn’t outweigh their destructive qualities.
Thompson says the city has been cutting down the elms for at least the last 10 years — using more funds to eradicate them than any other weed — but without out any noticeable decline in the tree population. Along the Santa Fe River, some areas have been noticeably thinned of the elms, leaving flattened stumps and hollowed dirt on the grass where large trees had been. Younger trees have been thinned at the stump, but tiny new sprouts can be seen growing from the base.
The U.S. Department of Agriculture’s instructions for removing the invasive tree read like a manual for eradicating a biblical plague, saying even chopping them down, chemically treating them and burning the trees may not be sufficient; goats are even suggested as a potential, last-ditch aid to eat the young trees.
Thompson says the city doesn’t use chemicals because there is public opposition to herbicide treatment, making eradication even more difficult — and unlikely. “Every day it gets worse,” he said.
The management of “the Siberian elm in the face of global warming, that is a tough question,” he said. “But we need to maintain our native forest as long as we can. And then we need to seek adaptable species that don’t escape cultivation.”
Wright agreed that the Siberian elm is destructive and can outcompete native species, but he said he would be “wary of suggesting that it is taking water destined for other plants or people.”
Sanna Sevanto, a tree physiologist at Los Alamos National Laboratory, called the elms “a double-edged sword” because they grow quickly, use a lot of water but also provide lush, shade canopies.
Because of their wide leaves, they also “release more water vapor into the atmosphere than areas like grasslands, and that basically maintains the patterns of local rainfall better — that is the part where they are good,” she said.
Sevanto, who also participated in the Southwestern forest ecology study with McDowell, said over the next 100 years temperatures are expected to be 9 degrees Fahrenheit higher year-round, enough heat to significantly shorten the winters and significantly decrease snowpack. Climate projections also estimate New Mexico will have half its current levels of moisture, which was also modeled in the study.
Though the study did not include Siberian elms, Sevanto said that under such conditions, elm leaves would be less durable than piñon needles, but older trees would still be able to survive. The roots below ground could hunt for water, allowing the elms to eventually sprout new saplings when there is rainfall.
“If it was a big tree and had tapped into a reserve of groundwater that is not sensitive to changes in precipitation, it would do OK,” she said.
McDowell said to really look at how well the elms would do in the next 100 years or so, scientists would have to look at the amount of carbon they absorb in contrast to water, as well as the number of displaced species, and weigh the costs.
As a graduate student, McDowell saw a lecture with renowned environmental biologist Harold Mooney, who posed this question about invasive species, like the elms: Do we “fight them at the beaches or let the new world begin?”
Fundamentally, Mooney was equating invasive species to the unstoppable evolution of nature as a result of humans’ impact within it, McDowell said.
“Do we want to capitalize on these invasive species?” he said.
Through his research, McDowell discovered that Santa Fe is likely to return to a more barren landscape, as a result of climate change, than it had a century ago. In the 1900s, he said, Santa Fe was a grassland, and despite the city having developed thick foliage since then, over the next hundred years, “we are going to keep losing [trees] long past what there was in 1900s.”
McDowell said it would be difficult to convince people to plant invasive species in the current climate. But that could change.
Siberian elms are “not going to be a panacea to solve carbon building in the atmosphere, but it might be something that people learn to like living around,” he said. “Because it may be one of the few things that lasts.”
Paul Schmitt, 67, who owns Sunsilk Landscaping and lives on Allendale Street in Santa Fe, an area populated with a variety of trees, pointed to a Siberian elm in his neighbor’s yard poking out over an adobe wall.
“It’s been pruned and cleaned out, and when it is cleaned out they are beautiful trees,” he said. Schmitt also has two large Siberian elms crowning in his backyard, an area otherwise lush with greenery and just-blooming peonies. The elms “provide a block from the western sun and cool the yard. They are tough, they are resilient. … You have to nurture it to get it to be really beautiful, but when you do, they are just stupendous.”
He said he has refused to remove them from people’s yards on landscaping jobs, and instead has told them, “We are going to clean it up.”
“And they come back and thank me,” Schmitt said.
Contact Rebecca Moss at 505-986-3011 or firstname.lastname@example.org.