Each spring, the streets of Northern New Mexico towns, including Taos, are littered with 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 taller than 70 feet 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, 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 piñón 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.
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 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.
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.
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.
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 No. 1 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. But a recent survey conducted in Taos found Siberian elms make up nearly 30 percent of the tree canopy there. Paul Bryan Jones, an arborist in Taos, said the benefits provided by the Siberian elms 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.
Jones said, "With climate change coming down the road, they may be an important tree to help with the shading and the wind breaks. ... We are going to have less and less water."
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 and the city's plumbers have been in a continual war removing the tree's invasive roots from sewer pipes.
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.
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.
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.
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.
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.
McDowell said it would be difficult to convince people to plant invasive species in the current climate. That could change.
Paul Schmitt, 67, who owns Sunsilk Landscaping and lives in Santa Fe, 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."