Sunday, October 17, 2004
Mesa in the Jemez Gives Insight Into Climate's Impact on Land
By John Fleck
Journal Staff Writer
FRIJOLITO MESA Craig Allen's trees are dying.
The ponderosa pines are gone completely from this patch of wilderness, and piñon are not far behind.
Insects have been the executioners, but warming temperatures and drought appear to have pronounced the death sentence, pushing trees to the brink for the bugs to finish off.
Allen, a 46-year-old federal biologist, has been studying the Jemez Mountains for more than two decades. He counts and measures the trees, tracks the growing grass and measures the dirt washing down the gullies, all in an effort to understand the complex interplay between climate and landscape.
Over the past two years, the one-two punch of warm weather and drought has brought extraordinary change.
"Fall of '02 is when they started to die," Allen explained on a recent visit as he took a group of federal scientists on a tour of this morgue of dead trees.
Mountain ecosystems are a canary in the climate-change coal mine, tough neighborhoods where plants and animals live at the margins and can easily be pushed over the edge when living conditions change.
A loose-knit group of scientists interested in the issue recently followed Allen up a steep trail into the wilderness, to see his field sites firsthand and talk about how mountain ecosystems throughout the western United States are changing.
Working under the auspices of the federally funded Western Mountain Initiative, the scientists have witnessed glaciers shrink and seedling trees begin appearing above what used to be timberline.
On a cool fall day recently, Allen bounded up the Bandelier National Monument trail leading from the visitors' center in Frijoles Canyon to the wilderness mesa to the south.
Frijolito Mesa, 6,500 feet in elevation, is one of the finger-like mesas that make up the Pajarito Plateau. To the west, the volcanic Valles Caldera rises to more than 10,000 feet, home to high conifer forests.
Frijolito Mesa spans the tenuous boundary where lowland piñon-juniper and upland conifer meet.
This is Allen's turf.
Gifted with boyish charm and a storyteller's knack, Allen moves easily among climatology, biology, archaeology and history, taking from each to piece together what has happened here over the centuries.
Living through the vagaries of weather one year at a time, it is easy to miss the big picture. One year is wet, the next dry, the next cold or warm it might seem random.
But if you take the long view, patterns begin to emerge, decades at a time when things tend to be wetter or drier than average.
Landscape embodies the long view. Trees grow and gullies form over decades. Plants spread up and down mountain sides depending on long-term climate variations.
Allen first came to the Jemez Mountains in 1979 and has been here pretty much ever since, first as a graduate student and then as a federal research scientist for the National Park Service and the U.S. Geological Survey's Jemez Mountains Field Station.
The drought has been, from a scientific perspective, Allen's great good fortune.
The period from 1978 to 1995 was wet. "As wet," he said, "if not wetter than any time period in the last thousand years."
Then came the winter of 1995-96 "a winter that was really snowless," Allen said. The following spring, the massive Dome Fire burned 16,000 acres, a hot "crown fire" that flashed through the high forest treetops, introducing firefighters to a type of fire they had not previously had to deal with.
The climate seesaw seemed to have tipped. As Allen watched, the Pajarito Plateau began to dry up.
Allen had already hunted down every bit of data he could to try to understand past droughts, from tree rings and historical photos to counting the carcasses of dead trees left by the drought of the 1950s.
What he had studied from a distance he could now watch happening in real time.
The effects of drought built steadily until they exploded across the mesa in 2002 after one of the driest winters on record. Trees pushed to the edge by the accumulated stress of drought died.
Drive most anywhere across northern New Mexico and you will see the dead piñons in the lower elevation and dying ponderosa and other conifers in the high country.
"The trees are what people notice and see," Allen explained.
But more subtle evidence is everywhere grasses struggling to survive, new flowering plants creeping in to fill the niche vacated by the drought-stressed collapse.
Much of what Allen is seeing today is similar to what happened in the 1950s but more extreme.
A look at weather records suggests an explanation. In addition to being drier, it is warmer. Globally, the four warmest years since the 1880s the earliest for which reliable thermometer records are available have all come during the current drought.
Locally, the pattern is the same. Weather records on the Pajarito Plateau only go back to the 1940s, but four of the 10 warmest years have come since 2000.
Most climate scientists think humans, by dumping greenhouse gases into the atmosphere from the exhaust pipes of our cars and power plants, are to blame for the warming.
Whatever the cause, the effects are being felt on the Pajarito Plateau.
Warmer weather means that whatever precipitation falls evaporates more quickly, leaving less water for the plants, Allen said. Warm weather also favors the bark beetles that swarm the woodlands and kill off drought-stressed trees, according to Allen.
Allen's wilderness is a microcosm of what is happening throughout the West, and there is no way to stop it, scientists say.
"There appears to be little or nothing that managers can do at this time to prevent or influence the course of this mortality event," a group of scientists led by Colorado State University researcher William Romme wrote in a letter to federal land managers last December. "Extensive mortality probably will continue until precipitation and temperatures return to more 'normal' conditions in the Southwest."
When that might happen is more guesswork than science. The deepest part of the drought of the '50s lasted more than a decade, and climate scientists expect the global warming trend to continue indefinitely.
Up on the Pajarito Plateau, Allen is doing his best to document and understand the changes.
He has a couple of acres on Frijolito Mesa that he and his colleagues have been intensely monitoring since 1993 measuring the soil runoff and counting the plants.
When he started, it was mostly piñon-juniper, with a single ponderosa, a head-high sapling.
The ponderosa is gone, as are most of piñon. In fact, little remains the same as when the study started a little more than a decade ago. "It's actually disorienting to me to walk through this watershed," Allen said as he lead his Western Mountain Initiative colleagues on a tour of the field site.
In the shadow of a dead piñon, Allen pointed to a small oak tree, an immigrant species showing up a lot these days in places where it did not formerly thrive.
"I think they're the future of this landscape," he said. "They're survivors."