The Abajo Mountains “Old Tree Story”

by April Baisan, Edu. Coordinator, Canyon Country Discovery Center
In 2015, scientists from the University of Arizona, Tucson, chanced upon a living Douglas Fir tree on the lower slopes of the northwest side of the Abajo Mountains, that, when analyzed, proved to be 800 years old, from the AD 1200s.
This is the oldest known living tree in the Four Corners area—a tree that started growing around the time that the Ancestral Pueblo people left the area completely, and around the time Genghis Khan and Marco Polo were in action in Europe and Asia.
The scientists figured out the age of the tree by counting its growth rings.
Scientists such as these are called dendrochronologists. “Dendro” means “branching” or “tree-like,” and “chronology” means “the study of time.” Hence, the study of climatic, geologic or other events over time, using tree “growth” rings as an indicator.
The width of tree rings shows the amount of tree growth in each year, which is used as a measure of the amount of precipitation for that year.
Knowing the amount of precipitation allows scientists to “reconstruct” (estimate) streamflow amounts for rivers in the same drainage (watershed) as the tree, from the past, before there were any measuring devices in place. This has great implications for water management in a fairly dry area like the American West.
In the Abajos, the dendrochronologists from the UofA Laboratory of Tree Ring Research have been at work since 2004. During this time they also analyzed rings from downed logs (dead trees, but that still have growth rings intact enough, i.e., not rotted away to provide good information) and identified older dates, including an oldest tree ring date from the AD 300’s.
This and a few similarly dated downed trees from near Price are the oldest known tree rings showing ancient climate (precipitation) information from the entire Upper Colorado River Basin, from Glen Canyon Dam upriver into Colorado and Wyoming.
Streamflow histories over many hundreds of years, such as we now have for the Colorado River, are much more valuable than for just 20 or even a few hundred years. Until the research was fully analyzed and published in 2007, the climate history of this area “only” went back into the AD 1500s.
As is well known, policy makers and scientists drew up the Colorado River Watershed Pact in 1922 which allocated water to seven western states and Mexico. Unfortunately it was based on only 20 years of actual streamflow data — data which happened to be much higher than the average, but they didn’t know this at the time.
As the 1900s came to an end and 100 years of measured streamflow data became available, as well as some 400 years of tree ring data, it became clear that the Colorado River Watershed is seriously over-allocated to the seven states, as well as Mexico.
Scientists had seen evidence from the 1500s to the 1900s that drought occurred, but until 2007, no one knew how bad it could be. The headline news in 2007 was the AD 1100’s “Mega-drought” of about 50 years. Contributions from other scientists showed that this drought happened not just in the Upper Colorado River Basin, but in California also, and probably in between.
The take-home here is that drought is normal for the West, and that a West-wide 50-year drought can make droughts of a few years or a decade, bad enough as they are, pale in comparison.
Monticello and surrounding communities can be proud of these ancient trees nearby, living and dead on the ground, that are assisting climate and ecosystem scientists as well as water planners all around the West in managing and allocating water resources for the future.
Even without government mandate, as responsible community members of the Colorado River Watershed during the current drought and beyond, we can use the scientific information in choosing to use our stored water (underground as well as above ground) wisely.
Let the rain wash your car (become more tolerant of a dusty car in between rains), use drought-tolerant landscaping and set up graywater systems (see the Utah Greywater Code) for watering a few shade trees in your yard.
Smart gardening and smart overall water use costs little but will benefit us down the road, dusty as it may be!