Region Faces Parched Future

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Bone dry springs.

Severe droughts.

Massive wildfires.

Violent storms.

Wilted wildflowers.

Welcome to climate change, Southwestern style.

Arizona climate researchers have finished several major studies predicting the impact of accelerating climate change on the Southwest — climate weirdness that looks a lot like the last few years.

Four recent studies from the climate research center at the University of Arizona have detailed a variety of impacts. That includes a study showing a perplexing shift in wildflowers, a shift to drier springs and more wildfires, the widespread decline of pinyon pines and reductions in the water flowing into reservoirs.

Taken together, the studies suggest that Payson’s success in winning rights to water from the Blue Ridge Reservoir may have come just in time to save Rim Country from the effects of what may evolve into an intensified struggle for water throughout the region.

One study predicted hotter, drier springs, according to computer modeling by UA Department of Geosciences researcher Stephanie McAfee.

A steady rise in global temperatures since the 1970s has already shifted the high-altitude jet stream to the north by more than 1,000 miles. That shift has dragged the winter and spring storm track with it. The change will result in fewer big winter storms in Arizona, Nevada, Utah, Southern California, Western Colorado and Western New Mexico, concluded McAfee.

As a result, April will likely become much drier. That could pose a big problem when it comes to wildfires, which pose the biggest danger to forested communities in May and June — normally the driest months of the year.

Most of the region’s big wildfires have taken place in June, just before the onset of the summer monsoon. McAfee’s study suggests the region may soon add April to its high-risk fire season.

McAfee said the region has already started to show the winter and spring changes due to global warming.

Her study relied on a statistical analysis that demonstrated that the steady northern shift of the storm track from 1978 to 1998 correlated with spring rainfall patterns.

Studies by the UA’s Tree Ring Research Laboratory headed by Tom Swetnam have also found that warm, dry springs lead to a big increase in wildfires. The tree ring lab uses the width of growth rings in trees to reconstruct past rainfall, year by year. They have pushed the record back nearly 1,000 years by taking cores from the largest trees, then added another 500 or 1,000 years by using big logs from trees used as roof beams in 800-year-old Indian ruins. Moreover, fires often leave scars also recorded in tree rings. Those tree records show that dry springs result in more frequent and larger fires.

Meanwhile, another study by UA researchers Sarah Kimball, D. Lawrence Venable and others published in Global Change Biology produced a seemingly contradictory result: cold-tolerating Sonoran Desert plants have actually gotten a boost from the warming trend.

Overall, the warming trend has resulted since 1982 in a significant decline in the number of winter annuals that produce the region’s intermittently spectacular wildflower displays.

However, the shift in the storm track that is resulting in more hot, dry springs has also started the winter storm season sooner — generally in November instead of December.

The researchers have been laboriously counting the number and diversity of wildflowers in an area near Tucson — including the most common showcase species like poppies and lupine.

They discovered that the most cold-tolerant wildflowers increased their germination rates, at the expense of the rest. Earlier work had shown that cold-tolerant annuals also do better on less water, which could account for the shift the researchers recorded.

The researchers said the findings demonstrated the complex and often unexpected way in which living things respond to big changes — like a shift in temperatures that triggers changes in the seasons.

In addition, UA researcher David Breshears and his colleagues have also documented a widespread decline in the number of pinyon pine — the scrubby, drought-tolerant pine tree that often grows at Payson’s elevation.

Pinyon pines have died off on some 2.5 million acres in the past few decades. The researchers blamed a decade of drought, record-high temperatures, a dwindling snowpack and other changes.

Other studies have predicted a 20 percent decline in flows in the Colorado River, with a 50 percent change that mammoth Lake Mead will go dry by 2020.

Comments

Tom Nye 4 years, 3 months ago

Study this. Global warming is a hoax!!!!!!!! These clowns can't tell what the weather will be in two wks but they want us to believe them when they tell us what will happen in twenty years, HA!! what a joke.

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