News
ISPE Faculty Spotlight
Dave Breshears: on the dusty trail of drought and die-offs
March 2, 2006
By Stephanie Doster
Dave Breshears
Dave Breshears knows stress.
From his office window at Los Alamos National Laboratory in New Mexico, where he used to work, Breshears watched as water stress—drought—and bugs wiped out nearly three football fields worth of piñon pine (Pinus edulis) in less than two years.
The rapid die-off, the focus of a study published by Breshears and his team in October 2005 in the journal Proceedings of the National Academy of Sciences, highlights the importance of his research: understanding how fast vegetation can change or succumb in ecosystems where water is limited.
His work can help scientists get a feel for “the potential for how big these die-offs can be,” especially if increasing temperatures and lower precipitation—conditions forecast by computer climate simulations—persist, said Breshears, a University of Arizona professor of natural resources and Institute for the Study of Planet Earth (ISPE) faculty member.
In his recent study, Breshears found that unusually high temperatures were associated with the drought that sparked the tree die-off outside his office and across thousands of acres throughout the Southwest. Bark beetles, which soon over ran and feasted on the susceptible, stressed trees, sounded the death knell.
The die-off was more extensive than one seen in the 1950s; even piñons in higher, typically wetter elevations could not withstand the recent dry spell, suggesting warmer temperatures played a role. “Scientists didn’t have very good information about how big and fast these systems can change” before the study, he said. “Just in a year or two we get all of this mortality. Drought can really whack these systems. We’re seeing wholesale mortality up and down the gradient. The assumption is it could be partly due to temperatures.” Breshears said the die-off likely will lead to runoff and erosion and will alter the ecosystem in a number of ways for decades. With such a hole in the piñon population, Breshears said he also expects a drastic cut in the production of piñon nuts, a food source for birds, small mammals, and people.
Most of Breshears’ work focuses on ecosystems within the grassland-forest continuum, in which the relative proportions of woody and herbaceous plants vary along habitat gradients that include grasslands, shrublands, savannas, woodlands, and forests.
He plugs in numbers and analyzes data in his Terrestrial Ecology Laboratory in Biosciences East, where he and his four-member team strive to develop new ways of measuring, understanding, and predicting hydrological and ecological processes—the relationship between runoff and where plants grow, for example—for water-limited ecosystems.
His work is highly interdisciplinary, tying together ecology, hydrology, geosciences, and atmospheric sciences to tackle public interest issues related to land use, pollution and soil contaminants, and global change.
Breshears is drawn to ecosystem issues that touch on “big, fast, potentially high-impact and long-lasting changes in the ecosystem,” he said. These include fire and drought—two forces that can wipe out trees and ground cover—and water and wind erosion. Erosion has a hand in a number of processes, from moving contaminants in the soil to uncovering archaeological sites to prohibiting the reestablishment of plants in a particular area.
“One question that I don’t think others have answered very well yet is, in any given system, how much of the overall erosion is driven by wind compared to how much is driven by water,” Breshears said. “That’s something we are looking at.”
When he’s not crunching numbers or working out in the field or in the classroom—he teaches dryland ecohydrology and vegetation dynamics—Breshears dons another hat: ISPE’s theme leader for ecosystem science.
In that role, Breshears helps bring together research programs in natural resources and ecosystem sciences to develop collaborations across academic disciplines, both within and outside the UA. Right now, one of his main goals is to help ISPE ensure that the university, with its strong tradition in earth and environmental sciences, can contribute to and participate in the National Ecological Observatory Network (NEON). The network is designed to span the United States and enable researchers to simultaneously measure a number of variables related to understanding ecological responses to changes in climate and land use.
“This is an incredible place to be. There is so much good environmental science, broadly defined. So much depth,” he said. “That’s part of why I’m so excited about being here.”