Patrick Shafroth, Ph.D.
Patrick B. Shafroth is a research ecologist with the U.S. Geological Survey, Fort Collins Science Center. Since 1991, Dr. Shafroth has conducted research on riparian ecosystems, primarily in arid and semi-arid regions of western U.S. He and his colleagues from the USGS and other institutions have focused their work on understanding relationships between surface and ground-water hydrology, fluvial processes, and the dynamics of native and introduced riparian vegetation. This research has often been conducted in the applied context of riparian ecosystem restoration with the goal of providing solid, objective scientific information that can be used to inform riparian restoration efforts. More specific restoration-related research areas include studies of large-scale flow experiments, dam removal, effects of invasive species control and associated restoration actions, and potential interactions with climate change.
Some of Dr. Shafroth’s current research includes studies of: vegetation and geomorphic responses to experimental flow releases downstream of dams on the Bill Williams River, Arizona; the Colorado River delta in Mexico and the U.S.; and the the Colorado River in Grand Canyon; vegetation and geomorphic responses to dam removal on the Elwha River, Washington, where the world's largest dam removals occurred recently; dynamics of non-native riparian plants along western rivers, including patterns of riparian vegetation recovery associated with biological control of Tamarix.
- Ph.D. in Plant Biology, Arizona State University, 1999
- M.S. in Forest Ecology, Colorado State University, 1993
- B.A. in Environmental Studies and Geography, University of California, Santa Barbara, 1989
Science and Products
Formation of arroyos in the late 1800s greatly increased erosion across the southwestern United States. Since the 1930s, however, this erosion has decreased, partly because of bank stabilization by introduced saltcedar. With Isleta Pueblo Indian Nation, the Aquatic Systems Branch developed a new sediment dating method using saltcedar tree rings. We applied the method in a landmark study of arroyo filling along the Rio Puerco, New Mexico. We then showed how aerial application of herbicide to control saltcedar accidentally renewed erosion. This erosion may now be amplified by a beetle introduced for saltcedar control.
Dam removal is an approach to river restoration that is becoming increasingly common. In most cases, dam removal is driven by considerations other than river restoration like dam safety, but how dam removal affects aquatic and riparian systems is of great interest in many dam removals. My work in this area has had two areas of focus thus far: 1) studies of vegetation and geomorphic change associated with dam removal along the Elwha River, Washington, where the world’s largest dam removals occurred in recent years; 2) syntheses of dam removal effects.
Throughout the world, riparian habitats have been dramatically modified from their natural condition. Dams, non-native species and climate change are often principal drivers of these changes, via their alteration of water and sediment regimes that determine key resources for riparian plants.
Because the underlying cause of riparian system alteration is often attributed to the effects of dams on flow regime, managing flow releases, particularly high flows, from dams is an often-advocated approach to river and riparian restoration. Our work has focused on understanding effects of managed high flow releases (a.k.a., pulse flows, controlled floods) from dams along rivers in the lower Colorado River basin.
Beginning in the early twentieth century, non-native trees and shrubs, including tamarisk (also commonly known as saltcedar) and Russian-olive, were introduced to the United States for use as ornamental plants and in erosion-control plantings. These plants spread extensively, becoming the third and fourth most frequently occurring woody riparian plants in the American West.
The foundation for applying science to river and riparian restoration contexts lies in a basic understanding of the factors that drive riparian vegetation dynamics. Much of our research is focused on clarifying relationships between streamflow, fluvial geomorphology, and riparian vegetation, including various feedbacks.
Landscape-scale processes influence riparian plant composition along a regulated river
Hierarchical frameworks are useful constructs when exploring landscape- and local-scale factors affecting patterns of vegetation in riparian areas. In drylands, which have steep environmental gradients and high habitat heterogeneity, landscape-scale variables, such as climate, can change rapidly along a river's course, affecting the relative...Palmquist, Emily C.; Ralston, Barbara; Merritt, David M.; Shafroth, Patrick B.
Riparian plant composition along hydrologic gradients in a dryland river basin and implications for a warming climate
Droughts in dryland regions on all continents are expected to increase in severity and duration under future climate projections. In dryland regions, it is likely that minimum streamflow will decrease with some perennial streams shifting to intermittent flow under climate-driven changes in precipitation and runoff and increases in temperature....Reynolds, Lindsay; Shafroth, Patrick B.
Secondary invasions of noxious weeds associated with control of invasive Tamarix are frequent, idiosyncratic and persistent
Control of invasive species within ecosystems may induce secondary invasions of non-target invaders replacing the first alien. We used four plant species listed as noxious by local authorities in riparian systems to discern whether 1) the severity of these secondary invasions was related to the control method applied to the first alien; and 2)...González, Eduardo; Sher, Anna A.; Anderson, Robert M.; Bay, Robin F.; Bean, Daniel W.; Bissonnete, Gabriel J.; Cooper, David J.; Dohrenwend, Kara; Eichhorst, Kim D.; El Waer, Hisham; Kennard, Deborah K.; Harms-Weissinger, Rebecca; Henry, Annie L.; Makarick, Lori J.; Ostoja, Steven M.; Reynolds, Lindsay V.; Robinson, W. Wright; Shafroth, Patrick B.; Tabacchi, Erich
Vegetation response to invasive Tamarix control in southwestern U.S. rivers: A collaborative study including 416 sites
Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant...González, Eduardo; Sher, Anna A; Anderson, Robert M.; Bay, Robin F.; Bean, Daniel W.; Bissonnete, Gabriel J.; Bourgeois, Bérenger; Cooper, David J.; Dohrenwend, Kara; Eichhorst, Kim D.; El Waer, Hisham; Kennard, Deborah K.; Harms-Weissinger, Rebecca; Henry, Annie L.; Makarick, Lori J.; Ostoja, Steven M.; Reynolds, Lindsay V.; Robinson, W. Wright; Shafroth, Patrick B.
A large-scale environmental flow experiment for riparian restoration in the Colorado River delta
Managing streamflow is a widely-advocated approach to provide conditions necessary for seed germination and seedling establishment of trees in the willow family (Salicaceae). Experimental flow releases to the Colorado River delta in 2014 had a primary objective of promoting seedling establishment of Fremont cottonwood (Populus fremontii) and...Shafroth, Patrick B.; Schlatter, Karen; Gomez-Sapiens, Martha; Lundgren, Erick; Grabau, Matthew R. ; Ramirez-Hernandez, Jorge; Rodriguez-Burgeueno, J. Eliana; Flessa, Karl W.
Integrating active restoration with environmental flows to improve native riparian tree establishment in the Colorado River Delta
Drastic alterations to river hydrology, land use change, and the spread of the nonnative shrub, tamarisk (Tamarix spp.), have led to the degradation of riparian habitat in the Colorado River Delta in Mexico. Delivery of environmental flows to promote native cottonwood (Populus spp.) and willow (Salix spp.) recruitment in human-impacted riparian...Schlatter, Karen; Grabau, Matthew R. ; Shafroth, Patrick B.; Zamora-Arroyo, Francisco
Dam removal: Listening in
Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals...Foley, Melissa M.; Bellmore, James; O'Connor, James E.; Duda, Jeff; East, Amy E.; Grant, Gordon G.; Anderson, Chauncey; Bountry, Jennifer A.; Collins, Mathias J.; Connolly, Patrick J.; Craig, Laura S.; Evans, James E.; Greene, Samantha; Magilligan, Francis J.; Magirl, Christopher S.; Major, Jon J.; Pess, George R.; Randle, Timothy J.; Shafroth, Patrick B.; Torgersen, Christian; Tullos, Desiree D.; Wilcox, Andrew C.
It takes more than water: Restoring the Colorado River Delta
Environmental flows have become important tools for restoring rivers and associated riparian ecosystems (Arthington, 2012; Glenn et al., 2017). In March 2014, the United States and Mexico initiated a bold effort in restoration, delivering from Morelos Dam a “pulse flow” of water into the Colorado River in its delta for the purpose of learning...Pitt, Jennifer; Kendy, Eloise; Schlatter, Karen; Hinojosa-Huertaf, Osvel; Flessa, Karl W.; Shafroth, Patrick B.; Ramirez-Hernandez, Jorge; Nagler, Pamela L.; Glenn, Edward P.
The long-term legacy of geomorphic and riparian vegetation feedbacks on the dammed Bill Williams River, Arizona, USA
On alluvial rivers, fluvial landforms and riparian vegetation communities codevelop as a result of feedbacks between plants and abiotic processes. The influence of vegetation on river channel and floodplain geomorphology can be particularly strong on dammed rivers with altered hydrology and reduced flood disturbance. We used a 56-year series of...Kui, Li; Stella, John C.; Shafroth, Patrick B.; House, P. Kyle; Wilcox, Andrew C.
Landscape context and the biophysical response of rivers to dam removal in the United States
Dams have been a fundamental part of the U.S. national agenda over the past two hundred years. Recently, however, dam removal has emerged as a strategy for addressing aging, obsolete infrastructure and more than 1,100 dams have been removed since the 1970s. However, only 130 of these removals had any ecological or geomorphic assessments, and fewer...Foley, Melissa M.; Magilligan, Francis J.; Torgersen, Christian; Major, Jon J.; Anderson, Chauncey; Connolly, Patrick J.; Wieferich, Daniel; Shafroth, Patrick B.; Evans, James E.; Infante, Dana M.; Craig, Laura
Coastal habitat and biological community response to dam removal on the Elwha River
Habitat diversity and heterogeneity play a fundamental role in structuring ecological communities. Dam emplacement and removal can fundamentally alter habitat characteristics, which in turn can affect associated biological communities. Beginning in the early 1900s, the Elwha and Glines Canyon dams in Washington, USA, withheld an estimated 30...Foley, Melissa M.; Warrick, Jonathan A.; Ritchie, Andrew C.; Stevens, Andrew; Shafroth, Patrick B.; Duda, Jeff; Beirne, Matthew M.; Paradis, Rebecca; Gelfenbaum, Guy R.; McCoy, Randall; Cubley, Erin S.
Ecological parameters in the Elwha River estuary before and during dam removal
The Elwha and Glines Canyon dams were removed from the Elwha River in Washington State from 2011 to 2014. We collected data for a variety of metrics in the estuary and on the river delta before (2006-2011) and during (2012-2014) dam removal to assess how increased sediment transport and deposition affected habitats, vegetation, invertebrates, and...Foley, Melissa M.; Shafroth, Patrick B.; Beirne, Matthew M.; Paradis, Rebecca; Ritchie, Andrew C.