Impacts of Saltcedar and Saltcedar Control on Wildlife in the Southwestern United States: Publishing Research Results

Project ID: 5524
Principal Investigator: Susan Broderick
Research Topic: Invasive Species
Funded Fiscal Years: 2011
Keywords: None

Research Question

We recently conducted Science and Technology (S&T) research to examine the question, "How do wildlife species respond to various types and scales of saltcedar control measures?" (Project 9331). The research quantified the effects on avian, mammalian, and insect communities across a wide range of saltcedar control measures including herbicide, mechanical, prescribed burning, and biocontrol in four Western river systems. The purpose of the research was to develop management guidelines that could be implemented by Reclamation resource managers conducting saltcedar control and riparian restoration programs for endangered species recovery, as well as to provide access at water management facilities for inspection, maintenance, and recreation in areas of heavy saltcedar infestations.

Data have been collected and partially analyzed on three taxa of wildlife from Reclamation saltcedar control projects on the Pecos, Canadian, Rio Grande, and Arkansas Rivers and the Las Vegas Wash over a 3-year period. However, a final report was not produced due to lack of funding in the last year of the planned study and a shift in focus away from saltcedar issues for the S&T Program beginning in 2007.

A Scientific Investigations Report co-edited by Pat Shafroth, Research Ecologist, U.S. Geological Survey; Curt Brown, Director, Research and Development, Bureau of Reclamation; and David Merritt, Riparian Plant Ecologist, U.S. Department of Agriculture's Rocky Mountain Research Station, published in 2010, stated in their summary of wildlife research needs, "needed are more experimental studies that compare (1) saltcedar-invaded habitats to native habitats and (2) saltcedar removal sites to both native and nonremoval sites." Additionally, it stated, "Wildlife-related research should focus, when possible, on multiple taxa, employing both control and experimental sites over several-year periods."

S&T Project No. 9331 looked at exactly those issues highlighted in quotes. With the rece

Need and Benefit

Saltcedar (Tamarix ramosissima) is considered an undesirable species in riparian areas of the Southwestern United States. Stands of saltcedar may occur in conjunction with increased soil salinity, wildfire frequency, frequency and intensity of flooding, and diminished native vegetation. This may be a case where the more tolerant saltcedar has moved into areas that are no longer suitable for native vegetation because of alterations in flow regimes and disconnection of the river with its flood plain. In some cases, invasion of saltcedar may impact Reclamation access at water management facilities for inspection, maintenance, and recreation.

Removal of saltcedar occurs and is supported by Reclamation in cases where river restoration is occurring. Reclamation has interests in a large number of riparian restoration projects. These projects are typically related to water delivery, water salvage, or avoiding impacts to endangered species. Reclamation is supporting restoration projects on the Truckee River, Trinity River, Las Vegas Wash, and Colorado River to name a few. A large amount of money has been directed towards these restorations, and it is estimated that $1 billion has been spent just in the Southwest since the 1980s. Restoration is largely used to ensure that Reclamation can continue to supply users with water and power, often through a "trade" of restoration for water. Questions, however, remain as to the value of these high dollar restorations for wildlife resources, and, in many cases, very little in the way of quantifying results has occurred.

Data and management guidelines developed from this research would provide Reclamation resource managers with the knowledge and tools to implement saltcedar control projects on Reclamation water projects that are designed to minimize impacts to endangered species such as the Southwest willow flycatcher, as well as candidate species such as the yellow-billed cuckoo and least Bell's vireo. Such knowledge would also help to avoid adverse impacts to neotropical migratory songbirds (under protection of the Migratory Bird Treaty Act) and other wildlife species.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Independent Peer Review

The following documents were reviewed by qualified Bureau of Reclamation employees. The findings were determined to be achieved using valid means.

Butterfly Assemblages Associated with Invasive Tamarisk (Tamarix spp.) Sites: Comparisons with Tamarisk Control and Native Vegetation Reference Sites (final, PDF, 1.5MB)
By Mr. S. Mark Nelson and Richard Wydoski
Publication completed on August 26, 2013

We studied butterfly assemblages at six types of riparian landscapes in five different watersheds in the southwestern US. Sites included a mix of saltcedar, native and saltcedar-treated. Significant differences were found between sites. The assumption that tamarisk removal is sufficient to recover sensitive species were not true in the cases we examined. Results support the importance of reinstating stream-flow regimes & suggest active restoration is needed to restore sensitive wildlife spp.

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Last Updated: 6/22/20