Click here to read the report. Here’s the executive summary:
In 2001, the U.S. Department of Agriculture approved the release of a biological control agent, the tamarisk beetle (Diorhabda spp.), to naturally control tamarisk populations and provide a less costly, and potentially more effective, means of removal compared with mechanical and chemical methods. The invasive plant tamarisk (Tamarix spp.; saltcedar) occupies hundreds of thousands of acres of river floodplains and terraces across the western half of the North American continent. Its abundance varies, but can include dense monocultures, and can alter some physical and ecological processes associated with riparian ecosystems.
The tamarisk beetle now occupies hundreds of miles of rivers throughout the Upper Colorado River Basin (UCRB) and is spreading into the Lower Basin. The efficacy of the beetle is evident, with many areas repeatedly experiencing tamarisk defoliation.
While many welcome the beetle as a management tool, others are concerned by the ecosystem implications of widespread defoliation of a dominant woody species. As an example, defoliation may possibly affect the nesting success of the endangered southwestern willow flycatcher (Empidonax traillii extimus).
In January 2015, the Tamarisk Coalition convened a panel of experts to discuss and present information on probable ecological trajectories in the face of widespread beetle presence and to consider opportunities for restoration and management of riparian systems in the Colorado River Basin (CRB). An in-depth description of the panel discussion follows.
The panel concluded that as the tamarisk beetle moves into the Lower Colorado River Basin (LCRB), the selection of management actions to support a transition to a healthy riparian system will depend on the unique suite of characteristics of each sub-basin and the goals of basin managers.
The panel emphasized the importance of basin-specific planning, the necessity of monitoring and inventorying to inform management, and that adaptive management practices will be essential for success relative to varying goals. The panel developed a framework to assist managers in selecting appropriate management strategies and identified future research needed to further inform restoration approaches and management decisions.