Tamarisk biocontrol, endangered species risk and resolution of conflict through riparian restoration

Abstract

A long-standing debate between wildlife agencies and biological control researchers and practitioners concerns Diorhabda carinulata Desbrochers (Coleoptera: Chrysomelidae) introduced to suppress invasive Tamarix spp. (Tamaricaceae), and potential impacts of Tamarix defoliation on endangered southwestern willow flycatchers using this non-native plant as nesting habitat in some western riparian ecosystems. The conflict and ensuing legal actions are currently centered on the presence of D. carinulata within the breeding range of the flycatcher in the Virgin River watershed, which has led to APHIS termination of permits supporting the biocontrol development program and has also affected other programs to develop biocontrol agents against environmental weeds. Central to concerns over wildlife is the lack of rehabilitation of native vegetation where biocontrol is expected, so there are current and planned efforts to promote restoration of native cottonwood-willow habitat to mitigate the anticipation decline in Tamarix cover. A strategic approach to riparian restoration is outlined which could facilitate sustainable, and scientifically documented recovery of this iconic habitat type. While the results of these efforts will not be known immediately, the process which is leading to riparian restoration has brought specialists from both sides of the debate together in search of resolution via collaboration, and if successful, may allow re-initiation of the Tamarix biocontrol program attendant with habitat enhancement for wildlife species of conservation concern.