Controlling invasive species in a fragmented management mosaic

Successfully controlling invasive species depends largely on the cooperation of neighbors. Noxious weeds don't pay attention to fence lines. So even if you successfully eradicate an invasive species on your property, there's a good chance you'll face reinfestation if your neighbors do nothing.

So what happens to invasive species control when the landscape becomes subdivided into smaller properties fragmenting the management mosaic? A new study published in the journal Frontiers in Ecology and the Environment addresses this issue in the case of the invasive plant yellow starthistle (Centaurea solstitialis) in California. The researchers theorize that increased fragmentation of the management mosaic results in lower incentives for landowners to control invasive species.

Yellow starthistle blanketing a hillsideOne reason for this is that as the number of property owners increases it becomes more likely that some will not want to undertake control of invasive species. This in turn creates source areas for future infestation making it an exercise in futility for everyone else to take action on their own land. The researchers also theorize that landowners with smaller properties bear less of the landscape damage from invasive species and therefore have less incentive to implement control efforts.

The researchers examined this issue by conducting surveys of 162 ranchers in the Sierra Nevada foothills of California. They found evidence that the fragmented management mosaic there is impeding efforts to control yellow starthistle - a weed damaging to livestock operations. For example they found that 25% of interviewees reported that neighboring weed sources reduced their investment in control efforts, because of the cost associated with continual reinvasion. The results of their interview suggest that hobby ranchers, newcomers, and non ranchers were unfamiliar with yellow starthistle and were less likely to control the weed or lacked incentives to do so. 

The implications of this research are disconcerting because the trend in California and much of the United States is towards further subdivision of properties and increased fragmentation of the management mosaic. The researchers recommend the formation of cooperative weed management areas or similar types of organizations to facilitate coordination among all stakeholders, enhance landowner incentives where they are lacking, and develop an overarching strategy that optimizes invasion control at the landscape scale. They also recommend that this be integrated with bottom-up community based initiatives and top-down regulations.

Information on how to develop CWMAs is available online with the Center for Invasive Plant Management.

Source:	Frontiers in Ecology and the Environment
Title:	When can efforts to control nuisance and invasive species backfire?
Authors:	Rebecca Epanchin-Niell, Matthew Hufford, Clare Aslan, Jason Sexton, Jeffrey Port, and Timothy Waring
	University of California, Davis