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Management of invasive Phragmites australis in the Adirondacks: a cautionary tale about prospects of eradication

Quirion, Brendan, Simek, Zachary, Dávalos, Andrea, Blossey, Bernd
Biological invasions 2018 v.20 no.1 pp. 59-73
Phragmites australis, accountability, ecological invasion, herbicides, invasive species, land management, plants (botany), probability, quantitative analysis, stems, weed control, Adirondacks, New York
Invasive plant management (largely mechanical and chemical) consumes an ever-increasing portion of budgets for land management organizations, but metrics of success, other than extent of areas treated or resources expended is rarely available. Here we assess success of managing 346 populations of invasive Phragmites australis (range 0.36–4134 m²; cover 37–75%) in the Adirondack Park in upstate New York, USA. We began by treating 18 patches in 2010 using herbicide; gradually adding patches treated annually or intermittently for a total of 334 by the end of the project period. We monitored each population annually and if P. australis was present mapped its spatial extent and estimated cover. We considered P. australis eradicated when live stems were absent from a site for at least three consecutive years. Our treatments reduced size and cover of P. australis populations and eradication was achieved at 104 of 294 sites. However, probability of eradicating P. australis over a 7-year project timeframe was 0.83 for the smallest patches (0.36 m²), whereas at medium (45 m²) and large patches (>3000 m²) probability of eradication decreased to 0.26 and 0.02, respectively. Our results question efficacy of managing large P. australis populations with the goal of eradication. We urge conservation organizations to clearly articulate management objectives beyond short-term suppression of target plants and to promote accountability by providing quantitative measurements of outcomes.