Canadian Forest Service Publications
Using a network model to assess risk of forest pest spread via recreational travel. 2014. Koch, F.H.; Yemshanov, D.; Haack, R.A.; Magarey, R.D. PLoS ONE (9):1-10.
Issued by: Great Lakes Forestry Centre
Catalog ID: 35573
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Long-distance dispersal pathways, which frequently relate to human activities, facilitate the spread of alien species. One pathway of concern in North America is the possible spread of forest pests in firewood carried by visitors to campgrounds or recreational facilities. We present a network model depicting the movement of campers and, by extension, potentially infested firewood. We constructed the model from US National Recreation Reservation Service data documenting more than seven million visitor reservations (including visitors from Canada) at campgrounds nationwide. This bi-directional model can be used to identify likely origin and destination locations for a camper-transported pest. To support broad-scale decision making, we used the model to generate summary maps for 48 US states and seven Canadian provinces that depict the most likely origins of campers traveling from outside the target state or province. The maps generally showed one of two basic spatial patterns of out-of-state (or out-of-province) origin risk. In the eastern United States, the riskiest out-of-state origin locations were usually found in a localized region restricted to portions of adjacent states. In the western United States, the riskiest out-of-state origin locations were typically associated with major urban areas located far from the state of interest. A few states and the Canadian provinces showed characteristics of both patterns. These model outputs can guide deployment of resources for surveillance, firewood inspections, or other activities. Significantly, the contrasting map patterns indicate that no single response strategy is appropriate for all states and provinces. If most out-of-state campers are traveling from distant areas, it may be effective to deploy resources at key points along major roads (e.g., interstate highways), since these locations could effectively represent bottlenecks of camper movement. If most campers are from nearby areas, they may have many feasible travel routes, so a more widely distributed deployment may be necessary.
Plain Language Summary
Long-distance dispersal facilitates the rapid spread of invasive forest species. Many long-distance dispersal pathways are associated with human activities. One pathway of concern is the movement of forest pests in firewood transported by campers. To illustrate one novel approach to account for long-distance, human-mediated dispersal, we apply a probabilistic network model that depicts the movement of campers and potentially infested firewood across the continental US and southern Canada. The model was parameterized with US National Recreation Reservation Service data, which document camper visits to federal campground facilities. The model can be used to identify likely origin locations if an area of interest was found to be invaded by a firewood-transported forest pest, or alternatively, to identify likely destinations were a pest to be moved from the target location in infested firewood. Model outputs provide guidance regarding the deployment of resources for surveillance, firewood inspections, or other forest biosecurity activities.