8.0 PRSR 03-09-2017 - Laserfiche WebLink

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• trunk. Dutch elm disease was first recorded in Minnesota near Monticello in 1961, and has since spread throughout the state. Minnesota relied heavily on American Elms (Ulmus americana) as shade trees on streets,with about 140 million in the state at the time of the outbreak.The disease is now present in all Minnesota counties,though elms remain an important component of many Minnesota forests. Emerald ash borer (EAB) is a non-native wood-boring beetle from Asia that was first identified in the United States in the summer of 2002. Likely transported from Asia to Michigan in ash wood used for pallets and other shipping materials,the beetle has now been confirmed in 15 states, including Minnesota.The beetle works by depositing larvae under the bark of the tree; these larvae then feed on the wood, eventually disrupting enough of the phloem to prevent the transport of nutrients throughout the tree.While Minnesota's cold weather can stymie the spread of the beetle, it continues to spread,with new outbreaks confirmed in and around the metro area. Quarantines are already in place around both Hennepin and Anoka counties,where infestations of the borer have been confirmed. Both of these counties share a border with Sherburne county,meaning that ash trees within the Conservation Area are at risk.With risks such as human movement of firewood and climate change ever-present,the likelihood that EAB might reach the property is high,though the search for effective biological controls and other deterrents is ongoing. Unless viable control or treatment options are developed,the elms and ash on the property are at risk of dying in the near future. When such large trees die,it will have a pronounced effect on the vegetation and the water in the river. These trees act to shade the water and provide habitat and improve water quality for fish and other species. When large trees die,they open up the canopy and create gaps,which in turn releases the understory that was formerly suppressed by the shade from such trees. If desirable species like native forbs, grasses, sedges,and shrubs exist in the understory,then this can be a good thing,since the result will probably be a net increase in bank stability and diversity. In the case of this property,these canopy gaps will likely be filled by buckthorn and Tatarian honeysuckle,which are poised to take advantage of such a situation. In order to avoid this undesirable scenario,active management is recommended. Removal of undesirable shrub species and replacing them with desirable native shrubs and herbaceous plant species is a recommended management strategy. For green ash in particular,the situation is particularly important,as this species makes up over 50% of the canopy in many areas of the floodplain forest.The principle of risk is highly applicable here; risk is often defined as the probability of a negative event weighted by its consequences. In the case of EAB,the consequences will be large and quite negative,as a loss of half the canopy on the property could have cascading consequences for invasive species,water quality,and wildlife.The probability that EAB arrives is high,though it is unclear when this will occur.While we plan to remove invasive species prior to this occurring,which will reduce some of the negative consequences, another potential strategy is to proactively remove Friends of the Mississippi River Bailey Point Nature Preserve NRMP 66