3.12 NON-NATIVE INVASIVE SPECIES (NNIS)

Transcription

1 3.12 NON-NATIVE INVASIVE SECIES (NNIS) Summary When the direct, indirect, and cumulative effects of the alternatives on NNIS are considered as a whole, Alternative 1 and Alternative 3 emerge as the two alternatives that have the greatest and a relatively high risk for contributing to weed spread and ecological impacts. Ongoing weed treatments on the Superior National Forest would be challenged to keep up with the rate of spread of weeds under these two alternatives. Alternative 4 would have the smallest risk for contributing to weed spread, and the overall amount of weed spread and ecological impacts under this alternative would be low. Ongoing treatments would minimize the rate of spread and the level of impacts under Alternative 4. The overall amount of weed spread and ecological impacts under Alternative 2 would be intermediate, and there would be a net increase of weed infestations despite ongoing forest-wide treatments. It is important to put these conclusions in perspective. Very little new construction is being proposed for the Travel Management roject, and the vast majority of management options being considered affect already-existing travel corridors. In a lot of cases, weed spread along these routes probably began when the route was originally constructed. All alternatives would contribute to the gradual degradation of native plant communities to some degree, but most weed-related impacts would remain along developed roads where they can be managed Introduction Non-native invasive species are generally defined by two characteristics: 1) they were not historically (i.e., pre-european settlement) present in a region s ecosystems, and 2) they have the ecological ability to invade and persist in native plant and animal communities, and often become dominant species at the expense of native species. Motor vehicle use of roads analyzed by the Travel Management roject could lead to the introduction or spread of non-native invasive species (NNIS). This potential effect is analyzed in this section, which describes the NNIS that are currently known to exist in the roject Area, as well as the effects of the alternatives on NNIS Analysis Methods One indicator is used to analyze the effects of the alternatives on NNIS; its value is displayed in Table Indicator 1: Miles of unclassified road that are proposed to be open for any motor vehicle use. The unclassified roads that would remain as unclassified roads in Alternative 1 would be designated as a national forest system road or trail or decommissioned under the other three alternatives. This indicator tracks on how many of these unclassified roads would be open for motor vehicle use, whether as unclassified roads in Alternative 1, or in their new class in Alternatives 2-4. This indicator is useful for distinguishing among alternatives because currently the vast majority of terrestrial non-native invasive plant occurrences are along roads on the Superior National Forest. This indicator considers all kinds of motor vehicle use since any vehicle is capable of spreading invasive plants. For example, unclassified roads that would be designated as national forest system roads but closed to OHV use are still counted in this indicator because car or truck use of the road could also spread weeds. Unclassified Environmental Assessment 3-47 Chapter 3 Non-native Invasive Species

2 roads that are proposed for decommissioning are not counted in this indicator because they would be closed to motor vehicle use Analysis Area The area covered by the analysis of direct and indirect effects includes all lands administered by the Superior National Forest within the Travel Management roject Area as well as BWCAW lands within 0.5 miles of unclassified roads proposed to be open for any motor vehicle use. This area was selected because this is where project activities would occur which cause the direct and indirect effects. This project does not propose activities inside the BWCAW, but effects to the wilderness will be considered as part of this analysis. The area covered by the cumulative effects analysis includes lands of all ownerships within the Travel Management roject Area as well as BWCAW lands within 0.5 miles of unclassified roads proposed to be open for any motor vehicle use. This cumulative effects analysis area was selected because non-national Forest lands within roject Area boundaries share a number of physical characteristics (e.g. bedrock features, land forming processes) with adjacent National Forest lands. These characteristics influence land uses, which in turn influence NNIS distribution throughout the Analysis Area, so the Analysis Area boundary makes a logical analysis unit for cumulative effects. The time period for direct and indirect, effects is a ten year period from the time project activities begin, because no effects of project activities will occur until implementation, and because weed spread occurs rapidly, so if weeds were going to colonize a road analyzed in this document, the weed spread will have taken place within 10 years. The time period for cumulative effects is 15 years, looking back 10 years at past actions and 5 years forward Affected Environment Table displays the non-native invasive plants that are known to occur within 200 feet of the routes analyzed for the Travel Management roject. This list was developed based on results from NNIS inventory data collected on the Superior National Forest. The inventory focused on OML 1-5 roads, but unclassified roads were not targeted during the inventory. Nevertheless, the acreages represented in Table are a good indication of the relative abundances of weeds on the Superior. Non-native invasive plants are typically spread in several ways such as vehicle wheels or bodies, livestock, wildlife, boat traffic, or human foot traffic. Non-native invasive plants typically enter an area along a corridor of ground disturbance such as a road or trail, and depending on numerous factors such as shade tolerance, degree of invasiveness, dispersal mechanisms, and habitat availability, may or may not spread into adjacent forested or non-forested ecosystems. Typical areas that have some weed infestation in the Analysis Area are roadsides, trails, portages, gravel pits, parking areas, campgrounds, helispots, and administrative sites. Mesic forested sites with shady understories on the Superior National Forest are fairly resistant to invasion by most NNIS. NNIS that disperse into such plant communities tend to get out-competed quickly by native shrubs, forbs, and trees. However, some NNIS are exceptions to this general observation. For example, garlic mustard, common buckthorn, and Siberian peabush can thrive in the understory of mesic native plant communities. Only one occurrence of a shade tolerant NNIS (Siberian peabush) occurs within 200 feet a route analyzed in this project. Conversely, there are a number of native plant communities typical of droughty, shallow-soiled sites that are susceptible to invasion by NNIS. These sites have less abundant shrub and forb layers, and as a Chapter 3 Non-native Invasive Species 3-48 Environmental Assessment

3 result are more likely to be invaded by NNIS, especially if some ground disturbance occurs. These types of sites correspond to Ecological Landtypes (ELTs) 7, 9, 11, 16, 17, and 18. These ELTs are locally abundant across the Analysis Area. The abundance of NNIS across the Analysis Area varies (Table ). Orange hawkweed, yellow hawkweeds, and oxeye daisy are the most abundant NNIS. They are found along most roads in the roject Area and pose a moderate ecological risk to native plant species. The high ecological risk species, Canada thistle, Siberian peabush, leafy spurge, purple loosestrife, and spotted knapweed, are much less abundant, totaling less than 7 acres for any given species. The other moderate ecological risk species, common tansy, plumeless thistle, cypress spurge, and St. Johnswort, are also less abundant, totaling less than 23 acres for any given species. The following analysis only considers the effects of moderate and high risk species. The low risk species do not pose enough of a threat to native plant communities to warrant consideration in the analysis. Table Non-native invasive plants known from within 200 feet of the routes analyzed for the Travel Management roject Species MN Status* Life History/ Habitat Summary Acres*** Ecological Risk** Siberian peabush Caragana arborescens lumeless thistle Carduus acanthoides Spotted knapweed Centaurea maculosa Canada thistle Cirsium arvense Bull thistle Cirsium vulgare Leafy spurge Euphorbia esula Cypress spurge Euphorbia cyparissias Orange hawkweed Hieracium auranticum Non-native Yellow hawkweeds Hieracium sp. No status S No status S No status erennial shrub, can spread by seed or vegetatively, used as reclamation species (Saskatchewan urple Loosestrife and Invasive Species roject 2005) Annual or biennial; spread by seed; occupies disturbed upland sites (Lym and Christianson 1996) Short lived perennial, spread entirely by seeds, dry to mesic uplands (Wilson and Randall 2002) erennial, spread by seed and rhizome, occupies disturbed sites (Lym and Christianson 1996) Biennial, spread by seed, occupies disturbed sites (Lym and Christianson 1996) Aggressive perennial, spread by seed and rhizome, dry to mesic uplands (Lym and Zollinger 1995) Moderately aggressive perennial spread by rhizome and seed (Czarapata 2005) erennial, spread by seed and rhizome, widespread in disturbed upland sites (Callihan et al. 1982) Several similar non-native invasive yellow hawkweeds occur in roject Area; perennial, spread by seed and rhizome, widespread in disturbed upland sites (Gleason and Cronquist 1991) 0.05 High Moderate 6.0 High 5.1 High 0.8 Low 0.8 High Moderate 283 Moderate 283 Moderate Environmental Assessment 3-49 Chapter 3 Non-native Invasive Species

4 Table Non-native invasive plants known from within 200 feet of the routes analyzed for the Travel Management roject Species MN Status* Life History/ Habitat Summary erennial, spread by seed and rhizome, dry to mesic uplands (Fitzsimmons and Burrill 1993) erennial, spread by seed and rhizome, widespread in disturbed upland sites (Gleason and Cronquist 1991) Aggressive perennial; spread by seed and rhizome; wetlands and road ditches (MNDNR 2006) erennial; spread by seed and rhizome; disturbed uplands (Voss 1996) Acres*** Ecological Risk** St. Johnswort Hypericum perforatum Oxeye daisy Leucanthemum vulgare urple loosestrife Lythrum salicaria Common tansy Tanacetum vulgare No status S S 0.9 Moderate 283 Moderate 0.5 High 22.1 Moderate * = rohibited noxious weed (Minnesota Rules ). rohibited noxious weeds must be controlled or eradicated as required in Minnesota statutes. S = Secondary noxious weed. These species may be added to the county prohibited or restricted list at the discretion of counties (Minnesota Rules ). ** Species represents either a low, moderate, or high threat to natural communities (USDA Forest Service 2005e). Risk given in table represents risk in the most susceptible habitat. *** Estimated acres based on miles of roads. Assume 10% weed canopy cover within 10 foot ROW on either side of road. Environmental Consequences Direct and Indirect Effects Alternative 1 (No-action) Indicator 1 (miles of unclassified road proposed to be open for any motor vehicle use) is 280 miles (Table ), the highest for any alternative. The likelihood and potential extent of weed spread would be highest for Alternative 1. Many unclassified roads would remain open to OHV use. Motor vehicle use of roads and trails would lead to an increase in the number of weed populations and weed acreage; this effect has been well documented (Ouren et al. 2007). Most of this increase would be roadside weed populations. None of the weed spread would be offset by road decommissioning. Wildlife and human foot traffic in the Analysis Area would also have the potential to spread NNIS, but the likelihood of spread by these means would be lower than from vehicle use. Most of the potential weed increase would be an increased number of roadside weed populations. Some of these new populations would be wind-dispersed species that could lead to new weed infestations in susceptible undisturbed habitats away from roads (e.g. hawkweeds colonizing rock outcrops or Canada thistle colonizing moist areas around wetlands). These new infestations would degrade the native plant community in the susceptible habitat and have a greater ecological impact than the new roadside weed populations. Illegal OHV use off of designated routes could also occur and contribute to weed spread, but this would likely be a minor component of new weed infestations. Chapter 3 Non-native Invasive Species 3-50 Environmental Assessment

5 Some weed species could conceivably spread from an unclassified road to the BWCAW as the result of wind, human, or wildlife dispersal. However, this is an unlikely scenario and would not contribute a great deal to overall weed spread for this alternative. Studies have shown that in Canada thistle (a winddispersed species), less than 5% of the seeds go more than 20 feet from the parent plant (Milt Haar, Univ. MN, pers comm.) NNIS that make it to the BWCAW would then have to establish in competition with undisturbed native vegetation. Using a very conservative buffer of 0.5 mile from the BWCAW, there are only approximately 10.8 miles of unclassified roads that could conceivably serve as a seed source for weeds. This represents a very small portion of the 280 miles for indicator 1, so it is not likely that Alternative 1 would contribute much to weed spread into the BWCAW. Table Indicator for NNIS Analysis Indicator Alt. 1 Alt. 2 Alt. 3 Alt. 4 Miles of unclassified road that are proposed to be open for any motor vehicle use Note: This indicator tracks miles of unclassified road open to motor vehicle use in Alternative 1, or these same roads in their new proposed travel management classification (e.g. OML 1, OML 2, etc.) in Alternatives 2-4 that are open to motor vehicle use. Alternative 2 (Modified roposed Action) Indicator 1 for the Alternative 2 is 145 miles (Table ). The likelihood and potential extent of weed spread would be moderate, less than Alternatives 1 and 3, but more than Alternative 4. Like Alternative 1, most of the increase would be roadside weed populations. Unlike Alternative 1, some of the weed spread would be offset by 157 miles of decommissioning proposed for Alternative 2. Most of the potential weed increase would be an increased number of roadside weed populations. Some of these new populations would be wind-dispersed species that could lead to new weed infestations in susceptible undisturbed habitats away from roads (e.g. hawkweeds colonizing rock outcrops or Canada thistle colonizing moist areas around wetlands). These new infestations would degrade the native plant community in the susceptible habitat and have a greater ecological impact than the new roadside weed populations. The ecological impact from invasive plants under Alternative 2 would be less than that caused by Alternatives 1 and 3, but Alternative 2 would have a greater ecological impact from invasive plants than Alternative 4. Illegal OHV use off of designated routes could also occur and contribute to weed spread, but this would likely be a minor component of new weed infestations. As described above for Alternative 1, some weed species could conceivably spread from an unclassified road to the BWCAW. However, this is an unlikely scenario and would not contribute a great deal to overall weed spread under Alternative 2. Within a one-half mile distance of the BWCAW, there are only approximately 1.3 miles of unclassified roads affected by this proposal that would be open for motor vehicle use, which is less than 1% of the miles in indicator 1. Alternative 2 would not contribute much to weed spread within the BWCAW. Environmental Assessment 3-51 Chapter 3 Non-native Invasive Species

6 Alternative 3 Indicator 1 for Alternative 3 is 224 miles (Table ). The likelihood and potential extent of weed spread would rather high, greater than Alternatives 2 and 4 but less than Alternative 1. Like the other alternatives, most of this increase would be roadside weed populations. However, unlike Alternative 1, some of this potential weed spread would be offset by nearly 78 miles of road decommissioning proposed for Alternative 3. Most of the potential weed increase would be an increased number of roadside weed populations. Some of these new populations would be wind-dispersed species that could lead to new weed infestations in susceptible undisturbed habitats away from roads (e.g. hawkweeds colonizing rock outcrops or Canada thistle colonizing moist areas around wetlands). These new infestations would degrade the native plant community in the susceptible habitat and have a greater ecological impact than the new roadside weed populations. The ecological impact from invasive plants under Alternative 3 would be greater than that of Alternatives 2 and 4, but the ecological impact would be less than that under Alternative 1. Illegal OHV use off of designated routes could also occur and contribute to weed spread, but this would likely be a minor component of new weed infestations. As described above for Alternative 1, some weed species could conceivably spread from an unclassified road to the BWCAW. However, this is an unlikely scenario and would not contribute a great deal to overall weed spread under Alternative 3. Within a one-half mile distance of the BWCAW, there are only approximately 3.4 miles of unclassified roads affected by this proposal that would be open for motor vehicle use, which is less than 2% of the miles in indicator 1. Alternative 3 would not contribute much to weed spread within the BWCAW. Alternative 4 Indicator 1 for Alternative 4 is 119 miles (Table ). The likelihood and potential extent of weed spread would the least of any alternative. Like the other alternatives, most of this increase would be roadside weed populations. However, unlike Alternative 1, some of this potential weed spread would be offset by nearly 184 miles of road decommissioning proposed for Alternative 4. Most of the potential weed increase would be an increased number of roadside weed populations. Some of these new populations would be wind-dispersed species that could lead to new weed infestations in susceptible undisturbed habitats away from roads (e.g. hawkweeds colonizing rock outcrops or Canada thistle colonizing moist areas around wetlands). These new infestations would degrade the native plant community in the susceptible habitat and have a greater ecological impact than the new roadside weed populations. The ecological impact from invasive plants under Alternative 4 would be less than that of Alternatives 1, 2, or 3. Illegal OHV use off of designated routes could also occur and contribute to weed spread, but this would likely be a minor component of new weed infestations. As described above for Alternative 1, some weed species could conceivably spread from an unclassified road to the BWCAW. However, this is an unlikely scenario and would not contribute a great deal to overall weed spread under Alternative 4. Within a one-half mile distance of the BWCAW, there are only approximately 1.2 miles of unclassified roads affected by this proposal that would be Chapter 3 Non-native Invasive Species 3-52 Environmental Assessment

7 open for motor vehicle use, which is only approximately 1% of the miles in indicator 1. Alternative 4 would not contribute much to weed spread within the BWCAW Cumulative Effects See Appendix B to the EA for a description of projects considered for cumulative effects along with resource-specific projects discussed below. Although the cumulative effects of the Travel Management roject on NNIS would vary by alternative, the past actions in the project area have influenced NNIS in similar ways among alternatives. ast actions influenced the composition and distribution of NNIS in the cumulative effects analysis area. For example, development of a transportation system (i.e. roads and railroads) provided corridors for the introduction and spread of these species. Mixed land ownership patterns in the analysis area have also contributed to development of the transportation system and NNIS spread. Cumulatively, these past actions influenced the present composition and distribution of these species in the analysis areas. The biggest consideration for cumulative effects is that none of the routes being analyzed in this project exist in isolation. Instead, they are all connected to other Forest Service, state, county, township, and other roads, some of which have NNIS along them. Increasing or decreasing the connectedness between the existing road/trail network and the routes being analyzed in the Travel Management roject would increase or decrease the likelihood and extent of NNIS spread. Alternative 3 would have the greatest number of loops and connections to the existing road system, so this alternative would have the biggest contribution to the cumulative spread of weeds. Alternative 4 would have the least number of loops and connections to the existing road system, so this alternative would have the least contribution to the cumulative spread of weeds. Alternative 2 would be intermediate between these two. Alternative 1 would also have an intermediate level of connectedness to the existing road system, and this connectedness would contribute moderately to the cumulative spread of weeds. Other ongoing and reasonably foreseeable actions in the cumulative effects analysis area are: timber sales and minerals management projects on county, state, private, and federal lands; road construction/maintenance on county, state, private, and federal lands; and OHV planning by the DNR in Lake, Cook, and St. Louis Counties. All of these actions would contribute to the spread of weeds in the analysis area. These actions would be occurring at approximately the same level for each alternative. In contrast to the actions above which cumulatively are contributing to the spread of NNIS in the analysis area, invasive plant treatments are an ongoing and reasonably foreseeable action that represents a beneficial cumulative effect. The forest-wide NNIS Management EA (USDA Forest Service 2006) would provide for weed treatments in the project area under all alternatives. These treatments would minimize impacts from NNIS spread directly, indirectly, and cumulatively caused by the Travel Management roject. The level of weed treatment would be approximately the same for each alternative. Approximately 20 and 85 infested acres were treated in 2006 and 2007, respectively. When all the actions described above are considered together, Alternative 4 emerges as the alternative that would have the lowest level of cumulative weed spread, while Alternative 3 would have the highest level of cumulative weed spread. Alternatives 1 and 2 would have intermediate levels of cumulative weed spread. Environmental Assessment 3-53 Chapter 3 Non-native Invasive Species

8 Conclusion Direct, Indirect, and Cumulative Effects When the direct, indirect, and cumulative effects of the alternatives on NNIS are considered as a whole, Alternatives 1 and 3 emerge as the two alternatives that have the greatest and a relatively high risk for contributing to weed spread and ecological impacts. Ongoing weed treatments on the Superior would be challenged to keep up with the rate of spread of weeds under these two alternatives. Alternative 4 would have the smallest risk for contributing to weed spread, and the overall amount of weed spread and ecological impacts under this alternative would be low. Ongoing treatments would minimize the rate of spread and the level of impacts under Alternative 4. The overall amount of weed spread and ecological impacts under Alternative 2 would be intermediate, and there would be a net increase of weed infestations despite ongoing forest-wide treatments. It is important to put these conclusions in perspective. Very little new construction is being proposed for the Travel Management roject, and the vast majority of management options being considered affect already-existing travel corridors. In a lot of cases, weed spread along these routes probably began when the route was originally constructed. All alternatives would contribute to the gradual degradation of native plant communities to some degree, but most weed-related impacts would remain along developed roads where they can be managed. Chapter 3 Non-native Invasive Species 3-54 Environmental Assessment