Native to Invasive
Anthropogenic changes cause native species to develop invasive traits: the case of the southern Vancouver Island common snowberry (Symphoricarpos albus).
Cypress Hunder-RookesKeywords: Symphoricarpos albus, Garry oak ecosystem,
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Figure 1. Representation of the common snowberry (Symphoricarpos albus).
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Ecological Genealogy
Throughout Vancouver Island the recruitment of the Douglas fir (Pseudotsuga menziesii) tree leads to a succession from oak-woodlands to closed conifer forests (Pellatt & Gedalof, 2014). However, along southern Vancouver Island, the extent of Douglas fir forests is restricted by edaphic conditions and cultural practices (Pellatt & Gedalof, 2014). The resultant oak savannahs are partly an outcome of a significant, long-term influence of eco-cultural practices by the Coast Salish First Peoples (Macdougall, Beckwith, & Maslovat, 2004). The use of fire management was deeply rooted in the Coast Salish First Peoples history and culture (Macdougall et al., 2004). Cultural controlled burning allowed the increased growth of plant species for human and animal consumption, led to more hunting opportunities, caused vegetation developed fire resistance, kept areas open, and succession to Douglas fir forest composition was arrested (Mccune et al., 2013; Mcdadi & Hebda, 2008).
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Figure 2. Restored Garry Oak ecosystem at Mt. Tzuhalem Ecological Reserve, Duncan, B.C. Photo: Dawn Fizzard. (Costanzo et al., 2011).
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Figure 3. Extent of oak ecosystem habitat loss on th Saanich Peninsula (Victoria) of southeastern Vancouver Island. The original range is derived from historical records of the mid-nineteenth century, including presettlement land surveys. The current range indicates areas that contain Quercus garryana and associated native ground flora. (Macdougall, Beckwith, & Maslovat, 2004).
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The openness of Garry oak savannahs was an attraction to European settlers as they arrived to Vancouver Island (Mccune et al., 2013). In 1843 Victoria was founded in the heart of the savannahs, and since then over 90% of the Garry oak savannahs have been degraded or converted by development, agriculture and forest infilling (Dunwiddie & Bakker, 2011; Mccune et al., 2013). The savannahs are now listed as one of Canada’s top ‘at-risk’ terrestrial ecosystems due to the number of associated threatened species (Parks Canada Agency, 2006). This has generated significant efforts of conservation and restoration, with the Garry oak as the flagship species (Dunwiddie & Bakker, 2011; Mccune et al., 2013). |
Present socio-ecological characteristics
The interruption of traditional management by the Coast Salish First Peoples on Vancouver Island has led to the continued replacement of Garry oak savannahs by Douglas fir forest, and ongoing species invasion (Dunwiddie & Bakker, 2011). The greatest threats to the remaining Garry oak ecosystems are continued habitat degradation and fragmentation, climate changes and the invasion of competitive species (Dunwiddie & Bakker, 2011). Although many management strategies for the Garry oak savannahs have focussed on these threats, there has been little discussion of the effects of native species, notably the common snowberry (Symphoricarpos albus), that have begun to outcompete other native species that are at risk.
Being very adaptable to different conditions, S. albus can be found in forests, clearings, and rocky slopes in dry to moist conditions (“Common Snowberry, Symphoricarpos albus,” 2017). S. albus spreads by suckering or by seed transportation via bird consumption (“GOERT 2019). Between 119,045 and 249,120 seeds are produced per kilogram of vegetative growth (“GOERT 2019). As a result S. albus has become highly invasive in areas around the world where it is not native, particularly the United Kingdom, creating dense thickets and displacing native species (Booy, Wade, & Roy, 2015). These traits have begun to allow S. albus to have similar effects on the protected Vancouver Island Garry oak ecosystems.
Being very adaptable to different conditions, S. albus can be found in forests, clearings, and rocky slopes in dry to moist conditions (“Common Snowberry, Symphoricarpos albus,” 2017). S. albus spreads by suckering or by seed transportation via bird consumption (“GOERT 2019). Between 119,045 and 249,120 seeds are produced per kilogram of vegetative growth (“GOERT 2019). As a result S. albus has become highly invasive in areas around the world where it is not native, particularly the United Kingdom, creating dense thickets and displacing native species (Booy, Wade, & Roy, 2015). These traits have begun to allow S. albus to have similar effects on the protected Vancouver Island Garry oak ecosystems.
Within Garry oak ecosystems, one of the significant threats to endangered native plants is the effect of shading by shrub species (Parks Canada Agency, 2006). The understory vegetation in many Garry oak savannahs is dominated by S. albus in the absence of traditional low-intensity fires (Parks Canada Agency, 2006). Along with the invasive Scotch broom (Cytisus scorparius), S. albus has been targeted by some Canadian initiatives as a crucial species for management projects. (Parks Canada Agency, 2006). The Nature Conservancy of Canada (NCC) has acknowledged the effects of these species and conducted shrub removal in experimental plots throughout Vancouver Island (Parks Canada Agency, 2006). Cutting back S. albus and C. scorparius has been found to be a beneficial, low disturbance technique reduce the density of these shading shrubs and allow light penetration to the endangered flora of the systems (Hague, Fehr, Griffin, Chaboyer, & Gomes, 2009). On Vancouver Island S. albus has been used as a common shrub in gardening and landscaping due to its quick growth rate and hedge-like structure. Restoration groups such as the Garry Oak Ecosystems Recovery Team (GEORT) have historically encouraged the planting of S. albus to promote Garry oak ecosystem recovery (“GOERT 2019). Additionally, S. albus has been used to combat IASs (Costanzo et al., 2011; District of West Vancouver, 2014). S. albus has been planted after IAS removal to replace IASs and has been used to create barriers against vigorous IASs (Costanzo et al., 2011; District of West Vancouver, 2014). However, the negative encroaching effect S. albus has on Garry oak ecosystem associates indicate that planting of this shrub should not be promoted. |
Figure 4. Symphoricarpos albus in fruiting stage (top) and in flowering state (bottom). (“Common Snowberry, Symphoricarpos albus,” 2017).
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Future Trajectory
With expansion of towns and cities on Vancouver Island, Garry oak ecosystems are continuously under threat. Fragmentation of land leads to less connectivity between sites, reducing genetic transfer of endangered species. Disturbance sites allow colonization by aggressive IASs as well as vigorous native species that both outcompete Garry oak associations. A changing climate will produce environmental variations that could lead to great success of invasive species (Government of British Columbia, 2016). It is predicted that growing seasons will be longer, there will be shifts in infectious diseases and pests, droughts will be more frequent, and sea levels will rise (Government of British Columbia, 2016). Continued management of the Garry oak ecosystem is essential for their survival but possible revaluation of management goals may be necessary. Historic restoration targets will be extremely difficult to attain and maintain with a changing climate and consistent human pressures. A possible method is to acknowledge the potential value of hybrid and novel ecosystems, with adaptable species that will inhibit invasive species growth, maintaining a shade-limited meadow structure (Hobbs et al., 2014).
As the climate changes on Vancouver Island, the success of S. albus can be anticipated to increase. In Europe where S. albus is an IAS, the species is stunted by extreme drought but flourishes with full sunlight on relatively moist, well drained and fertile soils (Gilbert, 1995). S. albus is extremely adaptable to habitats, which allows it to establish in most areas in both native and non-native ranges, spreading gregariously and relatively quickly (“Common Snowberry, Symphoricarpos albus,” 2017; Gilbert, 1995). Warming winters on Vancouver Island indicate that seed viability will increase, and high seed productivity will lead to greater numbers of established S. albus (“GOERT 2019). Additionally, S. albus is relatively fire resistant and has tolerance to residual herbicides (Gilbert, 1995). All of these factors may lead to a greater expansion of S. albus throughout Vancouver Island and within Garry oak ecosystems, indicating that proper management strategies must be developed quickly. This is especially important as conditions intensify for the "at risk" Garry oak ecosystem associates.
One concern when addressing management of a native species is its potential cultural significance. S. albus has been used by the Coast Salish First Peoples throughout their history (Turner, 2014). The berries have been used traditionally for their saponin properties as shampoo, and as an antiperspirant (Turner, 2014). Crushed berries can treat sores, rashes, burns, eye infections and warts (Turner, 2014). Root and twig teas have been used to treat stomach problems, fevers, bedwetting and tuberculosis (Turner, 2014). Structurally, branches were used to make brooms and arrows were made from shoots (“Common Snowberry, Symphoricarpos albus,” 2017). Additionally, S. albus was incorporated into stories and lore. The “berries [were] associated with snakes and with corpses and ghosts (widespread [in the Salish First Peoples]); said to be the Saskatoon berries of the people in the land of the dead (Stl’atl’imx [First Peoples])” (Turner, 2014). The traditionally importance of this species for Coast Salish First Peoples must be considered when combatting management strategies. Additionally, the Coast Salish First Peoples have a wealth of knowledge on the management of S. albus, having maintained the species historically in the Garry oak ecosystems.
Figure 5. Looking west toward Fort Victoria in the late 1840s. Plants shown include camas (Camassia spp.), Woolly Sunflower (Eriophyllum lanatum), Barestem Desert-parsley (Lomatium nudicaule), and Spring Gold (Lomatium utriculatum). Painting by Michael Kluckner. (Costanzo et al., 2011).
Future research should include surveillance of emerging ecosystems while protecting species at risk. Involvement with the Coast Salish First People is essential for respecting their traditions and culture. Additionally traditional ecological knowledge of the sites and the historic adaptations of the endangered species are fundamental when creating a management plan. By creating a complete picture of the land, good decisions can be made on how to handle native species that currently pose threats on the Garry oak ecosystems, hopefully leading to greater resilience for this threatened ecosystem.
Future research should include surveillance of emerging ecosystems while protecting species at risk. Involvement with the Coast Salish First People is essential for respecting their traditions and culture. Additionally traditional ecological knowledge of the sites and the historic adaptations of the endangered species are fundamental when creating a management plan. By creating a complete picture of the land, good decisions can be made on how to handle native species that currently pose threats on the Garry oak ecosystems, hopefully leading to greater resilience for this threatened ecosystem.
References
Booy, O., Wade, M., & Roy, H. (2015). Field Guide to Invasive Plants and Animals in Britain. Retrieved from https://books.google.ca/books?hl=en&lr=&id=OyDKBwAAQBAJ&oi=fnd&pg=PA1&dq=invasive+snowberry+in+ireland&ots=oDSvQ6rQbO&sig=AaILLSjJtpFbIAf2yAL5uL0TNvk#v=onepage&q=snowberry &f=false
Common Snowberry, Symphoricarpos albus. (2017). In Native Plants PNW. Retrieved from http://nativeplantspnw.com/common-snowberry-symphoricarpos-albus/
Costanzo, B., Eastmas, D., Engelstoft, C., Gorman, M., Hebda, R., Hook, F., … Webb, C. (2011). Restoring British Columbia’s Garry Oak Ecosystems: Principles and Practices. Victoria, British Columbia, Canada. Retrieved from http://docstore.library.uvic.ca.ezproxy.library.uvic.ca/Restoring_British_Columbias_garry_oak_ecosystems.pdf
District of West Vancouver. (2014). Excerpt from Invasive Plants Strategy Best management practices and target plant profiles Japanese Knotweed Scotch Broom Giant Hogweed. Retrieved from https://westvancouver.ca/sites/default/files/strategies/Invasive-Plant-Strategy-DWV-Schedule-A-Dec17-2014-web.pdf
Dunwiddie, P. W., & Bakker, J. D. (2011). The Future of Restoration and Management of Prairie-Oak Ecosystems in the Pacific Northwest. Northwest Science, 85(2), 83–92. http://doi.org/10.3955/046.085.0201
Gilbert, O. L. (1995). Symphoricarpos albus (L.) S. F. Blake (S. rivularis Suksd., S. racemosus Michaux). Journal of Ecology (Vol. 83). Retrieved from https://about.jstor.org/terms
GOERT : About Garry oak ecosystems. (2019). Retrieved March 3, 2019, from http://www.goert.ca/about/why_disappearing.php
GOERT : for Gardeners & Restoration Practitioners : Propagation Guidelines. (2019). Retrieved February 6, 2019, from http://www.goert.ca/propagation_guidelines/shrubs/symphoricarpos_albus
Government of British Columbia. (2016). Indicators of Climate Change for British Columbia. Retrieved from https://www2.gov.bc.ca/assets/gov/environment/research-monitoring-and-reporting/reporting/envreportbc/archived-reports/climate-change/climatechangeindicators-13sept2016_final.pdf
Hague, A., Fehr, B., Griffin, S., Chaboyer, S., & Gomes, T. (2009). Alumni Garry Oak Meadow Restoration Project. Retrieved from https://www.uvic.ca/socialsciences/environmental/assets/docs/courses3/ER341TermProject-ALUMNIGARRYOAKMEADOWRESTORATIONPROJECT.pdf
Hobbs, R. J., Higgs, E., Hall, C. M., Bridgewater, P., Stuart, F., Iii, C., … Suding, K. N. (2014). Managing the whole landscape: historical, hybrid, and novel ecosystems. Ecology and the Environment (Vol. 12). Retrieved from https://www-jstor-org.ezproxy.library.uvic.ca/stable/pdf/43187702.pdf?refreqid=excelsior%3Aa2328da88a8f287b6286e29ee2fc4a9f
Macdougall, A. S., Beckwith, B. R., & Maslovat, C. Y. (2004). Society for Conservation Biology Defining Conservation Strategies with Historical Perspectives: A Case Study from a Degraded Oak Grassland Ecosystem. Biology (Vol. 18). Retrieved from https://www-jstor-org.ezproxy.library.uvic.ca/stable/pdf/3589224.pdf?refreqid=excelsior%3A3e54892a3a444c17771b4d2826d5c0fb
Mccune, J. L., Pellatt, M. G., & Vellend, M. (2013). Multidisciplinary synthesis of long-term human-ecosystem interactions: A perspective from the Garry oak ecosystem of British Columbia. http://doi.org/10.1016/j.biocon.2013.08.004
Mcdadi, O., & Hebda, R. J. (2008). Change in historic fire disturbance in a Garry oak (Quercus garryana) meadow and Douglas-fir (Pseudotsuga menziesii) mosaic: A possible link with First Nations and Europeans. http://doi.org/10.1016/j.foreco.2008.03.012
Parks Canada Agency. (2006). Species at Risk Act Recovery Strategy Series Recovery Strategy for Multi-Species at Risk in Garry Oak Woodlands in Canada. Retrieved from http://www.sararegistry.gc.ca/the_act/default_e.cfm
Pellatt, M. G., & Gedalof, Z. (2014). Environmental change in Garry oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape. Biodiversity and Conservation, 23(8), 2053–2067. http://doi.org/10.1007/s10531-014-0703-9
Simberloff, D. (2013). Invasive Species: What Everyone Needs to Know. Retrieved from https://books.google.ca/books?hl=en&lr=&id=QzyBPA8SrN4C&oi=fnd&pg=PR5&dq=simberloff+invasive+species&ots=88w423xYM1&sig=nBlDrIgb8ZX1cMFai0TEY2k168c#v=onepage&q=simberloff invasive species&f=false
Turner, N. (2014). Ancient Pathways, Ancestral Knowledge : Ethnobotany and Ecological Wisdom of Indigenous Peoples of Northwestern North America. Retrieved from http://web.a.ebscohost.com.ezproxy.library.uvic.ca/ehost/ebookviewer/ebook/bmxlYmtfXzgxMjgwNF9fQU41?sid=618a5ff0-3daa-4744-9013-2069d140a795@sessionmgr4007&vid=0&format=EB&lpid=lp_Vol_2_vii&rid=0
Common Snowberry, Symphoricarpos albus. (2017). In Native Plants PNW. Retrieved from http://nativeplantspnw.com/common-snowberry-symphoricarpos-albus/
Costanzo, B., Eastmas, D., Engelstoft, C., Gorman, M., Hebda, R., Hook, F., … Webb, C. (2011). Restoring British Columbia’s Garry Oak Ecosystems: Principles and Practices. Victoria, British Columbia, Canada. Retrieved from http://docstore.library.uvic.ca.ezproxy.library.uvic.ca/Restoring_British_Columbias_garry_oak_ecosystems.pdf
District of West Vancouver. (2014). Excerpt from Invasive Plants Strategy Best management practices and target plant profiles Japanese Knotweed Scotch Broom Giant Hogweed. Retrieved from https://westvancouver.ca/sites/default/files/strategies/Invasive-Plant-Strategy-DWV-Schedule-A-Dec17-2014-web.pdf
Dunwiddie, P. W., & Bakker, J. D. (2011). The Future of Restoration and Management of Prairie-Oak Ecosystems in the Pacific Northwest. Northwest Science, 85(2), 83–92. http://doi.org/10.3955/046.085.0201
Gilbert, O. L. (1995). Symphoricarpos albus (L.) S. F. Blake (S. rivularis Suksd., S. racemosus Michaux). Journal of Ecology (Vol. 83). Retrieved from https://about.jstor.org/terms
GOERT : About Garry oak ecosystems. (2019). Retrieved March 3, 2019, from http://www.goert.ca/about/why_disappearing.php
GOERT : for Gardeners & Restoration Practitioners : Propagation Guidelines. (2019). Retrieved February 6, 2019, from http://www.goert.ca/propagation_guidelines/shrubs/symphoricarpos_albus
Government of British Columbia. (2016). Indicators of Climate Change for British Columbia. Retrieved from https://www2.gov.bc.ca/assets/gov/environment/research-monitoring-and-reporting/reporting/envreportbc/archived-reports/climate-change/climatechangeindicators-13sept2016_final.pdf
Hague, A., Fehr, B., Griffin, S., Chaboyer, S., & Gomes, T. (2009). Alumni Garry Oak Meadow Restoration Project. Retrieved from https://www.uvic.ca/socialsciences/environmental/assets/docs/courses3/ER341TermProject-ALUMNIGARRYOAKMEADOWRESTORATIONPROJECT.pdf
Hobbs, R. J., Higgs, E., Hall, C. M., Bridgewater, P., Stuart, F., Iii, C., … Suding, K. N. (2014). Managing the whole landscape: historical, hybrid, and novel ecosystems. Ecology and the Environment (Vol. 12). Retrieved from https://www-jstor-org.ezproxy.library.uvic.ca/stable/pdf/43187702.pdf?refreqid=excelsior%3Aa2328da88a8f287b6286e29ee2fc4a9f
Macdougall, A. S., Beckwith, B. R., & Maslovat, C. Y. (2004). Society for Conservation Biology Defining Conservation Strategies with Historical Perspectives: A Case Study from a Degraded Oak Grassland Ecosystem. Biology (Vol. 18). Retrieved from https://www-jstor-org.ezproxy.library.uvic.ca/stable/pdf/3589224.pdf?refreqid=excelsior%3A3e54892a3a444c17771b4d2826d5c0fb
Mccune, J. L., Pellatt, M. G., & Vellend, M. (2013). Multidisciplinary synthesis of long-term human-ecosystem interactions: A perspective from the Garry oak ecosystem of British Columbia. http://doi.org/10.1016/j.biocon.2013.08.004
Mcdadi, O., & Hebda, R. J. (2008). Change in historic fire disturbance in a Garry oak (Quercus garryana) meadow and Douglas-fir (Pseudotsuga menziesii) mosaic: A possible link with First Nations and Europeans. http://doi.org/10.1016/j.foreco.2008.03.012
Parks Canada Agency. (2006). Species at Risk Act Recovery Strategy Series Recovery Strategy for Multi-Species at Risk in Garry Oak Woodlands in Canada. Retrieved from http://www.sararegistry.gc.ca/the_act/default_e.cfm
Pellatt, M. G., & Gedalof, Z. (2014). Environmental change in Garry oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape. Biodiversity and Conservation, 23(8), 2053–2067. http://doi.org/10.1007/s10531-014-0703-9
Simberloff, D. (2013). Invasive Species: What Everyone Needs to Know. Retrieved from https://books.google.ca/books?hl=en&lr=&id=QzyBPA8SrN4C&oi=fnd&pg=PR5&dq=simberloff+invasive+species&ots=88w423xYM1&sig=nBlDrIgb8ZX1cMFai0TEY2k168c#v=onepage&q=simberloff invasive species&f=false
Turner, N. (2014). Ancient Pathways, Ancestral Knowledge : Ethnobotany and Ecological Wisdom of Indigenous Peoples of Northwestern North America. Retrieved from http://web.a.ebscohost.com.ezproxy.library.uvic.ca/ehost/ebookviewer/ebook/bmxlYmtfXzgxMjgwNF9fQU41?sid=618a5ff0-3daa-4744-9013-2069d140a795@sessionmgr4007&vid=0&format=EB&lpid=lp_Vol_2_vii&rid=0