BC Conservation Data Centre: Conservation Status Report
Bolboschoenus fluviatilis
river bulrush
| Scientific Name: | Bolboschoenus fluviatilis |
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| Scientific Name Synonyms: |
Scirpus fluviatilis
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| English Name: | river bulrush |
| Provincial Status Summary | |
| Status: | S2S3 |
| Date Status Assigned: | April 30, 2019 |
| Date Last Reviewed: | April 30, 2019 |
| Reasons: | Only three occurrences of river bulrush are presumed extant in BC and only one may have good viabilty. The occurrences are widely separated, with two in south-central BC, and another on the west coast of Vancouver Island. One may be in an Ecological Reserve. Population size is unknown. The range extent is ca. 2300 kmē, and the Area of Occupancy is estimated to be 12 square kilometers. Trends are unknown. Identifiable threats are livestock trampling and lake/river water level management. |
| Range | |
| Range Extent: | D = 1,000-5,000 square km |
| Range Extent Comments: | The estimated range extent is 2,288 square kilometres from Hesquiat to Osoyoos Lake. |
| Area of Occupancy (km2): | CD = 3-25 |
| Area of Occupancy Comments: | The estimated area of occupancy is 12 square kilometres or 3 - 4 square kilometre grid cells. |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | The total number of extant known occurrences of river bulrush is 3, one at Hesquiat and two near Osoyoos. There are five historial records. Frank Lomer (pers. comm. 2010) first observed and collected a specimen in 1996 from a large wetland area near the north end of Osoyoos Lake. In the early 2000's (est. 2004), he observed a small, probably dead clump to the east of this site in an open, livestock trampled area near a barn. The 1972 'Osoyoos Lake' collection of T.C. Brayshaw may be from the same location but there are no accurate location data for this collection. His herbarium label states: 'Shallow water, sandy bottom in bay' which indicates along Osoyoos Lake itself. Although observations are few, the taxon occurs in areas that are far apart with extensive appropriate habitat between. Additional populations possibly occur; some populations are consistently sterile and thus have been overlooked. |
| Number of Occurrences with Good Viability / Ecological Integrity: | B = 1 - 3 |
| Comments: | At least the main portion of the occurrence north of Osoyoos Lake appears to have good viabilty but needs to be resurveyed. F. Lomer (pers. comm. 2010) found a clump of this species south of the wetlands in or around 2004 but it had been growing in a dry watercourse and the area had been heavily trampled by cattle. The two other occurrences were observed in 1972 (Osoyoos Lake) and 1974 (Hesquiat), over 35 years ago, and, because they have not been re-surveyed, there is no information on their viability. Herbarium specimens were made from both of these sites but details about viabilty were not made at that time. |
| Number of Occurrences Appropriately Protected & Managed: | U = Unknown |
| Comments: | The site north of Osoyoos Lake reported by F. Lomer may is possibly protected within the Hayne's Lease Ecological Reserve. Because the Hesquiat population has not been relocated, its exact location is unknown and an assessment of its protection is not available (N. Turner pers. comm. 2010). |
| Population Size: | A = 1 - 50 individuals |
| Comments: | Population size was not noted for the populations when they were observed, although F. Lomer (pers. comm. 2010) noted that the population in the wetlands was larger than than the one near the road. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Moderate, non-imminent threat |
| Comments: | No threats were identified when populations were observed in 1972 (at an unknown location along Osoyoos Lake) and in 1974 (at Hesquiat). Part of the population north of Osoyoos Lake has been trampled by livestock and water levels appeared to have been markedly lower than normal since the plant was stranded (F. Lomer pers. comm. 2010), so livestock and irregular water management or drought are threats to this species. However, in this type of habitat (in shallow water along rivers and lakeshores), potential threats would include developments such as houses or docks, water use by ranches or homes, recreational activities such as hiking or boating, pollution from road or livestock waste runoff, and invasive alien species, especially Phalaris arundinacea, which frequent areas of disturbance in the south Okanagan Valley. In eastern North America, this species has been greatly reduced in some sites following invasion of exotic species (Jarchow and Cook 2009). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | U = Unknown |
| Comments: | Short-term trends are not known. Two of the occurrences have not been observed since 1972 and 1974, respectively, and short-term trends cannot be assessed. Trends have not been assessed for the Osoyoos Lake observations from 1996 and 2004 as the populations have not been revisited. However, because disturbance is probably absent or strictly limited, the plants within the wetland there are probably relatively stable. |
| Long-Term Trend: | U = Unknown |
| Comments: | Long-term trends are not known. Two of the occurrences have not been observed since 1972 and 1974, respectively, and long-term trends cannot be assessed. Trends have not been assessed for the Osoyoos Lake observations from 1996 and 2004 as the populations have not been revisited. However, because disturbance is probably absent or strictly limited, at least the plants within the wetland are probably relatively stable. |
| Other Factors | |
| Intrinsic Vulnerability: | BC=Moderately vulnerable to not intrinsically vulnerable. |
| Comments: | This species matures quickly, reproduces frequently, and/or has high fecundity so that that populations probably recover quickly from decreases in abundance. It also successfully reproduces asexually and expands patches via rhizomes. The wetland ecosystem favoured by this species tends to be resilient to changes in composition and structure and quickly recover. |
| Environmental Specificity: | B=Narrow. Specialist or community with key requirements common. |
| Comments: | This species is a wetland specialist but key requirements (slow-moving waters in wetland habitats and other abiotic and/or biotic factors) for this species are common within the generalized range of the species. |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | Research needs include assessing the size, viability, and reproductive success of the known occurrences, and assessing threats at the known sites. A monitoring program should be designed and implemented. |
| Inventory Needs: | A survey in Hesquiat for this species has not been completed since the original collection 1974. The Hesquiat site needs to be resurveyed and data collected on habitat, population size, condition, threats, and viability. The extensive oxbow-associated wetlands to the north of Osoyoos Lake where F. Lomer observed river bulrush in the south Okanagan Valley have not been thoroughly surveyed and a detailed survey is required (F. Lomer, pers. comm. 2010). New sites need to be sought through targeted surveys in southern BC in high potential habitat, especially in the south Okanagan Valley. Ownership of the lands where this species is found needs to be assessed. |
| Stewardship | |
| Protection: | Protection needs are required to be evaluated after the populations are revisited and described. The exact location of the 1996 observation by F. Lomer north of Osoyoos lake needs to be confirmed so that it can be determined whether this species lies within the Ecological Reserve or not and whether it is otherwise protected. |
| Management: | Management needs are required to be evaluated after the populations are revisited and described. Protection can be achieved through voluntary stewardship agreements, purchase from willing sellers, and land use designations on Crown lands. A primary objective should be to protect both of the known populations. Maintaining multiple populations will help to mitigate the effects of catastrophic loss at any one site. Reserves should be large enough to maintain natural communities and ecological processes that sustain the plant populations. If protection of all populations is not considered feasible, sites could be prioritized based on numbers of plants present, productivity of site, and significance of site for maintaining species distribution (Cliff Paintbrush Recovery Team 2009). |
| Version | |
| Author: | McIntosh, T.T. and M. Donovan |
| Date: | April 24, 2015 |
| References | |
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Batten, R. 2018. Vascular plant GeoCAT range extent and index of AOO maps supporting status assessment 2017_18 for British Columbia Conservation Data Centre. March 2018. Victoria, BC. 450 pp.
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British Columbia Conservation Data Centre. Botany Program. 2000. Database containing records of rare plant collections and observations in the province of British Columbia.
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Cliff Paintbrush Recovery Team. 2009. Recovery strategy for cliff paintbrush (Castilleja rupicola) in British Columbia. Prepared for the B.C. Minist. of Environ., Victoria, BC. 18 pp.
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Jarchow, M.E and B.J. Cook. 2009. Allelopathy as a mechanism for the invasion of Typha angustifolia. Plant Ecol. 204(1):113-124.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2015. Conservation Status Report: Bolboschoenus fluviatilis. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 10, 2026).