BC Conservation Data Centre: Conservation Status Report
Artemisia tridentata / Pseudoroegneria spicata
big sagebrush / bluebunch wheatgrass
| Scientific Name: | Artemisia tridentata / Pseudoroegneria spicata |
|---|---|
| English Name: | big sagebrush / bluebunch wheatgrass |
| Provincial Status Summary | |
| Status: | S2? |
| Date Status Assigned: | May 12, 2022 |
| Date Last Reviewed: | May 12, 2022 |
| Reasons: | This grassland community has a narrow geographic range and is a matrix ecosystem within a large proportion of its range. There is a high degree of disturbance and the ecosystem is declining due to ongoing urban development. It is threatened by continued livestock grazing, alien plant invasion, conversion to agricultural use (serious) and urbanization (extreme). The long term effects of climate change with respect to range expansion and contraction are uncertain. |
| Range | |
| Range Extent: | D = 1,000-5,000 square km |
| Range Extent Estimate (km2): | 4494 |
| Biogeoclimatic Unit: |
BGxh1/01
BGxh2/01 BGxh3/01 BGxw1/04 BGxw2/00 PPxh1/00 PPxh2/05 |
| Range Extent Comments: | The range extent estimate of this ecological community is based on Version 9 of the Biogeclimatic Ecosystem Classification (BEC) map (B.C. Ministry of Forests, Lands, and Natural Resource Operations. 2014). Terrestrial Ecosystem Mapping (TEM) estimates are similar, however the Grassland Conservation Council (2004) estimated a range extent of 1346 km2, based only on non-forested areas with site conditions suitable for supporting this community. This ecological community is the dominant climatic ecosystem in the very dry hot Bunchgrass subzone (BGxh) (929 km2 within the Okanagan, Thompson and Fraser river valleys). It is a minor component (989 km2) in the moist warm Bunchgrass (BGmw) of the Alkali Lake region of the Cariboo and in the very dry hot Ponderosa Pine (PPxh) subzone (450 km2 of grasslands) where it occurs on some of the driest sites. TEM projects from both the Cariboo and the Okanagan regions, covering 44% of the range of this community, have been mapped in the Bunchgrass (BG) and Ponderosa Pine (PP) zones and also within the grassland phase of the very dry hot, Okanagan Interior Douglas-fir (IDFxh1a). |
| Area of Occupancy (km2): | DE = 100-1,000 km² |
| Area of Occupancy Comments: | Estimates of area of occupancy vary depending on the estimates of range and the mapping source (see Range Comments). Iverson (pers. comm. 2013) reported that this ecosystem may occupy 537 km2. This estimate is based on 50% of BGxh grasslands and 5% of PPxh and BGxw of the grasslands range as calculated by the Grassland Conservation Council (2004). Terrestrial Ecosystem Mapping data for currently mapped areas (see Range Comments) (44% of the range of this community) indicate an area of occupancy of 153 km2 (99 km2 in the Cariboo and 54 km2 in the Okanagan-Similkameen) (Yearsley et al. 2013). |
| Spatial Pattern: | Matrix |
| Occurrences | |
| Number of Occurrences: | U = Unknown |
| Comments: | Very little of the available ecosystem mapping has been extracted as element occurrences. |
| Number of Occurrences with Good Viability / Ecological Integrity: | U = Unknown |
| Percent Area with Good Viability / Ecological Integrity: | E = Good (21-40%) |
| Comments: | It is unlikely that many sites exist in excellent range condition due to extensive overgrazing and slower recovery for grasslands at low elevations. There are extensive infestations of invasive alien plants in many areas, particularly the Okanagan. In the Okanagan, Lea (2008) estimated only 20% of the remaining grassland area to be in good to excellent range condition, 61% in fair range condition and 19% in poor range condition. However in the Cariboo, grassland TEM projects indicate that 85% of the mapped area is in good or better range condition (Yearsley et al. 2013). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | AB = Very high - high |
| Comments: | This ecological community is highly threatened by the cumulative effects of recent urbanization (extreme severity, small scope), agricultural conversion (serious severity, low scope), domestic overgrazing, (moderate severity, pervasive in scope), invasion by alien species (moderate to serious severity, pervasive in scope), recreational impacts (ranging from negligible to serious severity, small in scope), and fire suppression (low to moderate severity, small scope). Fire exclusion (compared to the historical fire regime of frequent low-intensity fires) contributes to degradation of the ecosystem, primarily through higher densities of sagebrush. This ecosystem often occurs at low elevations and is not as susceptible to forest encroachment as other grassland ecosystems. Recovery after disturbance can be good unless many invasive alien plants are present. A combination of climate change effects are predicted to result in reduced soil moisture over the long term due to warming trends (Spittlehouse 2008), contributing to habitat alteration. The severity of these within a 10 year time frame is uncertain but anticipated to be of slight impact at this time. Compounding factors of existing disturbance levels, sources of alien species invasion and climate change effects on temperature and soil moisture add to the uncertainty of long term ecological integrity. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | F = Decline of 10-30% |
| Comments: | The distribution of this ecosystem is declining due to urban encroachment, rural residential development, and other anthropogenic development. Although range condition may have improved over past decades due to improved range practices, many areas are in early seral condition due to continued domestic grazing. Alien plant invasion is extensive and a high number of alien species have invaded these grasslands within the Okanagan and Thompson. |
| Long-Term Trend: | DE = Decline of 30-70% |
| Comments: | Within the South Okanagan - Similkameen TEM area, there has been a loss of 33% of this ecological community from 1800 to 2007 (Lea 2008). Remaining areas have also been degraded by earlier land use practices such as long term intensive cattle grazing. |
| Other Factors | |
| Intrinsic Vulnerability: | B=Moderately vulnerable |
| Comments: | Under natural disturbance conditions this grassland may recover in a few decades. More extreme anthropogenic disturbance is non-recoverable. |
| Environmental Specificity: | C=Moderate. Generalist or community with some key requirements scarce. |
| Comments: | This grassland ecosystem occupies conditions typical of B.C.'s interior warm dry climatic regions that support grassland development. In some areas it is more restricted to dry sites within a forested matrix. |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | |
| Stewardship | |
| Protection: | |
| Management: | |
| Version | |
| Author: | Iverson, K.E., C.M. Cadrin, and H.K. Yearsley |
| Date: | August 30, 2013 |
| References | |
|
B.C. Ministry of Forests, Lands, and Natural Resource Operations. Biogeoclimatic Ecosystem Classification (BEC) Map, WHSE_FOREST_VEGETATION.BEC_BIOGEOCLIMATIC_POLY [ESRI ArcSDE format]. Version 9. Ministry of Forests, Lands, and Natural Resource Operations, Forest Analysis and Inventory Branch, Victoria, B.C. Updated Regularly.
|
|
|
B.C. Ministry of Forests, Lands, and Natural Resources Operations. 2012. Biogeoclimatic Map, ABEC_BC [ESRI Interchange format]. Version 8. Minist. of Forests, Lands, and Natural Resource Operations. Forest Analysis and Inventory Branch, Victoria, B.C. ftp://ftp.for.gov.bc.ca/HRE/external/!publish/becmaps/GISdata/PreviousVersions/ (current as of Feb. 10, 2012).
|
|
|
Flynn, Samantha. 2000. Plant Association Status Ranking 1999-2000. Access Digital Database. BC Ministry of Environment, Conservation Data Centre. Victoria, BC.
|
|
|
Grasslands Conservation Council of British Columbia. 2004. BC grasslands mapping project: A conservation risk assessment. Final report. 116 pp.
|
|
|
Iverson, Kristi. 2012. Ecosystem status report for Purshia tridentata / Hesperostipa comata (antelope-brush / needle-and-thread grass) in British Columbia. Prepared for B.C. Ministry of Environment, Conservation Data Centre, Victoria, B.C. 34 pp.
|
|
|
Lea, T. 2008. Historical (pre-settlement) ecosystems of the Okanagan Valley and Lower Similkameen Valley of British Columbia - pre-European contact to the present. Davidsonia 19(1): 3-36.
|
|
|
Lloyd, D., K. Angove, G. Hope, and C. Thompson. 1990. A guide to site identification and interpretation for the Kamloops Forest Region. B.C. Minist. For., Res. Branch, Victoria, B.C. Land Manage. Handb. No. 23. 399pp.
|
|
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. 2013. Conservation Status Report: Artemisia tridentata / Pseudoroegneria spicata. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 5, 2026).