COSEWIC Assessment and Status Report on the Hairy Braya Braya pilosa in Canada ENDANGERED 2013 COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows: COSEWIC. 2013. COSEWIC assessment and status report on the Hairy Braya Braya pilosa in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. ix + 30 pp. (www.registrelep- sararegistry.gc.ca/default_e.cfm). Production note: COSEWIC would like to acknowledge James G. Harris for writing the status report on Hairy Braya, Braya pilosa, prepared under contract with Environment Canada. This report was overseen and edited by Bruce Bennett, Co-chair of the COSEWIC Vascular Plants Specialist Subcommittee. For additional copies contact: COSEWIC Secretariat c/o Canadian Wildlife Service Environment Canada Ottawa, ON K1A 0H3 Tel.: 819-953-3215 Fax: 819-994-3684 E-mail: COSEWIC/[email protected] http://www.cosewic.gc.ca Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur le Braya poilu (Braya pilosa) au Canada. Cover illustration/photo: Hairy Braya — photo by J. Harris. Her Majesty the Queen in Right of Canada, 2013. Catalogue No. CW69-14/672-2013E-PDF ISBN 978-1-100-22437-4 Recycled paper COSEWIC Assessment Summary Assessment Summary – May 2013 Common name Hairy Braya Scientific name Braya pilosa Status Endangered Reason for designation This plant is restricted globally to a very small area in the Northwest Territories. It is endangered by the loss of habitat through very rapid coastal erosion and saline wash resulting from storm surges, and by permafrost melting. These events appear to be increasing in frequency and severity as a consequence of a significant reduction in sea ice cover on the Beaufort Sea and changes in weather patterns. These indirect impacts of climate change are expected to continue into the foreseeable future. Occurrence Northwest Territories Status history Designated Endangered in May 2013. iii COSEWIC Executive Summary Hairy Braya Braya pilosa Wildlife Species Description and Significance Hairy Braya (Braya pilosa) is a long-lived perennial mustard with one to many stems 4.0-12 cm long, erect to ascending to almost prostrate and moderately to densely hairy. It is distinguished from other Braya species by its large flowers and globose (nearly spherical) fruits with very long persistent styles. Hairy Braya is a narrow endemic of arctic Canada that likely played a crucial role in the evolution of other Braya species. Distribution Hairy Braya is only known to occur on Cape Bathurst in the Northwest Territories of Canada. There are 13 populations on the northern portion of Cape Bathurst and on the nearby Baillie Islands. Hairy Braya is restricted to an area that remained ice-free during the Pleistocene and it has apparently been unable to move into surrounding glaciated areas over the millennia since the ice receded. Habitat Hairy Braya grows on bluffs and dry uplands on patches of bare, calcium-rich sandy or silty soils. It typically grows with Arctic Willow, Entire-leaved Mountain-avens, and various grass species including Richardson’s Fescue, Arctic Wheatgrass, Arctic Bluegrass, and Alkali Grass.These habitats appear to be quite limited on Cape Bathurst. Patches of suitable habitat are often separated by large areas of wet tundra, or by eroded cliffs or salinized soils. Coastal areas southwest of Cape Bathurst are rapidly eroding, and a decrease in arctic sea ice is likely hastening the erosion of Hairy Braya habitat along the coast. iv Biology Hairy Braya was lost to science from 1850 to 2004. As a result, very little is known about the biology of the species. However, the large, fragrant flowers suggest that the plant is insect-pollinated, and seeds germinate readily. There is some genetic and morphological evidence that two related species, Smooth Braya and Greenland Braya may have arisen from Hairy Braya, and it is possible that hybridization between these species, both of which overlap in distribution with Hairy Braya, may be ongoing. Population Sizes and Trends Precise counts of the number of individuals have not been made, but estimates of the number of mature individuals observed in 2011 range from about 12,000 to 16,000. Populations on coastal bluffs subject to rapid erosion are clearly at risk of declining. The total number of individuals in one coastal population plummeted between 2004 and 2011. It can be expected that similar populations on eroding shorelines will be similarly affected. Trends and fluctuations in population sizes on protected sections of the coast and on inland bluffs have not been determined, but population sizes appear to be stable. Threats and Limiting Factors The most obvious threat to Hairy Braya is a loss of habitat due to rapid erosion and saline wash of coastline habitat resulting from storm surges and permafrost melting. These events appear to be increasing in frequency and severity as a consequence of a substantial reduction in ice cover on the Beaufort Sea over the past few decades. These impacts of anthropogenic climate change are expected to continue into the foreseeable future, and therefore it is unlikely that coastal erosion rates will decrease. Protection, Status, and Ranks Hairy Braya is ranked as critically imperilled globally (G1) and nationally (N1) by NatureServe, and has been assessed as Threatened in the Northwest Territories. Due to the remoteness of Cape Bathurst, Hairy Braya faces little direct threat from human activities. Cape Bathurst includes the calving grounds of the Cape Bathurst caribou herd and a local conservation plan recommends that the area be managed so as to eliminate, to the greatest extent possible, potential damage and disruption. v TECHNICAL SUMMARY Braya pilosa Hairy Braya Braya poilu Range of occurrence in Canada (province/territory/ocean): Northwest Territories Demographic Information Generation time (usually average age of parents in the population; indicate 10+ years based on if another method of estimating generation time indicated in the IUCN other Braya species. guidelines (2008) is being used). Generation time is at least 10 years, and likely 20+years. The age of the youngest and oldest breeding individual has not yet been determined. Is there a [observed, inferred, or projected] continuing decline in number of Yes mature individuals? Coastal populations are declining due to erosion, but inland populations are stable. Estimated percent of continuing decline in total number of mature 2-5% individuals within 2 generations. [Observed, estimated, inferred, or suspected] percent [reduction or unknown increase] in total number of mature individuals over the last [10 years, or 3 generations]. Several hundred mature plants were lost between 2004 and 2011 due to erosion; however only a single population was known until 2011 so the total loss cannot be quantified. [Projected or suspected] percent [reduction or increase] in total number of 5% decrease mature individuals over the next [10 years, or 3 generations]. The total population is projected to decline by 5% over the next 10 years, based on the loss of coastal populations. [Observed, estimated, inferred, or suspected] percent [reduction or unknown increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future. Populations in coastal areas subject to erosion will continue to be eliminated, but once they are gone, remaining populations are likely to remain stable. Are the causes of the decline clearly reversible and understood and No ceased? Decline resulting from increase erosion from reduced sea ice is understood but not reversible within a useful timeframe. Are there extreme fluctuations in number of mature individuals? No Extent and Occupancy Information Estimated extent of occurrence 250 km² Index of area of occupancy (IAO). This is a minimum estimate that is likely 64 km²+ to increase with more survey effort. Is the total population severely fragmented? No Number of locations∗ 5 Locations are based on the impact of the most plausible threats, such as coastal erosion, potential effects of storm surges, and potential flooding. ∗See Definitions and Abbreviations on COSEWIC website and IUCN 2010 for more information on this term. vi Is there an [observed, inferred, or projected] continuing decline in extent of Yes, observed occurrence? If the most westerly populations are lost there will be a decline in extent of occurrence. Is there an [observed, inferred, or projected] continuing decline in index of Yes, observed and area of occupancy? projected The loss of four at-risk coastal populations would reduce the IAO by 16 km². Is there an [observed, inferred, or projected] continuing decline in number Yes, observed and of populations? projected Four or perhaps five coastal populations will likely be lost to erosion. Is there an [observed, inferred, or projected] continuing decline in number Yes projected. of locations*? Is there an [observed, inferred, or projected] continuing decline in [area, Yes, observed extent and/or quality] of habitat? Coastal habitat is rapidly eroding. Are there extreme fluctuations in number of populations? No Are there extreme fluctuations in number of locations∗? No Are there extreme fluctuations in extent of occurrence? No Are there extreme fluctuations in index of area of occupancy? No Number of Mature Individuals (in each population) Population (major threat) N Mature Individuals 1 (storm surge) 32 2 (storm surge) 240 3 (coastal erosion) 160 4 (coastal erosion) 160 5 (coastal erosion) (>240 but <800) 6 (storm surge) >8,000 7 (storm surge) 80 8 (storm surge) 80 9 40 10 (>240 but <800) 11 (coastal erosion) (>240 but <800) 12 (coastal erosion) (>240 but <800) 13 (>240 but <800) Total 12,000-16,000 Quantitative Analysis Probability of extinction in the wild is at least [20% within 20 years or 5 Not Done generations, or 10% within 100 years].