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Recovery Strategy for the California Buttercup (Ranunculus californicus) in Canada

Table of Contents

California Buttercup in flower.
© Matt Fairbarns

Recommended citation:

Parks Canada Agency. 2013. Recovery Strategy for the California Buttercup (Ranunculus californicus) in Canada. Species at Risk Act Recovery Strategy Series. Parks Canada Agency, Ottawa. vii + 24 pp.

For copies of the recovery strategy, or for additional information on species at risk, including COSEWIC Status Reports, residence descriptions, action plans, and other related recovery documents, please visit the Species at Risk Public Registry.

Cover illustration: California Buttercup, photograph courtesy of Matt Fairbarns.

Également disponible en français sous le titre

« Programme de rétablissement de la renoncule de Californie (Ranunculus californicus) au Canada »

© Her Majesty the Queen in Right of Canada, represented by the Minister of the Environment, 2013. All rights reserved.

ISBN 978-1-100-22450-3

Catalogue no. En3-4/167-2013E-PDF

Content (excluding the illustrations) may be used without permission, with appropriate credit to the source.

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Preface

The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996) agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of recovery strategies for listed Extirpated, Endangered, and Threatened species and are required to report on progress within five years.

The Minister of the Environment and the Minister responsible for the Parks Canada Agency is the competent minister for the recovery of the California Buttercup and has prepared this strategy, as per section 37 of SARA. It has been prepared in cooperation with Environment Canada, the provincial government of British Columbia, and the Songhees Nation.

Success in the recovery of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy and will not be achieved by the Parks Canada Agency, or Environment Canada, or any other jurisdiction, alone. All Canadians are invited to join in supporting and implementing this strategy for the benefit of the California Buttercup and Canadian society as a whole.

This recovery strategy will be followed by one or more action plans that will provide information on recovery measures to be taken by Environment Canada and/or the Parks Canada Agency and other jurisdictions and/or organizations involved in the conservation of the species. Implementation of this strategy is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.

The recovery of California Buttercup will be coordinated with the recovery of at-risk species inhabiting maritime meadows associated with Garry Oak ecosystems (Parks Canada Agency 2006).

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Recommendation and Approval Statement

The Parks Canada Agency led the development of this federal recovery strategy, working together with the other competent minister(s) for this species under the Species at Risk Act. The Chief Executive Officer, upon recommendation of the relevant Park Superintendent(s) and Field Unit Superintendent(s), hereby approves this document indicating that Species at Risk Act requirements related to recovery strategy development have been fulfilled in accordance with the Act.

Recommended by:

____________________________________________________
Helen Davies
Field Unit Superintendent, Coastal BC, Parks Canada Agency

Approved by:

____________________________________________________
Alan Latourelle
Chief Executive Officer, Parks Canada Agency

signature

 

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Acknowledgements

Thank you to Matt Fairbarns for writing the initial draft of this recovery strategy. The Garry Oak Ecosystems Recovery Team (GOERT) is the recovery team for the California Buttercup and is thanked for their involvement in the development of this recovery strategy. Thank you to the various landowners who support recovery of this species on their land and provided access for surveys.

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Executive Summary

The Canadian population of the California Buttercup (Ranunculus californicus Benth.) was assessed as Endangered in 2008 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), and in February 2011 the population was listed as Endangered under Canada’s Species at Risk Act (SARA) Schedule 1.

The California Buttercup is a low growing perennial herb with lemon-yellow, flowers (with up to 16 petals), and hairy stems ranging from 15–50 cm tall. It ranges from British Columbia south along the coast to Baja California, but the Canadian population is widely disjunct from the nearest Oregon population. The Canadian population of California Buttercup comprises <1% its global range. In Canada, California Buttercup is known from four confirmed populations, three recently confirmed to be extant, all occurring along the southeast coast of Vancouver Island.

The key factors limiting the recovery and survival of the California Buttercup population in Canada are its specificity to rare maritime meadow habitats, limited dispersal abilities, small area of physical occupancy, and small, highly fragmented populations that constrain genetic diversity. Further, California Buttercup populations are threatened by invasion of alien plants, encroachment by native herbaceous and woody vegetation, potential hybridization, recreational activities, livestock grazing, trampling and habitat conversion.

The population and distribution objectives for California Buttercup in Canada are to maintain the four confirmed extant populations and prevent a decline in distribution while exploring the feasibility of establishing and/or augmenting populations to increase abundance and distribution. Broad strategies to be taken to address the threats to the survival and recovery of the California Buttercup are presented in section 6.1 Strategic Direction for Recovery.

Critical habitat for the recovery of California Buttercup is identified in this recovery strategy. The best available information has been used to identify critical habitat; however, there are significant knowledge gaps. Additional critical habitat will need to be identified in upcoming planning documents to meet the population and distribution objectives.

Further recovery action for California Buttercup will be incorporated into one or more action plans by 2018.

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Recovery Feasibility Summary

The recovery of the California Buttercup in Canada is considered feasible based on the criteria outlined by the Government of Canada (2009):

  1. Individuals of the wildlife species that are capable of reproduction are available now or in the foreseeable future to sustain the population or improve its abundance.

    Yes. All three populations recently confirmed to be extant support numerous reproductive individuals and seeds could be collected from these populations to be used for restoration.

  2. Sufficient suitable habitat is available to support the species or could be made available through habitat management or restoration.

    Yes. There is sufficient suitable habitat to support self-sustaining populations and additional suitable habitat could be made available through active habitat stewardship or restoration, if needed.

  3. The primary threats to the species or its habitat (including threats outside Canada) can be avoided or mitigated.

    Yes. Further habitat loss can be prevented by relocating recreational use such as camping, picnicking and walking. Although pre-contact First Nations burning regimes may be difficult to restore, and may no longer be effective due to the presence of invasive alien plants, surrogate actions including shrub and tree cutting, and dormant season mowing, may be used as alternatives to fire to control shrub and tree encroachment. Competition, suppression and space pre-emption by invasive alien shrubs, grasses, and forbs may be mitigated using an integrated pest management approach.

  4. Recovery techniques exist to achieve the population and distribution objectives or can be expected to be developed within a reasonable timeframe.

    Yes. Recovery success will be tied primarily to threat reduction through habitat stewardship, in combination with long-term population monitoring and inventory.

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1. COSEWIC Species Assessment Information

Date of Assessment: November 2008

Common Name: California Buttercup

Scientific Name: Ranunculus californicus

COSEWIC Status: Endangered Reason for Designation: A perennial species restricted to two small island groups adjacent to Victoria, BC. The four small confirmed populations are found within coastal meadow habitats where the extensive spread of invasive plants places the species at risk. Potential impacts on the populations include planned enlargement of communications towers at one site and unauthorized recreational visitors to the island habitats.

Canadian Occurrence: British Columbia

COSEWIC Status History: Designated Endangered in November 2008. Assessment based on a new status report.

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2. Species Status Information

The Canadian population of California Buttercup (Ranunculus californicus) was assessed as Endangered in 2008 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), and in February 2011 the population was listed as Endangered under Canada’s Species at Risk Act (SARA). Provincial, state, and global conservation ranks for California Buttercup in other jurisdictions where it occurs are provided in Table 1.

The California Buttercup population in Canada comprises less than 1% of its global range.

Table 1. Conservation ranks for California Buttercup. Sources: B.C. Conservation Data Centre 2011, NatureServe 2011.
LocationRank*Rank description
GlobalG5Secure
CanadaN2Imperilled
British ColumbiaS1Critically imperilled
United StatesN5Demonstrably secure
CaliforniaSNRNot ranked
OregonSNRNot ranked
WashingtonS1Critically imperilled

* NatureServe Conservation ranks are based on a one to five scale, ranging from critically imperilled (1) to demonstrably secure (5). Status is assessed and documented at three distinct geographic scales global (G), national (N), and state/province (S).

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3. Species Information

3.1. Species Description

California Buttercup is a low-growing, hairy, herbaceous perennial that produces numerous stems from a central root crown. Mature plants bear 2-8 cm long, lobed, long-stalked basal leaves with blunt teeth. The sprawling to erect, 15–50 cm long stems produce several flowers in an open inflorescence. The flowers have numerous (up to 16) shiny lemon-yellow petals, unlike most species of buttercup that typically have only five petals. It is also distinguished from similar buttercup species (such as the Western Buttercup; Ranunculus occidentalis) by the noticeably curved beak on the seeds (COSEWIC 2008). California Buttercup may interbreed with Western Buttercup forming plants which are intermediate in appearance (Brayshaw 1989). Further details on the appearance of California Buttercup, and the hybrids it forms with Western Buttercup, are found in the status report (COSEWIC 2008).

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3.2. Population and Distribution

California Buttercup occurs from southwestern British Columbia south along the coast to Baja California, including inland areas of California, with a Canadian population that is widely disjunct from the nearest US populations in Oregon (Figure 1; COSEWIC 2008). This severely limits the possibly of a metapopulation dynamic or gene flow with US populations. In Canada, California Buttercup is known only from small island clusters to the south and east of Victoria on the southeastern side of Vancouver Island.

Canadian populations are presumed to be independent with little gene flow or potential for rescue effect from US populations and have shown the ability for long-term persistence prior to the influence of human activity (COSEWIC 2008). Further, the two island groups where the species is confirmed are about 6 km apart, and seed dispersal across the intersecting ocean is unlikely (COSEWIC 2008). Loss and degradation of Garry Oak ecosystems has also created a highly fragmented habitat (GOERT 2002; Lea 2006) which further limits seed dispersal between suitable habitats. For the purposes of this recovery strategy, populations separated by 1 km or more, are considered a separate population.

California Buttercup is restricted to a very small area in Canada (<20 km2). Four California Buttercup populations have been confirmed in Canada, at Trial Islands, Discovery Island, West Chatham Island, and Alpha/Griffin Islands (Figure 2). A potential fifth population, reported from Saturna Island, requires further inspection because there is debate regarding the species identity (COSEWIC 2008) and plants could not be verified in 2010 because they did not flower. Population information for the four confirmed populations, collected in 2005 (provided in the status report), supplemented with information gathered in 2010, suggest that the Canadian populations of California Buttercup fluctuate between 3,077 to 12,508 mature plants in total (Table 2). Population sizes differ widely in their historic numbers, some sites only have tens of plants, others have a few hundred, and in the case of Griffin Island, several thousand.

In 2010, buttercup plants with “extra” petals were observed at two locations not noted in the COSEWIC status report (2008): Beacon Hill Park and Uplands Park on Vancouver Island. The identity of plants at these two locations could not be determined because of insufficient identifiable characteristics. These two populations are not included in (Table 2) because further investigation is required before they are accepted as California Buttercup populations.

There are not sufficient data to directly determine a trend in the number of mature individuals or the area occupied by the Canadian population. Overall, a decline in the species abundance in Canada is inferred, based on indirect evidence (a decline in habitat quality) (COSEWIC 2008).

Table 2. General location, population size and land tenure for California Buttercup in Canada with population number corresponding to numbers on map in Figure 2.
Population1General locationPopulation size (year counted)Land Tenure
1.1Trial Island10 (2005)
0-50 plants2 (2010)
Non-federal land
1.2Lesser Trial Island170-180 (2005)
68 (2010)
Non-federal land
2Discovery Island35 (2005)
30–40 (2010)
Non-federal land
3.1Alpha Islet400-600 (2005)
5,250-5,350 (2010)
Non-federal land
3.2Griffin Island1,900-2,100 (2005)
6,000-7,000 (2010)
Non-federal land
4West Chatham Island570-590 (2005)
No data (2010)
Federal lands
5Saturna Island< 50 (2005) identity requires confirmation
Failed to find3 (2010)
Non-federal land

1 First number indicates population and number in decimal place indicates the subpopulation.

2 Approximately 50 plants were found with ≥ 8 petals per flower; most species of buttercup that typically have only five petals. However, California Buttercup has a curved beak on the seeds; confirmation of species identity was not possible because fruit did not mature.

3 Four non-flowering plants were found which could have been California Buttercup, Western Buttercup or a hybrid between the two.

Map of the North American distribution
Figure 1. Distribution of California Buttercup in North America (from COSEWIC 2008). Solid black regions indicate species native range.
Map of British Columbian distribution
Figure 2. Distribution of California Buttercup in Canada (adapted from COSEWIC 2008). Stars indicate confirmed populations (#1-4) and a potential fifth population on Saturna Island (#5). Numbers refer to the populations and subpopulations listed in Table 2.

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3.3. Needs of the California Buttercup

California Buttercup is intrinsically rare in Canada due to the limited area capable of supporting the species (COSEWIC 2008) as well as certain factors that may limit its survival. In Canada, California Buttercup is restricted to maritime meadow habitats associated with Garry Oak ecosystems (Figure 3). It is further restricted to locations within 100 m of the ocean, in the mildest and driest portion of islands near southeastern Vancouver Island. It is possibly intolerant of moderate to heavy shading and competition from trees and shrubs. It is also intolerant of prolonged seepage or inundation.

Photograph of Habitat of California Buttercup at Lesser Trial Island
Figure 3. Habitat of California Buttercup at Lesser Trial Island. Photo by Matt Fairbarns.

A number of factors may limit the survival and recovery of California Buttercup in Canada:

  • Dependence on highly specific maritime meadow habitats associated with Garry Oak ecosystems, most of which have been lost or damaged by habitat conversion (i.e., the loss of suitable habitat, often as a result of urban development), forest encroachment, and/or a shift to ecosystem dominance by invasive alien plants.
  • A lack of long-distance dispersal of seeds or fruits limits the potential for local rescue effects or establishment in unoccupied habitat areas (COSEWIC 2008).
  • Extremely small population sizes (<100 plants in some cases) may constrain the species’ genetic diversity, and increase its vulnerability to extirpation due to demographic stochasticity and chance events including those which operate at a small scale.

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Introduction / Species Information