Gentiana wingecarribiensis - critically endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the herb Gentiana wingecarribiensis L. Adams as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Gentiana wingecarribiensis L. Adams from Part 1 of Schedule 1 (Endangered species) of the Act. Listing of Critically Endangered species is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. Gentiana wingecarribiensis L. Adams (Wingecarribee Gentian), of the plant family Gentianaceae, is an erect to decumbent, hairless annual (sometimes biennial or ephemeral) herb 2.5-12 cm tall with a slender unbranched taproot. It lacks a basal rosette of leaves. The stem is sometimes branched. The cauline leaves are opposite in 4-7 pairs, sessile, broadly ovate to oblong-ovate, keeled, 2-9 cm long, 2.5-6 mm wide with more or less recurved apices and minutely scabby margins. Flowers 1-9, solitary, terminal, more or less erect, usually 5-merous (rarely 4); the calyx is narrowly funnel-shaped, 6-10 mm long; the corolla is 10-17 mm long, narrowly bell-shaped, up to 11 mm diam., greenish outside, sky blue to purplish blue inside with longitudinal inside, with 5 (rarely 4) spreading major lobes each 2-3 mm long, and smaller folded lobes between them; stamens 5, enclosed within the corolla tube; stigmas 2, linear, c 3 mm long, persistent on fruit; fruit a capsule, broadly ovoid or obovoid, 2-valved, (1-)4-6 mm long at the end of a 12-25 mm stipe; seeds numerous, up to several hundred per capsule, orange-brown. (Description adapted from Adams & Williams 1988 and Kodela 2008); colour photos are available at www.threatenedspecies.environment.nsw.gov.au/tsprofile/profile.aspx?id=10347 , accessed 24 June 2009).

 

2. Gentiana wingecarribiensis is endemic to New South Wales, and is known only from two upland wetlands in the Southern Highlands district of the Central Tablelands: Wingecarribee Swamp, west of Robertson, and Hanging Rock Swamp, north of Wingello. The two populations are separated by about 19 km. Surveys and monitoring since the early 1990s have recorded the species from six highly localised sub-populations, four at Wingecarribee Swamp and two at Hanging Rock Swamp. Searches of other potential habitat in the Southern Highlands region have not revealed other populations (Kodela 2008). G. wingecarribiensis has an Extent of Occurrence of approximately 40 km2 if the disjunction between the two populations is excluded. G. wingecarribiensis has an Area of Occupancy of 8 km2, based on occupancy of two 2x2 km grid cells, the scale recommended for assessing area of occupancy by IUCN (2008); the actual ground area of recorded sites is very much smaller than this.

 

3. Gentiana wingecarribiensis usually grows in narrow ecotonal areas, usually no more than 15 m wide, of open low sward between the swamps (which are dominated either by sedges and Sphagnum, or sedges and Leptospermum), and the higher grassland and pasture. Occasional records show some ability to colonise both parts of the swamp proper, and non-swamp (but spring-fed) shrub-sedge-Sphagnum associations nearby (Kodela et al. 1994; Kodela 2008). Plants may root directly in the ground or in Sphagnum hummocks. The flowers on any one plant open in succession over a period of 2-3 months from about September or October. The corolla only opens in bright sunlight and/or as a response to change in temperature; it closes in dull or cold conditions, and plants are then very inconspicuous. The very localised nature of the sub-populations suggest highly specific habitat requirements and possibly specific requirements for seed survival, germination and growth, and the distribution is best interpreted as highly fragmented within, as well as between, the two main occurrences.

 

4. Plant numbers fluctuate greatly at and between the sites from year to year, and field observations (Kodela 2008) suggest that Gentiana wingecarribiensis is prone to very erratic rates of recruitment, although it is uncertain whether this results from variation in viability of seed, germination problems, or low seedling survival rates. Attempts to germinate seed ex situ have not succeeded (C. Offord pers. comm. from unpublished data). Longevity of seed in the soil is not known.

 

5. Gentiana wingecarribiensis has been listed as an Endangered species under Schedule 1, Part 1 of the Threatened Species Conservation Act 1995, since its inception. It is currently listed as an Endangered species under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (TSSC 2008). It is not known to occur in any conservation reserves. Protection for a small proportion of Gentian sites on Sydney Catchment Authority land at Wingecarribee Swamp is afforded by a Permanent Conservation Order under the Heritage Act 1977. The habitat of G. wingecarribiensis is partly included in the Endangered Ecological Community ‘Montane peatlands and swamps of the New England Tableland, NSW North Coast, Sydney Basin, South East Corner, South Eastern Highlands and Australian Alps Bioregions’ as listed under the Threatened Species Conservation Act 1995 (NSW Scientific Committee 2005), and is also partly included in the ‘Temperate Highland Peat Swamps on Sandstone’ as listed under the Environment Protection and Biodiversity Conservation Act 1999 (TSSC 2005; DEWHA (undated)).

 

6. Targeted surveys and monitoring of populations of Gentiana wingecarribiensis (albeit with some irregularity and some sites omitted in some years) date from 1992 at Wingecarribee Swamp, and 1994 at Hanging Rock Swamp. Accurate censuses are impeded by the cryptic nature of the plant and its low stature among taller vegetation, but total numbers of plants detected have varied widely from year to year, from zero to around 500 (Kodela 2008). A major drop in numbers over the drought years since 2001 has been observed (Kodela 2008; Sydney Catchment Authority in litt. Sept. 2009); this coincides, at Wingecarribee Swamp, with continuing habitat changes following the 1998 swamp collapse. The most recent report of occurrence of the Gentian at Wingecarribee Swamp is a single quadrat record in 2004 (Sydney Catchment Authority in litt. Sept. 2009, number of plants unknown), and prior to that in 2001 (Kodela 2008). No plants have been found at Hanging Rock Swamp since 2006.

 

7. There is a reasonable inference that there are likely to have been two major episodes of past decline of Gentiana wingecarribiensis. It is likely to have been more widespread in Wingecarribee Swamp prior to flooding of the western portion to form Wingecarribee Reservoir in the mid-1970s (Kodela et al. 1994; Kodela 2008). The collapse of the remaining portion of Wingecarribee Swamp in 1998 has resulted in changed drainage and vegetation patterns, loss of much of the open-sward ecotonal habitat along the swamp margins, burial of at least one Gentian site by surged peat, and more accentuated wet/dry cycles for much of what suitable habitat remains. These episodes have occurred in addition to slower processes that have probably contributed to past fragmentation and decline, including human disturbances (past clearing and draining of swamp margins), natural processes of vegetation and drainage change within the swamps and their margins, and variation in rainfall and other climatic factors. Past cattle grazing may have had mixed effects, with some loss of plants but also maintenance of the open habitat the plant requires. Kodela (2008) reported occurrence of plants in areas where competing growth of grasses was reduced by grazing by macropods, wombats and goats, and reduced recruitment in years when there was abundant competing grass growth. Invasion by weeds, including aggressive exotic pasture grasses such as Anthoxanthium odoratum (Sweet Vernal Grass) and Holcus lanatus (Yorkshire Fog), has been reported as a threat (Kodela 2008), as is increased competition from native species following the collapse of Wingecarribee Swamp and changed grazing regimes. Physical effects associated with human access to the swamp through Gentian habitat, and physical and chemical effects associated with current and future weed control measures, especially in habitat at Wingecarribee Swamp, are also risk factors. Current management prescriptions for publicly administered weed control programs, and current environmental monitoring, address this risk for some parts of the past and potential habitat of Gentiana wingecarribiensis (Sydney Catchment Authority in litt. Sept. 2009), but these factors remain potential threats for the future and in other parts of the habitat. The drying trend expected in eastern New South Wales as a result of climate change (Hennessy et al. 2004) is likely to have an adverse effect on G. wingecarribiensis. ‘Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands’, ‘Anthropogenic Climate Change’, and ‘Invasion of native plant communities by exotic perennial grasses’ are all listed as Key Threatening Processes under the Threatened Species Conservation Act 1995. ‘Loss of terrestrial climatic habitat caused by anthropogenic emissions of greenhouse gases’ is listed as a Key Threatening Process under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.

 

8. Gentiana wingecarribiensis L. Adams is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing an extremely high risk of extinction in New South Wales in the immediate future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2010:

 

Clause 6

The species has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time frame appropriate to the life cycle and habitat characteristics of the taxon:

(a) a very large reduction in population size,

based on either of the key indicators:

(a) an index of abundance appropriate to the taxon, or

(b) geographic distribution, habitat quality or diversity, or genetic diversity.

 

Clause 7

The geographic distribution of the species is estimated or inferred to be:

(a) very highly restricted,

and either:

(d) a projected or continuing decline is observed, estimated or inferred in either of the key indicators:

(a) an index of abundance appropriate to the taxon, or

(b) geographic distribution, habitat quality or diversity, or genetic diversity; or

(e) at least two of the following three conditions apply:

(i) the population or habitat is observed or inferred to be severely fragmented;

(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations,

(iii) extreme fluctuations are observed or inferred to occur in either of the key indicators:

(a) an index of abundance appropriate to the taxon, or

(b) geographic distribution, habitat quality or diversity, or genetic diversity.

 

Clause 8

The estimated total number of mature individuals of the species is:

(a) very low,

and either:

(d) a projected or continuing decline is observed, estimated or inferred in either of the key indicators:

(a) an index of abundance appropriate to the taxon, or

(b) geographic distribution, habitat quality or diversity, or genetic diversity; or

(e) at least two of the following three conditions apply:

(i) the population or habitat is observed or inferred to be severely fragmented;

(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations,

(iii) extreme fluctuations are observed or inferred to occur in either of the key indicators:

(a) an index of abundance appropriate to the taxon; or

(b) geographic distribution, habitat quality or diversity, or genetic diversity.

 

Clause 9

The total number of mature individuals of the species is observed, estimated or inferred to be:

(a) extremely low.

 

 

Dr Richard Major

Chairperson

Scientific Committee

 

Proposed Gazettal date: 05/11/10

Exhibition period: 05/11/10 - 21/01/11

 

References:

 

Adams LG, Williams JB (1988) Gentiana sect. Chondrophyllae (Gentianaceae) in Australia. Telopea 3, 167-176.

 

DEWHA (undated) Temperate Highland Peat Swamps on Sandstone. Species Profile and Threats Database. Department of Environment, Water, Heritage and the Arts. http://www.environment.gov.au/cgi-bin/sprat/public/publicshowcommunity.pl?id=32&status=Endangered (accessed 25 June 2009)

 

Hennessy K, Page C, McInnes K, Jones R, Bathols J, Collins D, Jones R (2004) ‘Climate change in New South Wales. Part 1: Past climate variability and projected changes in average climate’. CSIRO Marine and Atmospheric Research, Aspendale, Victoria.

 

IUCN (2008) ‘Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.’ (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland). (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf ).

 

Kodela PG, James TA, Hind PD (1994) Observations on the ecology and conservation status of the rare herb Gentiana wingecarribiensis. Cunninghamia 3, 535-541.

 

Kodela PG (2008) ‘Conservation status of Gentiana wingecarribiensis L. Adams (Gentianaceae) in New South Wales’. A report to the Scientific Committee (NSW TSC Act 1995) [unpublished].

 

NSW Scientific Committee (2005) Montane peatlands and swamps of the New England Tableland, NSW North Coast, Sydney Basin, South East Corner, South Eastern Highlands and Australian Alps bioregions. Final Determination. NSW Scientific Committee, Sydney. http://www.environment.nsw.gov.au/determinations/MontanePeatlandsEndSpListing.htm (accessed 25 June 2009)

 

TSSC (2008) ‘Commonwealth Conservation Advice on Gentiana wingecarribiensis (Wingecarribee Gentian)’. Threatened Species Scientific Committee. Department of the Environment, Water, Heritage and the Arts. http://www.environment.gov.au/biodiversity/threatened/species/pubs/18033-conservation-advice.pdf (accessed 25 June 2009)

 

TSSC (2005) Listing Advice. Temperate Highland Peat Swamps on Sandstone. Threatened Species Scientific Committee. Department of the Environment, Water, Heritage and the Arts. http://www.environment.gov.au/biodiversity/threatened/communities/pubs/32-conservation-advice.pdf

Page last updated: 28 February 2011