Allocasuarina inophloia population in the Clarence Valley Local Government Area - endangered population listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list a population of the small tree Allocasuarina inophloia (F.Muell. & F.M.Bailey) L.A.S.Johnson in the Clarence Valley Local Government Area as an ENDANGERED POPULATION in Part 2 of Schedule 1 of the Act. Listing of Endangered populations is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Allocasuarina inophloia (F.Muell. & F.M.Bailey) L.A.S. Johnson (family Casuarinaceae) is not currently listed as an Endangered species in Part 1 of Schedule 1 or a Critically Endangered species in Part 1 of Schedule 1A and as a consequence populations of this species are eligible to be listed as Endangered populations.

2. Allocasuarina inophloia, or stringybark she-oak, is described by Wilson and Johnson (1990) as: “Dioecious small tree, with open spreading crown, 3–10 m high. Branchlets drooping or ascending; articles 4–7 mm long, 0.5–0.6 mm diam.; ridges slightly rounded-convex; teeth erect, not overlapping. Cones on peduncle 3–8 mm long; cone body 10–20 mm long, 9–12 mm diam.; bracteoles usually divided into 3 or 4 rugose pyramidal bodies with acute to obtuse apex (or rarely with only 1 pyramidal protuberance). Samara 5.0–6.0 mm long, dark brown.” The bark is “very ribbony-fibrous” (Wilson and Johnson 1990).

3. Allocasuarina inophloia occurs in the North Coast, Northern Tablelands, Northwest Slopes and Northwest Plains botanical subdivisions of NSW. A larger number of populations are known from southern Queensland, with some disjunct populations in far north Queensland. In NSW, it is found in woodland from Torrington and Emmaville to Yetman (Wilson and Johnson 1990). Recently, a population of  A. inophloia has been found on private land at Kungala in the Clarence Valley, near Grafton on the eastern side of the Great Dividing Range. This has been confirmed as  A. inophloia by K Wilson (in litt. November 2011). Previously, the most easterly population known was from Torrington, north of Glen Innes, some 150 km to the west and on the other side of the Great Dividing Range. Consequently, the population in the Clarence Valley is considered to be disjunct and near the limit of the species’ geographic range.

4. The population of Allocasuarina inophloia in the Clarence Valley Local Government Area (LGA) has an estimated area of occupancy of 4 km² based on a 2 x 2 km grid cells, the scale recommended for assessing area of occupancy by IUCN (2010). The extent of occurrence is also estimated to be 4 km² based on a minimum convex polygon enclosing all mapped occurrences of the species, the method of assessment recommended by IUCN (2010). Hence, the geographic distribution is considered to be highly restricted.

5. There is little information available on the ecology of Allocasuarina inophloia, although it is known to be capable of resprouting via dormant buds in the trunk and canopy after fire and drought (Croft et al. 2007). The population in the Clarence Valley LGA is located along the top, or just below the top, of a narrow ridge (Allocasuarina species, e.g. see Pannell & Myerscough 1993).

6. The population is threatened by habitat loss which would result from a proposal to quarry sandstone from the site. Both fire and drought may cause plant mortality in Allocasuarina inophloia (Croft et al. 2007) and the appropriate fire regime for this species needs to allow for the interaction between fire and drought. ‘Clearing of native vegetation’ is listed as a Key Threatening Process under the NSW Threatened Species Conservation Act 1995. The small size of the population also makes it susceptible to stochastic events.

7. The population of Allocasuarina inophloia (F.Muell. & F.M.Bailey) L.A.S.Johnson in the Clarence valley Local Government Area is eligible to be listed as an Endangered population as, in the opinion of the Scientific Committee it is facing a very high risk of extinction in New South Wales in the near future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2010:

Clause 11 Criteria for listing determinations by Scientific Committee

(a) it is disjunct or near the limit of its geographic range.

Clause 13 Highly restricted geographic distribution of population and other conditions 

The geographic distribution of the population is estimated or inferred to be highly restricted and:

(a) 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) the geographic distribution, habitat quality or diversity, or genetic diversity.

Associate Professor Michelle Leishman
Chairperson
Scientific Committee

References:

Croft P, Hunter JT, Reid N (2007) Depletion of regenerative bud resources during cyclic drought: what are the implications for fire management? Ecological Management and Restoration 8, 187-192.

IUCN Standards and Petitions Subcommittee (2010) ‘Guidelines for Using the IUCN Red List Categories and Criteria Version 8.1.’ Prepared by the Standards and Petitions Subcommittee in March 2010. (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf)

Pannell JR, Myerscough PJ (1993) Canopy-stored seed banks of Allocasuarina distyla and  A. nana in relation to time since fire.  Australian Journal of Botany 41; 1-9.

Wilson KL, Johnson LAS (1990) Casuarinaceae. In: ‘Flora of New South Wales’ Vol. 1 (Ed. GJ Harden) p. 507-517. (University of NSW Press, Kensington)