Macrozamia johnsonii - reject a proposal to delist an endangered species

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to REJECT a proposal to remove Macrozamia johnsonii D. Jones & K. Hill from Part 1 of Schedule 1 (Endangered Species) of the Act.

 

The Scientific Committee has found that:

 

1. Following the exhibition of a Preliminary Determination in April 2010 to support a proposal to remove Macrozamia johnsonii D. Jones & K. Hill from the Schedules of the Act, information obtained during the exhibition period has indicated that there is sufficient uncertainty in the risk assessment to conclude that a decision to delist the species would be premature.

 

2. Macrozamia johnsonii D. Jones & K. Hill (family Zamiaceae) is a long-lived dioecious cycad endemic to far north-eastern New South Wales, in the Dalmorton area south-west of Grafton. At maturity it has a short above-ground trunk to 1.5 m tall. Mature and immature plants have numerous bright green fronds with 150-250 pinnae. Mature plants and older juveniles are capable of surviving fires, and crowns resprout. It is most closely related to the central Queensland endemic species M. moorei F. Muell., but the latter develops a tall, massive trunk and has grey-green fronds. Seedlings of the two species also differ markedly in several characters, as detailed by Jones and Hill (1992).

 

3. The species is now known from at least 287 site records, with an extent of occurrence of 22 200 ha and an area of occupancy of at least 10 100 ha (Binns & Meek 2008). These estimates are within the geographic range threshold recommended for Endangered status by IUCN (2001)and IUCN (2008). To meet the criteria for Endangered status under the regulations of the Threatened Species Conservation Act 1995, there must also be evidence of continuing decline, or the species must meet two of three conditions concerning severe fragmentation, extreme fluctuations or occurrence within a small number of locations. The Scientific Committee is of the opinion that the species does not meet any two of these latter criteria but considers that there is evidence of continuing decline as a result of forest harvesting. This conservation assessment is consistent with that of Binns & Meek (2008), who also identified continuing decline. The extent of decline, which the Committee considered to be of a non-trivial magnitude (NSW Scientific Committee 2010) however, is important in determining whether the species meets the criteria for Endangered.

 

4. Based on estimates of suitable habitat area, and assuming that mean plant density is the same for all tenures, approximately 59% of the total population of Macrozamia johnsonii is thought to occur in State Forest, 30% in National Park, and 11% on private land (Binns & Meek 2008). Of the population present in State Forests 44% is estimated to be contained within logging exclusion zones (E. Robinson in litt. Jan 2011), resulting in an estimated 33% of the total population of M. johnsonii being potentially harvestable from State Forests and 11% from private land. Due to physical and economic constraints the actual area harvested is usually less than the potential harvest area, with modelling of previous forestry activity predicting that between 21% and 32% of M. johnsonii habitat in State Forests will be logged in the next 100 years (E. Robinson in litt. Jan 2011). There are also records, however, of logging contractors failing to observe management exclusion zones, and the extent of logging exclusion zones may be attributable to the presence of this species (S. Barnes in litt. Jan 2011), such that these exclusion zones may change if the species were delisted. There is therefore some uncertainty concerning the proportion of the species area of occupancy that is potentially vulnerable to threats from forest harvesting, but nonetheless, it can be concluded that the area is non-trivial.

 

5. Estimation of the magnitude of decline in areas subjected to timber harvesting is dependent upon a knowledge of the rates of adult mortality, juvenile recruitment into the adult population and age of maturity. The Scientific Committee’s Preliminary Determination was based on the estimates of Binns and Meek (2008), who used the best available information to calculate the worst case rate of decline. They estimated long-term population reduction due to logging as 18% within the potential harvest area (if annual mortality is 1% and age of reproductive maturity is 20 years), or 45% within the harvest area (if annual mortality is 2% and age of reproductive maturity is 40 years). However, there are uncertainties in these estimates of potential population reduction.

 

6. There are other potential, but unquantified factors that affect the species’ populations dynamics, including changed fire regimes and plant pathogens; that also justify a precautionary approach to assessing the conservation status of the species. In particular, some species of cycad are susceptible to die-back disease (Phytophthora cinnamomi) (Environment Australia 2002; McDougall 2005; Cahill et al. 2008) for which movement of soil on machinery and vehicles is a vector. Neither the susceptibility of M. johnsonii, nor the likelihood of infection, are as yet quantified.

 

 

7. In view of the above the Scientific Committee has determined to REJECT a proposal to remove Macrozamia johnsonii D. Jones & K. Hill from Part 1 of Schedule 1 (Endangered Species) of the Act. The Scientific Committee is of the opinion that Macrozamia johnsonii D. Jones & K. Hill remains eligible to be listed as an Endangered species in Part 1 of Schedule 1 of the Act as it is facing a very high risk of extinction in New South Wales due to its highly restricted geographic distribution and a projected continuing decline in the near future.

 

Associate Professor Michelle Leishman

Chairperson

Scientific Committee

 

Proposed Gazettal date: 05/10/12

Exhibition period: 05/10/12 – 30/11/12

 

References and further reading:

 

Binns DL, Meek P (2008) Population size, habitat and conservation status of an Endangered species, Macrozamia johnsonii (Zamiaceae). Cunninghamia 10: 373-380

 

Cahill DM, Rookes JE, Wilson BA, Gibson L, McDougall KL (2008) Turner Review No. 17. Phytophthora cinnamomi and Australia’s biodiversity: impacts, predictions and progress towards control. Australian Journal of Botany 56(4): 279–310

 

Environment Australia (2002) Threat abatement plan for dieback caused by the root-rot fungus Phytophthora cinnamomi. Environment Australia, Canberra.

 

Forster PI (2007) Chapter 2: recovery plans for endangered cycads: a model set of objectives and actions using the example of Cycas megacarpa from Queensland, Australia. In: AP Vovides, DW Stevenson, and R Osborne (eds), Proceedings of Cycad 2005 – the 7th International Conference on Cycad Biology. Memoirs of The New York Botanical Garden, vol. 97. The New York Botanical Garden Press, NY, USA.

 

Hill KD (2003) Chapter 4: Regional overview: Australia. In: Cycads. Status survey and conservation action plan. IUCN/SSC Cycad Specialist Group. IUCN, Gland Switzerland and Cambridge UK.

 

IUCN (2001) Red List Categories and Criteria. Version 3.1. Prepared by the IUCN Species Survival Commission. IUCN, Gland Switzerland and Cambridge, UK.

 

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)

 

Jones DL and Hill KD (1992) Macrozamia johnsonii, a new species of Macrozamia section Macrozamia (Zamiaceae) from Northern New South Wales. Telopea 5, 31-34.

 

Jones DL (1993) Cycads of the world. Reed, Chatswood, NSW.

 

Jones DL (2002) Cycads of the world. Reed New Holland, Frenchs Forest, NSW.

 

McDougall KL (2005) Appendix 4. The responses of native Australian plant species to Phytophthora cinnamomi. In ‘Management of Phytophthora cinnamomi for biodiversity conservation in Australia: Part 2. National best practice’. (Eds E O’Gara, K Howard, B Wilson, GEStJ Hardy). Department of the Environment and Heritage: Canberra.

 

NSW Scientific Committee (2010) Guidelines for interpreting listing criteria for species, populations and ecological communities under the NSW Threatened Species Conservation Act Version 1.2. NSW Scientific Committee, Hurstville

Page last updated: 05 October 2012