234 Monitoring Threatened Species and Ecological Communities
B o x 17. 2. Box Range zieria Zieria buxijugumNSW (TSC Act) threat status: Critically endangered
Federal (EPBC Act) threat status: Endangered
SoS prioritisation parameters: Expected benefit (B) = 0.9; Likelihood of success (L)
= 0.75; Cost (C) = A$0.29 million over 50 years.
Species description: An erect shrub <3 m only known to occur in a single
population ranging over 0.25 ha. Habitat comprises rhyolite rocky outcrops in
vegetation community dominated by Melaleuca armillaris. The species is likely to be
an obligate seeder that is killed by fire.
Site description: Small, east-facing rocky outcrop on private property close to
Gnupa State Forest, ~20 km north-west of Eden.
Threats under management: (1) overgrazing by native macropods; (2) potential for
degrading land management practices; (3) risk of extinction via stochastic events
due to small population size.
Monitoring method: Full population census annually in addition to detailed
monitoring of mortality and growth rate of seedlings within permanent plots.
Model development and target-setting: No quantitative models are available for
this system, so a conceptual model was developed based on expert opinion. The
critical driver of the Zieria populations was identified as macropods removing
recruiting plants, which negatively impacts the population (overgrazing). Based on
this conceptual model and given the observed population response to the addition
of mesh plant guards (2012–2016), a significant rate of recruitment and population
growth in response to the proposed fencing of most of the population is predictedϭεΘρ ϭεερ ϮϬϬρ ϮϬϭρ ϮϬϮρ ϮϬϯρ
zĞĂƌϬρϬϭϬϬϭρϬϮϬϬϮρϬϯϬϬϯρϬκϬϬκρϬŽƵŶƚŽĨŝŶĚŝǀŝĚƵĂůƐF i g. 17. 5: Box Range zieria Zieria buxijugum monitoring data for the Pambula
management site 1986–2016 (solid triangles) and long-term population target expressed
as a confidence interval or control limits (broken lines). Data provided by John Briggs
(Office of Environment and Heritage).