Meryta latifolia (Shade Tree)

Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)

1. Scientific name, common name (where appropriate), major taxon group

Meryta latifolia (Shade Tree)

2. National Context

This species is endemic to Norfolk Island and not currently listed under the EPBC Act or State legislation.

3. How judged by TSSC in relation to the EPBC Act criteria.

TSSC judges the species to be eligible for listing as critically endangered under the EPBC Act. The justification against the criteria is as follows:

Criterion 1 - Decline in numbers

Since European settlement 80% of the native vegetation on Norfolk Island has been cleared. A significant decline in population numbers is inferred due to the extensive land clearing, unrestricted grazing and significant habitat degradation. There has been widespread establishment of large populations of invasive weed species and high levels of seed predation by rats. Recruitment has been further limited by rats rats regularly destroying the entire top portion of mature stems preventing flowering. Whilst it is possible that the population decline since European settlement could be as high as 80%, there is, however, a lack of information about generation times and no quantitative data is available for recent rates of decline.

Therefore, the species is not eligible for listing under this criterion.

Criterion 2 - Geographic distribution

The species is very restricted in its geographic distribution, the extent of occurrence being 3.681km2. The species is considered to be severely fragmented, the total female population being approximately 20 plants. Five of the ten sites contain only one or two plants and only one site has more than 13. Although one site contains approximately 115 individual plants the total reproductive population at all sites is limited to approximately 20 female plants. Continuing declines in the number of mature individuals, number of locations and subpopulations, extent of occurrence, area of occupancy, and quality of habitat are projected for several reasons including: lack of formal protection or management programs, the vulnerability of small populations to stochastic disturbance events (eg cyclones), ongoing competition with invasive weeds, predation by rats, senescence of over-mature plants and sex ratio bias. The species is adapted to moist forest conditions and is therefore susceptible to unfavourable climate change (projected increases in the incidence of drought and extreme rainfall events that cause physical damage).

Therefore, the species is eligible for listing as critically endangered under this criterion.

Criterion 3 - Population size and decline in numbers or distribution

The species is dioecious, having separate male and female plants. Whilst the total number of mature individual plants is 149, the effective reproductive population is controlled by the very limited number of surviving female plants, approximately 20. The species is considered to be severely fragmented, the total female population being approximately 20 plants. Five of the ten sites contain only one or two plants and only one site has more than 13. Although one site contains approximately 115 individuals regeneration is not occurring at this site. Continuing declines in the number of mature individuals, and number of locations and subpopulations are projected for several reasons including: lack of formal protection or management programs, the vulnerability of small populations to stochastic disturbance events (eg cyclones), ongoing competition with invasive weeds, predation by rats, senescence of over-mature plants, and sex ratio bias. The species is adapted to moist forest conditions and is therefore susceptible to unfavourable climate change (projected increases in the incidence of drought and extreme rainfall events that cause physical damage).

Therefore, the species is eligible for listing as critically endangered under this criterion.

Criterion 4 - Population size

The species is dioecious, having separate male and female plants. Whilst the total number of mature individual plants is 149, only approximately 20 are female and thus the effective reproductive population is most appropriately determined to be the number of female plants and is extremely low.

Therefore, the species is eligible for listing as critically endangered under this criterion.

Criterion 5 - Probability of extinction in the wild

There is no quantitative data available against this criterion.

4. Conclusion

The effective number of mature plants capable of reproduction is approximately 20 and the total population is considered to be severely fragmented. Five of the ten sites contain only one or two plants and only one site has more than 13. The geographic distribution is precarious for the survival of the species and is very restricted, having an area of occurrence of 3.681km2. Continuing declines in the number of mature individuals, number of locations and subpopulations, extent of occurrence, area of occupancy, and quality of habitat are projected for several reasons including: lack of formal protection or management programs, the vulnerability of small populations to stochastic disturbance events (eg cyclones), ongoing competition with invasive weeds, predation by rats, senescence of over-mature plants, and sex ratio bias. The species is adapted to moist forest conditions and is therefore susceptible to unfavourable climate change (projected increases in the incidence of drought and extreme rainfall events that cause physical damage). The species is eligible for listing as critically endangered under criteria 2,3 and 4.

5. Recommendation

TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by including in the list in the critically endangered category: Meryta latifolia (Shade Tree)