Gnarled Mossy Cloud Forest on Lord Howe Island - critically endangered ecological community listing

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Gnarled Mossy Cloud Forest on Lord Howe Island is the name given to the ecological community characterised by the species assemblage listed in paragraph 2.

2. Gnarled Mossy Cloud Forest on Lord Howe Island is characterised by the following assemblage of species:

3. The total species list of the community is considerably larger than that given above, with many species present in only one or two sites or in low abundance. The species composition of a site will be influenced by the size of the site, recent rainfall or drought condition and by its disturbance history (including canopy gaps formed from storms or lightning strikes). The number of species, and the above ground relative abundance of species will change with time since disturbance, and may also change in response to changes in the disturbance regime. At any one time, above ground individuals of some species may be absent, but the species may be represented below ground in the soil seed banks or as dormant structures such as bulbs, corms, rhizomes, rootstocks or lignotubers. The list of species given above is of vascular plant species; the community also includes non vascular plants, micro-organisms, fungi, cryptogamic plants and a diverse fauna, both vertebrate and invertebrate. These components of the community are less well documented.

4. Gnarled Mossy Cloud Forest on Lord Howe Island is confined to Lord Howe Island in New South Wales. On the island it is restricted to the summit plateau of Mt Gower (some 27 ha) and in a greatly reduced form and extent on the narrow summit ridge of Mt Lidgbird.

5. Gnarled Mossy Cloud Forest on Lord Howe Island is currently recognised following the work on vegetation classification on Lord Howe Island by Pickard (1983) who describes the community as Gnarled Mossy Forest. Other studies describe the community as Moss Forest (Oliver 1916), Cloud Forest (Mueller-Dombois & Fosberg 1998) and Mossy Cloud Forest (Harris et al. 2005). Recent work (Harris et al. 2005) has detailed the species composition and internal variation within the community, along with its conservation significance. Small scale patch dynamics are likely to be key drivers of turnover in plant populations in Gnarled Mossy Cloud Forest. These small scale disturbances include tree death and fall, storm and lightning damage. Extensive Providence Petrel (Pterodroma solandri) burrowing may also influence plant recruitment. Many non-vascular plants are dependent upon cloud cover and the structure provided by the trees and shrubs.

6. Gnarled Mossy Cloud Forest on Lord Howe Island is a forest 2-8 m tall, depending on aspect and whether it occurs on ridges or in drainage lines. On the summit plateau of Mt Gower, the dominant species are Zygogynum howeanum and Dracophyllum fitzgeraldii (Pickard 1983, Harris et al. 2005). Associated trees include Cryptocarya gregsonii, Elaeocarpus costatus, Leptospermum polygalifolium subsp. howense, Negria rhabdothamnoides, Pittosporum erioloma, Symplocus candelabrum, and the palms Hedyscepe canterburyana and Lepidorrhachis mooreana. Tree Ferns (Cyathea spp.), large tussock sedges (Machaerina insularis and Gahnia howeana), ferns Blechnum fullagarii, Blechnum contiguum, Blechnum howeanum, Grammitis wattsi and other ferns, mosses and lichens are abundant. Gnarled Mossy Cloud Forest on Lord Howe Island also occurs on the summit ridgetop of Mt Lidgbird above 750 m elevation, but is much more exposed and restricted in area (Pickard 1983). A vegetation plot on the summit of Mt Lidgbird in Gnarled Mossy Cloud Forest had a dominant canopy of Hedyscepe canterburyana, Cryptocarya gregsonii, Dysoxylum pachyphyllum, Negria rabdothamnoides, Pittopsorum erioloma and Cyathea macarthurii, along with Grammitis diminuta, Carex sp., Olearia mooneyi, Rapanea myrtillina, Zygogynum howeanum, Lordhowea insularis, Gahnia howeana, Negria rabdothamnoides, Coprosma lanceolaris, Dendrobium moorei, Coprosma putida, Macropiper hooglandii, Microsorium scandens, Asplenium milnei, Asplenium surragatum, Elatostema grande, Hymenophyllum sp. (Hutton and Auld unpubl. data).

7. Some 86% of the vascular plant species in Gnarled Mossy Cloud Forest on Lord Howe Island are endemic to Lord Howe Island and approximately 17% are endemic to this community or only occur within it and on adjacent slopes below (Harris et al. 2005). There is extensive development of non-vascular epiphytes (Pickard 1983). Ramsay (1994) details the mosses of Lord Howe Island and lists 105 species, in 58 genera and 36 families. 20% of these are endemic to the island and some 37 taxa are recorded from the Mt Gower area, with 15 species apparently confined to the southern mountains (Ramsay 1994).

8. Gnarled Mossy Cloud Forest on Lord Howe Island is readily distinguished from adjacent communities as it only occurs on summit plateau and ridgetops of the two southern mountains of Lord Howe Island and the adjacent communities lack the extensive development of non-vascular epiphytes and several endemic mountain vascular plant species. Dracophyllum-Metrosideros scrub (of Pickard 1983 and Mueller-Dumbois & Fosberg 1998) occurs on benches below the summits. Pickard (1983) notes that Gnarled Mossy Cloud Forest on Lord Howe Island is floristically distinct but close to Dracophyllum-Metrosideros scrub and Hedyscepe canterburyana closed forest, neither of which are considered to be part of the Gnarled Mossy Cloud Forest community.

9. Gnarled Mossy Cloud Forest on Lord Howe Island is a key component contributing to the southern mountains biodiversity hotspot on Lord Howe Island (DECC 2007), particularly for plants and invertebrates. Cassis et al. (2003) found that the assemblage of terrestrial invertebrates in the Gnarled Mossy Cloud Forest exhibits high species richness, high levels of endemism to Lord Howe Island and many species are restricted to the Gnarled Mossy Cloud Forest.

10. Several threatened taxa occur within the Gnarled Mossy Cloud Forest on Lord Howe Island. These include:

Birds: Lord Howe Woodhen, Gallirallus sylvestris (Vulnerable under Environment Protection and Biodiversity Conservation Act (EPBC)), Endangered under the NSW Threatened Species Conservation Act (TSC); Providence Petrel, Pterodroma solandri (Vulnerable under TSC Act), Silvereye (Lord Howe Island subsp.), Zosterops lateralis tephropleurus (Vulnerable under TSC Act), Pied Currawong (Lord Howe Island subsp.), Strepera graculina crissalis (Vulnerable under TSC Act). These birds also occur at lower elevations but Gnarled Mossy Cloud Forest forms key core habitat for the petrel and woodhen in particular;

Invertebrates: Lord Howe Island earthworm, Pericryptodrilus nanus (Endangered under TSC Act) is confined to this community and dependent upon it. Four endemic snails are listed under the EPBC Act as Critically Endangered. These are Pseudocharopa whiteleggei, Pseudocharopa lidgbirdi, Mystivagor mastersi and Gudeoconcha sophiae magnifica. All are restricted to the Gnarled Mossy Cloud Forest. Cassis et al. (2003) identify a number of invertebrates (ants, beetles and spiders) that are found in the cloud forest that should be considered for listing as threatened;

Plants: Lepidorrhachis mooreana (Little Mountain Palm) (Critically Endangered under the TSC Act). This palm is endemic to Lord Howe Island and is confined to the Gnarled Mossy Cloud Forest.

11. The Gnarled Mossy Cloud Forest on Lord Howe Island is threatened by a number of factors. The exotic Ship Rat Rattus rattus has been on Lord Howe Island for some 90 years. It is having an impact on the two endemic palm genera (Hedyscepe and Lepidorrhachis) in the Gnarled Mossy Cloud Forest by consuming a large proportion of their seeds (Baker and Hutton 2006, Auld et al. 2010). The effect of rats on other plants and animals is poorly known, but rats consume seeds and leaves of a number of other taxa (Auld and Hutton 2004), including Dietes robinsoniana which occurs in the Gnarled Mossy Cloud Forest. Rats may also impact on a number of invertebrates. Some 7% of the summit plateau of Mt Gower is baited to reduce rat impacts and there is a plan to try to eradicate rats across the whole island. ‘Predation by the Ship Rat Rattus rattus on Lord Howe Island’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

12. Gnarled Mossy Cloud Forest is confined to mountain summits. There is no bioclimatic zone for component species to move into with warming temperatures. Climate change may also affect the frequency of severe storms and cloud formation (timing, duration, frequency) on the mountains and hence the moisture regime and species survival in the cloud forest (Auld and Hutton 2004). The ‘lift-cloud-base hypothesis’ states that the climate of tropical mountains is showing signs of gradual change due to an elevation in sea surface temperatures (Pounds et al. 1997, 1999; Still et al. 1999). Still et al. (1999) suggest that under a changing climate there are likely to be upward altitudinal shifts in the areas that experience cloud formations. Pounds et al. (1999) suggest that such a change may have contributed to frog and toad decline in a Costa Rican Cloud Forest. If this prediction holds for Lord Howe Island, then there may be reduced formation of clouds on the southern mountains and reduced moisture availability. This is likely to have negative impacts for species occupying both the cloud forests themselves and the associated mountain slopes. In particular, epiphytes may be very sensitive to changes in microclimate resulting from predicted global climate changes (Benzing 1998) yet these plants play a key role in light, hydrological and nutrient regimes in the forests in which they occur (Foster 2001). Predicted changes in global mean air temperatures from Global Circulation Models forecast a change of 1.5 up to 6°C by 2100 (IPCC 2007). Specific predictions for Lord Howe Island have not been developed although Australian National University (2009) suggests that average annual air temperature is expected to rise by 1.3 ± 0.6°C by 2030. Further they suggest that “The consequential impacts of a rise of the cloud layer, caused by rising sea surface temperatures, constitute a major climate-related threat to the island’s plant communities. This cloud layer provides a source of precipitation (occult precipitation) and maintains the humidity required by about 86% of the island’s endemic plant species including the dwarf mossy forest that dominates the summit of the peaks on Lord Howe Island” and “Change in the semi-permanent cloud cover that envelops the summits of Mt Gower (875 m) and Mt Lidgbird (777 m) is a major climate-related threat to the vegetation communities of the island (Garnaut 2008). The precipitation provided by this cloud cover and the humidity it provides during periods of low rainfall are important to summit vegetation communities. The precipitation derived from the cloud layer is also an essential source of water for flora and fauna at lower elevations.” ‘Anthropogenic climate change’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

13. A small number of minor weeds have been recorded within the community. Most are facilitated by disturbance and take advantage of cliff edges or areas of tree fall, lightning strike, tree death and other minor disturbances. These weeds may compete with native plants for recruitment in canopy gaps and cliff edges. This is an ongoing issue, especially if more aggressive weeds invade. Weeds identified so far include: Agrostis avenaceus, Arenaria serpyllifolia, Avena barbata, Bromus carthartius, Ehrharta erecta, Lolium perenne, Luzula longiflora, Paspalum sp., Poa annua, Polycarpon tetraphyllum, Potentilla indica, Pseudognaphalium luteo-album, Rumex sp., Solanum nigrum, Sonchus oleraceus, Sporobolus africanus, Stellaria media, Vulpia bromoides on Mt Gower and Ageratina adenophora, Lilium formosanum, and Solanum nigrum on Mt Lidgbird.

14. The plant pathogen Phytophthora cinnamomi has been found on Lord Howe Island and could potentially spread to the summit via walkers or birds. Currently there are few data on the susceptibility of key Lord Howe Island endemic plants to this pathogen (see Auld and Hutton 2004). A number of potentially susceptible species are major structural dominants in the Gnarled Mossy Cloud Forest. ‘Infection of native plants by Phytophthora cinnamomi’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995. Species occurring as part of the Gnarled Mossy Cloud Forest on Lord Howe Island and belonging to the Family Myrtaceae (Metrosideros nervulosa and Leptospermum polygalifolium ssp. howense) may be susceptible to exotic rusts including Myrtle Rust which is present on mainland NSW. ‘Introduction and establishment of Exotic Rust Fungi of the order Pucciniales pathogenic on plants of the family Myrtaceae’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

15. Gnarled Mossy Cloud Forest on Lord Howe Island is eligible to be listed as a Critically Endangered Ecological Community 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 18 Restricted geographic distribution of ecological community

The ecological community’s geographic distribution is estimated or inferred to be:

and the nature of its distribution makes it likely that the action of a threatening process could cause it to decline or degrade in extent or ecological function over a time span appropriate to the life cycle and habitat characteristics of the ecological community’s component species.

Clause 19 Reduction in ecological function of ecological community

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

as indicated by any of the following:

Dr Richard Major
Chairperson
Scientific Committee

Gazettal date: 28/10/11
Exhibition period: 28/10/11 – 20/01/12

References:

Auld TD, Hutton I (2004) Conservation issues for the vascular flora of Lord Howe Island. Cunninghamia 8, 490-500.

Auld TD, Hutton I, Ooi MKJ, Denham AJ (2010) Invasive species on oceanic islands: disruption of recruitment in narrow endemic palms. Biological Invasions 12, 3351-3361.

Australian National University (2009) Implications of climate change for Australia’s World Heritage properties: A preliminary assessment. A report to the Department of Climate Change and the Department of the Environment, Water, Heritage and the Arts by the Fenner School of Environment and Society, the Australian National University.

Baker WJ, Hutton I (2006) Lepidorrhachis. Palms 50, 33–38.

Benzing DH (1998) Vulnerabilities of tropical forests to climate change: The significance of resident epiphytes. Climate Change 39, 519-540.

Cassis G, Meades L, Harris R., Reid C, Carter G, Wilkie L, Jeffreys E (2003) Lord Howe Island Terrestrial Invertebrate Biodiversity and Conservation. Report to the NSW National Parks and Wildlife Service by the Australian Museum Centre for Biodiversity and Conservation Research.

DECC (2007) Lord Howe Island Biodiversity Management Plan. Department of Environment and Climate Change (NSW), Sydney.

Foster P (2001) The potential negative impacts of global climate change on tropical montane cloud forests. Earth Science Reviews 55, 73-106.

Garnaut R (2008) Garnaut climate change review: Interim report to the Commonwealth, State and Territory governments of Australia, June 2008.

Harris R, Cassis G. Auld T, Hutton I (2005) Floristics and structure of the mossy cloud forest of Mt Gower summit, Lord Howe Island. Pacific Conservation Biology, 11, 246-56.

IPCC (2007) Climate Change 2007: The physical science basis. Contributions of working group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. (Cambridge University Press Cambridge)

Mueller-Dombois, D, Fosberg, FR (1998) Vegetation of the Tropical Pacific Islands. (Springer-Verlag, New York)

Oliver WRB (1916) The vegetation and flora of Lord Howe Island. Transactions and Proceedings of the New Zealand Institute 49, 94-161.

Pickard J (1983) Vegetation of Lord Howe Island. Cunninghamia 1, 133-265.

Pounds JA, Fogden MPL, Savage JM, Gorman GC (1997). Tests of null models for amphibian declines on a tropical mountain, Conservation Biology 11, 1307-1322.

Pounds JA, Fogden MPL, Campbell JH (1999) Biological response to climate change on a tropical mountain. Nature 398, 691-615.

Ramsay HP (1994) The Mosses of Lord Howe Island. Telopea 2, 549-558.

Still CJ, Foster PN, Schneider SH (1999) Simulating the effects of climate change on tropical montane cloud forests. Nature 398, 608–610.