Lagunaria Swamp Forest on Lord Howe Island - critically endangered ecological community listing

NSW Scientific Committee - final determination

The Scientific Committee has found that:

4. Species that are characteristic of Lagunaria Swamp Forest on Lord Howe Island include:

5. The total species list of the community may be larger than that given above, with many species present at only one or two sites or in very small quantities. The species composition of a site will be influenced by the size of the site, recent rainfall or drought conditions and by its disturbance history. The number of species, and the above ground relative abundance of species may 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 soil seed banks or as dormant structures such as bulbs, corms, rhizomes or rootstocks. The list of species given above is of vascular plant species, the community also includes micro-organisms, fungi, cryptogamic plants and a diverse fauna, both vertebrate and invertebrate. These components of the community are poorly documented.

6. The distribution of the community is restricted on Lord Howe Island to low-lying swampy areas at altitudes below 20 m. This distribution was mapped by Pickard (1983), who estimated that its original distribution may have covered as little as 6 ha, distributed across five restricted locations on the island. The community has undergone a very large reduction in geographical distribution with greater than 95% of the community estimated to have been lost (Pickard 1983, Auld and Hutton 2002). None of the locations are protected within the Lord Howe Island Permanent Park Preserve. Lagunaria Swamp Forest on Lord Howe Island falls entirely within the jurisdiction of the Lord Howe Island Board. Individual plants of Lagunaria patersonia may be scattered through the forests from sea level to about 600 m elevation on Lord Howe Island, but such locations do not form a part of the Lagunaria Swamp Forest on Lord Howe Island community. This very highly restricted distribution is combined with a number of ongoing and potential future threats and is likely to cause a decline in extent over a time span appropriate to the life cycle and habitat characteristics of the ecological community's component species.

7. Lagunaria Swamp Forest on Lord Howe Island has been seriously depleted by land clearing at all sites of its occurrence. The remaining fragments are only a few square metres in area, and are degraded by edge effects, weed invasion, alteration to water regimes, and from cattle grazing. The community has been completely eliminated from some of its original locations, including an area behind Blinkys Beach, which was cleared in 1975 during construction of the airstrip (Pickard 1983). The remnants are likely to include only a sample of the original flora and at least some appear to be transitional assemblages with other vegetation communities. However, since the initial listing of the community as Endangered in 2003 (the highest category then available), there have been a number of restoration activities undertaken by the Lord Howe Island Board to begin to restore this community. These are summarised as a part of the Biodiversity Plan for Lord Howe Island (DECC 2007). Actions have involved habitat plantings and fencing of remnants, or in some cases previously occupied habitat, in order to exclude cattle. These actions have reduced the immediate threat of grazing pressure and are an important first step in initiation of restoration of the community, but a long and ongoing effort is required to successfully restore parts of the community.

8. A very large reduction in ecological function has been indicated by the following changes to the community. Many of the dominant trees (Lagunaria patersonia) have been removed from existing stands (Auld and Hutton 2002) leading to a change in structure of the ecological community. The species composition has also changed with the invasion of exotic species including Ageratina adenophora (Crofton weed), Ageratina riparia, (Mistflower), Apium graveolens (Celery), Araucaria heterophylla (Norfolk Island Pine), Cakile edentula (American Sea Rocket), Chloris sp., Cirsium vulgare (Spear Thistle), Cyperus sp., Erodium sp., Euphorbia sp., Gnaphalium sp., Hypochaeris radicata (Catsear), Ipomoea cairica, Lilium formosanum (Formosan Lily), Nerium oleander (Oleander), Oxalis debilis, Pennisetum clandestinum (Kikuyu), Plantago sp., Potentilla indica (Indian Strawberry), Rumex sp., Ricinus communis (Castor Oil Plant), Solanum nigrum (Nightshade), Stenotaphrum secundatum (Buffalo Grass) and Trifolium sp. Clearing of habitat within and around the community may have altered the water flow regimes, disrupting the ecological processes within the community. Water regimes are a key driver of the existence of this community as it occurs in low lying, run on areas, often near the outlets of small creeks. Extensive clearing and subsequent grazing by cattle has led to degradation of all former patches of the community. A golf course now occupies the upslope area of one remnant and may impact on water quality in this remnant. Future impacts with rising sea levels are likely to lead to an encroachment of mangroves into the community and necessitate its movement upslope onto existing grazing land, should that be available. 'Clearing of native vegetation' is listed as a Key threatening Process under the Threatened Species Conservation Act 1995.

9. Lagunaria Swamp 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 2002:

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:

(a) a very large reduction in geographic distribution.

Clause 26

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

(a) very highly restricted,

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 27

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:

(a) a very large reduction in ecological function,

as indicated by any of the following:

(d) change in community structure,

(e) change in species composition,

(f) disruption of ecological processes,

(g) invasion and establishment of exotic species,

(h) degradation of habitat

(i) fragmentation of habitat.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 13/08/10
Exhibition period: 13/08/10 - 08/10/10

References:

Auld TD, Hutton I (2002) Survey of remnant sites of Lagunaria patersonia Swamp Forest on Lord Howe Island. Unpublished report.

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

NSW Scientific Committee (2003) Final Determination to list Lagunaria Swamp Forest on Lord Howe Island, as an endangered ecological community accessed 29th October 2009.

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