Peter Juniper, Accredited AABR Member
Seal Rocks, is located on the NSW Mid North Coast, and is one of the jewels of the area. On Saturday, 10th August 2024, AABR held a walk and talk field trip to Seal Rocks.
A beautiful place known for its surf, rugged coastline and rainforest. During the walk the characteristics of littoral rainforest, the significance and value of littoral rainforest, its threats, and the efforts invested in aiding the recovery of the Seal Rocks littoral rainforest were discussed.
The littoral rainforest of interest this field day, covers approximately 30 ha within Myall Lakes National Park on Worimi country. Littoral rainforest is characterised by its thick shady canopy of evergreen leaves which exclude 70 % or more of the sky. It occurs within two km of the coast. Depending on wind exposure and aspect, this forest varies from very low vine thickets to tall forest supporting strangler figs and epiphytic ferns. This littoral rainforest is quite complex and diverse. In NSW Plant Community Types (PCTs) are used for vegetation classification. Littoral rainforest contains Lower North Sands Littoral Rainforest (PCT 4114) and Sydney Coastal Lillypilly-Palm Gallery Rainforest (PCT 3039). On the very frontline of the coast this vegetation changes to the more sclerophytic Coastal Sands Littoral Scrub-Forest with its characteristic coastal banksias (Banksia intergrifolia) and bracelet honeymyrtle (Melaleuca amillaris). According to Alex Floyd’s classification scheme the littoral rainforest qualifies as Suballiances 19 and 23.
As a subtype of subtropical rainforest, littoral rainforest has plant species derived from ancient Gondwana flora that existed over 100 million years ago, and more recently from southeast Asian flora over the past 20 million years or so. Plant structural types found in the Seal Rocks littoral rainforest include strangler figs, palms, epiphytic ferns, orchids and moss, wiry vines and heavy lianas, shade adapted shrubs and ground layer species, such as ginger and ferns.
Photo: Peter Juniper
Littoral rainforest in NSW has been greatly affected by extensive coastal development. Given its limited extent and the variety of threats that surround these areas this type of ecological community is listed as endangered under State and Federal legislation. The rainforest at Seal Rocks supports a number of species also listed as endangered or vulnerable to extinction (under NSW Biodiversity Conservation Act 2016 and Commonwealth Environmental Protection and Biodiversity Conservation Act 1999):
- the rainforest cassia (Senna aclinis) which grows in a wide range of plant communities but has a low population density with a highly fragmented distribution and
- the magenta lilly pilly (Syzygium paniculatum). Widely planted as a street and garden tree this tree species is limited to approximately 1200 individual wild trees distributed across 44 locations, of which only 18 are protected within conservation reserves. Seal Rocks is one of six priority management sites listed for the preservation of the magenta lilly pilly under the NSW Office of Heritage and Environment Save our Species program.
Notable animals observed in and above the forest include dingos, the noisy pitta and osprey, while the endangered long-nosed potoroo has been recorded nearby.
The remains of middens located behind Number One beach indicate this area had been visited by people for a very, very long time. This site would have been a rich site for seafood, forest foods and is near the spectacular Sugarloaf Point Blowhole which must have had quite some signifance to the Worimi.
By the late 19th century, the area was often passed by ships – some were wrecked on offshore rocks. Beginning in 1875, construction of a lighthouse on nearby Sugarloaf Point prevented further shipwrecks. This was followed by a seasonal lobster harvesting industry which led to a more developed fishing industry and village, the first dwelling being built in 1917. Thus, the effect of coastal development on the distribution and health of littoral rainforest in the area was mounting.
More recently, the littoral rainforest, featured during the AABR field day, has been disturbed by the presence of a thoroughfare road (now sealed), an old unsealed road (now overgrown), a former house and garden (some foundation work and two tall Norfolk Island trees remain), and a former fish co-op – occupied by a large formal camping ground, and a history of informal camping within the forest. The littoral rainforest has also been disturbed by other factors such as bush fire and fire mitigation machine work at its margins and a powerline corridor (now buried).
Photo: Fiona Miller (NPWS)
The walk started at the main beach carpark with a discussion about what is littoral rainforest, National Park’s role in managing littoral rainforest and what extinction is – relevant to illustrating the precarious existence of some of the endangered species present at the site. Whilst progressing along Seal Rocks (which divides the littoral rainforest into two sections) the restoration of a former powerline corridor along the road edge was discussed. The powerline is now underground and rainforest regrowth occupies this corridor. We look forward to the time when the forest has enclosed this road with a full canopy – a realistic vision for all of us who manage this site. Even now the trees on either side are beginning to touch in two places.
A diversion into some of the tallest rainforest on site took us into a cool shaded forum to discuss rainforest structure, dynamics and the effect weeds and vines, both native and exotic, can have on the rainforest and the importance of managing these plants.
Photo: Peter Juniper
Some of the weeds found at this site were decorative species and had probably escaped from past gardens now lost to recovering rainforest, existing gardens adjoining the site and from greater distances via bird and wind dispersal. These weeds include the climbing species climbing asparagus (Asparagus plumosus) and coastal morning glory (Ipomea cairica). By being able to climb, these species are able to seek sunlight, proliferate and shade out the native tree, shrub and ground layers. Blocking sunlight will stop the recruitment of new plants in the forest. Asparagus species have been controlled with herbicide spray (glyphosate and metsulfuron) while coastal morning glory is bulk removed by hand. Resprouting roots are controlled by cutting/scraping and painting with concentrated glyphosate.
Native vines are an essential component of the littoral rainforest at Seal Rocks. However, even these can cloak and shade native vegetation. Thus where young rainforest trees are recolonising the rainforest edge or filling canopy gaps within the forest, these vines must be managed. To allow maximal growth rates in such trees, the vines are judiciously thinned to reduce their shading capacity. However, littoral rainforest is subject to the pruning effects of salt laden winds. This effect is most evident on the frontline of the forest where tip pruning caused by the salt winds stunts the trees, creating a canopy as low as two metres high. The canopy of the forest reaches much higher where the landform protects the forest from wind. Therefore, the control of native canopy vines must be limited to retain a protective ‘skin’ over the canopy to reduce exposure to and beneath the forest canopy.
The exotic shrub bitou bush (Chrysanthemoides monilifera subsp. rotundata) is another major factor affecting littoral rainforest in NSW. At Seal Rocks bitou bush is of most concern on the seaward frontline of the forest where a mosaic of heath species and low windswept littoral rainforest occurs. It can also establish within the forest’s natural canopy gaps. Bitou bush was introduced into Australia from South Africa accidentally in the early 20th century, and used from the late 1940’s to late 1960’s as a revegetation tool for sand mining operations. It is now considered as a Weed of National Significance and Key Threatening Process to Biodiversity in NSW as it is a very effective invader on both disturbed and undisturbed plant communities. Depending on the time of year, location and size, bitou bush has been treated with a foliar spray of dilute metsulfuron (this has minimal effects on the coastal native heath species in winter), spot spraying with glyphosate and metsulfuron or is simply cut to a stump which is painted with glyphosate concentrate.
The day’s walk progressed to a formal path that took attendees to the windswept forest and heath edge above the coastal cliffline. The transition from littoral rainforest to open sclerophytic heath species was an interesting point to show how the rainforest creates a cooler, more moist microclimate that is protected from the warmer air and seabreeze outside. Here the significant effect of the seabreeze on the vegetation and value of the protective canopy was apparent.
In 2001, the littoral rainforest was protected within Myall Lakes National Park and in 2006 a program of regeneration began. This effort was expanded in 2014 with Commonwealth grant funding and a later partnership with Midcoast Council. We envision a time when the rainforest will have matured over previously disturbed areas and even reach over Seal Rocks Road. Such recovery will greatly expand the size of the forest and increase its resilience into the future.
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