Coastal Scrub

Coastal Scrub is found on primary sand dunes or coastal limestone soils from 0 to 200 m above sea level with a rainfall from 700 to 1200 mm a year.  About 30% of the area once supporting Coastal Scrub in Victoria falls on public land while about a fifth is represented in conservation parks and reserves.  About 60% of all Coastal Scrub has been permanently cleared for agriculture, urban or marine development.

Coastal Scrub is made up of a dense layer of sprawling and spreading shrubs, usually 2-5 m tall, interspersed with tussock grasses, herbs (some of which are succulent) tufted and rhizomatous grasses and robust sedges.  The ecosystem becomes more of a grassland and herbland closer to the sea and grades into Banksia Woodland on the landward side.  There is usually no single dominant species in Coastal Scrub but the Coast Tea-tree (Leptospermum laevigatum), Coast Wattle (Acacia longifolia subsp. sophorae), Seaberry Saltbush (Rhagodia candolleana) and Coast Beard-heath (Leucopogon parviflorus) are the most consistently recorded shrubs.  The robust grasses Hairy Spinifex (Spinifex sericeus) and Coast Tussock-grass (Poa poiformis) are the principal species nearest to the coast while the large shrubs Moonah (Melaleuca lanceolata) or Boobialla (Myoporum insulare) may become dominant inland of secondary dunes.

Coastal Scrub
Coastal Scrub 


The mammalian fauna consists of large browsers (wallabies, wombats), medium-sized ground omnivores and insectivores (echidna , occasional bandicoots, and potoroos), small ground insectivores, herbivores and omnivores (antechinus, rats, mice), small and medium-sized arboreal marsupials (pygmy-possums,  possums), and bats.  Most of the birds are a mixture of woodland and heathland species, particularly those that feed near the ground (thornbills, , honeyeaters, scrubwrens, whistlers, rosellas, currawongs, robins, pardalotes, cuckoos, parrots, fairy-wrens), coastal species (gulls, terns, waders, chats, cormorants) and birds of prey (falcons, kites, eagles, harriers).   The reptiles are mostly small ground-dwelling skinks, dragons and snakes.  Frogs are generally absent.

Coastal Scrub is subject to two major ecological influences - unstable calcareous sands and salty off-shore winds - both of which shape the physical and biological nature of its inhabitants.   The poor water-holding capacity and relative infertility of the soils means that root systems must be very efficient at extracting nutrients.   The instability of the substrate means that sand-binding species, such as Spinifex and Tussock Grass, are essential for establishing a soil for others to colonise.  The shrubs are usually dense, tolerant of wind-pruning and provide shelter for understory species, many of which provide additional shelter and assist in soil stabilisation (Sword-sedge, Club-sedge, Mat-rush).  Climbers and scramblers are a common component of the vegetation as they can cope with mobile soils by growing over them and the smaller shrubs (Clematis, Bower Spinach, Climbing Lignum).  The combination of the climbers and shrubs creates an additional wind-break for the spaces between the shrubs.  Many of the smaller, ground-cover herbs and grass are mat-forming (Kidney-weed, Bidgee-widgee, Sea-celery, Salt-grass) and several are succulent (Bower Spinach, Karkalla), all of which are useful adaptations to moving soils.

Coastal Victoria has been a drawcard for settlement, fishing and recreation since the earliest days of settlement.  Thousands of rough tracks to the beach have been created, overgrown and re-established many times in the past 150 years.  Most of the early townships were rough, irregular collections of shacks and cottages, often associated with small jetties and boat moorings.  The local vegetation was quickly cleared for beach access, firewood and grazing for livestock and the inevitable problems of severe erosion and exposure of dwellings to marine storms resulted from this.  By the mid 1880s erosion of primary sand dunes was so acute that a statewide plan to stabilise the dunes was put in place and the European Marram Grass (Ammophila arenaria) was one of the species that was actively planted to address the problem.

Along with the disturbance to the Coastal Scrub came other non-native species such as thistles (Cirsium, Sonchus), daisies (Hypochoeris, Arctotheca), annual and perennial grasses (Lagurus, Holcus, Sporobolus), shrubs (Lycium, Coprosma) and climbers (Delairea, Asparagus).  So successful has the invasion of non-native species been to Coastal Scrub that 40% of the most commonly recorded plant species are those that have been introduced since European settlement.   Even some native species have increased in numbers, in some areas, to become a sort of natural environmental weed.  Chief amongst these are Coast Tea-tree and Coast Wattle, both of which have clearly increased in abundance and density in Coastal Scrub after disturbance.

Significant changes in the vertebrate fauna include the extinction of the Rufous-bellied Pademelon (Thylogale billardierii) which was apparently very common in Coastal Scrub at the time of European settlement but was probably completely extinct by the early 1900s.  It isn't clear how many animals were present in Victoria but there are estimates of Pademelons in their thousands near Lake Entrance.  What caused the extinction is also unclear but it is probably a combination of vegetation removal, predation by foxes and hunting.  In some parts of the Victorian coast line the Hog Deer (Cervus porcinus), a native of India and Sri Lanka, has become moderately common and has possibly partially filled the niche of the Pademelons - although it is probable that the larger Black Wallaby has expanded into the Pademelon habitat better.  Hog Deer are more abundant in heathlands and woodlands a little way in from the coast but Coast Scrub has become a refuge for some populations in eastern Victoria.

Non-native vertebrates are very common in Coastal Scrub many of which are typical of urban and rural Victoria (Rabbit, House Mouse, Myna, Blackbird, Starling, House Sparrow, Turtle-dove, Goldfinch).  Their populations are maintained by the same mechanisms that support them elsewhere, non-native plant species providing a food supply, other food from human rubbish (which also support expanded Silver Gull numbers), reduced numbers of native animal competitors and structural changes to the vegetation such as road networks, clearings, car parks, local housing.

Coastal Scrub, more than most other ecosystems, has been vulnerable to invasion by non-native plant and animal species.  Unlike many Victorian ecosystems, which usually have ecological characteristics that make them unfavourable sites for colonising by alien species (mostly European), Coastal Scrub is climatically and geologically similar to coastal areas in many other parts of the world, so it presents fewer barriers.  A graphic example of this is the fact that sites near Melbourne and smaller coastal towns support a wide range of plants which are escapees from local gardens.   Most mature ecosystems require at least some form of disturbance, and this often needs to be severe, before alien species will invade, but Coastal Scrub is based on a moving and unstable substrate which is almost constantly changing.  Storms will regularly remove large areas of the ecosystem and initiate a cycle of re-establishment of the vegetation by colonisers from nearby scrub.  The history of Coastal Scrub has shown that coloniser species from other countries are often just as, or even more, capable of doing this job as the natives.  As a consequence native thistles and daisies (Actites, Senecio) are often replaced by similar alien species (Sonchus, Arctotheca), as are native grasses (Austrostipa replaced by Lagurus) and succulent herbs (alien Carpobrotus may replace the native species) .  There are also analogous alien shrub species such as African Box-thorn which has similar leaves, red fleshy fruit and white flowers to the native Sea Box which it will compete with.

An increasingly important form of disturbance of Coast Scrub is the informal change and damage done to the vegetation by impromptu fishing and camping spots which are created by recreational users.  The upsurge of four-wheel drive vehicles has increased this sort of damage in the past couple of decades by allowing more and more parts of the coast to be accessible.  The heavy vehicles are often used to forge new tracks and push down vegetation for camping and parking sites and they are implicated in the transport of alien plants to new sites.

 

© Paul Gullan, Viridans Biological Databases