Nature, culture and history
Natural environment
Geology
This rugged landscape has its origins about 400 million years ago when this area lay deep under the ocean. Sand and mud carried down ancient rivers were deposited in this ocean environment, known as the Hodgkinson Basin. Over about 60 million years, sediments accumulated in the basin and consolidated into rock. Earth upheavals around 360 million years ago compressed and heated these original sedimentary rocks, transforming them into metamorphic rocks. They were then squeezed upwards, creating high mountain ranges.
From about 310 to 260 million years ago, molten rock (magma) from deep within the Earth's crust pushed up into the older rocks above. The magma slowly cooled to form bodies of granite deep underground. Over 100 million years, the softer metamorphic rocks of the old mountain ranges gradually eroded, in places exposing the more resistant granites. Both types of rocks form today's underlying landscape.
About 100 million years ago the north-east coast of Australia began to break up. Parts of the landscape sank, creating the Queensland Trough and Coral Sea. Another part was lifted high above sea level and the cliff along its edge formed the edge of the continent - the Great Escarpment. Rivers falling over the escarpment gradually eroded it back, eventually creating the meandering edge of today's tableland and carving out gorges, such as the Barron and Johnstone river gorges.
More recently - a mere seven million years ago - there was a period of violent volcanic activity, particularly on the Atherton Tableland. Hot magma pushed its way to the surface, dumping vast amounts of volcanic material - lava and ash - on the surface of the Atherton Tableland and parts of the coastal lowlands.
Lava flowed like water down river valleys to the lowest parts of the landscape. Some flowed all the way over the Great Escarpment onto the coastal plain.
One of these lava flows filled up the original valley of the Johnstone River. The lava cooled to form a dense layer of basalt, diverting the river into two streams - the North and South Johnstone. Today these two rivers run around the basalt flow, joining again near Innisfail before draining into the ocean. The Palmerston Highway actually travels along the basalt flow in what once was the original Johnstone River valley.
Rainforest
The geology and terrain of the landscape have created conditions ideally suited to the development of rainforest. Basalt rocks weathered to produce fertile deep red-brown soils; the surrounding high mountains intercept moist winds from the ocean and more than 4m of rain falls each year. At this relatively low altitude (330m), the climate remains warm all year round.
Not all rainforests are the same. The most complex rainforests have developed in areas with the highest rainfall, the richest, most fertile soils and a warm climate. The rainforest in the Palmerston area is one of the most complex, diverse and species-rich in Australia. Known as complex mesophyll vine forest, it has the largest variety of plants, the tallest trees bearing the largest leaves, with the most vines, ferns and epiphytes. The Palmerston rainforest is particularly important as it represents the largest remaining continuous stand of this forest type growing on basalt soils.
Trees
The canopy in the Mamu rainforest is about 25m high with the tallest trees emerging above the canopy to a height of about 30m high. Trees that form the closed canopy are long-lived, relatively slow-growing species known as climax species. The canopy is dominated by Johnstone River hardwoods (Backhousia bancrofti), left intact after selective logging early last century. Many other species are also present including satin ashes, silky oaks, tamarinds, figs, mahoganies, walnuts, laurels and beeches.
After a disturbance creates a gap in the canopy, fast-growing short-lived tree species, known as pioneers, appear in the rainforest understorey. Pioneers such as bleeding hearts (Homalanthus novoguineensis), chinky pines (Polyscias murrayi) and stinging trees (Dendrocnide moroides) are readily observed competing for space and light around the elevated walkway and tower.
Many rainforest trees produce fruits - some produce year-round while other species produce fruits only in particular months. This means that at any time of the year a wide variety of fallen fruits, in many colours and shapes, can be found scattered along the tracks and walkways.
Several trees along the walking tracks produce their flowers and fruits on their trunks (known as cauliflory). Bumpy satinash (Syzygium cormiflorum) produce large fluffy white flowers followed by white apple-like fruits from their bumpy trunks. Many Davidson's plums (Davidsonia pruriens) grow along the walking tracks; some of these are also trunk-fruiting, producing large dark purple plums from their trunks as well as their branches.
Strangler figs Ficus spp. can be seen from the elevated walkway. Fig trees germinate in the branches of other trees, sending down roots to the ground while growing up towards the light, overshadowing their hosts. A fig's roots coalesce into a living lattice around their host tree, which eventually dies as a result of being out-competed for life-sustaining resources.
Epiphytes
On the tower and elevated walkway, epiphytes (plants that grow on other plants without harming them) positioned high in the canopy can be viewed more easily than from down on the ground. Basket ferns (Drynaria rigidula) and bird's nest ferns (Asplenium australasicum) grow on high branches, often forming huge clumps, using humus formed from dead leaves for extra energy. Orchids, including spider orchids (Dendrobium tetragonum) with their attractive spider-like flowers, can also be found growing on tree trunks. Orchids' spongy roots can absorb water and nutrients quickly.
Creepers and climbers
From the vantage point of the elevated walkway, many kinds of creeping and climbing plants can be seen working their way towards the sunlit canopy. Native monsteras (Epipremnum pinnatum) and (Rhaphidophora australasica) clamber up tree trunks; Rhaphidophoras only germinate in deep shade at the bases of large trees which will support their weight.
Climbing pandanus (Freycinetia excelsa), with spiky-edged leaves, throw out long untidy stems that cling to tree trunks with tiny rootlets. Lawyer cane (Calamus motii) send out prolifically hooked tendrils that reach around until they catch onto something for support. Pothos vines (Pothos longipes) creep up tree trunks using claw-shaped rootlets. Each "leaf" on these creepers is a flattened stem (containing chlorophyll for photosynthesis) ending with a proper leaf. Supplejacks (Flagellaria indica) send out curling tendrils at the end of each of their leaves that twine around other vegetation as the plants climb upwards.
Understorey plants
Cycads (Bowenia spectabilis) with shiny dark green fern-like leaves grow prolifically on the forest floor and can be seen along the tracks. Native ginger (Alpinia caerulea) with bright blue berries in autumn and winter are also common on the shaded forest floor. Native bananas (Musa banksii) can be seen from the elevated walkway. Similar in appearance to commercially-grown bananas, native bananas produce fruits - actually banana-shaped berries - that contain many seeds.
Rainforest community
Mammals
Several mammal species live in the Palmerston rainforest but are not usually seen during the day. Red-legged pademelons (Thylogale stigmatica), a small rainforest wallaby, are active mostly at night, feeding on fallen leaves and fruits. Lumholtz's tree-kangaroos (Dendrolagus lumholtzi) browse on leaves during the night and sleep during the day crouched in a sitting position in the crown of a tree or on a branch. Despite their appearance they are efficient tree climbers and spend little time on the ground. Musky rat-kangaroos (Hypsiprymnodon moschatus) are small primitive rat-like marsupials that forage on the forest floor in the early morning and late afternoon. White-tailed rats (Uromys caudimaculatus) forage in the canopy and on the ground mostly at night, gnawing through seeds and nuts as well as fruits and small invertebrates. Musky rat-kangaroos and white-tailed rats are known to scatter-hoard rainforest fruits well away from where they fell and were collected. This benefits rainforest trees by dispersing their seeds far and wide. Green ringtail possums (Pseudochirops archeri) spend most of their time in the canopy feeding exclusively on rainforest leaves, mainly from fig trees. They are nocturnal, feeding and moving about under cover of darkness and sleeping curled into tight balls on a branch by day. Spectacled flying-foxes (Pteropus conspicillatus) camp in the rainforest canopy during the day (although their noisy squabbling indicates they rarely sleep) and fly off at dusk to feed on fruits and flowers.
Birds
More than 150 species of birds live in the rainforest of Wooroonooran National Park. Many rainforest plants rely on fruit-eating birds for seed dispersal - birds eat the fruit, fly away and deposit unharmed seeds in their droppings. Brightly-coloured fleshy fruits in the rainforest canopy attract fruit-eating birds including wompoo fruit-doves (Ptilinopus magnificus), rose-crowned fruit-doves (Ptilinopus regina), purple-crowned fruit-doves (Ptilinopus superbus), superb fruit-doves (Ptilinopus superbus) and white-headed pigeons (Columba leucomela).
Cassowaries (Casuarius casuarius johnsonii) are extremely important as they are the only animal able to disperse large rainforest seeds effectively. They swallow fruit whole, digest the pulp and pass the unharmed seeds in large piles of their dung, which are distributed over a large area throughout the rainforest. Some plants are completely reliant on the cassowary to reproduce successfully as their seeds must pass through a cassowary's digestive system in order to germinate. Cassowary dung, which contains hundreds of seeds gathered over hectares of forest, can often be seen on the Mamu walking tracks. A male cassowary and his three chicks were frequently encountered in the area during construction of the Mamu facilities.
Large flocks of topknot pigeons (Lopholaimus antarcticus) can be seen flying effortlessly over the rainforest canopy and gorge from the tower and elevated walkway at Mamu. They perch on high branches and feed on fruits in the canopy. Brilliant white against the rainforest backdrop, sulphur-crested cockatoos (Cacatua galerita) can be seen flying alone or in flocks over the canopy. Calling raucously, they land on high branches to feed on fruit and strip away bark to catch insects. Small nectar feeders such as Macleay's honeyeater (Xanthotis macleayanus) perform acrobatics as they climb around branches and flowers to probe for nectar.
Other birds prey on rainforest animals. Tiny agile birds such as white-eared monarchs (Carterornis leucotis) and grey fantails (Rhipidura albiscapa) flutter among leaves in the outer canopy snapping up insects in flight. Noisy pittas (Pitta versicolor) fossick on the forest floor, hammering snails on rocks while forest kingfishers (Todiramphus macleayii) dart down from high branches to seize large insects or small reptiles from the ground. Victoria's riflebirds (Ptiloris victoriae) forage on trunks and branches, hammering into decayed wood for large beetles and search foliage for fruits. A male riflebird often displays for mates from a high branch near the cantilever at Mamu. Laughing kookaburras (Dacelo novaeguineae) are often seen perched on high branches or handrails before swooping down to grasp insects and small reptiles on the ground. Grey goshawks (Accipiter novaehollandiae) soar over the gorge and fly through the canopy, launching sudden strikes at their prey such as honeyeaters. Owls such as lesser sooty owls (Tyto tenebricosa multipunctata) use their exceptional senses to hunt at night. Small prey such as rodents, possums and insects are taken from both the forest floor and canopy.
Reptiles
Several kinds of lizards, including skinks and geckos live at Mamu. During the night, tree-dwelling leaf-tailed geckoes (Saltuarius cornutus) lie motionless on tree-trunks waiting to ambush insects. Another tree-dwelling lizard, Boyd's forest dragon (Hypsilurus boydii), has a distinctively crested head but is well camouflaged and therefore rarely seen. On the forest floor, the rarely seen prickly rainforest skink (Gnypetoscincus queenslandiae) hunts for prey in rotting wood, while the ever-present rainbow skinks (Carlia spp.) are commonly heard and seen rustling through the leaf litter foraging for invertebrates.
Snakes also live in the Mamu rainforest although they are rarely seen. Common tree snakes (Dendrelaphis punctulata) are slender, agile non-venomous snakes that are active during the day, hunting small birds and reptiles. They are good climbers and are sometimes seen around the elevated walkway. Jungle carpet pythons (Morelia spilota) may be seen during the day basking in the sun but are mostly active at night. A non-venomous snake, carpet pythons ambush and then subdue their prey, including rats and birds, by constriction. Carpet pythons vary greatly in colour and pattern - the Palmerston variety has very distinctive and striking yellow and black markings. Amethystine (scrub) pythons (Morelia kinghorni) also live in the Mamu rainforest and can grow to lengths of more than 5m. In winter, scrub pythons congregate at the bottom of rocky valleys such as Johnstone River gorge. Scrub pythons are rarely seen as they are mostly active at night.
From the vantage point of the elevated walkway, red-bellied black snakes (Pseudechis porphyriacus) can sometimes be seen sunning themselves on the forest floor. Growing to two metres in length, they are iridescent black above with bright red or pink scales along the edge of the belly. These generally shy snakes are venomous and prey on frogs and small reptiles. Unlike pythons and tree snakes, red-bellied black snakes are ground-dwellers and cannot climb.
Invertebrates
Many kinds of invertebrates (animals without backbones) live in the rainforest and play important roles in the rainforest community. Ants, termites, bees, butterflies, moths, stick insects, beetles, spiders, worms, slugs and snails are variously rainforest pollinators, decomposers and recyclers as well as sources of food for other animals.
Butterflies including the brilliant blue Ulysses butterfly (Papilio ulysses joesa) and the distinctive green, gold and black Cairns birdwing butterfly (Ornithoptera euphorion) are easily seen from the elevated walkway as they flutter about, taking nectar from flowers. Butterflies begin their lives as caterpillars which are very fussy eaters, feeding on only one or two species of plants. Birdwing butterfly caterpillars feed on a species of vine that contain toxins to deter predators. The caterpillars are immune to the toxin and store it in their bodies as protection against predators.
Australia's largest moth, the Hercules moth (Coscinocera Hercules), is present at Mamu in late winter and spring but is only active at night. The handsome brown wings span up to 30cm (one foot) wide. The males have long tapered "tails" on each wing but have a smaller overall wing area than females. Adult females do not feed and live for about 10 days only - they mate, lay eggs and die shortly afterward. Hercules moth caterpillars are pale green/blue with long yellow spikes and grow up to 12cm (five inches) long. Their food plant is the bleeding heart tree (Homalanthus novoguineensis), common in the Mamu rainforest.
Zodiac moths (Alcides zodiaca) are readily confused for butterflies because they fly during the day and have large pretty wings patterned with bands of black, blue and tan. They mimic poisonous swallowtail butterflies - which deters predators. Zodiac moth caterpillars feed on the day moth vine (Omphalea queenslandiae) that grows along the elevated walkway.
Cyclones
Cyclones are a natural part of this landscape. In March 2006, tropical cyclone Larry snapped and uprooted trees, brought down limbs and stripped trees of leaves and small branches. This opened the canopy and left large mounds of debris covering the forest floor. Although the damage was severe, nature immediately began to adapt and take advantage of the new situation.
Fungi, insects and other invertebrates consumed and broke down (decomposed) fallen plant material releasing nutrients back into the soil for use by other plants. The forest "decomposers" in turn provided food for a range of animals, from birds and reptiles to mammals. Within a few months of the cyclone, most trees showed signs of "aerial coppicing" with flushes of leaves like pompoms appearing along branches and trunks. Many "pioneer" seedlings, particularly stinging trees, sprang to life on the newly-sunlit and well-mulched forest floor.
The damage from Larry will be evident for years to come - or until the next cyclone.
Culture and history
Culture
Rainforest people
The Mamu rainforest is the homeland of the Ma:Mu Aboriginal people. Many generations of Ma:Mu people have lived here - they have a strong and enduring connection with their rainforest country.
The culture of north Queensland's rainforest Aboriginal people is unique. Clan groups had very small ranges with a relatively high population density, compared to other Aboriginal societies. This was possible because they had strategies for intensive use of the rainforest's rich resources and a well-developed system of social regulation.
A network of well-travelled walking tracks traversed the Mamu rainforest, linking campsites and ceremonial grounds maintained as open cleared areas for seasonal tribal or clan gatherings.
The Ma:Mu people constructed large circular mia mias (houses) up to 3m in diameter, using lawyer cane for the framework that they weather-proofed with layers of fronds. The surrounding area was temporarily "home" until the group moved on, following seasonal food sources.
Ma:Mu people had a detailed understanding of their rainforest environment and the phases of the moon and the seasons. They recognise six different seasons each featuring a particular group of foods and the signs that indicate when they are ready to harvest.
During the dry months, Ma:Mu women collected fruits such as quandong and Davidson's plum, as well as yams, palm-hearts and new shoots of plants such as tree ferns.
During the wetter months, toxic plants formed a staple part of their diet. Women collected toxic seeds such as cycads, black bean, yellow walnut and black walnut and treated the seeds to make them edible. Treatment involved cooking, mashing or slicing then soaking in running water to leach out the toxins.
Ma:Mu men hunted a variety of animals. Brush-turkeys and scrubfowl were chased into large cone baskets and their nests raided for eggs in spring. Cassowaries, wallabies, snakes, goannas and bats were also hunted. Traps and nets were sometimes used for hunting large animals.
The river and creeks provided eels and freshwater turtles as well as fish. Bark and leaves were pounded in small pools of water to release toxins that stunned fish, making them easy to catch.
Ma:Mu people carved their distinctive cross-boomerangs, as well as shields, long fighting sticks and swords from rainforest trees. Disputes between men were often settled by formal duels that were controlled to avoid serious injury. Stone was used for making tools - giant axes, grindstones, hammerstones and nutcracking stones.
Europeans bring change
As Europeans arrived in the region in the late 1800s, miners, timber-getters and farmers increasingly penetrated the Ma:Mu people's lands. They occupied their hunting grounds, encroached upon their food supplies and began to clear the rainforest. Many Aboriginal people starved or were killed. Massacre sites such as Palmerston Rocks are still remembered today.
The dense nature of the rainforest offered temporary protection for Ma:Mu people and aided their resistance. In the late 1880s, "food camps" attracted Aboriginal people out of the rainforest and into towns. Many Ma:Mu people were taken into missions.
The remaining Ma:Mu people worked for settlers, clearing and farming the land. As the region developed, they were employed in road-building, timber-getters, forestry and other industries. From the 1880s, the early sugar plantations brought South Sea Islander, Chinese and Italian labourers into the area. The region became a "melting pot" of cultures and lifestyles.
History
Early encounters
European explorer, Christie Palmerston, passed through the area in 1882 while seeking a possible railway route from the coast to the Atherton Tableland. With Aboriginal guides, he followed their traditional walking tracks for part of the way. Palmerston encountered many Aboriginal inhabitants of the rainforest, including Ma:Mu people and, in his own words did not hesitate to "give them a taste of the rifle".
Palmerston's track, although not chosen as the eventual route for the railway, forms much of the highway that today bears his name.
While some early Europeans, such as artists and botanists, were enthralled by rainforests as "novel, contrary and eccentric", most newcomers valued the "wild untamed scrubs" for the resources they offered.
In 1873 explorer George Dalrymple landed in the Johnstone River area where botanist Walter Hill recorded that "the soil cannot be surpassed as the most valuable discovery in Australia". Dalrymple's reports of dense rainforests were equally enthusiastic and cedar timber-getters arrived in the area in 1874. By the 1880s much of the accessible cedar was cleared.
Timber-getters were closely followed by gold prospectors. In the late 1890s there was a short-lived gold rush to the nearby Jordan Creek Goldfield on Jordan, Henrietta and Douglas creeks. Several hundred prospectors toiled in the rainforest but thick vegetation and deep topsoil hampered alluvial mining and yields were poor. By 1901 few prospectors remained.
Several gold mines were established but only one, the Jordan Creek Wyreema mine, had any success. Mining continued sporadically over the years but in all, little gold was won from the rainforest.
Timber
As the region developed, demand for timber increased, tree species other than red cedar were targeted and rainforest timbers became a very valuable resource. The timber industry created great wealth for the region.
Rainforest timbers were commonly held to be an inexhaustible resource. From the 1920s however there was growing concern over indiscriminate cutting of rainforests and the pressure to settle and clear the "rich scrub soils". In the 1920s-1930s several State forests and timber reserves were gazetted in the Palmerston area, despite opposition from land settlement proponents. Managed for wise use of timber, these areas were logged but ultimately protected from clearing.
Although logging in the vicinity of the walkway continued until the late 1930s, logging in nearby State forests in the Palmerston area continued until the 1980s. All but the most inaccessible areas of rainforest were extensively harvested for 100 years - loggers from Millaa Millaa on the tableland eventually met up with loggers from Innisfail.
Farming
In the late 1880s a banana industry developed on the lower Johnstone River. Chinese miners left inland goldfields to farm bananas and a small fleet of sampans transported 1,000,000 bunches of bananas each year to Geraldton (Innisfail) for shipping to southern ports.
Sugar however quickly became the major industry in the lower Johnstone River area. From 1882 Chinese, South Sea Islander and Aboriginal labourers cleared the rainforest, and in 1885, the Goondi sugar mill was established. It attracted labourers from all corners of the world, with many settling in the area.
On the upper reaches of the North Johnstone River, the Palmerston rainforest was more inaccessible. A tramway built through to Nerada in the early 1900s opened up the country for banana farming and timber removal. Little development took place however, until the Innisfail - Millaa Millaa road, following Palmerston's old track, was completed in 1935. Small lots (150-220 acres) were offered for selection. Settlers who "won" their land in the ballot had to clear 25 acres of rainforest each year for three years. Most established dairy farms; others grew bananas and vegetables or fattened cattle and pigs. In the 1960s a tea industry began with plantations at Nerada. Land selection and rainforest clearing continued until the 1950s with the opening of the adjacent Maalan lands.
Tourism
From the 1930s rainforests began to be more appreciated for their scenic and recreational values rather than for the resources they offered. The new Palmerston road also opened the way for tourism as the rainforests, waterfalls and scenic gorges of the Palmerston area became seen as places for recreation - walking, picnicking and sight-seeing. The first national park in the Palmerston area was declared in 1941.
World Heritage listing
Community attitudes towards the use of rainforest resources, such as timber, were already changing when in the 1970s botanists, Dr Len Webb and Geoff Tracey, overturned accepted wisdom and argued that our rainforests originated in Gondwana more than 100 million years ago.
This realisation, along with new scientific discoveries and recognition of their beauty, saw rainforests gain symbolic value. Logging of rainforests began to be questioned and the fight for their preservation for ecological, aesthetic and scientific values began.
In December 1988, 900,000ha of the Wet Tropics was inscribed on the World Heritage list and the logging industry was shut down to conserve the rainforest. The Wet Tropics gained World Heritage listing for its outstanding and important natural values:
- living records of the evolution of land plants, marsupials and song birds
- high levels of biodiversity and endemism (species found nowhere else)
- habitats important for the conservation of threatened species
- areas of exceptional natural beauty.
Today much of this area is also protected as national parks, providing for conservation of natural and cultural values and the enjoyment of visitors.
Community attitudes
Today the Wet Tropics community plays an active role in rainforest conservation. Each year hundreds of landholders, Landcare groups and volunteer groups lend a hand. They plant native rainforest trees in agricultural and residential areas, create wildlife corridors, protect riparian habitats, help control weeds, operate plant nurseries, educate the public and survey wildlife. These community conservation activities create a "culture of caring" for the natural environment and encourage others to appreciate the value of our rainforests.
Ma:Mu people are also involved in rainforest restoration and conservation. They have witnessed immense changes to their traditional rainforest country and culture. Today they are reconnecting with their culture in modern ways, while still respecting the old ways. They are involved in bush tucker gardens, revegetation programs and tourism ventures.
Constructing the Mamu walkway
Consultation and co-operation
A consortium led by Hutchinson Builders Pty Ltd was contracted by the EPA to construct the walkway during 2007-2008. Regional and state tourism organisations and the Cassowary Coast Regional Council as well as the Wet Tropics Management Authority were closely involved with the development of the original walkway proposal.
During construction, the EPA consulted with the Innisfail Disability Focus Group, Disabilities Services Queensland and Guide Dogs Queensland to ensure that facilities cater for people who have impaired mobility or vision. The Johnstone Ecological Society provided input about the protection and presentation of the natural values of the rainforest.
Elevated walkway design
The main design challenge was to find ways to build the elevated walkway safely and efficiently on a steep slope, in thick rainforest and in a high rainfall area.
The elevated walkway was built in sections. Each section is supported by a steel tower up to 15m high, 2m x 2m square with a 4m diameter circular top. The circular-tower-tops serve as resting points and passing locations for larger groups of visitors, preventing congestion on the walkway and enhancing visitors' experiences.
The prefabricated walkway sections between the towers are 10m long and 1.5m wide. The relatively short walkway sections allowed the builders to move them into place through the existing trees with minimal clearing of vegetation required.
The cantilever is a straight section of walkway, 40m long and 2m wide, that extends 10m beyond the last supporting tower. A glass viewing panel at the end provides for an unobstructed and excellent view. The observation tower is 5m x 5m square and 37m high with two viewing levels and a roof shelter. The elevated walkway, cantilever and observation tower have been designed to withstand cyclonic winds.
Environmental sustainability
Every effort was made to construct the walkway in an environmentally sustainable way; that is, minimising adverse environmental impacts during construction and for the life of the structure.
Cyclone Larry tore through this area in March 2006, opening the canopy in several places. The route of the walkway uses these natural openings to reduce the need for further clearing. A detailed botanical assessment was carried out before the walkway route was finalised, to reduce even further the risk of damaging significant plants.
An old forestry track was used for access to the construction site. When the elevated walkway and tower were completed, the access track became the ground-level Forest walk.
Cyclone debris and vegetation that had to be cleared were retained and mulched for rehabilitating around the construction site. Plants grown at the EPA nursery at Lake Eacham, from seed and seedlings sourced around the walkway site, were used for revegetation.
Environmentally sustainable, durable materials were selected for the project. Planks made of 100 percent recycled plastic were used for the elevated walkway decking and for the wall cladding of new buildings. Recycled plastic was also used for seats. Using recycled plastic products reduces the amount of plastic waste sent to landfill. The recycled plastic planks are resistant to rotting and corrosion, and can be expected to outlast timber by many years. Using recycled plastic also reduces maintenance. Unlike timber, plastic does not become quickly coated in slippery growth, so there is no need to clean it with chemicals and high pressure hoses.
Unpainted galvanised steel was chosen as the most durable material for the supports and beams of the walkway, cantilever and observation tower. Using materials that do not need to be painted reduces maintenance and minimises the risk of paint flaking and leeching into the rainforest. To reduce the risk of corrosion, the steel sections are open rather than closed.
The EPA and Hutchinson Builders carefully selected construction materials and equipment that reduced impacts during construction. These included:
- prefabricated sections for the elevated walkway, cantilever and observation tower
- a lightweight, extendable tower crane with a small "footprint"
- a fully enclosed generator that is almost silent and is sealed to prevent fuel spills
- equipment that is as small as possible for the job.
Strict hygiene procedures were used to reduce the risk of introducing weeds or diseases to the site via soil brought in from other areas. These included:
- A wash-down bay to clean construction machinery, vehicles and people's boots.
- Cranes and other site vehicles were kept on site at all times during construction, to further reduce the risk of contamination.
- New portable toilets were bought for the construction site to prevent soil contamination from previous use at other sites.
A site induction video was shown to all staff to familiarise them with the importance of the site and the environmental protection measures required. There was regular monitoring of work practices to ensure compliance with the project's Environmental Management Plan.
- For a summary of sustainability information, see How green is the walkway?
Last updated: 10 June 2009