Tropical Topics - Weeds in the wet tropics by lindayy


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									                       Tropical Topics
An      interpretive                       newsletter               for      the       tourism             industry

Weeds in the wet tropics                                                                    No. 27 April 1995

    Notes from the                          Don’t give a weed a break
                                            In the 1840s someone decided that a Central American flowering plant would
        Editor                              look good in their garden in Calcutta in India. It grew well. It spread throughout
                                            India, across Asia to Siam (Thailand) and on to China, the Pacific islands and
A weed is a plant which grows where         Papua New Guinea. Within a century it was also well established in Africa.
it is not wanted. A plant introduced to
improve pasture may be unwelcome
in our back yards. A plant which we         Siam weed, Chromolaena odorata, is         boots or to machinery used overseas.
admire in our gardens may well cause        now considered one of the world’s          The Department of Lands has been
the destruction of native vegetation.       worst weeds. It is fast-growing and        spraying the infestation with
This issue of Tropical Topics               competitive. In open areas it forms        herbicides; the third program is due to
concentrates on environmental               dense tangled bushes which can             start at the end of this month. It is
weeds, specifically those which             cause intense bushfires in the dry         hoped that the weed is confined to the
endanger the natural environment in         season. It can climb up to 20m on          Tully area and can be controlled but
                                            trees, smothering them with its dense      there are concerns it may have been
the wet tropics.                            growth. Growing over a metre in just a     carried further.
                                            couple of months it can overwhelm
Each component in an ecosystem has          sugar cane and other crops and it is       Siam weed is not the only weed
natural checks on its population            toxic to stock.                            threatening the wet tropics. As can be
growth; over time providers and                                                        seen on the following pages vines and
consumers have struck a balance.            Australia was thought to be one of the     creepers, trees, shrubs and grasses all
However, when one element of an             few tropical areas free from this weed     have a destructive potential. However,
ecosystem is transplanted into              — until July 1994 when a DPI botanist      very few of these weeds are able to
another it usually travels without its      spotted it near Mission Beach. No one      establish themselves in unbroken
enemies, the diseases and predators                              knows how it got      rainforest. If a siam weed seed is
which would normally check its                                    there but the        dropped under the forest canopy it
growth. Some plants fail to thrive in an                           feathery seeds      can’t grow in the dim light. However, if
alien situation, others fit in to some                              may easily have    the same seed is deposited wherever
degree and yet others achieve                                        attached          there is a break — along a river bank,     Illustration courtesy Department of Lands
outrageous success — at the expense                                   themselves to    in a clearing, at the roadside or
of the locals. A successful weed is                                    a visitor’s     anywhere there has been a
hardy, fast-growing, competitive,                                                      disturbance — it will spring to life and
aggressive, reproduces quickly and                                                     quickly destroy surrounding
abundantly and disperses with ease.                                                    vegetation. The more the forest is
                                                                                       disturbed the more danger there is of
It is difficult to predict which plants                                                weeds attacking the remaining part.
will become weeds. A species may, at                                                   The best way to defend the rainforest
first, adapt to its new environment                                                    is not to give the weeds a break.
without appearing to be a problem.
This is known as the lag phase. Then
it may suddenly launch into the
expansionist phase — a rapid
population increase which may                                               Siam weed has a similar growth habit to
eventually dominate neighbouring                                           lantana, soft hairy roughly triangular leaves,
vegetation.                                                                soft round stems, no prickles and masses of white
                                                                          or pale lilac flowers in winter. The Department of
                                                                         Lands is keen to hear of any sightings of the plant.
                                                                         If you see it call the Innisfail office on (070)
                                                                         61 1446 or your local Department of Lands office.
Weeds in the water
Water weeds are a widespread problem in Australia. Many species have been introduced to decorate garden ponds or
aquariums and have then found their way into natural waterways where they have become pests.
Water weeds usually grow very fast under tropical                    Some biological control of four serious waterweeds,
conditions, some infestations doubling in size each week.            salvinia, water hyacinth, alligator weed and water lettuce
They form dense mats of vegetation on the surface of the             has been achieved by releasing weevils and beetles which
water which:                                                         feed on these species. There is no known predator for
• reduce light reaching submerged plant species                      cabomba.
• use up oxygen in the water, depriving and killing fish and
other aquatic creatures                                              It is essential for aquarium and pond owners and those
• restrict the movements of water-based                              dealing in water plants to be aware of the potential problems
animals including waterbirds                                         not just of proven pest plants but also of those not yet
• choke drains and restrict the flow of                              released on the environment. Unwanted aquatic plants
water                                                                should be burned or composted and NEVER NEVER
• clog up pumps, seriously                                           dumped in waterways. Pond owners should also be careful
affecting irrigation and                                             to prevent water plants being carried away when there is
aquaculture equipment                                                heavy rain and flooding. (Likewise, unwanted fish should
• foul boat engines and                                              never be released into waterways.)
restrict navigation,
watersports, swimming and                                            The best native plants to use are
fishing                                                              probably Blyxa species and stoneworts
• cause water loss, at up to four times the normal                   — Chara and Nitella species. Others
evaporation rate, through rapid transpiration from the leaves        are Pacific and ferny azolla (Azolla
•           during floods, together with trapped debris, can         filiculoides, A. pinnata), hydrilla
               cause the collapse of bridges and fences.             (Hydrilla verticillata), clasped pondweed
                • restrict livestock access to water sources         (Potamogeton perfoliatus) and ribbonweed
                 • endanger stock and children who may               (Vallisneria gigantea). (See Waterplants
                  become entangled and drown                         book in Bookshelf) Please remember that
                   • provide breeding places for disease-            even native plants can cause problems if
                    carrying mosquitoes.                             introduced to the wrong area so please do
                                                                     not dump them in watercourses. Also,
                                                                     please do not collect from the wild. Some
                                                                     natives are rare or threatened.
                             Water hyacinth (Eichhornia
                              crassipes) (left) has beautiful
                              purple flowers and despite its         Cabomba, or fanwort, (Cabomba
                            remarkable abilities to clean            caroliniana) (right) is a popular aquarium
                            up polluted water, has become            plant from America which is causing
                             an invasive and unwanted                problems in ponds, lakes, dams and quiet
                                            species all over         rivers in Queensland. In some areas it
                                            the tropical             has been declared a category P2
                                          world outside its          plant. Sale of cabomba is illegal in
native Brazil. In Queensland it is a category P2/P3 weed.            Queensland.

What is a declared plant?                                                                 In a word
A declared plant (formerly termed ‘noxious plant’) is a plant considered a                Exotic is a word which conveys a positive
serious enough pest to warrant its control being enforced under legislation (the          image to most people. Exotic holidays,
Rural Lands Protection Act 1985-1988).                                                    exotic food, exotic fruits — the word has
                                                                                          come to mean things which are strange or
Declared plants are placed in various                                                     unusually colourful or beautiful. In fact,
categories, though some plants may                                                        the word means foreign, from outside
be in more than one category.                                                             that country. While we can safely admire
                                                                                          exotic animals and plants when we travel,
P1 — plants which do not occur in                                                         if transported elsewhere they can become
Queensland and whose introduction                                                         pests. Pigs, foxes, cats, rabbits and so on
into the State is PROHIBITED.                                                             are all exotic animals — but unwanted in
P2 — plants which are to be                                                               natural areas of Australia. Similarly many
completely DESTROYED throughout                                                           exotic plants can become exotic weeds.
an area.
P3 — plants whose numbers and
distribution should be REDUCED in an        Rubber vine (Cryptostegia                     Weeding in the Wet
area.                                       grandiflora) (above) is a declared            It is tempting, when the ground is wet, to
P4 — plants which should be                 category P3 weed. A garden escapee,           pull up all those nasty weeds by the
PREVENTED FROM SPREADING                    originally from Madagascar, it                roots. However, this may leave the soil
beyond places in which they occur.          threatens mainly dry rainforest and           vulnerable to soil erosion and simply
P5 — plants which should be                 riverside forest. It invades                  prepare the ground for the next generation
CONTROLLED only on land under the           agricultural land and is poisonous to         of germinating seeds. A more effective
control of a Government Department          stock, costing the grazing industry           method is to snip the offending plants
or Local Authority.                         about $8 million each year.                   and cover the ground with a thick layer
                                                                                          of newspaper and mulch. Few weeds will
For more information contact your local Department of Lands office.                       survive this treatment.
2 Cartoon illustration courtesy ACT Parks and Conservation Service                 Plant illustrations courtesy Department of Lands
Nature notes
A diary of natural events creates a pleasing journal which grows richer with the passage of time. Watching for the
recurrence of an event after noting it in a previous year, and trying to understand what could have caused changes in
timing, is intriguing.

These notes are from the author's own notebook, or were offered by researchers and fellow naturalists. Readers will,
inevitably, note variations between their observations and those appearing here. If you do not keep a nature diary perhaps
this will inspire you to begin one.

                                                                                         Banana bush is a shrub or small
                                                                                         shrubby tree named for the bright
                                                                                         yellow fruit it produces at about this
                                                                                         time of year. Carried in pairs, these
                                                                                         split open when ripe to reveal bright
                                                                                         red flesh in which the seeds are

Shell vine (Connarus conchocarpus)is
one of the woody lianes of wet tropics
rainforests. Its bright pink to red fruit
have started dropping, and will
continue to appear on the forest floor
over the next couple of months. When        The fruits of white cedar will begin to
mature they split open showing a dark       turn yellow towards the end of the
seed with a small fleshy yellow aril.       month, the crop being eagerly awaited
However, they are sometimes opened          by several bird species including fig
beforehand by sulphur-crested               birds and orioles. White cedar, also
cockatoos, presumably because of            known as Persian lilac, which gives an
competition from other birds.               indication of how widespread this tree       Banana bush is currently known as
                                            is, is in the same family as red cedar       Tabernaemontana pandacaqui, but
                                                        and spur mahogany. Trees in      was formerly classified as Ervatamia
                                                          this family — Meliaceae —      angustisepala. Although Latin or
The distinctive small tree                                  produce a variety of fruit   Greek names for plants can sound
known as bleeding heart                                       ranging from those         confusing they often provide
(right) will usually carry                                       with a fleshy aril      interesting historical geographic or
flowers this month.                                               (spur mahogany) to     botanical information. The genus name
The flowers are                                                   those with wind-       Ervatamia, for example is a latinised
either male or                                                    distributed seeds      abbreviation of the name by which this
female, borne on                                                  (red cedar). White     plant is known in parts of southern
short spikes                                                      cedar (Melia           India.
which push                                                        azedarach) has a
upwards among                                                     thinly-fleshed fruit   Botanists have recently shifted banana
the leaves or at                                                 enclosing a very hard   bush into the genus
the ends of twigs. Fruit of the bleeding    stone. This contains two to five small       Tabernaemontana. Translated as
heart (Omalanthus novo-guineensis,          seeds, not just a single seed as casual      ‘mountain tavern’, this was the name
formerly O. populifolius) is very           inspection might suggest. The ripe           which an Austrian physician gave
important to several species of             fruit hang from the tree for several         himself by translating his own surname
bowerbirds and pigeons, so a prolific       months serving as an arboreal larder         of Bergzabern into the Latin
tree on the uplands is busy with the        for the birds.                               Tabernaemontanus! This physician,
comings and goings of a rich variety of                                                  who lived and worked in Germany in
birds. The leaves, which turn a bright                                                   the sixteenth century, was honoured
red when aged, show a small cup-                                                         by botanists because he wrote an
shaped gland at the base, the secretion                                                  important guide to the medicinal
from which may attract small insects.                                                    properties of a number of plants.
The leaves are an important food for                                                     Acknowledgements to Rebel Elick,
Daintree River ringtail possums and to                                                   Esther Cullen and various texts.
a lesser extent for Herbert River
ringtails. They are the only food for
caterpillars of the Hercules moth.

                                                                   Weeds in the wet tropics
                                                                       Invaders from the garden
            Thunbergia illustration courtesy Department of Lands

                                                                       One day, somewhere in the wet tropics,                                                           Singapore daisy (Wedelia trilobata)
                                                                       someone may have cleared a drain of                                                              (below) is a useful ground cover with
                                                                       choking vegetation, or cleaned up their                                                          bright green leaves and sunny yellow
                                                                       garden. The easiest way to get rid of the                                                        flowers.
                                                                       rubbish was to dump it on the nearest
                                                                       patch of bush or river. From there the
                                                                       broken fragments of one plant, Sanchezia
                                                                       parvibracteata, (below) were carried
                                                                       away on flood waters. Landing on the
                                                                       banks of a hospitable creek they took
                                                                       root. Soon a large shrub had grown, from
                                                                                     which other fragments fell
                                                                                      and took root. Sanchezia
                                                                                       became king of the river
                                                                                        bank, excluding native
                                                                                        plants as it spread in
                                                                                        dense thickets. This          Thunbergia grandiflora is among the most
                                                                                        invader would have            rapidly growing and destructive weeds in          Have you ever tried to get rid of it? If
                                                                                         expanded its territory       the wet tropics. Introduced as a garden           so you will know how tenacious it is,
                                                                                             indefinitely had it      creeper it escaped from cultivation and           appearing repeatedly after being
                                                                                                not been stopped      established itself along lowland rainforest       sprayed and/or pulled up and
                                                                                                 in its tracks by     edges and river courses. From there it began      apparently eradicated. It is extremely
                                                                                                 poison sprays        its stunningly successful invasion. Climbing      aggressive and spreads readily,
                                                                                                administered by       rapidly up and over rainforest trees it           forming thick swards in sunny and
                                                                                              Department of           smothered them completely, reducing them          shady places. Ground covers are
                                                                                                    Environment       to dead stumps which eventually fell. All         valued for their ability to suppress
                                                                                                      and Heritage    that could then be seen was a wasteland, a        weeds — but when they escape into
                                                                                                            staff.    carpet of triumphant thunbergia. Its              the wild they perform the same
                                                                                                                      destructive march has been measured at            function, forming thick invasive
                                                                                                                      0.6ha per year.                                   carpets which suppress native
                                                                                                                                                                        seedlings. There is particular concern
                                                                                                                      Physical attacks on thunbergia usually just       that Singapore daisy planted at island
                                                                                           Sanchezia, a South         help it to spread. It reproduces mainly by a      resorts will become destructive.
                                                                                           American shrub with        tuberous root-system, the tubers reaching         Many other popular ground covers
                                                                                          large dark green yellow-    massive sizes and weighing as much as             are also potential threats (see the
                                                                                          veined leaves (left) and    70kg. Even small pieces of these will sprout      What-not-to-plant guide on page 7).
                                                                                         clusters of yellow trumpet   so, if they are transported by river or in land
                                                                                         flowers, is common in        fill, they can start new infestations.            Clitoria laurifolia, a shrub with a
                                                                                        tropical gardens. It has      Herbicides have been used with success,           pretty blue flower, is another
                                                                                       infested creeks between        particularly along the Mulgrave River, south      imported pest, originally from tropical
                                                                                     Cairns and Innisfail, notably    of Cairns. However, the story does not end        America. It has invaded the
                                                                                    Henrietta Creek in                there. Once the affected area has been            understorey of melaleuca swampland
                                                                                  Wooroonooran (formerly              cleared of thunbergia it is vulnerable to         in Edmund Kennedy National Park,
                                                                              Bellenden Ker) National Park. Please    further invasion by other weeds. A program        north of Cardwell, where it had
                                                                          do not buy, sell or grow this plant and     of revegetation and further vigilant weed         produced dense thickets before it
                                                                       if it is in your garden please remove it —     eradication is necessary to rehabilitate the      was discovered and control measures
                                                                       and dispose of it thoughtfully.                area.                                             begun.

                                                                       Fire danger
                                                                                                  The notorious weed lantana (left) is yet another garden runaway which
Lantana illustration courtesy Department of Lands

                                                                                                   was brought from America in the mid 1800s. Now almost four million
                                                                                                   hectares in eastern Australia are infested, a particular headache for
                                                                                                   farmers whose stock are poisoned by the plant. In the wet tropics
                                                                                                  Lantana camara grows on better soils on cleared land and in disturbed
                                                                                                  open forest; the worst invasions of the wet tropics have taken place in
                                                                                                    eucalypt forest in the Herbert River area. It doesn’t like shade so will
                                                                                                     not invade intact rainforest but does grow at its edges. There it can
                                                                                                     cause damage by burning fiercely when dry and damaging nearby
                                                                                                     Non-native grasses are even more of a fire hazard. Guinea grass
                                                                                                     (Panicum maximum) and molasses grass (Melinis minutiflora) grow
                                                                                                     lushly after rain providing a large fuel load which, when dry, burns
                                                                                                     more readily and hotter than native grasses. This damages the
                                                                                                    rainforest edge, pushing it back and allowing the grasses and other
                                                                                                   exotic species to become further established. When they burn, the same
                                                                                                 thing happens again, the rainforest margin continually retreating under
                                                                                               fire. This is common throughout the wet tropics and is particularly obvious
                                                                                              on hillsides.

Commercial runaways                          over. It is capable of invading natural areas
                                             which are free from human disturbance.

                                              The main area affected by pond apple is
                                              the Russell River, near Innisfail, this
                                              infestation extending north to Gordonvale
                                              and south to Cardwell. It is also growing on
                                             the Daintree River and in other spots. Since
                                             the fruits can survive long periods floating                       No one
                                             in water and are eaten and dispersed by              knows how harungana
                                             pigs and cassowaries this weed is likely to     (Harungana madagascariensis)
                                             spread rapidly.                                 (above) arrived in the wet tropics.
                                                                                             It may have been introduced as an
                                                Pond apple can be killed by fire which       ornamental garden tree in the Babinda
                                                does not destroy melaleuca but it is         area where it was first recorded in 1937. It
                                                difficult to burn many swamp areas. The      has not yet spread more then about 30km

                                                                                                                                                Pond apple illustration courtesy Dr J.T.Swarbrick. Copyright Weed Science Consultancy
                                               best control is achieved with chemicals but   but is now considered to have moved into
                                             the process is laborious and slow and the       an expansionist phase.
                                             sites often inaccessible. However, if nothing
                                             is done it is predicted that melaleuca          Harungana is a pioneer species which
                                             ecosystems in the wet tropics will be           germinates en masse and establishes itself
                                             gradually lost to this invader.                 quickly, easily and in large numbers
                                                                                             wherever there has been any sort of
                                             Ironically, pond apple is rare in its native    disturbance — at the rainforest edge,
                Probably the worst           Florida where it was extensively cleared for    along tracks, roads, drains and rivers
             invader of the wet tropics to   agriculture. Now Melaleuca quinquenervia,       (such as the Russell) and in clearings. Its
         date has been pond apple            introduced from Australia, is seriously         spreading roots sucker, producing
(Annona glabra) (above). A native of         threatening the native vegetation!              numerous new plants sometimes several
tropical America and Africa, it was                                                          metres from the adult. If it is cut or blown
brought to Australia (possibly in 1912)      A number of other plants which were             down it suckers again. Other species
to be used as root stock for its close       introduced for commercial purposes also         cannot compete with this and harungana
relative the custard apple which doesn’t     threaten the wet tropics. Coffee plants have    quickly dominates until the canopy over a
otherwise grow well in wet soils. It is a    spread from plantations into rainforest         few hectares consists exclusively of this
shrubby tree which reaches about 15m.        around the Atherton Tableland and               species.
It is salt-tolerant and can stand            Kuranda. Spread quickly and easily by birds
immersion in fresh water so has              and other animals, this plant, an               Harungana produces numerous seeds
energetically established itself in          understorey species by nature, flourishes in    which may be dispersed by small birds,
lowland seasonal swamps and along            the forest. Many plants have been removed       fruit bats, by water and on machinery.
drains. It is particularly destructive in    from Lake Barrine National Park. While not      Researchers have found it thriving 2½km
melaleuca swamps where it forms a            yet a major problem, coffee may become          into undisturbed rainforest in small gaps
dense understorey which prevents             one. Chukrasia velutina is a cabinet timber     created by tree falls, landslips and so on
young trees from developing. As              tree, related to red cedar, a small number of   as well as dominating disused logging
mature melaleucas gradually die there        which were planted near Lake Tinaroo in the     tracks throughout the Wooroonooran
are no young ones to replace them and        1960s. Its seeds are wind dispersed and now     (formerly Bellenden Ker) National Park.
pond apple thrives; in areas where           that the original trees are mature, seedlings   Since it is found up to altitudes of 1800m
melaleucas have been killed by salt          are being found in large numbers. It seems      in its native Africa, there are fears that
water, pond apple has completely taken       to be on the verge of a population              over the next 20-30 years the forest in this
                                             explosion.                                      park, right up to the mountain tops, could
                                                                                             become dominated by this aggressive
Troublesome natives                                                                          species. Many of the more accessible
Although most weeds are exotic plants, under certain                                         trees have been poisoned successfully
circumstances even the natives can cause problems. There                                     and eradication of this species may be
are two ways this can happen.                                                                possible although the longer the problem
                                                                                             is left the more difficult and expensive it
When a plant is moved from one part of Australia to                                          will become.
another it may dominate the local ecosystem. This has
happened with sweet pittosporum (Pittosporum                                                 Harungana is a large tree which grows to
undulatum), a rainforest shrub which, after being                                            25m or more. It has bunches of small pale
introduced as an ornamental plant, is now invading                                           flowers and orange-brown fruit. Its most
southern Australian eucalypt forests. There it crowds out                                    characteristic feature is its orange sap
the young trees, just as pond apple does with melaleuca in                                   which can be seen if leaves are broken off
the wet tropics. Cadagi (Eucalyptus torelliana), familiar                                    or if the bark is scraped.
from north-east Queensland rainforests especially around
Kuranda, is considered an invasive plant in southeast                                        Camphor laurel (Cinnamomum
Queensland.                                                                                  camphora) is causing similar problems on
                                                                                             the Atherton Tableland. Originally from
Natives can also dominate an environment which has been altered,                             China, Japan and Taiwan, it has spread
allowing certain local species an unfair advantage. In the wet tropics native vines grow     along creek lines and edges of rainforest,
vigorously following cyclone damage. The opening up of rainforest artificially by            excluding rainforest species and
roads and other clearings allows them additional opportunities.                              preventing regeneration of native forest.
                                                                                             Its very fertile seeds are spread by birds
Merremia peltata (above) is a native vine which has grown up over much of the                and like harungana it suckers from the
roadside vegetation along the Daintree road.                                                 roots and is very difficult to kill.

    Questions & Answers                                                                       Facts and Stats
                                                                                              on weeds
    Q What are the effects of fresh water         growing.                                    There are about 15-20 000 native
    (rain) on the reef?                           Blue coral (the uncommon Heliopora          plants in Australia. Naturalised plant
                                                  caerulea) actually has pigments in its      species ( those which have become
    A Fresh water, because it is less dense       skeleton due to the presence of iron        part of the environment) range from
    than salt water, floats on top and usually    salts, although in the living animal this   about five percent of all plants in the
    diffuses without changing the salinity        colour is masked by brown tissues.          Northern Territory to 31 percent in
    too much. However, a massive amount           Other corals have red or black skeletons.   Tasmania with an overall proportion of
                                                  However, none of these are true hard        at least 15 percent. Of these about half
    of rain falling on the reef at low tide can
                                                                                              invade native vegetation and probably
    affect the corals. The next tide should       corals, their tentacle structure more       a quarter are serious or very serious
    bring in salt water to remedy the             closely resembling soft corals. The         environmental weeds or have the
    situation but if there is continuous          colour of some soft corals, for example     potential to be so. Weeds, mainly
    heavy rain for several days the corals,       the Gorgonians, is caused by crystalline    those affecting agriculture, cost
    which require a certain degree of salinity,   structures in their tissues, called         Australia an estimated 3 billion dollars
    become stressed and may ‘bleach’.             sclerites or spicules.                      each year.
    Most hard corals have, living in their
    tissues, algal cells (zooxanthellae)          Of course, colour appears to change         Over 60 introduced plant species are
    which provide the corals with much of         with depth; even in the clearest water      declared noxious for Queensland. Of
    their food in return for a home. However,     the long wavelengths (reds) are             those, 31 percent were introduced
                                                                                              deliberately as ornamental plants.
    stressful conditions such as high             excluded beyond the first 10-15 metres.
    temperatures or fresh water can lead to       Only short wavelengths of light — the       In 1992 eight species of weeds were
    the corals expelling the zooxanthellae        blues — can penetrate deep into the         identified as the most destructive to
    — a process known as bleaching                ocean.                                      native plant communities in the Wet
    because the corals then appear to be                                                      Tropics World Heritage Area. They
    almost pure white (see question below).                                                   were pond apple/cherimoyer (Annona
    Continued stress may eventually lead                                                      glabra) (tropical American and
    to the corals’ death.                                                                     African tree), Harungana
                                                                                              madagascariensis (African tree), blue
    Q Besides zooxanthellae, what causes                                                      sky vine (Thunbergia grandiflora)
                                                                                              (Indian vine), Turbina corymbosa
    colour differences in coral?                                                              (American vine), Lantana camara
                                                                                              (American shrub), Sanchezia
    A The colours of coral are caused by a                                                    parvibracteata, (South American
    combination of the zooxanthellae, which                                                   shrub), Clitoria laurifolia (tropical
    are a brownish colour, and the natural                                                    American shrub) and Coffea species
    pigments of the coral tissue. The                                                         (originally tropical African shrub).
    zooxanthellae colour acts as a
    background, enhancing the tissue                                                          Over 3200km of roads cross the Wet
    colour. This can be appreciated when                                                      Tropics World Heritage Area.
    bleaching takes place and the corals                                                      Together with powerlines and
                                                                                              railways they provide long breaks in
    become very pale versions of their                                                        the canopy allowing light-loving weeds
    normal hues. This is due to the visual                                                    to develop, particularly where the soil
    effect of the white background skeleton,                                                  has been disturbed.
    normally masked by the zooxanthellae.
    In healthy staghorn corals, the more                                                      A study of tourist vehicles in Kakadu
    intense colours at the branch tips                                                        National Park found that 70 pecent of
    indicate points where the colony is                                                       them were carrying seeds, many of
                                                                                              them alien to the area.

                                                                                              Siam weed poisons over 3000 cattle
                                                                                              each year in the Philippines. Up to
Tourist talk                                                                                  87 000 seeds have been recorded from
                                                                                              just one siam weed plant in India.

     ENGLISH          GERMAN                 JAPANESE                                         There is a plus side to pond apple —
                                                                                              its fruits are a food source for
    weed              Unkraut                za sso                                           cassowaries, although these
    exotic            nicht-heimich          gairai shu no                                    threatened birds therefore serve to
    introduced        eingefuehrt            mochi komareta                                   disperse the seeds.
    native            heimich                jisei no
                                                                                              If you have any queries about noxious
    grass             Grass                  kusa                                             (harmful) weeds contact your local
    vine              Wein                   tsu ru                                           council or Department of Lands office.
    tree              Baum                   ju moku                                          For information about crop weed
    shrub             Busch/Strauch          tei boku                                         control contact the Department of
                                                                                              Primary Industries.
    invade            eindringen             shin nyu suru
    smother           ueberwuchern           so shi suru
The what-not-to-plant guide
As can be seen on previous pages, a large number of serious weeds in the wet tropics, and indeed in all of Australia, were
originally introduced as garden ornamentals. When planting your personal or resort garden there are some particularly
troublesome species which it is best to avoid. Bear in mind that the plants least likely to cause trouble are those native to
the local area. They will also grow well and, in the case of resorts, provide a uniquely Australian experience for visitors.

                                           Neither Thunbergia grandiflora, nor        Passiflora coccinea) have beautiful
                                           its close relative Thunbergia              flowers but are also dangerous plants.
                                           laurifolia, can be sold. Interestingly,    If a vine is required several natives
                                           thunbergia belongs to the family           such as bower climber (Pandorea
                                               Acanthaceae which includes other       jasminoides) with pink trumpet flowers
                                               bad weeds such as Sanchezia            and Tecomanthe hillii with
                                             parvibracteata (see page 4), metal       spectacular bunches of pink flowers
                                           plant/red ivy (Hemigraphis colorata),      are very decorative. (But take care —
                                           Stephanophysum longifolium, a              many vines can be invasive.)
                                           scrambling plant and Perilepta
                                           dyeriana. It is a good idea to avoid       Singapore daisy (Wedelia trilobata)
                                           planting all imported plants from this     has already been mentioned (page 4).
African tulip                              family.                                    Other ground covers with a tendency
tree (Spathodea campanulata) is                                                       to smother everything in their path are
grown widely for its attractive scarlet    Thunbergia is by no means the only         wandering jew (Tradescantia and
flowers (above) but this tree’s            destructive vine, there are many many      Zebrina species), metal plant/red ivy
windblown seeds are rapidly                others. Turbina corymbosa, a native        (Hemigraphis colorata) and peacock
spreading the species throughout the       of tropical America and a member of        fern (Selaginella willdenovii).
wet tropics. Why not plant the local       the morning glory family, has been
flame tree (Brachychiton acerifolius)      found behaving like thunbergia on the
instead? Its dramatic red flowers          banks of the Barron River. Certain
attract rainbow lorikeets.                 passion flowers (particularly
Please don’t buy, sell or grow the above plants — and if weeding them out please dispose of them thoughtfully. Don’t
dump them in bushland.

Ecotourism — towards a definition?
In future the 1990s may well be seen as the decade of ecotourism. It may also be seen as a time when the tourism industry,
academics and natural and cultural resource agencies all jumped on the bandwagon, only some of them understanding the
concept of ecologically sustainable development (ESD) while others simply indulged in the marketing benefits.
So, what exactly is ecotourism? Don’t panic if you can’t answer.
You are not alone! Even the authors of the National Ecotourism   Ecotourism — how do you measure up?
Strategy (yes, there is one!) have recognised that “the term     So, what is the ‘ecotourism factor’ of your tour program or
‘ecotourism’ has been widely open to misinterpretation by        operation? A simple way to determine this is to study the
planners, operators, managers, marketers and the media.”         following four key elements of ecotourism (defined within
(Wright 1993)                                                    the National Ecotourism Strategy) and ask yourself the
                                                                 questions below.
Hector Ceballos-Lascurain, who first coined the notorious
term, defined ecotourism as: “Tourism that involves travelling   • The natural environment
to relatively undisturbed natural areas with the objective of    Is your operation based on the natural environment and
admiring, studying and enjoying the scenery and its wild         does it include cultural values?
plants and animals, as well as any cultural features found
there.” (Hector Ceballos-Lascurain 1991)                         • Ecological and cultural sustainability
                                                                 Does your operation attempt to minimise environmental
However, this definition doesn’t really address ESD. Peter       impacts, for example, through use of environmentally-
Valentine includes it: “Ecotourism is nature-based tourism       friendly cleaning agents, and support local communities?
that is ecologically sustainable and is based on relatively
undisturbed natural areas; is non-damaging and non-              • Education and interpretation
degrading; provides a direct contribution to the continued       Does your operation provide educational or interpretive
protection and management of protected areas used; and is        programs for increasing public awareness of environmental
subject to an adequate and appropriate management regime.”       and cultural issues and values?
(Valentine 1991)
                                                                 • Provision of local and regional benefits
But this omits cultural appreciation and conservation elements.  Does your operation use locally-based companies and
Ceballos-Lascurain includes it in yet another definition:        facilities, employ local guides with specialised knowledge
“Environmentally responsible travel and visitation, to enjoy     and purchase provisions and services in the area?
and appreciate nature and accompanying cultural features,
that promotes conservation, has low visitor impact and
provides for beneficially active socioeconomic involvement
of local populations.” (Ceballos-Lascurain, 1992)

     Contributed by Margot Warnett, DEH Townsville

If you’d like more information on ecotourism in Australia, a copy of the National Ecotourism Strategy can be obtained
from the Federal Department of Tourism Tel: (06) 27 97111.
Weeds in the Wet Tropics World              Plant Invasions — the incidence of          Noxious Weeds of Australia
Heritage Area of north Queensland           environmental weeds in Australia            W.T.Parsons and E.G.Cuthbertson
Stella Humphries and Peter Stanton          Kowari 2 — Australian National Parks        Inkata Press (1992)
Wet Tropics Management Agency               and Wildlife Service (1991)
(1992)                                                                                  A massive tome dealing with harmful
                                            Less specific to the wet tropics, but a     weeds all over Australia. However,
This report identifies and deals            useful look at weeds with papers from the   recently discovered environmental
particularly with the eight species which   ninth Australian Weeds Conference.          weeds of the wet tropics such as
most threaten the wet tropics                                                           harungana and sanchezia are not
environment (see facts and stats).          Australian Water Weeds                      included.
                                            Australian Water Resources Council
The biology, distribution, impact and                                                   Pestfact
control of five weeds of the Wet Tropics    An informative collection of one booklet    Department of Lands
World Heritage Area                         and nine leaflets.                          These excellent pestfact sheets on a
Dr J.T.Swarbrick                                                                        number of weeds and feral animals are
Wet Tropics Management Agency               Waterplants in Australia                    available from offices of the Department
(1993)                                      G.R.Sainty and S.W.L.Jacobs                 of Lands.
                                            Australian Water Resources Council
The first of three reports, this looks at                                               Poster
pond apple, harungana, turbina,             An excellent field guide to natives and     Bushland Weeds is an excellent colour
sanchezia and coffee. Two later reports     exotics with colour photos and key.         poster produced by Brisbane City
deal with chemical control.                                                             Council. Call (07) 225 0411 for a copy.

 This newsletter was produced by the Queensland Department of Environment and Heritage (now The Environmental
 Protection Agency) with funding from the Wet Tropics Management Authority.

                                            For further information contact...
  Opinions expressed in Tropical
  Topics are not necessarily those of       Stella Martin
  the Department of Environment and                                                     Wet Tropics Management Agency
                                            The Editor                                  (For general infomation on the Wet
  Heritage (EPA).                           Tropical Topics                             Tropics World Heritage Area only.)
                                            Environmental Protection Agency             PO Box 2050
  While all efforts have been made to       PO Box 2066                                 CAIRNS QLD 4870
  verify facts, the Department of           CAIRNS QLD 4870                             Ph: (07) 4052 0555
  Environment and Heritage (EPA)
                                                                                        Fax: (07) 4031 1364
  takes no responsibility for the
                                            Ph: (07) 4046 6674                          Website:
  accuracy of information supplied in
                                            Fax: (07) 4046 6751
  Tropical Topics.

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