Weeds
to Watch
Alien
invasive plants (weeds) are a major environmental threat along the
coast. For example, half of the alien invasive plants (82 species
of the 166 recorded species) over the 12 889 km of coastline in Western
Australia are found within metropolitan coastal dunes.
Weeds
arrive and establish in native ecosystems for a variety of reasons.
Some escape from gardens or agriculture, others are deliberate introductions
for restoration (particularly the case for some coastal species),
while others are global vagrants, hitching a ride on cargo, in soil
or as contaminants in seed for agriculture.
A
key reason why weeds are so prevalent in coastal ecosystems is linked
to how weeds require disturbance for seedling recruitment and plant
establishment. The tendency of coastal dune communities for both natural
and artificial disturbance provides a foothold for weed species to
establish in the same way increased fire frequency in bushland habitats,
such as Bold Park in Perth, has resulted in the opening of the canopy
leading to the spread of a number of weed species. Coastal weeds also
capitalise on high winds and sand movements that are prevalent along
the Western Australian coast to distribute seeds across a wide area.
Listed
below are some of the weeds to watch out for in the Town of Cambridge
dunes. If you spot any of these weeds or would like to help eradicate
them from the dunes please contact
us.
Leptospermum
laevigatum (Victorian Tea-tree)
The Victorian tea-tree is most significant woody weed threat on the
WA coast. This once-popular hedging plant and windbreak species planted
extensively from 1915 onwards has now invaded coastal swales and nearcoastal
bushland areas forming dense often impenetrable thickets that can
only be effectively controlled by direct removal (cutting of the stem
at or near ground level). Along parts of the south coast, Victorian
tea-tree now threatens many native plant communities, particularly
those in low-lying or seasonally wet sites. The plant is unable to
resprout from stems cut below a green leaf, providing a ready means
for controlling the plant.
Retama
raetam (White Broom)
A native to north Africa and parts of the Mediterranean and Middle
East, the species produces abundant, long-lived seeds and vigorously
resprouts from the stem base following cutting. Adapted to arid areas,
this weed thrives in dune swales and is found from Bunbury to Two
Rocks. The City Beach dunes represent the largest stand of the species
with some thousands of plants covering many hectares with seedlings
now spreading north along West Coast Highway. The plant is considered
one of the most significant weeds of seasonally arid regions around
the world with potential to become a major global environmental weed.
The arrival and spread of white broom highlights the vulnerability
of the dunes to invasion by alien plants. As with any natural coastal
or bushland habitats, a non-local species poses the same threat of
becoming a weed as foreign species. The most prudent control policy
is to remove all non-local species from restoration or conservation
areas before the species develops an invasive habit and to ensure
that only local native species are used in restoration programs.
Cambridge Coastcare (Inc)
Copyright 2007. Disclaimer.
