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We are researching the impacts of Paspalum vaginatum as a weed
of the estuaries in the upper latitudes of New Zealand. We read
your web page Paspalum
vaginatum: An alternative to Bermudagrass with interest, as it gives
an insight into the value of this grass for golf course turfs. Especially
where the use of chemical herbicide can be minimised with the application
of saline water to favour P. vaginatum.
However, the promotion of this grass as an environmentally-friendly grass
to an international audience raises concerns for the integrity of indigenous
saline communities around the world.
Already widespread in many countries, P. vaginatum is recognised
for its competitive nature with indigenous plant species in saline and
saltpan areas, particularly where there is not an equivalent indigenous
grass species already inhabiting that niche. It has the ability to outcompete,
and exclude indigenous plants, and occupy spaces for which there is no
indigenous vegetation (see photo). This has far-reaching effects, for
which in New Zealand are similar to that of the introduced Spartina
spp. and include the following:
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Paspalum vaginatum invading and plugging
up the coastal estuary of the Tairua River, on the coast of the rugged,
bush-clad Coromandel Peninsula of the North Island, New Zealand. |
- Out-competes native estuarine plant species changing the composition
and structure of the natural vegetation associations, and endangers
threatened species populations
- Has a high stem and root density which excludes burrowing fauna, such
as cockles (Austrovenus stuchburyi)
- Reduces access to the food of birds and fish
- Alters fish spawning grounds (eg., flounder), and bird roosting sites
- Increases cover for the predators of estuarine-feeding birds, changing
the behaviour of these birds
- Alters the estuarine hydrology patterns from the accumulation of sediments
(and the associated ramifications of this, eg. increased flooding upstream
which leads to further deposition of fine silts in the estuary which
may be to the detriment of filter-feeding shellfish and the growth of
indigenous estuarine vegetation)
- Changes the nutrient regime of the estuary with the contribution of
organic detritus
These combined ecological effects lead to the cultural, recreational,
and aesthetic values that people hold for these estuaries
being compromised. There is also an economic value in estuaries in their
role as sea-fish nursery grounds which is also
compromised.
Therefore, the promotion of P. vaginatum in areas other than where
it naturally occurs (ie., Central America) will lead to values
similar to those outlined above being compromised. I stongly appeal to
you to mention these ecological effects of P. vaginatum on
your web page so that turf managers can make a more informed decision
about introducing this grass to new environments.
I hope this is of interest to you. I would value your reply.
Kind regards,
Hamish Kendal,
natural.solutions@wave.co.nz
Natural Solutions Marine and Terrestrial
Ecologists,
www.ecologist.co.nz
RD2
COROMANDEL
Phone: (07) 866 0770
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