Exotic weeds invade ecosystems and cause reductions in plant and
animal biodiversity, alteration of food chains, reduction of
species abundances and alteration of assemblage structure of
existing flora and faunal communities. These negative effects can
severely reduce the ecosystem services provided by a previously
valuable area, and important functions of natural ecosystems (such
as maintenance of water quality, pollinator services, and
maintenance of local biodiversity) can be compromised.
Among the invasive weeds most likely to have negative effects on
ecosystems are grasses, because they compete successfully with
native species in a wide range of ecosystem types, and can alter
critical ecosystem processes, such as fire-proneness and nutrient
cycling, of the invaded ecosystem. Introduced pasture grasses
comprise a third of the worst environmental weeds in Australia.
Para grass has become established in waterways where it causes
economic and ecological problems, such as flow reduction and
increases in sedimentation, as well as reduction in the
attractiveness of wetlands to water birds, and reduction in fish
diversity. Evidence from Australian wetlands invaded by para grass
suggests that it turns diverse wetland plant communities into a
monoculture, drastically reducing both floral and faunal diversity.
These changes are unlikely to be reversed simply by removing
vegetation. In this case, vegetation removal on its own may simply
degrade habitat further, rather than enhance it.
In this study, we examined the influence of para grass control,
on amphibians and reptiles in a northern Australian wetland –
the Townsville Town Common Conservation Park. We also examined
uninvaded wetland areas adjacent to the para-grass-affected areas,
to quantify the reptile and amphibian assemblages present in
uninvaded wetlands. Finally, we observed the habitat use of an
abundant predator (keelback snakes) to predict the responses of
native fauna to the removal of the weed, and to understand some of
the mechanisms responsible for these responses.
