Conference 2003
Greening the City:
Bringing Biodiversity Back
into the Urban Environment
Abstract:
Do
Weeds Benefit Native Wildlife in Urban Areas?
Margaret Stanley (Landcare Research, Auckland)
Conflicts can arise where
weed control targets an alien plant that provides a resource for
one or more native species, particularly where the weed is beneficial
to a charismatic vertebrate.
The use of weeds as sources
of food and habitat by native wildlife is becoming common in many
countries, due to clearance of native vegetation and/or its replacement
by invasive weeds.
There have been public
concerns in New Zealand, particularly in urban areas, that weed
control could leave native fauna without essential resources. However,
in most cases, alien plants are not essential resources, and use
of weeds by native species is the result of availability or preference
rather than dependence.
Research has also demonstrated
the inferior quality of resources provided by invasive weeds in
comparison to native plants. Weed exploitation by native species
may have a number of 'ripple' effects on ecosystems:
- Increase the spread
of weeds in natural areas through fruit consumption and seed dispersal;
- Native species may
no longer fulfil their function as pollinators and dispersers
of native plant species;
- Extra resources could
result in unnaturally high population numbers which could in turn
result in detrimental economic and ecological consequences.
If, however, there is
a risk that weed control could have a negative impact on a threatened
or ecologically important species using the weed, management strategies
could be put in place to ensure that alternative resources are available
when the weed is controlled. Emphasis must be placed on retaining
overall biodiversity in urban areas, rather than focusing on the
conservation of single vertebrate species.
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