Environmental Engineering Reference
In-Depth Information
are implemented and used to refi ne the approaches taken. It is also important to
build knowledge of how an invasive species responds to diff erent control measures
and the conditions under which they are applied. More eff ective and e
cient
measures can be developed through both observations and systematic experimen-
tation where the species is being managed under fi eld conditions.
Successful containment or control programmes require that their targets are
detected. The precision required of detection methods will vary with the cir-
cumstances, including the specifi c objectives of the programme and the control
methods. Early in a containment attempt, reliable but general information on dis-
tribution and abundance may be adequate to develop and begin implementing a
management programme. As knowledge of a species' distribution and abundance
improves, the programme can be modifi ed. Detection may use casual sightings but
a systematic sampling procedure will yield a more reliable picture of the distribu-
tion and abundance of an invasive species on which to base a more refi ned contain-
ment or control programme. There will, of course, be a trade-off between effort
spent on detection and effort spent on other aspects of containment and control.
Especially in the case of newly discovered, high-impact, rapidly invasive species,
an early response to an initial detection can be critical, and such a response should
not be delayed by efforts to delineate its distribution in detail.
As resources available for managing invasive species will always be insuffi cient to
address all problems, the species to be targeted and the locations where effort will
be expended must be prioritized. Containment and control are usually devised as
strategies to be applied against particular species though management of multiple
invasive species may be a general objective in particular locations, for example, in
areas of high conservation value (see section 5.3.5). Examples of location-focused
priorities include cases of predator control to conserve remnant populations of
threatened bird or mammal species (e.g. Risbey
et al
.
2000; Burrows
et al
.
2003;
Innes
et al
.
2004) However, even in situations where more than one species is
being targeted, each invasive species will often require specifi c treatment at the
operational level. Once a decision has been made that an invasive species is to
be targeted for containment or control, a strategy is required that is appropriate
to the objective (containment versus control), the species, and the environment
(ecological, social and economic) that it is invading.
h e containment of an invasive species should generally be directed at the per-
iphery of its distribution. h is may or may not be the case where the objective is
control. Decisions about where control eff ort should be directed may be made
with reference to local, catchment, regional, or continental scales, and there may
be some confl ict between decisions at these various scales. h e interests of a man-
ager of an individual unit of land will be focused mainly on actions directly relevant
