Environmental Engineering Reference
In-Depth Information
6
Sean T. Murphy and Harry C. Evans
Concerns about the impact of invasive species on biodiversity have raised the pro-
fi le of invasive species to that of an agent of major global threat and change. Thus
the discussion on how to prevent and manage invasive species is no longer just
an agricultural one. Biological control through the use of host-specifi c natural
enemies, which has essentially been developed and moulded by the agricultural
sector for over 100 years, has been seen by many in recent times as a potentially
effective and environmentally benign tool, suitable for use against invasive species
in natural ecosystems. The biological control strategy includes several techniques.
The most common technique that has been used against invasive species is the
'introduction' or 'classical' approach, which involves the utilization of coevolved
host-specifi c natural enemies from the native range of the target species.
Globally, most work on classical biological control has been for the control of
arthropod and plant invaders but eff orts have been made on invasive mammals,
invasive marine organisms, and other species. h ere have been many successes in
biological control and many 'moderate' successes (where only partial control was
achieved), but there have also been many more failures. h e technology has also
been clouded by occasional situations where general natural enemies have been
introduced for control of a target, but have also ended up feeding on non-target
species. Nonetheless, the practice of classical biological control utilizing host-
specifi c natural enemies has continued and over the years the agricultural sector
has, with inputs from the ecological science community, evolved various protocols
that try and address safety and minimize ecological risks. Modern biological con-
trol is now underpinned with these and a weight of other scientifi c and technical
guidance to maximize success and minimize risk.
Here we review the relevant major points about the science, practice, and eco-
nomics of classical biological control to illustrate the potential of the tool for use
in natural ecosystems; the focus will mainly be on the biological control that has
been developed for plant and arthropod invaders as most eff ort has been against
these species. We then discuss some of the methods that have been developed,
or are under development, to illustrate how practitioners are trying to promote
'best practice', particularly in relation to safety. We also look at more general
