Environmental Engineering Reference
In-Depth Information
h us, eradication of pest and weed populations is an attractive option for pest
managers because successful removal of all individuals in the target population
may (a) forestall any adverse impacts before these manifest themselves (e.g. the
prompt removal of wallabies from Great Barrier Island; Eadie et al . quoted in
Clout and Russell (2006)), and (b) reverse any impacts and restore the system to its
previous state or at least set the aff ected ecosystem along more acceptable trajector-
ies (Fukami et al . 2006). Eradication also does not require the complex knowledge
and ongoing commitment to e ciently and eff ectively manage pests under the
alternative of a sustained control strategy (Choquenot and Parkes 2001).
4.3 Feasibility
However desirable it might be, attempts at eradication can be counterproductive
if they are not feasible. The costs of promoting eradication when it is not possible
obviously include failure and, at worst, abandonment of the problem, when a
properly planned, sustained control campaign might have addressed the prob-
lem. For example, there was a hiatus of a decade in effective management of rab-
bits in New Zealand between the abandonment of the 'last rabbit' policy in the
early 1980s and the implementation of sustained control in priority areas in the
early 1990s (Gibb and Williams 1994). The costs of unachievable eradications
also include foregone opportunities to act elsewhere and a return to scepticism,
especially among funding agencies. This leads to risk aversion exactly when we
need some considered risk-taking if we are to aim higher. Thus, as part of good
planning, most eradication proposals start with a feasibility study. This is aimed
at convincing funding agencies that (a) eradication is needed either to eliminate
current impacts or as a precaution; (b) it is possible if obligate conditions can be
met and any constraints are either managed or acceptable; and (c) the programme
is adequately funded.
h ere have been several attempts to set criteria to assess whether or not eradica-
tion is feasible. h e suggested criteria mix essential rules and desirable attributes,
which are often overlapping, and some have suff ered from defi nition drift. h ey
have also refl ected their authors' backgrounds. For example, Parkes (1990a) focused
on obligate biological criteria for vertebrates on islands; Panetta and Lawes (2005)
and Cacho et al . (2006) stressed detectability and delimitation of infestation for
weeds on mainlands; Bomford and O'Brien (1995) included economic and social
criteria; Myers et al . (2000) and Baker (2006) included organizational commit-
ment as criteria; and Cromarty et al . (2002) stressed the planning process. h ese
criteria may be summarised in a more parsimonious set of three essential rules that
cover both island and mainland eradications:
The average annual long-term rate of removal in source populations must be
greater than the annual intrinsic rate of increase. This rule covers the older 'all
at risk and rates of removal' criteria, and is applicable to situations where we
have source-sink populations or where Allee effects have been argued to negate
 
 
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