Biology Reference
In-Depth Information
Burnett et al. (2006) conclude that too little effort, i.e., funding, is being spent.
Yet the cost of increasing funding to an “optimal program”, i.e., a permanent
severe reduction in Miconia, although not eradication, would require only a
onetime sixfold increase over current expenditures. Such an optimal program
Kaiser (2006) would reap enormous gains in obviating plant removal costs in the
future, by several orders of magnitude, plus preventing further environmental
damage by Miconia.
The optimal control envisioned by Kaiser (2006) and Burnett et al. (2006)
takes no account, however, of the spatial distribution of Miconia, so that the
cost/benefit of removing a tree is the same as any other tree. This simplification
of the contribution a single tree may make in establishing a new focus - far
removed from the main foci of the invasion - does not account for the ability or
likelihood of the descendants of an isolated plant to become established in here-
tofore unoccupied territory. One product of this simplification is that where an
invader is widespread but in low numbers - exactly the circumstances under
which new foci arise (Moody and Mack 1988) - the cost of detecting and
destroying these individuals is not cost effective. The optimal goal is then inter-
preted as maintaining the invader's populations in low numbers but not seeking
total eradication (Burnett et al. 2006; Kaiser 2006). Although permanently hold-
ing an invader at low numbers may be functionally equivalent to its eradication
(e.g. the current status of
B. vulgaris
in the northern US), the risks are not identi-
cal. First, maintaining these low levels requires a consistent control effort. And
policy-makers anywhere are inclined to withdraw funds once the perceived haz-
ard has been reduced to a low level, e.g.
Hydrilla verticillata
in Florida (Mack
and Foster 2004). Total eradication makes the consequences of such withdrawal
of funds less hazardous. Second, continuing to destroy all known foci of an inva-
sion and any new populations as they are detected may not achieve eradication,
but it may come very close.
3.7 “Weeds Won't Wait” to be Eradicated: The Aborted
Eradication of
Crupina vulgaris
As the spread of
Miconia
in French Polynesia and Hawai'i illustrates, delay in
initiating an eradication program yields ominous consequences. As Westbrooks
has long warned “Weeds won't wait!” (R.G. Westbrooks, pers. comm.), their
invasions inexorably unfold, unless we apply determined intervention. Westbrooks'
epigram is especially relevant to the timeliness of an eradication campaign; yet
irreparable delay has occurred far too often, even if the underlying reasons differ.
The invasion of
Crupina vulgaris
(Common crupina) in the western US has
become a case study in which well intended but prolonged assessment of an
unfolding invasion, coupled with last minute and equivocal environmental con-
cern, eventually blocked an ambitious eradication project at probably the last
feasible opportunity for success. Simberloff (2003b) has recently outlined the
