Biology Reference
In-Depth Information
a
b
0.14
0.6
0.11
0.3
0.08
0
0.05
RN
RA1
RA2
RA3
RN
RA1
RA2
RA3
Risk aversion
Risk aversion
0%
5%
3%
15%
0%
5%
3%
15%
Mean annual collective prevention
Mean annual collective control
Fig. 17.3
The impact of risk aversion over four monetary discount rates. For both figures the
horizontal axes are increasing levels of risk aversion by managers. Units of collective prevention
in the left figure are the average number of prevention events that take place on an annual basis,
whereas units of collective control in the right figure are the average number of control events
(e.g., molluscicide applications) on an annual basis (from Finnoff et al. 2005)
2005). Control is intuitively more attractive to managers because it negatively
impacts existing invaders from the ecosystem, whereas prevention is perceived to
only eliminate the chance of invasion. Finnoff et al. also indicate that prevention
and control are substitutes for each other, and that delays in the implementation of
control increase the probability of invasions occurring.
17.3.1 Tools
Many tools used to control, contain, or eradicate invasive plants are available to land
managers of natural resource production systems. In general, the methods used to reduce
the abundance or vigor of unwanted vegetation vary only slightly according to habitat,
i.e., whether they are used in agriculture, natural resource production systems such as
rangeland or forest plantations, or natural ecosystems. Excellent discussions of the meth-
ods and tools used for weed control are provided by Aldrich (1984), Ross and Lembi
(1985, 1999), Radosevich et al. (1997), Muyt (2001), and Coombs et al. (2004).
17.3.2 Establishing Priorities
Hobbs and Humphries (1995) suggest an approach to set management priorities
based on land value and the degree of site disturbance (risk of invasion) for areas
