Strategic Planning for Species Conservation: A Handbook - IUCN

Strategic Planning for Species Conservation
is often the only way to evaluate management approaches intended to prevent rare but
catastrophic events (see example in Box 8.2).
Modelling can also explore the range of possible or likely outcomes that can arise from one
or more uncertain and often interacting processes (see example in Box 8.3).
Box 8.2 An example of the use of PVA modeling to evaluate alternative
management approaches: disease risks to island foxes.
Epidemic disease was known to be a threat to the Critically Endangered island fox since one
subspecies had experienced a massive population crash associated with an outbreak of infection
with canine distemper virus (Timm et al. 2000). In developing a recovery plan for island foxes
under the US Endangered Species Act, two potential approaches to the management of epidemic
disease were considered (USFWS in prep): (a) intensive monitoring to detect outbreaks, with
vaccination and quarantine; or (b) pre-emptive vaccination of a small proportion of the population
as had been proposed for other endangered canids (Haydon, Laurenson and Sillero-Zubiri 2002;
Vial et al. 2006). However, experimentation was impossible since disease epidemics occur very
rarely, and the existence of only one wild population of each island subspecies would effectively
preclude replicated trials. The two approaches were therefore simulated within wellparameterised
PVA models (Doak and Bakker unpubl. data); this indicated that, given the small
size of the islands, it would be essentially impossible to detect and respond to an epidemic before
infection had spread through the population, whereas pre-emptive vaccination could be expected
to substantially reduce the risk of disease-associated extinction. The latter approach was
therefore adopted by land managers responsible for island fox conservation, after captive trials
had confirmed that vaccination conferred no ill effects (Swarts 2006; Timm et al. 2002).
Another area of Action in which mathematical modelling – particularly statistical modelling –
is extremely useful is in the design of surveys and monitoring programmes. Estimates of
population sizes, and trends in population size, are often considered critical for evaluating
the outcomes of entire conservation programmes, as well as for measuring the
effectiveness of particular Actions. However, the most appropriate methods vary greatly
according to circumstances. General methodologies are available (see, for example,
Buckland et al. 2001; Legg and Nagy 2006; MacKenzie et al. 2005; Shrader-Frechette and
McCoy 1993; Williams, Nichols and Conroy 2002), but further modelling may be valuable for
tailoring methods for particular species or circumstances (see, for instance, Barnes 2002;
Karanth and Nichols 2002; Plumptre 2000; Sims et al. 2006; Taylor and Gerrodette 1993).
8.4 Monitoring the effectiveness of Actions: indicators of
success
The implementation of any management approach should be combined with monitoring of
its effectiveness, as this allows refinement of successful approaches and abandonment of
unsuccessful ones. Such monitoring is especially important for novel approaches which
have not been fully evaluated for a particular species or set of circumstances.
In many SCSs, monitoring of wildlife populations will be recommended as its own discrete
Action, or set of Actions; such monitoring will be needed to determine whether progress has
been made towards achieving the agreed Goals.
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