Strategic Planning for Species Conservation: A Handbook - IUCN

Strategic Planning for Species Conservation
(c) compare the level of each possible agent of decline with that in areas, or at times,
where the species is/was not in decline; for example determine whether harvest levels
have increased over time, or whether local population extinctions have occurred in
areas where habitat destruction has occurred. Use these comparisons to identify one
or more likely agents of decline;
(d) test the hypothesis that the agent(s) of decline have been correctly identified by
experiment: in most cases the experimental “treatment” can be a management
intervention designed to combat the threat, and so confirmation of the cause of
decline can be combined with active efforts to conserve the species.
Although Caughley and Gunn’s (1996) method may appear labour-intensive, this level of
scientific rigor is entirely appropriate for such a critical component of SCS planning.
Moreover, their approach need not be arduous if (as is often the case) there is clear
evidence for decline being associated with some straightforward factor such as overharvest
or habitat destruction (e.g., see Box 5.3). If the causes of a species’ decline are less
straightforward – for example if they involve interactions between more than one factor –
then the extra effort made to identify the causes will be worthwhile, since management
interventions directed only at the most obvious factor may fail to halt or reverse declines.
Often threats may be so confounded that the identification of the key factor in population
decline is very difficult. For example, in highly fragmented environments, a species may be
more subject to predation by other natural predators, may be more prone to be hunted by
humans (because humans have easier access to small patches of their habitat), may be
more apt to raid crops and hence be killed by humans, and may be more likely to suffer
effects of malnutrition due to reduced food availability or compressed animal density. Each
of these threats might be dealt with in a somewhat different way (e.g., predator reduction,
poaching patrols, crop field deterrents, and artificial feeding, respectively), especially if what
appears to be the ultimate threat (habitat fragmentation) is not readily rectified. Rigorous
studies to disentangle these confounded effects are unlikely to exist for most species. In
the absence of hard data, a listing and discussion of all the possibly important threats may
spur future studies and provide more avenues for potentially effective conservation than a
best guess about a single dominant threat. Population responses to conservation efforts
will in the end give the best indication of what the threats were. For example, if improving
anti-poaching measures is associated with an increase in population size, then over-hunting
can be assumed to have been a key threat.
The first two steps of Caughley and Gunn’s (1996) “recipe” – studying the species’ natural
history and identifying possible causes of decline – are likely to have been conducted prior
to the development of a SCS, at least for some species in each taxon. Key aspects of the
species’ natural history will have been summarised earlier in the Status Review. The
“threats” section should thus list evidence for and against particular factors representing
threats to species persistence, based on the correlational methods outlined in Caughley and
Gunn’s (1996) step (c), or, where available, on experimental evidence from their step (d).
Box 5.3 provides some examples of threat analyses based on these sorts of evidence; note
that the analysis process is not always arduous. The examples are chosen to show how
threat analyses can sometimes be conducted for groups of species as well as for single
species.
When a list of multiple threats is generated during the threat analysis process, it may be
helpful to categorise these into most serious, less serious and so on, so as to ensure that
resources and efforts are focused on those Objectives and Actions that will have the
greatest effect in saving the species.
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