Ecological applications of niche theory - Ecological Applications: Toward a Sustainable World - page 46

not be optimal habitat in the absence of trout. However, the fundamental niche of
G. anomalus , in contrast to that of trout, encompasses the higher temperatures and
lower oxygen concentrations associated with reduced stream fl ow.

2.3 Conservation of
endangered species
- each to its own
niche

Conservation of species at risk may involve establishing protected areas (Section
2.3.1) or translocating individuals to new locations (Section 2.3.2). Both approaches
involve identifying geographical areas that provide for the niche requirements of
the species concerned; they therefore have much in common with the invader stories
in the previous section.
Before proceeding further, however, I should highlight an uncomfortable fact of
life faced by conservation managers - not everyone thinks like them. Opposing
views are frequently fi rmly held because conservation often involves setting aside
areas where exploitation is restricted or prohibited. The hunters, fi shers, loggers and
farmers can then reasonably demand indisputable evidence for the need to curtail
their activities, something that can be diffi cult to prove to the satisfaction of all.
Section 2.3.1 presents a case study where this reality is confronted by an expert
panel approach to defi ning a conservation reserve network that, as a simultaneous
aim, seeks to minimize the exclusion of loggers from forest they value.

2.3.1 Monarch's
winter palace under
siege

Overwintering habitat in Mexico is absolutely critical for the monarch butterfl y
( Danaus plexippus ), which breeds in southern Canada and the eastern USA. The
butterfl ies from a huge 2.6 million km 2 area east of the Rocky Mountains form dense
winter colonies in forests of oyamel trees ( Abies religiosa ) on just 11 mountains in
central Mexico. A group of experts was assembled to defi ne objectives, assess and
analyze the available data, and produce alternative feasible solutions to the problem
of maximizing the protection of overwintering habitat while minimizing the use of
land of value for logging (Bojorquez-Tapia et al., 2003).
The critical dimensions of the butterfl y's overwintering niche include relatively
warm and humid conditions (permitting survival and conservation of energy for
their return north) and availability of streams (resource) from which the butterfl ies
drink on clear, hot days. The majority of known colony sites are in forest on mod-
erately steep slopes, at high elevation (

2890 m), facing towards the south or south-
west, and within 400 m of streams (Figure 2.6a-d). According to the degree to which
locations in central Mexico matched the optimal habitat features, and taking into
account the desire to minimize inclusion of prime logging habitat, a modeling
approach similar to that outlined in Section 2.2.1 was then used to delineate three
scenarios. These differed according to the area the government might be prepared
to set aside for monarch butterfl y conservation (4500 ha, 16,000 ha, or no constraint;
Figure 2.7a-c). The experts preferred the no-constraint scenario, which called for
21,727 ha of reserves (Figure 2.7c), and despite the fact that their recommendation
was the most expensive it was accepted by the authorities.
A similar approach has been used for the rare rufous bristlebird ( Dasyornis broad-
benti ), threatened by habitat loss in southwestern Australia (Gibson et al., 2004).
Bristlebird locations were recorded using a global positioning system on early
morning visits in the breeding season. Then the relationships between bird presence
and absence and a variety of niche dimensions were determined. Negative associa-
tions between bristlebird presence and increasing elevation, distance-to-creek, dis-
tance-to-coast and solar radiation indicated preferences for areas of relatively low

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