220.127.116.11. Captive Breeding and Translocations
Another way in which humans have dealt with endangered wildlife populations
has been through captive breeding and translocations. These techniques have
been put forward in the past as methods to deal with future population pressures
caused by climate change (Peters, 1992). However, although captive breeding
and translocation are effective tools for conservation of some species, they
may be appropriate for only a handful of species (see Box 5-8).
Box 5-8. Limitations of Captive Breeding and Translocation
to Conserve Biological Diversity Threatened by Climate Change
In some cases, threatened populations of sensitive species could be augmented
or reestablished through captive breeding for reintroduction, especially
if the degree of climate change proves to be small or moderate. In combination
with habitat restoration, such efforts may be successful in preventing
the extinction of small numbers of key selected taxa. Similarly, translocation
of wildlife between areas within their natural range also might mitigate
the effects of small to moderate climate change. This strategy has been
applied successfully to augment or restore depleted populations of various
species (Boyer and Brown, 1988).
Captive breeding for reintroduction and translocation are likely to be
less successful if climate change is more dramatic. Such change could
result in large-scale modifications of environmental conditions, including
loss or significant alteration of existing habitat over some or all of
a species' range (Myers et al., 2000). Captive breeding and translocation
therefore should not be perceived as panaceas for the loss of biological
diversity that might accompany dramatic climate change, especially given
the current state of the environment. Populations of many species already
are perilously small; further loss of habitat and stress associated with
severe climate change may push many taxa to extinction.
One limitation to captive breeding is the lack of space available to
hold wildlife for breeding purposes. Zoos and offsite breeding facilities
can be expected to accommodate no more than a small fraction of the number
of species that might be threatened. Recent studies have indicated that
no more than 16 snake species and 141 bird species could be accommodated
and sustained in accredited North American zoos and aquariums in long-term
management programs (Quinn and Quinn, 1993; Sheppard, 1995).
Captive breeding programs are expensive, and locating funding to support
large numbers of programs could be difficult (Hutchins et al., 1996).
For example, it costs US$22,000 to raise a single golden lion tamarin
in the United States and reintroduce it to its native Brazil (Kleiman
et al., 1991). Part of the cost associated with such programs includes
the extensive scientific studies that must be conducted for the program
to be successful. Reintroduction is technologically difficult and unlikely
to be successful in the absence of knowledge about the species' basic
biology and behavior (Hutchins et al., 1996). Rearing and release strategies
must be tested experimentally, and released animals must be monitored
to assess the efficacy of various methods (Beck et al., 1994). In the
case of black-footed ferrets (Mustela nigripes) and golden lion tamarins,
it took more than a decade to develop the knowledge base required for
If wildlife translocation involves moving species outside their natural
ranges, other problems may ensue. Exotic species can have devastating
effects on host ecosystems, including extinction of native fauna (McKnight,
1993). The unpredictable consequences of species introductions means that
translocation is severely limited in its ability to conserve species that
are threatened by climate change.
Finally, reintroduction and translocation programs cannot be successful
if there is no appropriate habitat left for captive-bred or translocated
animals to be released into (Hutchins et al., 1996). Not all of the habitat
components that are necessary for a species to survive can be translocated.
Entire suites of plant and invertebrate species may be critical elements
for a species to succeed in a new environment, but no techniques exist
for translocating intact biological communities. Although captive breeding
and translocation have potential value for well-studied animals, these
strategies appear to be impractical for the vast number of species threatened
by rapid climate change.
18.104.22.168. Replacing Lost Ecosystem Services
Humans may need to adapt not only in terms of wildlife conservation but also
to replace lost ecological services normally provided by wildlife. It may be
necessary to develop adaptations to losses of natural pest control, pollination,
and seed dispersal. Although replacing providers of these three services sometimes
may be possible, the alternatives may be costly (Buchmann and Nabhan, 1996).
Finding a replacement for other services, such as contributions to nutrient
cycling and ecosystem stability/biodiversity, are much harder to imagine. In
many cases, such as the values of wildlife associated with subsistence hunting
and cultural and religious ceremonies, any attempt at replacement may represent
a net loss.
In many agricultural/silvicultural systems, pesticides are used to prevent
losses to pests (insects, pathogens, some vertebrates). In the past 50 years,
pesticide use worldwide has increased more than 25-fold (Worldwatch Institute,
1999). The estimated cost of pesticide use in the United States in the mid-1990s
was US$11.9 billion (equivalent to 4.5% of total U.S. farm production expenditures),
and worldwide use was US$30.6 billion (Aspelin and Grube, 1999). Given that
these values are for systems that still had some natural pest control, changes
in wildlife distributions might necessitate changes in economic expenditures
However, pesticides often kill more than the target species, possibly eliminating
natural predators that keep pest populations low. For example, increased pesticide
use in Indonesia between 1980 and 1985 led to the destruction of the natural
enemies of the brown planthopper. Subsequent increases in planthopper numbers
caused reductions in rice yields estimated to cost US$1.5 billion (FAO figures
cited in Pimentel et al., 1992).
Adaptation to loss of natural pollinators may be possible in some cases. Farmers
sometimes lease bee colonies to pollinate their crops. Although this may be
an option for the ~15% of crops fertilized by domestic honeybees, it may not
be an option for crops typically fertilized by wild pollinators or for the 250,000
types of wild plants that are pollinated by 100,000 different invertebrate species
(Buchmann and Nabhan, 1996).