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> We'd all prefer to maintain sites in the wild untouched, however, we'd
> be very foolish if we didn't learn the lessons of history and have at
> least one, if not several, actually as many as is humanly possible,
> backup populations in captivity. A natural disaster, war, or famine,
> not to mention the countless other human activities such as poaching,
> construction, changing the natural flow of water, can all wipe out a
> species at any moment. Endlessly debating the genetic merits of
> captively produced plants is a deadly waste of time if it discourages
> continued propagation of a species on the brink.
The raison d'etre for the genetic diversity debate has been basically that
one side maintains that captive propagation (of plants or animals) is the
only sure-fire way to prevent extinction, and some from that side use this
attitude to rationalize or justify illegal activity. This attitude (and
unscrupulous individuals) has surfaced among reptile and fish enthusiasts,
aviculturists, and all manner of plant people. The other side (count me
in) maintains that in the first place the _only_ important thing is the
ecosystem, and if we don't preserve that then there is little point in
preserving individual species, except as pets/houseplants. They maintain
further that if large captive stocks of the most attractive/famous species
from a particular ecosystem exist, then selling the protection of that or
other similar ecosystems to the public and politicians can be a problem.
This is not to say that there shouldn't be captive stocks, just that their
importance in the conservation of ecosystems (the only important thing,
remember?) is minimal to nonexistent. One of the more powerful arguments
against the conservation value of such captive stocks is that the genetic
content and fitness of any but the parental stock of any species is a
mystery, and thus the further down the generational trail we go with such
stocks, the higher the probability that most or all individuals will be
maladapted to all but captive conditions. Unfortunately, the only way to
know whether this has happened is to attempt to reintroduce some
later-generation individuals to the wild, and by its nature this is an
experiment that can't work, even if the reintroduction is an apparent
success. The _only_ reasonable set of circumstances for reintroduction is
that the species in question was eliminated directly from that ecosystem,
whether by overcollecting, disease, overhunting, etc., the ecosystem is
otherwise undamaged (yeah, right) and very little time has passed since
that direct extermination was completed. If too much time has passed, the
ecosystem very likely will have changed, perhaps dramatically, in response
to the loss of that species, and may become utterly unsuited for that
species. If the organism was eliminated by habitat destruction,
reintroduction is pointless, even to so-called "rehabilitated" habitats.
> If just one individual, whether they worked for an institution or
> they were a private enthusiast, had simply bothered to breed
> the Passenger pigeon in captivity they'd still be alive today.
> So what if they'd be genetically less diverse than their wild
> ancestors were three centuries ago, it certainly beats the
> actual outcome of events! Even if the entire stock were the
> descendants of just a few pairs the world today would be a
> richer place.
In fact, the passenger pigeon was bred in captivity (particularly in
Europe) quite often throughout the 19th century (source: A.W. Schorger,
_The Passenger Pigeon: Its Natural History and Extinction_, 1955,
University of Wisconsin Press), but little interest was expressed because
the bird was so abundant--it was probably the most abundant vertebrate
ever (should we be concentrating our captive breeding efforts on Drosera
rotundifolia instead of Sarracenia oreophila?). Its extinction was caused
partially by market hunting, but especially by the destruction of the
midwestern beech forests, a habitat that is now conspicuous by its
absence. The beech forests contained the nesting sites of these birds,
and really successful wild reproduction may have depended behaviorally on
the presence of very large flocks concentrated in small areas of these
forests. There is no chance that these birds could be reintroduced
successfully to native habitat today, because there is no such habitat.
This may be heresy, but I feel that the presence in zoos of the only
remaining birds would be hardly more enriching than the presence in
museums of those same specimens as properly-executed study skins. The
important thing was the ecosystem, and it's gone. Museums are generally
much better and more substantive long-term repositories for defunct
ecosystems and their contents than are zoos.
I agree, it really is pointless to argue about the preservation of genetic
diversity in captive stocks. If we are naturalists as many of us claim to
be, the bulk of our conservation energies should be directed toward
preservation of as much open space and natural ecosystem as possible, and
to attempt to convince the public and the politicians of the urgent
necessity for population control. We can (and in my opinion, we should)
keep plants/animals too for the gratification and learning experience, but
only within ethical and legal constraints--we are kidding ourselves if we
think our hobby is more critical to conservation than the preservation of
ecosystems, no matter how much genetic diversity we attempt to preserve.
Sean Barry