Is Cultivation Conservation?
A conversation about Digitostigma ("Astrophytum") caput-medusa brought up ideas about cultivation as a form
of conservation. On the plus side, it is better to have a species in cultivation than to not have it exist at all.
Also, it does seem that nursery grown plant material is finally alleviating the pressures on cactus populations
in the wild, at least in some cases. The WWF report compiled by TRAFFIC on Chihuahuan Desert plants, called
"Prickly Trade" bears this out, at least in part.
However, there are several ways in which cultivation is a poor substitute for respectful stewardship of wild plants
and can even exacerbate the depletion of vital wild populations. Del Weniger in Cacti of the Southwest (p. 151),
relates the following story regarding Mammillaria wrightii:
Hallenbeck, after a most concerted hunt in 1934, involving many people and covering a huge territory, finally found a
stand of nearly fifty specimens of what may have been this cactus near Anton Chico, New Mexico. He promptly took
them all, explaining his action by saying that he believed those were all that existed and he felt bound to take
every one to preserve the species. I think no better criticism of this sort of wholesale gathering of rare plants
need be made than to note that not one of his collected plants or any of their offspring can be traced today, but
that there have been a few specimens collected in the wild in the years since then, proving that nature is the
best preserver of her children after all.
Whether reasons are noble (science, preservation, rescue and salvage) or self-serving (quick profit, acquisition
of specimen sizes as quickly as possible, "collector’s fetish") the end result is the same: ecosystem
disruption. There is much that remains mysterious about desert ecosystems, but we know with certainty that the
balances in place are generally extremely fragile. For example, total seed production versus seeds that themselves
become well enough established to produce more seed. This crucial cycle of population viability clearly shows
that the ratio of produced seed versus resulting mature, reproducing plants is gigantic, especially in the very
slow growing, highly restricted endemics. It is not uncommon in Saguaros, for example, that for every 100,000
seeds produced, only one reproducing plant makes it.
Deserts are usually highly "tuned". Removal of even dead plant material has effects (nesting, insects,
soil strata, etc.) Cryptogamic soils that take decades to form can be degraded in a single brief instant of
heavy-footed tromping.
Genetic interrelationships in these interdependent desert environments are poorly understood. But it’s clear that
cultivation greatly reduces the genetic diversity of particular species. Very few growers maintain strict protocols
of record-keeping and pollination techniques and those who do (Mesa Garden,
for example) are more concerned with preserving a particular genetic lineage than trying to replicate
complex ecosystem genetics.
When Pediocactus knowltonii was first discovered around 1960, biologists estimated a total population of
100,000 plants. By 1970 the number had fallen to 1,000; almost entirely due to cactus diggers. In the 30 years since
then the in situ population estimate has climbed to about 9,000. One wonders: of the 99,000 plants removed
from the wild, how many are still alive and producing seed? As NM Game and Fish points out with the population at
9,000, a single very dedicated collector could still wipe the species out in the wild. This is not a unique situation
and in fact for many plants the situation is even more dire.
As growers we can inspire people to take better care of the wild environments our plants come from. But our plants are
not substitutes for their wild counterparts. Think of the many thousands of miles one would have to travel to try to
put our plants back where their seed or parents came from! And cultivated plants have been shown time and again to be
too soft and not well-adapted, even after a generation or two, to wild conditions. Re-introduction of species extinct
in the wild has proven to be far more difficult than we imagined.
Author: Peter Breslin, Santa Fe, New Mexico
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