The WWF report compiled by TRAFFIC on Chihuahuan Desert plants, called “Prickly Trade” bears this out, at least in part. Mexico harbors the greatest diversity of endemic, endangered, and newly discovered cactus species, with an abundance of natural and human capital to develop a viable industry of cactus nurseries. The report pushes that growers should be offered incentives to propagate species for export markets because of commercial demand for cacti endemic (native) to Mexico. In particular, propagation efforts should focus on rare, recently discovered, or recently described species for which demand is high but plants are lacking in the marketplace. Cactus propagation efforts under way at various universities throughout Mexico may have the capacity and technology to share with local growers and communities interested in growing cacti for domestic or export markets.
However, those species are highly sought after by foreign collectors and continue to appear in the international marketplace in spite of Mexico’s laws prohibiting illegal collection. The number of specimens entering trade illegally is believed to be small but may be significant enough to destabilize wild populations of some species. This practice undermines the competitive advantage of Mexican growers to propagate and sell endemic cacti in the marketplace.
In the United States, the cactus trade involves fewer cactus species but considerably more plant material. The primary markets are southwestern U.S. cities with an arid climate where consumers are trying to conserve water by resorting to desert landscaping with plants like cacti instead of water-intensive gardens. Contrary to their best intentions, gardeners and homeowners are addressing one conservation issue at the expense of another. Whatever actions are taken to advance Cactaceae conservation in the Chihuahuan Desert of the United States, it is clear that a multifaceted strategy is needed to protect cactus species and populations from unsustainable harvest levels and methods that may undermine their ecological role, evolutionary potential, and contribution to local economies.
As evident, 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 relates the following story regarding Mammillaria wrightii:
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.) Crypto-gamic 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 (Knowlton’s Cactus) 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.