The problem of commercial collection is different in the United States and Mexican parts of the desert, said Robbins. "Mexico is home to many more rare, endemic and endangered species than the United States. These face a greater threat from over-zealous collectors from Europe and Asia who have been known to remove dozens, even hundreds, of specimens at a time," he said.
Harvesting can severely deplete wild populations that are already hampered by restricted ranges, harsh environments and low levels of seed production.
Trade in the United States may involve fewer cacti species than in Mexico, but a much greater mass of vegetation is destined for the Southwestern states' bustling Xeriscaping market.
Xeriscaping is the practice of landscaping with native plants in dry environments to conserve scant water resources.
However, this practice could in fact be mitigating one environmental condition at the expense of another. "City officials are encouraging homeowners and businesses to xeriscape," said Robbins. "Residents are heeding this conservation message a little too well by purchasing fully-grown plants collected from nearby deserts, in numbers that may exceed sustainable limits," he said.
The report cites evidence that nearly 100,000 succulents, with an estimated value of $3 million, were harvested from the wild cactus population in Texas between 1998 and 2001. These plants were mostly destined for xeriscaping in Arizona.
Although commercial cultivation is well established in Arizona and California, the market is now large enough to absorb specimens from other sources, said Robbins. Plants culled from the wild also increase profit margins for traders, as they don't require time-consuming and expensive greenhouse cultivation.
"The landscape trade is relatively new, and covers not just cacti, but many other succulents, such as yuccas, agaves, and ocotillos," said Jackie Poole, a botanist with the Texas Parks and Wildlife Department in Austin. "While landscaping with Chihuahuan Desert plants has not really caught on in Texas most of our plants are shipped to Arizona," she said.
However, commercial collection isn't as great a threat as it once was, said Poole. She has photographs that depict "millions" of small cacti piled up in the small town of Lajitas, Texas, waiting to be potted up and sent to supermarkets and variety stores. Now, much of the trade has been taken over by commercial nurseries growing cacti from seed.
While trade in Chihuahuan Desert cacti species is a major challenge, habitat destruction, especially around cities, is also a problem, added Poole. "And putting the species back into a sea of concrete and asphalt really doesn't solve the problem," she said.
SOURCES AND RELATED WEB SITES