Fortress Conservation Won’t Work Out for The Cactus Family
Succulence is a form of plant growth or “habit” that has arisen in numerous plant families across many portions of the globe. This habit can range from a subtle fleshy feeling of the plant organ (stems, leaves, flower petals, etc.) in species like common purslane (Portulaca oleracea) to gross modifications of the entire plant into an enlarged water storage body, as in most members of the cactus family (take the saguaro, Carnegiea gigantea, as a conspicuous example of this habit). Although the stonecrop family—the Crassulaceae—is commonly referred to as the “succulent family”, there is no one true “succulent family”. In fact, the succulent habit, in one form or another, has evolved in approximately 70 families of flowering plants and occurs in upwards of 15,000 different species (Nyffeler et al. 2008; Griffiths and Males 2017). Succulence is therefore evolutionarily labile within flowering plants, with multiple unrelated lineages having made numerous transitions between non-succulence and succulence. Succulence is most common in warm and arid environments where water evaporation is high (Evans et al. 2014), though clearly not all plants growing in such conditions are succulent. The succulent condition has also arisen in numerous other habitats besides hot and dry ones, for example in epiphytic, arctic-alpine, and rock-dwelling contexts (Griffiths and Males 2017).
Succulent plants are amongst the most popular for horticulturalists and other plant enthusiasts to grow. The forms of many of them speak to something within many of us, paradoxically redolent of the exotic while perhaps invoking in us some primeval, inexplicable, faded sense of nostalgia for our warm and dry ancestral homelands. Based on where many succulent plants generally grow natively, a host of them were rare in nature to begin with (as in, pre-Industrial times) through their narrow ecological specializations within restricted geographical areas. Some such species may only be found on one outcrop or mountain, one geological formation, or one soil or ecosystem type (e.g., Stellaria sanjuanensis in the Caryophyllaceae is restricted to ancient alpine volcanos in southern Colorado: Sharples and Tripp 2019). Perhaps in part due to the rarity of many succulents in combination with their awe-inspiring growth forms, individuals of many species can fetch rather high prices.
A new extinction crisis is upon us, however, and it is all the more invisible because it does not directly involve charismatic mammals—or any other animals, for that matter. Succulent species such as members of the cactus family are widely known for their slow-growing life history, often needing multiple years to multiple decades to achieve reproductive age in the wild. Despite millions of years of evolution into an impressive diversity of forms, humans are facilitating the extremely rapid extinction of many, and perhaps most, major lineages within the cactus family (Goettsch et al. 2015; Phippen 2016). Much of the cactus family (the Cactaceae, comprising ca. 1500 species across the New World) is now experiencing declines in the wild, these declines directly linked to human harvesting and other anthropogenic disturbances (Goettsch et al. 2015). This is not a new or surprising phenomenon. Instead, it is an increasingly disturbing trend, with widespread wild-poaching being as lucrative as some other illicit smuggling activities in the Americas (Kennedy 2008). The Kennedy (2008) BBC report cites $10,000 as within the range of purchase price variation for a single individual of some cacti species. That kind of price might even make the most environmentally-conscious people in the most affluent countries on the planet consider quitting their day jobs. But for someone a little less well off, such a sum can make the difference between health and decrepitude, prosperity and decline, land and no-land, between life and death itself.
Fortress conservation, in which wildlands are protected from all human development and agriculture, and in which human tourism and recreation are given priority status, will not entirely work out for the cacti and other threatened groups of plants. The amount of wild-poaching experienced by members of the cactus family has reached striking levels, both in the United States and elsewhere, regardless of whether species lie in protected areas (Goettsch et al. 2015). Enthusiasts in the United States and in dozens of other countries want “exotic” plants such as cacti at home to show off to friends, family and acquaintances, and this ultimately does nothing for anybody, least of all the plants. The only thing it is doing is causing many members of the cactus family and others to spiral further towards irreversible, mortal decay. It is not only indoor home enthusiasts chipping away at wild populations from their armchairs. The phenomenon is also the result of a well-intentioned yet devastating action: the trend towards aridland landscaping in areas lacking an abundance of freshwater (WWF 2003). Unceasing human development has by necessity even rendered the green lawn in many places to be a public shame, but it is unclear that the current shift towards arid landscaping is as benign as intended.
The Crassulaceae (or “stonecrops”) and other families also have many members under threat of extinction in the face of poaching for the novelty industries, regardless of whether these plants are protected within a “fortress” or not. In some well-publicized cases of poachers coming from abroad to the United States, members of the genus Dudleya in California have been suffering from high levels of poaching in recent times (Lanyon 2018). The price tags on these plants alone—much like the price tags associated with illicit parts of rare animals—suggest that these plants will not be around with us much longer if something does not change. Carnivorous plants are equally charismatic as succulent plants to horticultural enthusiasts, and the trend for these lineages is paralleling the trend being experienced by many succulent plants (Shockman 2015). Myriad examples of other plant lineages under threat will go unmentioned here. However, most lineages of succulent and other plants are severely lacking in global threat assessments at present, and these plants may simply disappear before such assessments can even be conducted (Goettsch et al. 2015).
The World Wildlife Fund, Traffic, and others have the right idea, that of encouraging local people in areas with threatened wild plants to both protect and cultivate these plants under the umbrella of their own natural resource heritages. But the reach of such suggestions and efforts has only extended so far. The aridlands of the western United States and Mexico, for example, where cacti and other succulents are particularly diverse, have long been ignored by conservation-oriented non-profit organizations, probably under the common misperceptions that deserts are 1) not particularly biodiverse, and 2) not particularly subject to widespread human development and disturbance. Neither presumption could be further from the truth. Deserts are more biodiverse than many temperate habitats, and the deserts of southwestern North America in particular are undergoing burgeoning levels of agricultural and residential development at present (e.g., Brunson and Huntsinger 2008). Unfortunately, most poaching events of rare or vulnerable species can never be reported; these events are sometimes merely only discovered long after the poach has transpired (if discovered at all), and such events are even more rarely discovered in progress in the field.
There is already a worldwide battalion of people, though, who are capable of mitigating these extirpation trends tomorrow. The present message is thus a call, a plea, to the people who are in the best position—the only position—to mitigate, to perhaps even prevent, the extirpation of significant numbers of succulents and many other species. Only the existing master growers of these plants can help solve the extremely concerning phenomenon of rampant wildland plant depletions. Master growers: you are needed to propagate and sell as many of these beloved rarities as possible. Project forth a veritable stock into houses, greenhouses, and gardens across the world. Propagate and sell, donate, give, extend. The only way, as I see it, to save much of the cactus family and many other lineages beyond now is to propagate, distribute, and thereby drive down the prices of wild-caught individuals. It is in the power of the master growers to save the succulents and the other horticultural novelties which they so adore and which are dramatically declining in nature. We must pounce and act immediately upon trendy and popular new houseplant and garden rarities. As with the cases revolving around California Dudleya and others, the solution to eliminating the poaching problem lies in horticulturalists and other enthusiasts stepping up production (Lanyon 2018); this increased production will perhaps in limited cases need to be input with a few legally-harvested wild individuals or seed stocks in order to be successful. But the only way to significantly bring down the prices of these novelties—thereby eradicating their desirability and lucrativeness as poaching targets—is to saturate the market with availability.
Of course, some cacti will remain with us ever onwards no matter what happens to wildland populations of vulnerable species. Many species of prickly pear (Opuntia species) and cholla (Cylindropuntia species), for example, are widespread across southwestern North America, thriving in both disturbed and wild areas. More importantly, these species are not generally sought out by horticultural enthusiasts—they are not “cute”, “pretty”, or “exotic-looking” cacti, nor are they generally practical to grow indoors. In that sense, the cactus family as a whole is not facing immediate risk of extinction (but see Goettsch et al. 2015). We do, however, face a near future that may lack some of the most charismatic and rare members of the Cactaceae and others if additional measures beyond strictly fortress-style conservation are not enacted. A typical fortified wildland cannot well exclude poachers who are intent on penetrating the fortress. Therefore, greater creativity towards confronting the wild plant poaching problem is necessary. Wild animals, fungi, and microbes are dependent on these and thousands of other threatened plant species for their own survival. Many of the threatened plant lineages also have attractive, conspicuous, showy flowers, which make these plants almost as attractive to humans as they are to wild foragers and pollinators. Can we imagine a landscape in the deserts of the New World that lacks the promise of magnificent cactus blossoms on a warm spring day after a few recent rains or snows? How else might such a world look?
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Evans, M., Aubriot, X., Hearn, D., Lanciaux, M., Lavergne, S., Cruaud, C., Lowry II, P.P. & Haevermans, T. 2014. Insights on the Evolution of Plant Succulence from a Remarkable Radiation in Madagascar (Euphorbia). Systematic Biology 63(5): 697–711.
Goettsch, B. et al. 2015. High proportion of cactus species threatened with extinction. Nature Plants: 15142.
Griffiths, H. & Males, J. 2017. Succulent plants. Current Biology 27(17): PR890–R896.
Kennedy, D. 2008. Poachers threaten Mexico’s cacti. http://news.bbc.co.uk/2/hi/7290318.stm.
Lanyon, C. 2018. California’s succulent smugglers: plant poachers seed Asia’s desire for dudleya. https://www.scmp.com/magazines/post-magazine/long-reads/article/2163157/californias-succulent-smugglers-plant-poachers.
Nyffeler, R., Eggli, U., Ogburn, M. & Edwards, E. 2008. Variations on a Theme: Repeated Evolution of Succulent Life Forms in the Portulacineae (Caryophyllales). Haseltonia 14: 26–36.
Phippen, J.W. 2016. Busting Cactus Smugglers in the American West: How undercover agents infiltrated the global black market for cactus. https://www.theatlantic.com/science/archive/2016/02/cactus-thieves/470070/.
Sharples, M.T. & Tripp, E.A. 2019. RAD Sequencing Rejects Long Distance Disjunction in Stellaria (Caryophyllaceae) and Yields Support for a New Southern Rocky Mountains Endemic. Taxon, in press.
Shockman, E. 2015. The little-known world of endangered plant poaching. https://www.pri.org/stories/2015-11-30/little-known-world-endangered-plant-poaching.
WWF. 2003. Cactus poaching, legal harvesting a growing threat to Chihuahuan Desert cacti. http://wwf.panda.org/?5402/cactus-poaching-legal-harvesting-a-growing-threat-to-chihuahuan-desert-cacti.