Lessons from the history of Agave: ecological and cultural context for valuation of CAM

Abstract

Background and Scope

Crassulacean acid metabolism (CAM) is an intriguing physiological adaptation in plants that are widespread throughout many ecosystems. Despite the relatively recent mechanistic understanding of CAM in plant physiology, evidence from historical records suggests that ancient cultures in the Americas also recognized the value of CAM plants. Agave species, in particular, have a rich cultural legacy that provides a foundation for commercially valued products. Here, we review that legacy and potential relationships between ancient values and the needs of modern-day climate adaptation strategies.

Conclusions

There are many products that can be produced from Agave species, including food, sugar, fibre and medicines. Traditional knowledge about agricultural management and preparation of plant products can be combined with new ecophysiological knowledge and agronomic techniques to develop these resources in the borderland region of the southwestern USA and Mexico. Historical records of pre-Columbian practices in the Sonoran desert and remnants of centuries-old agriculture in Baja California and Sonora demonstrate the climate resilience of Agave agriculture. Commercial growth of both tequila and bacanora indicates the potential for large-scale production today, but also underscores the importance of adopting regenerative agricultural practices to accomplish environmentally sustainable production. Recent international recognition of the Appellation of Origin for several Agave species produced for spirits in Mexico might provide opportunities for agricultural diversification. In contrast, fibre is currently produced from several Agave species on many continents. Projections of growth with future climate change suggest that Agave spp. will be viable alternatives for commodity crops that suffer declines during drought and increased temperatures. Historical cultivation of Agave affirms that these CAM plants can supply sugar, soft and hard fibres, medicines and food supplements.

INTRODUCTION

Crassulacean acid metabolism (CAM) is one of the most fascinating physiological mechanisms observed in plants. More than 34 families include species that use CAM, representing 6 % of all vascular plants (Winter and Smith, 1996). CAM plants have a 24 h cycling of carbon that provides the chemical energy supply for photosynthetic light reactions even during times when stomata are closed. This has tremendous advantages for plants growing in hot and dry climates, but it is also beneficial for some aquatic plants, and CAM plants inhabit regions with a wide range of climatic conditions (Gilman and Edwards, 2020). The advantages of CAM have earned some CAM plants cultural significance throughout history by offering provisions in extreme climatic conditions.

Reflecting on the history of CAM research, which has provided profound insight into the plasticity of photosynthetic mechanisms, it is also appropriate to consider the many cultural associations with CAM plants. Although CAM plants are underrepresented in commercial agricultural production, several species make significant contributions to agricultural resources (Davis et al., 2019). For example, pineapples [Ananas comosus (L.) Merrill] are globally traded fruits highly valued in food systems (Bartholomew et al., 2002; Ming et al., 2015), aloe varieties (360 Aloe spp.) are globally renowned for their medicinal qualities (Grindlay and Reynolds, 1986; Katerere, 2018), vanilla (107 Vanilla spp.) is a prized culinary spice (Fouché and Jouve, 1999; Cameron, 2011), blue agave (Agave tequilana Weber var. azul) is well known for the spirit tequila (Valenzuela-Zapata, 1997), and many types of orchids (family Orchidaceae with >29 000 spp.) are revered in ornamental horticulture (Arditti, 1992; Silvera et al., 2009; De et al., 2014). All these highly valued plants use CAM, although notably, the many varieties of orchids range in CAM expression from no CAM to strong CAM (Silvera et al., 2009, 2010). These agriculturally important CAM plants have historical legacies associated with cultural identities in different regions of the world (e.g. Valenzuela-Zapata and Nabhan, 2004; Cameron, 2011).

All species in the Agave genus, >200 in total, are presumed to be obligate CAM plants, and this taxonomic group has a prominent cultural identity; the goddess Mayahuel still permeates art, symbols and even advertising as the divine figure embodied in Agave plants (Radding, 2012). Although the early works by Klaus Winter and others (e.g. Park Nobel especially for Agave) highlighted the significance of CAM in plant physiology, the cultural significance of this specially adapted group of the plants was evident in history well before western science documented it. Large-scale production of Agave species for human consumption is evident in North America even during pre-Columbian times (e.g. Ortiz-Cano et al., 2020). Researchers such as Gentry (1982, 2004), Valenzuela-Zapata and Nabhan (2004), Vargas-Ponce et al. (2007, 2009) and others have documented the many landraces of Agave and their relationship to cultural history in the Americas. A text edited by Colunga-GarcíaMarín et al. (2007) provides a thorough account of traditional uses of Agave, which range from food and medicine to fibre and construction materials. The rich history of this genera thus lends itself well to an emerging model for rediscovery of natural resources through traditional ecological knowledge (Kimmerer, 2012). Rediscovery of traditional ecological knowledge has the power to guide diversification strategies for sustainable agriculture with changing climatic conditions, sometimes with equal or greater impact than biotechnology (IPES, 2016).

This paper reviews several Agave species, their traditional uses, cultural values and the potential for application to future agricultural production. Although we learned much about the amazing potential of CAM photosynthesis over the last 50 years that is being used for biotechnological advances in photosynthetic systems (e.g. Yuan et al., 2020), there is also tremendous value associated with the careful cataloguing of plants that exhibit CAM traits in the wild (e.g. Winter, 2019). With the insight from new mechanistic knowledge about CAM, additional light can be shed on the cultural value of CAM plants, both historically and for the future. The history of Agave use might have something to teach us as we reach critical thresholds for climate change.

OVERVIEW OF HISTORICAL USES AND CULTIVATION OF AGAVE

Most Agave species are native to Mexico, with 75 % of the 200 known species present throughout the country (García-Mendoza, 2002; Eguiarte et al., 2021). The uses of Agave include food, fibre, construction materials, fermented beverages, antimicrobial agents, anti-inflammatory agents, dietary supplements and biofuel (e.g. Gentry, 1982; Colunga-GarcíaMarín et al., 2007; Davis et al., 2019). In the native range of Agave in Mexico, some communities harvest plants from the wild (e.g. Martínez-Palacios et al., 1999) and others rely on traditional semi-domestication strategies, with subsistence farming of Agave plants in both forest and grassland areas. The density of plants in semi-domestication ranges from 20 to 3000 plants per hectare (Martínez-Palacios et al., 1999). Historically, these plants were used to make everything from brooms to sandals to beverages, but the most common traditional use that persists today is for the fermented beverage pulque (Escalante et al., 2016). Pulque has a lower alcohol content than the internationally recognized liquors (mescals) and purported health benefits in some cases (Escalante et al., 2016). Industrial production of mescal (as reviewed in a section below) followed a long tradition of fermenting wild and domesticated varieties of Agave plants (Fig. 1).

Fig. 1.

Time lines of documented uses of Agave species for food (pink); fibre (blue); pulque and medicines (yellow); and mescals and other spirits with an Appellation of Origin in Mexico (grey).

Fibre production from Agave fourcroydes also has a long history in Mexico. Henequen, sometimes also called sisal, was produced during the Mayan era (Colunga-GarcíaMarín and May-Pat, 1993, 1997; Colunga-GarcíaMarín, 2007). This fibre provided the foundation for a rope and twine industry that expanded in the 1800s and peaked in the mid-1900s (Evans, 2007). After synthetic fibre production began, the Agave fibre industry declined substantially (Evans, 2007; Davis and Long, 2014). Agave lechuguilla also provides fibre materials in Mexico, but is primarily marketed in local rural economies, especially in the region of Coahuila where it borders Tamaulipas and Texas (Castillo-Quiroz et al., 2012). Agave sisalana has been produced commercially for fibre, originating in Mexico and then developed agriculturally throughout eastern Africa, India and Brazil (Gentry, 1982). Tanzania was the leading producer of sisal in the 1960s, but this industry was displaced by synthetic fibre production (Davis and Long, 2014; Davis, 2022). Today, Brazil has the greatest agricultural production of Agave fibre (Davis, 2022).

There is evidence of Agave use in North America during prehistoric times. Hammerl et al. (2015) reported Agave dental quids found in human remains, dated between 1200 and 1400 years BC, at the Loma San Gabriel in Durango, Mexico (Fig. 1). In Mesoamerica and Aridamerica, Agave cultivation was a subsistence strategy amongst pre-Columbian groups (Colunga-GarcíaMarín, 1997; Nabhan, 1985; Nabhan et al., 2020). During pre-Hispanic times, Agave was cultivated in a similar manner, with annual seed crops, in Mesoamerica (Anderies et al., 2008; Nabhan et al., 2020). The cultivation and economic importance of ancient Agave or ‘Maguey’ in Mesoamerica can be traced to the Aztec empire in the highlands of central Mexico, where significant improvement in cultivation practices occurred at ~759 AD, and further south in the Mayan region at ~700 and 600 AD (Nichols et al., 2000). In the Aridamerica region in south-central Arizona, cultivation of Agave as a staple crop by the Hohokam occurred at ~1150 AD (Fish and Fish, 1992). Likewise, Trombold (2017) reported Agave cultivation in north-central Mexico, in the Zacatecas region at La Quemada archaeological site, between ~1000 and ~1200 AD.

Evidence from pre-Hispanic times suggests that Agave cultivation intensified as a strategy to ensure food availability during times of drought and famine in both Mesoamerica and arid regions of the Sonoran and Chihuahuan deserts (Nichols et al., 2000; Anderies et al., 2008; Trombold, 2017). Pre-Hispanic archaeological sites of Agave are often accompanied by evidence of roasting pits or earthen ovens for Agave and food preparation. Remnants of Agave industries for goods (i.e. fibre, clothes) have been found at sites in western Mexico Colima, southern Zacatecas, Paquime and south-central Arizona regions (Zizumbo-Villarreal et al., 2013; Fish and Fish, 2014; Minnis and Whalen, 2015). Today, as in pre-Hispanic times, several products made from Agave continue as part of Indigenous traditions in rural areas from southern to northern Mexico and borderlands with the USA (Esparza-Ibarra et al., 2015; Ortiz-Cano et al., 2020). Colunga-GarcíaMarín and May-Pat (1993) highlighted the different parts of Agave and subproducts in eight categories of traditional uses: drinks, clothes, construction, food, ornamental, domestic uses, agriculture and livestock.

The physiological advantages of CAM are key factors defining the natural and cultural history of Agave in different regions across Mexico and in the borderlands of Mexico and the USA (Gentry, 1972, 1982; Yetman et al., 2002; Ortiz-Cano et al., 2020; Eguiarte et al., 2021). Remains of Agave goods at archaeological sites provide evidence of the importance of the natural diversity of the genus and its uses in pre-Hispanic times (Fish and Fish, 1992). The water-use efficiency, soluble carbohydrates, waxy cuticles and strong fibres of Agave are all traits associated with CAM; these products from Agave became embedded in the traditional practices amongst tribal groups and continue in modern times in rural Mexico and borderland regions (Bruman, 2000; Yetman et al., 2002; Cervantes Mendívil et al., 2007; Fish and Fish, 2014). Today, the most well-known examples of commercial and traditional use of Agave are for spirit drinks and fibre (Fig. 1).

DETAILED HISTORY OF AGAVE CULTIVATION FOR FIBRE

The strong Agave fibres, grown by these CAM plants to support the weight of large succulent leaves, have been important for Indigenous people of North America since before recorded history. Agave fibre can be traced in history from ancestral people to modern Indigenous groups and geographically from southern Mexico to northern Mexico and borderlands with the USA. Andres Perez de Ribas, a Jesuit monk, reported that Indigenous people used Agave fibre for clothes between 1591 and 1620 in northern Sinaloa region (Rojo and Radding, 2019). The Chichimecas, who lived in several regions of northern Mexico for ~9000 years with few lifestyle changes until European arrival in America, used Agave extensively for fibre (Ruíz and Orozco, 2023). Fibre from A. lechuguilla was a valuable resource for the Chichimecas and was used to build traps, fishing nets, ropes, sandals, clothing, bow strings and string for tying arrowheads.

Currently in north-west Mexico, fibre extraction from Agave among Indigenous people occurs only rarely. Engerrand (1936) reported that the Tarahumara tribe in Chihuahua Mexico substituted the use of Agave fibre for cotton or wool. In southern Sonora, a few people in the Mayo tribe continue to extract fibre from Agave to produce rope and burlap bags (Yetman et al., 2002). In rural communities of the Chihuahuan Desert, particularly in the state of Coahuila, fibre extraction from A. lechuguilla produces important revenues for local economies in the region (Castillo-Quiroz et al., 2014). A census from 2005 estimated that 52 000 families produced fibre from A. lechuguilla as an economic activity in the Chihuahuan desert (López-Serrano et al., 2021). Small groups of Indigenous people, such as the Otomi people in Ixmiquilpan Hidalgo, have preserved the tradition of extracting fibre from A. lechuguilla since pre-Hispanic times (CCMSS, 2022).

Yucatan is the centre of biodiversity of A. fourcroydes, which was used to produce henequen fibre by the Mayans (Garcia-ColungaMarin and May-Pat, 1993). In the Mayan region of southern Mexico, it has been hypothesized that Mayans used Agave ~2600 BC (Turner and Miksicek, 1984). Historically, the major fibre industry from Agave was the production of henequen at large colonial haciendas and plantations in southern Mexico (Wells, 1982). The Spanish villages in Yucatan date back to colonial times in the 1500s (Barteet, 2015). Spaniards in the Yucatan region occupied the Mayan land and developed irrigation technology for agriculture, such as the invention of the noria system (wells operated by working animals, typically mules or donkeys) (Barteet, 2015). The Mexican industry of fibre production intensified and reached its maximum between 1870 and 1901 owing to the mechanization of fibre extraction in the late 1800s and early 1900s (Garcia-ColungaMarin and May-Pat, 1993).

Since colonial times, the henequen industry relied on Mayan peons (Indigenous people enslaved and tied to an owner). Even after the Mexican revolution and redistribution of land, the henequen industry was controlled by landholders (Wells, 1982) who exploited thousands of Indigenous people in Mexico (Arias López et al., 2013). Espinoza (2007) suggested that the success of the fibre industry in southern Mexico was attributable to the historical domination of European and upper-class social groups who enslaved Indigenous societies in Mexico (Lundberg, 2019). It has been reported that 300–400 hacendados (hacienda owners) owned >1000 henequen haciendas (Wells, 1982). A few families controlled and monopolized the henequen industry in Yucatan, such as the Peón family, who owned land titles ≤7000 ha in size since 1841 (Wells, 1982). In 1914, the largest plantation of henequen produced only 196 tons of fibre (Wells, 1982). By 2017, the production of fibre reported was 12 813 tons annually across 6461 ha cultivated with A. fourcroydes, generating a revenue of 59.2 million pesos in Yucatan (Wells, 1982; SEGOB, 2022b).

In the first half of the 1800s, conflict between the government and the Yaqui tribe in southern Sonora resulted in entire families of Yaquis being expelled and deprived of their land, forcing them to move and work in the Yucatan region (Arias López et al., 2013). Yaqui families were captured, transported in trains and integrated into henequen plantations at haciendas in the Yucatan region. In the 1900s, it has been estimated that 8000 Yaquis were relocated to the Yucatan peninsula to work at henequen and sugarcane plantations or salt ranches (Arias López et al., 2013). The Yaqui history in Yucatan has been traced and recorded by Teodoro Buitimea Flores, a member of the Yaqui tribe in charge of recovering the history of the Yaqui in Mexico. Prior historical accounts have overlooked the suffering of Indigenous children, both male and female, in Yucatan and other industries of Agave (T. Buitimea Flores, Superior Technological Institute of Cajeme (ITESCA), Outreach Extension Office Vicam, Son, MX, pers. comm.).

The terms ‘henequen’ and ‘sisal’ have been exchangeable to name hard fibre of A. fourcroydes and A. sisalana. In the late 1800s, A. sisalana fibre attracted the British and Germans, and samples from Mexico were sent to botanical gardens in Europe, then later propagated and introduced in the German colonies for Agave fibre in Eastern Africa (Brockway, 1979). Brown (2002) indicated that 1000 bulbils of A. sisalana were sent to Florida in 1893 and from there to Germany. Later, Agave was introduced to the Phillipines, Brazil, India and other countries in Asia (Brown, 2002). The distribution of A. sisalana in southern Mexico is not clear, but it has been hypothesized that it was propagated and used by Indigenous people in villages around the Chiapas region (Gentry, 1982, 2004; Brown, 2002). In 2021, the sisal industry produced 300 000 tons of fibre, valued at 75 million USD, and the major producers are reportedly Brazil (120 000 tons), Tanzania (30 000 tons) and Kenya (25 000 tons) (DNFI, 2020). Although the global fibre industry peaked in the 1960s, then declined as synthetic fibres were introduced (Davis and Long, 2014), Agave fibre production has remained relatively consistent in Mexico over the last decade, nationally ranking fourth in global production (Davis, 2022).

REGIONALIZED PRODUCTS FROM AGAVE SPECIES IN THEIR HISTORICAL RANGES

Amongst products made of Agave, spirit drinks have the most defined commercial and geographical history in Mexico and the southwestern US borderland regions (Salazar Solano, 2007; Salazar Solano and Mungaray Lagarda, 2009; Pérez-Akaki et al., 2021). The process of CAM in Agave plants leads to a reliable accumulation of soluble carbohydrates in the stem and leaf tissues (e.g. Jones et al., 2020), and these sugars are easily fermented to yield alcohol. Throughout history, farmers have developed their signature drinks using different endemic species available in the arid, semi-arid and temperate regions (Bruman, 2000). The most distinctive examples of regionalized Agave spirits in their historical commercial ranges are pulque, mescal and tequila (Bruman, 2000; Serra and Carlos, 2010; Escalante et al., 2016). Beginning in pre-Hispanic times, pulque was made of Agave salmiana, Agave atrovirens and Agave mapisaga by the Tlaxcaltecas, Otomi, Toltecs and Aztecs (Escalante et al., 2016). Pulque is likely to be the oldest drink consumed from Agave in America, and its crafting has been estimated to originate 3500 years ago (Escalante et al., 2016).

In recent decades, the Appellation of Origin, also called Designation of Origin, for Agave spirits has helped distilled Agave drinks to reach their maximum commercial and cultural–legal recognition (Pérez-Akaki et al., 2021). In Mexico, the Designation of Origin system for Agave spirits is similar to those used in Europe in the wine and food industry that protect regional products from specific geographical ranges, with particular artisanal processes, varieties and history, providing economic alternatives amongst regional farmers (Ortiz-Cano et al., 2020). In western Mexico, tequila was the first Agave spirit recognized through a Designation of Origin and, internationally, an Appellation of Origin (Fig. 1; Bowen, 2015; Pérez-Akaki et al., 2021). Another example is the mescal named bacanora, produced from Agave angustifolia in Sonora, Mexico, which in recent years has gained international presence in Europe amongst the highest quality international spirits (Arizona Public Media, 2020). As the signature for bacanora, the Designation of Origin establishes the exclusive use of A. angustifolia plants for its production in 35 municipalities along the Sierra Madre Occidental mountain range in Sonora, Mexico (Fig. 2). Likewise, the Designation of Origin establishes that tequila can be produced legally only from Agave tequilana Weber var. azul in 125 municipalities in the State of Jalisco, 30 in Michoacan, 7 in Guanajuato, 8 in Nayarit and 11 in Tamaulipas (Fig. 2; Consejo Regulador del Tequila, 2022).

Fig. 2.

Regional Appellation of Origins denoted with a heat map of density of occurrences (plant counts per kilometre squared) indicating centres of cultivation (in red) for Agave tequilana used for tequila (A) and Agave angustifolia used for bacanora (B) throughout Mexico. (Data source: GBIF, 2022; map generated with GADM CC-BY, https://gadm.org/license.html.)

The Designation of Origins for Agave spirits is recognized internationally under the Lisbon Agreement for the Protection of Appellation of Origin, and the registered Appellation of Origin has attracted Mexican producers of Agave to international markets. The increasing international interest and demand for Agave spirits has also increased the revenues from the tequila and mescal industry in Mexico. In 2021, the tequila industry reached its maximum commercial production in history, producing 527 million L. Internationally, the USA had the highest demand, selling $5200 million USD worth of tequila. In 2020, 374 million L of tequila were produced from 20 000 ha cultivated with A. tequilana Weber var. azul, with yields of 77.6 tons per hectare (SEGOB, 2022a; Statista, 2022). Likewise, in 2021 the mescal industry reached a new historical maximum production of 8.1 million L.

Although bacanora was the earliest of the Agave spirits to be traded internationally, and there are many other spirits produced through traditional practices, the tequila industry is currently the largest and most well known. In the following sections, we review the colonial period that changed agricultural production of Agave in Mexico, provide a history of changes associated with the development of tequila, then provide a historical review of bacanora development for comparison.

Agave regional developments during colonial Spanish period

When Spaniards arrived in Mesoamerica during the early 1500s, they found that Indigenous people produced goods and drinks made of Agave (Walton, 1977; Bruman, 2000; De León Meza, 2017). In central Mexico, the Spanish found that people living in cities also cultivated Agave, while nomadic tribes consumed Agave extensively as a staple food and used it to produce goods (e.g. cloth, rope, bags; Evans, 1992; Gutiérrez-Coronado et al., 2007; Serra and Carlos, 2010). Nomadic Chichimecas and Tlaxcaltecas harvested and roasted wild Agave or maguey (mixcali, mescal) in small ovens (Sánchez Soto, 2016). The Aztecs cultivated Agave in terraces on piedmont slopes in the valley of Chihuactepan, a region that they had occupied since 1000 AD (Córdova and Parsons, 1997; Evans, 2007). During the second half of the 1500s and into the early 1600s, the Spanish explored western Mexico with the help of Indigenous allies (Tlaxcaltecas, Huejotzingas and Purepechas), and they observed that the Caxcanes and the Tecuexes consumed Agave although they did not cultivate it (De León Meza, 2017).

The Spaniards found water and large extensions of fertile land that was suitable for agriculture and livestock in regions of western and northern Mexico (Tercero, 1936). In western Mexico, they recorded the arid regions around the volcano in what is now Jalisco state, where Agave was grown extensively by the Indigenous people (Valenzuela-Zapata and Nabhan, 2004). The Spanish strategy of establishing Franciscan and Jesuit parishes at missions, cofradias and villages enabled agriculture in the western and northern regions (Chance and Taylor, 1985; De León Meza, 2017). Jalisco continues to be the primary growing region for A. tequilana today.

European and Indigenous agricultural practices enabled the introduction of seedlings, grains, trees, fruits, flowers, bulbs and root grafts along with techniques such as decks, terraces and gardens in the different regions of Mexico (Brown and Fournier, 2014). Colonial settlements enabled agriculture of Iberoamerican crops and intermixing of regional plants endemic to Mesoamerica and Aridamerica (Brown and Fournier, 2014; Saldaña and Colín, 2014). For example, during Spanish exploration campaigns to northern Mexico, aided by the Tlaxcaltecas, Agave species were introduced to arid regions of the Chihuahuan desert. The Tlaxcaltecas brought with them A. salmiana, which naturalized to San Luis Potosi, Saltillo and Zacatecas regions (Saldaña and Colín, 2014). Nowadays, A. salmiana populations are part of the landscapes of arid regions in northern Mexico (Gentry, 1982). The ecological signature of colonial Spanish crops and species intermixing in northern and western Mexico has been estimated to affect several thousand endemic species in the region (Saldaña and Colín, 2014).

Colonial trading routes established within the first 100 years of Spanish colonial occupation, such as the ‘El Camino Real’, which connected Aridamerica and central colonial regions, crossing regions of northern and western Mexico, helped Spaniards to identify endemic species, including Agave species, that were used later in the colonies (Saldaña and Colin, 2014). The ‘El Camino Real’ route favoured the mescal industry and Tequila region to cultivate Agave in monoculture (Saldaña and Colín, 2014). It has been reported that mescal wine was produced initially in western Mexico and that Jalisco later became the main region for mescal (Walton, 1977).

Agave cultivation in the Tequila region

Jacques et al. (2003) hypothesized that the word Tequila relates to the two words ‘Titicuilas’ and ‘Tequitl’. The Titicuilas were a tribe that inhabited the piedmont of a volcano near the city of Tequila. The word Tequitl, from the Nahuatl language, means work. Historically since the 1800s, Tequila has become the prime region for cultivating Agave in the Americas. The Tequila region includes the states of Jalisco, Guanajuato, Nayarit, Michoacan and Tamaulipas (DOF, 2022a). In 1974, the Designation of Origin of Tequila was created to protect the spirits made of A. tequilana Weber var. azul in the Tequila region (DOF, 2022a).

Tequila has been broadly associated with Mexican National Identity (Bowen and Gaytan, 2012 ). In 2006, UNESCO declared human patrimony of the Agave landscapes in Tequila, at Amatitan, Arenal and Magdalena (UNESCO, 2022). Despite Spanish colonial policies that prohibited liquor production from Agave in the early New Spain, tequila has been produced for ~235 years and is one of the oldest industrial Agave Indigenous drinks crafted and distilled in North America (Jacques et al., 2003). Tequila made of A. tequilana Weber var. azul originated from the integration of the Indigenous traditional ecological knowledge and European agricultural practices (Colunga-GarcíaMarín et al., 2007; Valenzuela, 2011). Thus, modern-day tequila can be considered a mestizo drink (mestizo is commonly used in Latin America to denominate the cultural intermix between Indigenous and European people) (Walton, 1977). The accumulated knowledge since pre-Hispanic times for harvesting and selecting Agave traits, combined with European monoculture systems brought by the Spanish to America, enabled cultivation of Agave in the region of Tequila (Walton, 1977; Cedeño Cruz, 2003).

Evidence of cultivation of Agave in Tequila goes back to 1726, with the story of Luis Clemente Gonzalez, an Indigenous tribal leader who inherited 500 Agave plants in the Amatitan region (Tena Meza et al., 2015). Spanish interest in cultivating Agave started during the period of colonial intendancies, when the Spanish monarchy intensified control over the peninsular Spaniards after the second half of the 1700s (De León Meza, 2017). The rights for mescal and cultivation of Agave were provided to Prudencio Cuervo, who owned the Haciendas de San Martin and Guadalupe. At the hacienda San Martin in 1756, the first alambique (copper distillatory) was reported for distilling mescal (De León Meza, 2017). The hacienda San Nicolas, owned by Rafael Montaño in 1777, recorded 2810 cultivated Agave plants and 500 plants that were mature and ready to be harvested (Goyas Mejía, 2012).

Although the main production in these haciendas was sugarcane, Rene De León Meza (2017) indicated that, in the Hacienda of San Martin inventory of 1787, there were 50 000 cultivated Agave plants, and by 1801 the number had increased to 364 407 plants. In the late 1800s, different haciendas produced thousands of litres of tequila. For example, by 1888, the hacienda Cuisillos near Guadalajara produced 1000 cargas de mescal (colonial Spanish units), equivalent to 188 630 L of tequila (Goyas Mejía, 2012). After 212 years of the Agave industry in the Tequila region, by 1999 the production reached 800 tons of plants for tequila. In 2021, 75 % of the national production of Agave across Mexico was produced in the Tequila region, and 1 777 000 tons of A. tequilana plants were produced (Mexicampo, 2022).

Botanical history of Agave tequilana

Selection of Agave species occurred in pre-Hispanic times by Indigenous Mesoamericans and Aridamericans (Evans, 1992; Trombold, 2017). Pre-Columbian Indigenous groups knew the differences between species of Agave in the different regions of Mesoamerica and Aridamerica and could identify and select species based on traits (e.g. leaf colour, phenology) (Gentry, 1982). They domesticated species and naturalized species to different geographical ranges in Mesoamerica and Aridamerica (Gentry, 1982). Some species, such as A. tequilana Weber var. azul, evolved from A. angustifolia (Rodriguez Garay et al., 2009).

The botanical history of the Agave genus started during early Spanish occupation of Mesoamerica and Europe in the mid-1500s. The first records of the ecology of Agave in colonial times can be found in the Codex Nutal, Florentino and Borgia (Jacques et al., 2003). In Europe, Carolus Clusius, a French naturalist from the Leiden Botanical Garden, was attracted to Agave species introduced in Spain; Agave plants were among the first plants to be classified botanically, investigated and cultivated for research purposes (Ubrizsy in Savoia and Heniger, 1983). Carl Linnaeus published the first description of Agave americana in 1753 in the Species Plantarum (Trelease, 1908; Muriá, 2012). At the end of the 1700s, in Tequila, monocultures of Agave started with the beginning of commercial Agave production in North America. Don Cenobio Sauza introduced tequila to the USA for the first time at the Chicago World’s Fair in 1893 (Academia Patrón, 2022). In the early 1900s, the French naturalist Leon Diguet published the first book describing the cultivation procedures for A. tequilana in the Tequila region (Diguet, 1910). Today, several Mexican states and regions, with a variety of climatic and environmental conditions, have technical guides for cultivating Agave for tequila.

Agave tequilana Weber var. azul is one of the most studied Agave species in the world as a crop, with comprehensive evaluations taxonomically, physiologically, economically, ecologically and genetically. The high industrial demand for A. tequilana has contributed significantly to the motivation for exploring alternative propagation techniques. Since the early 2000s, tissue culture has been used to produce Agave plants (Jacques et al., 2003). Recently, micropropagation and genetic transformation have been considered to be techniques with great potential to mass produce plants (Bautista-Montes et al., 2022).

The French botanist Fréderik Albert Constantin Weber described A. tequilana F.A.C. Weber taxonomically in 1902 (Weber, 1902; GBIF, 2022). At that time, there were four varieties deemed superior for mescal use: chato, siquin, azul and pata de mula (Diguet, 1902). The blue cultivar (azul) of this species became the preferred crop plant for tequila (Gentry, 1982) and has been named A. tequilana Weber var. azul, as recognized by the Tequila Regulatory Council (Consejo Regulador del Tequila, 2022). Recently, A. tequilana has been reclassified as part of the Asparagaceae and Agavoideae family, which was formerly named Agavaceae (Jiménez-Barron et al., 2020).

Another milestone in the history of Agave as a crop was reached by Nobel and Valenzuela (1987), who reported the environmental productivity index of A. tequilana in Jalisco. The environmental productivity index quantifies the relationship between growth and the light, temperature and water conditions of a site, predicting the effect of soil and environmental factors on CO₂ uptake, and can be used to predict suitable regions for Agave cultivation (Garcia-Moya et al., 2011). This model has been a keystone for understanding Agave species as an alternative drought-tolerant crop for current and future climate change (Davis et al., 2011, 2017, 2021; Cushman et al., 2015; Stewart, 2015; Owen et al, 2016; Ortiz-Cano et al., 2020).

Ecological challenges of tequila production

After >200 years of the tequila industry using A. tequilana, several ecological challenges have intensified in recent years. Gentry (1982) reported A. tequilana populations thriving in the wild in western Jalisco. In contrast, monocultures of Agave have disrupted pollinator corridors, particularly for nectarivorous bats, promoting international concern and a generalized problem that affects several Agave species in neighbouring regions of Tequila and in geographical regions across Mexico and the borderlands with the USA (Trejo-Salazar et al., 2016; Burke et al., 2021; IUCN, 2022). In addition, the low genetic diversity of A. tequilana monocultures threatens the genetic diversity of the species, particularly with current and expected climate change (Ruiz Mondragon et al., 2022). The high industrial demand has caused conflict over water, compromising the capacity of A. tequilana as a crop in marginal and non-marginal lands (Fucikovsky, 2001). Moreover, industrial monopolies in the tequila industry have led to diseases, soil erosion, chemical pollution, shifts from traditional crops to Agave, and replacement of Agave landraces for mescal in the Tequila region, causing social injustice for small producers and Indigenous people (Zizumbo-Villarreal et al., 2013; Bowen, 2015; Cabrera-Toledo et al., 2022).

Agave cultivation in the Bacanora region

Historically, domestication, cultivation and commercial uses of Agave have occurred in the biodiversity centres of Agave in northern Mexico and the borderlands with the USA (Eguiarte et al., 2021). Hodgson et al. (2018) and Hodgson and Salywon (2013) found several Agave species domesticated by pre-Columbian people in central and southern Arizona. Gentry (1972) described the wide geographical range of A. angustifolia across Sonora, Mexico and commented about the long cultural history amongst Indigenous groups who make bacanora in the Sierra Madre Occidental in Sonora, Mexico. Salazar Solano (2007) suggested that the mescal bacanora received its name from Bacanora, Sonora, a town in the Sierra Madre Occidental, and it originated as part of the Opata traditions called Vitzo or Cuviso (Gutiérrez-Coronado et al., 2007).

Historically, bacanora originated in the traditional knowledge and ancestral techniques practised by the Opata in Sonora (Shaul and Hill, 1998; Cervantes Mendívil et al., 2007). The Opata were culturally connected with other populations in the Sonoran Desert, such as the Tepiman, the Yuman and the Hohokam, who cultivated Agave in central-southern Arizona (Shaul and Hill, 1998). The artisanal crafting methods for the baking, floral stalk emasculation and fermentation of A. angustifolia heads have been used since pre-Hispanic times (Fig. 1), and they remain current in the modern bacanora industry (Fish and Fish, 1992; Cervantes Mendívil et al., 2007; Gutiérrez-Coronado et al., 2007). In the 17th century, Jesuit Spaniards documented consumption of fermented drinks from Agave amongst Piman people in the region (Gutiérrez-Coronado et al., 2007).

After the introduction of the alambique in Sonora, wild A. angustifolia became the feedstock of mescal in the region (Fig. 3). Production of Sonoran spirits, or aguardientes, began around the 1800s and included bacanora, lechuguilla and mezcal ceniza (Frisby Morales et al., 2018). When La Reforma in the 1850s established rights and permits for artisanal mescal producers that freed them from taxation by the Catholic Church, a boost in the industry of bacanora followed. Between 1900 and 1910, the bacanora industry, with 75 distilleries, produced the majority of Sonoran mescals. In 10 years, production increased from 436 406 to 832 111 L of mescal, generating revenue of ~941 307 pesos. The current value of the volume of bacanora produced in the early 1900s is ~115 million pesos, ~$6 million USD.

Fig. 3.

Agave angustifolia plantation (A) and Agave salmania plantation (B) in Sonora Mexico (Coahuilo). These plantations are well known for high-yielding plants that produce aguamiel (Agave sap). In B, Nazario Gonzalez (owner) and Professor Antonio Hernandez are pictured inspecting the plants. (Photographs courtesy of Dr Jose Antonio Hernandez Herrera, Universidad Antonio Narro.)

The production of bacanora was prohibited from 1915 to 2000 (Salazar Solano, 2007). In 2000, the bacanora industry gained legal recognition through Designation of Origin (Fig. 2) and by the NOM-168-SCFI-2005 (DOF, 2022b). Today, with ~1000 producers, bacanora has reached its highest production in the last 20 years, with 300 000 L of mescal worth 70 million pesos or $3 636 570 USD (Consejo Regulador del Bacanora, 2015).

Ecological challenges of the bacanora industry.

The bacanora industry started in the early 1900s, and production depended on a combined system of producing plants in commercial plantations and harvesting wild Agave populations (Cervantes Mendívil et al., 2007). Producers were aware that wild Agave could not provide enough material to sustain production (Salazar Solano, 2007). During 75 years of prohibition, illegal production of bacanora significantly reduced the regenerative capacity of wild Agave in Sonora (Cervantes Mendívil et al., 2007). After the end of prohibition, the original system from the early 1900s for A. angustifolia production was reactivated in the bacanora industry. However, ecological sustainability and low wild Agave regeneration time remain major challenges to growth of the bacanora industry in Sonora (Núñez Noriega and Salazar Solano, 2009). Current climate science education and outreach programmes are needed in order to continue the Agave industry. Moreover, promotion of a more diversified spirit industry using different Agave species might reduce the ecological pressure on A. angustifolia in Sonora.

Bacanora industry in its historical range at the borderlands of Sonora and Arizona.

Mescal bacanora plays an important geographical role in the historical economy of the borderlands in Sonora, Mexico and Arizona, USA (Salazar Solano and Mungaray Lagarda, 2009). Arizona territory, annexed to the USA in 1863 during the early stages of the bacanora industry in Sonora (Argüello, 1988; Salazar Solano, 2007; Taylor, 2008; Massoth, 2016), resulted in the naturalization of a large population of Mexican citizens, with roots in Sonora, Mexico, to the Union of the USA (Taylor, 2008). Salazar Solano (2007) found 1891 records that reported trading and exporting of mescal along the borders of Sonora with Arizona. Bacanora was probably the first Agave spirit with international demand in the US territory. In the last 100 years, the flux of immigrants throughout the borderlands has increased the demand for mescal. In the borderlands with Arizona, the ‘nostalgic market’, driven by the preference of Sonoran immigrants for bacanora (Salazar Solano and Mungaray Lagarda, 2009), has increased the international demand for bacanora in the USA.

The history, value and ecology of bacanora in the borderlands have attracted the attention of Arizonans, particularly to research the potential for sustainable commercial production and conservation of Agave in the USA (McDaniel, 1985; Davis et al., 2017). Current international cooperation across the borderlands includes conservation efforts by the University of Arizona Borderlands Restoration Network, the Fondo para el Bacanora para el Desarrollo Sostenible (FOBADES) and the Instituto Nacional de Investigaciones Agrícolas, Forestales y Pecuarias (INIFAP) in Sonora, Centro de Investigación en Alimentos y Desarrollo (CIAD). All these organizations have played a crucial role in studying ecological and sustainable strategies, with input from small farmers, which benefit the bacanora industry and wild Agave populations in Sonora and borderlands with Arizona (Fig. 4). Such cooperation is essential for a new mescal industry with less environmental impact. In the last 10 years, a new bacanora culture, with women leading the industry, has positioned bacanora as a competitor with the highest standard spirits in the European Union (Domínguez-Arista, 2020).

Fig. 4.

Commercial plantation for bacanora with agroforestry and conservation of Agave angustifolia populations supported by FOBADES and the Borderlands Restoration Network in Sonora, Mexico (sign pictured on the left). Dr Hector Ortiz-Cano (right) and Daniel Moroyoqui (centre and right) are pictured at the Javier Figueroa plantation in Alamos, Sonora, Mexico.

REVIEW OF RECENT FIELD TRIALS OF AGAVE OUTSIDE THE HISTORICAL RANGE

Although there are many current examples of Agave species in agricultural production in Central and South America and in subtropical–tropical climates in Africa and Southeast Asia, there have also been recent studies to test the feasibility of Agave for agriculture outside the typical commercial range, in North America (Davis et al., 2017) and Australia (Holtum et al., 2011). A field experiment in Maricopa, Arizona (at latitude 33°N) indicated that A. americana was more tolerant of the occasional cold temperatures during winter months than both A. tequilana and A. fourcroydes (Davis et al., 2017). The yields of A. americana were limited by a specialized pest, Scyphophorus acupunctatus (agave snout weevil), but reached 9.3 dry Mg ha⁻¹ year⁻¹, even with the pest, because the weevil attacks only plants that reach a certain size (Davis et al., 2017). Agave americana also demonstrated tolerance of arid conditions at the site, persisting with as little as 300 mm of annual water input. In Australia, at a site near Ayr, Queensland (latitude 20°S), where annual precipitation is greater (947 mm) and winters are milder, A. tequilana Weber var. azul was very productive outside its home range (Yan et al., 2020). Yields of 7.2–21.6 dry Mg ha⁻¹ year⁻¹ were reported at the site after 5 years, with nearly half of the biomass composed of sugar (Yan et al., 2020).

Although the history of agricultural production in Mexico and South America reveals the importance of Agave species for human use, recent studies indicate that a much wider range is possible. In addition to the field trials described above in the USA and Australia, model projections indicate that Agave production could extend far beyond its current range (Owen et al., 2016; Davis et al., 2021). The growing range of A. tequilana is projected to expand with climate change, as warmer temperatures reduce the susceptibility to cold at higher latitudes (Owen et al., 2016). The northern latitudinal range of A. americana is already greater than that of A. tequilana, but projections with climate change indicate that the range can extend even further north (Davis et al., 2021).

Although the temperature tolerances for these species are remarkable owing to CAM (Nobel, 1996, Nobel et al., 1998; Davis et al., 2022), the drought tolerance of Agave species is perhaps even more important for climate adaptation in agricultural landscapes (Davis et al., 2014, 2022). Where yields of current commodity crops are expected to decline (Bezner Kerr et al., 2022), Agave species might thrive in the future. Agave has the potential to produce the same amount of fibre that cotton crops yield, with less than a tenth of the water requirement (Davis et al., 2021). The theoretical yield of a CAM crop in drought conditions is 2.5 times greater than that of a C₄ crop and 4.5 times greater than that of a C₃ crop (Borland et al., 2009; Davis et al., 2014). The high concentration of soluble carbohydrates remains consistent in Agave biomass in conditions with and without drought (Jones et al., 2020), suggesting that it can be a reliable source of calories, sweetener or bioethanol.

PROJECTIONS FOR THE FUTURE, WITH CLIMATE CHANGE AND DIVERSIFICATION

The historic Paris Agreement achieved during the 21st Conference of Parties (COP21), organized as part of the United Nations Framework Convention on Climate Change, led to unprecedented commitments from the global community to address greenhouse gas emissions, but the COP27 in Egypt in November 2022 revealed that the world is not on target to limit warming in the atmosphere of the Earth. The reality, even with renewed and improved commitments, is that climate change will continue in the near future. Warming of ≥2 °C is likely, and it is essential to start evaluating the resilience of agricultural crops that provide essential resources. Productivity levels of many crops are decreasing because of climate change (Bezner Kerr et al., 2022).

Recent model projections of potential production indicate that A. americana has the potential to expand in geographical range with climate change and could yield greater biomass, sugar and fibre even with +4 °C warming (Davis et al., 2021). The CAM traits allow this species to thrive even with severe drought events and extreme temperatures. Agave americana tolerates temperatures ≤63 °C (Nobel and Smith, 1983) and, with as little as 300 mm annual precipitation, can achieve greater yields than a soybean field with prime soils and ample rainfall (Davis, 2022). CAM plants, such as A. americana, offer viability and resilience in a warmer world, thereby supporting climate adaptation.

Although they are not considered key commodity crops today, traditional uses of Agave might teach us something about their associated ecosystem services (Nabhan, 2013). In an analysis of mission records and agricultural biodiversity on the Baja Peninsula in Mexico, Agave species were discovered to have persisted over the last three centuries in small farming sites that span the latitudinal range of the peninsula (De Grenade and Nabhan, 2016). These sites have average annual precipitation ranging from 97 to 308 mm, with average annual maximum temperatures of ≤47 °C (De Grenade and Nabhan, 2016). Agave species were planted as one of the perennial food crops on small farms in these sites between 1697 and 1768, and they were found persisting in the same locations recently (De Grenade and Nabhan, 2016). This is supporting evidence of the potential for Agave species to serve climate adaptation goals for agriculture.

TRADITIONAL KNOWLEDGE FOR FUTURE REGENERATIVE AGRICULTURE

Dryland farming systems enabled Pre-Columbian farmers to cultivate Agave in the driest regions of North America (Fish et al., 1985; Mikulska, 2001; Garcia-Moya et al., 2011; Fish and Fish, 2014; Trombold, 2017; Nabhan et al., 2020). Water catchment techniques on slopes, rock mulching, rock alignments, terraces, nurse plants and intercropping are among the strategies used to cultivate Agave (Homburg and Sandor, 2011; Fish and Fish, 2014; Ortiz-Cano et al., 2020). Records from the 16th and 17th centuries, in the Codex Florentino, illustrate cultivation of Agave by Indigenous farmers in late phases of Mesoamerica and the early Spanish colonial period in Mexico (Ortiz et al., 2020). Colunga-GarcíaMarín et al. (2007) and Gentry (1982) suggested that the first cultivated commercial Agave plantations were established at the end of the 17th century. Modern Agave cultivation derives from ancestral agricultural practices (Ortiz-Cano et al., 2020). Early pre-Columbian farmers observed the drought tolerance, monocarpic habit, biomass accumulation, sugar accumulation after floral stalk emasculation, sexual and asexual reproduction, and the productive potential of Agave species in the mosaic of climates across Mesoamerica and Aridamerica, which are now regions of Mexico and the southwestern USA (Adams and Adams, 1998; Cervantes Mendívil et al., 2007; Nabhan et al., 2020).

Ancestral dryland farmers understood the topography, soil fertility, rainfall water management, suitable crops and climate for dry regions (Fish and Fish, 1992, 2014; Ortiz-Cano et al., 2020). Groups such as the Toltecas, Mexicas, Chalchihuites and the Hohokam made marginal lands productive by cultivating Agave (Mikulska, 2001; Fish and Fish, 2014; Trombold, 2017). Mikulska (2001) suggested that farmers from central Mexico in the Huaxteca region used microregions to adapt their agricultural strategies. Dry regions or marginal lands, with ≤500 mm precipitation, were used to cultivate corn and Agave, whereas areas with 2500 mm of precipitation and with annual evapotranspiration of 1000 mm were considered humid, and upper mountain higher elevation areas were cold regions. Likewise, farmers from the Sonoran Desert identified zones in mesic environments for Agave cultivation at the Tucson and Phoenix basin (Homburg and Sandor, 2011; Fish and Fish, 2014). In the current climate, ancestral dryland farming knowledge and its legacies in the landscape offer alternatives for developing sustainable agricultural strategies to cultivate Agave, integrating suitable species while reducing the irrigation water required with rising temperatures and droughts (Ortiz-Cano et al., 2020; Davis et al., 2022).

Cultivation of Agave has evolved from a subsistence farming strategy to an industrial crop, highly specialized and with a sophisticated monoculture scheme (Borland et al., 2011; Davis et al., 2011; Garcia-Moya et al., 2011; Cushman et al., 2015). Drought tolerance, CAM metabolism and broad genetic diversity of Agave enable species to adapt to unpredictable rainfall conditions in the driest regions of North America and offer an alternative crop with potential to adapt to future warming and drought conditions (Davis et al., 2022). However, accelerated agro-industrial development and inflated demand of Agave subproducts threaten Agave ecosystems and biodiversity (Stewart et al., 2015). Regions such as the borderlands of Mexico and the south-western USA play an important role for the future of Agave as a crop (Borland et al., 2011; Lewis et al., 2015). The abundant legacies of ancestral traditional ecological knowledge and cultural connection with Agave as a crop open opportunities for direct application of regenerative agriculture strategies for cultivating Agave and for conservation of biodiversity in the region (Levin, 2022). For example, Agave silvopastoral systems, in combination with tissue culture to mass produce plants, have shown potential for conservation efforts of A. angustifolia in the current drought and climate in Sonora, Mexico (Cervantes Mendívil et al., 2007; Sánchez et al., 2020). Likewise, Agave agroforestry and traditional ecological knowledge could revitalize small rural economies and, alternatively, create sustainable management strategies to preserve fragile Agave ecosystems (Torres-García et al., 2019).

AGAVE DEVELOPMENT FOR THE FUTURE

When evaluating the potential for Agave production in the future, it might be useful to consider the historical development of a commercial cropping system with similar ancestral roots. Today, corn (Zea mays) is the most widely produced cereal crop in the world, but its agricultural origins date back to pre-Columbian times (García-Lara and Serna-Saldivar, 2019), similar to Agave. Corn and Agave originate from similar geographical regions, and there are 64 races of corn associated with Mexico (García-Lara and Serna-Saldivar, 2019). In the near future, the environmental change associated with climate might require diversification of crops and the adoption of more climate-resilient alternatives, such as Agave. Just as the traditional knowledge of corn guided agricultural development in North America over the last two centuries, there is a legacy of traditional knowledge around Agave that can provide a foundation for developing climate-resilient agriculture in the region.

Agave species might have more diversified uses than corn, but they can also be a source of animal feed, food, sweeteners and biofuel (the primary products made from corn). The cultural legacy of Agave provides traditional knowledge about benefits of these CAM plants that can support human health in a changing climate. Despite the tremendous historical success of corn as an agricultural product, yields are expected to decline in some regions as climate change continues (Bezner Kerr et al., 2022). Cultural histories of the Americas identify corn as an important subsistence crop in the borderland region of Sonoran Arizona and Mexico (Katz et al., 1974). Agave species were equally important in this region, although more concentrated in the southerly portion of the Sonoran Desert (Gentry, 1982). With atmospheric warming and increasing intensity of drought in this region, the northern range for some Agave species will likely expand (Davis et al., 2021, 2022) and can, potentially, offset losses of other cropping systems in the northern Sonoran Desert region.

New work revitalizing traditional knowledge of regenerative agricultural practices indicates that A. angustifolia and similar relatives (A. americana, A. lechuguilla, etc.) can thrive in agroforestry systems or with specialized soil amendments. Intercropping Agave and mesquite trees, for example, allows trees to help maintain the soil moisture balance with deep-rooted systems that can draw water to the soil surface and canopy shading that prevents soil evaporative losses (Nabhan et al., 2020; Fig. 4). This strategy provides resilient crop production in times of extreme drought, while also fostering a carbon mitigation strategy (Lehner and Rosenberg, 2017). Rock mulching can also be used to retain soil moisture, as described in the previous section, and is another traditional practice that was recently described in sites in the borderland region of the southwestern USA (Fish et al., 1985; Ortiz-Cano et al., 2020). Rock mulch reduces the evaporative losses from soil, making more water available for plant growth (e.g. Diaz et al., 2005).

Traditional knowledge can inform both land management and nutritional opportunities associated with ancient crops. After centuries of agricultural development in the USA, it was discovered that ancient and traditional processing of corn with alkali results in increased nutritional value of corn-based products (Katz et al., 1974). A review of traditional practices for managing and processing Agave reveals that there are health benefits of these plants that are under-realized (Davis et al., 2019). Agave species have been identified as having anti-inflammatory and anti-carcinogenic properties (Colunga-GarcíaMarín and May-Pat, 1993; Yokosuka et al., 2000; Jin et al., 2004; Hackman et al., 2006; Garcia-Morales et al. 2022). Traditional methods of roasting the plants in earthen pits might contribute to the beneficial health properties of fermented products. Even without fermentation, traditionally roasted leaves of A. americana have nutritional value owing to the greater protein and increased digestibility of other nutrients (Laferriere et al., 1991) after roasting. Agave plants can also be a substantial source of calcium and iron (Laferriere et al., 1991).

CONCLUSION

Crassulacean acid metabolism is expressed prominently in the Agave genus, and the traits associated with this physiological condition allow for many products valued by people, e.g. sugar, medicine, fibre and food. The sugar, medicinal compounds and vitamins beneficial for humans are made possible by the storage of soluble carbohydrates and secondary compounds in the large vacuoles of these succulent plants. The large vacuoles allow for 24 h carbon cycling that is fundamental for CAM plants. Leaf structures associated with succulent CAM plants are adapted to maintain rigidity and turgor pressure in extreme drought and heat. The water-use efficiency associated with CAM is made possible by both water storage and hydraulic isolation of the plants, requiring strong but flexible fibres to support the mass of water inside the plant, while preventing contact between the plant tissue and the soil. The long cellulosic fibres that support this leaf structure are desirable for weaving textiles and ropes.

The concentrated sugars in the plant tissues of Agave plants are also valuable for fermented beverages and spirits. Although the profitability of Agave spirits has led to investment in agricultural production of A. tequilana and A. angustifolia that is internationally acknowledged (tequila and bacanora), other potentially valuable products generated from the many known species of Agave are less recognized. The Appellation of Origin now protects six different mescals from exploitation in non-native regions, but further agricultural development of Agave in the borderlands for food, sugar, fibre and medicine has promise. The political, ecological and agronomic history of Agave in the region suggests that there is great potential for this group of CAM plants to provide climate-resilient agricultural resources. The water-use efficiency, drought tolerance and heat tolerance made possible by CAM physiology have allowed Agave species to provision humans for thousands of years, and these traits continue to hold promise for a future with changing climate.