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Current Perspectives on the Economic Botany of the Genus Aloe L. (Xanthorrhoeaceae) ⁎ O.M

Current Perspectives on the Economic Botany of the Genus Aloe L. (Xanthorrhoeaceae) ⁎ O.M

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South African Journal of 77 (2011) 980–987 www.elsevier.com/locate/sajb

Current perspectives on the economic botany of the genus L. (Xanthorrhoeaceae) ⁎ O.M. Grace

Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey TW9 3AB, United Kingdom Department of Botany, Natural History Museum of Denmark, Sølvgade 83, Copenhagen 1307, Denmark

Abstract

Aloe L. (Xanthorrhoeaceae) is a genus of over 500 species found on the African continent, Arabian Peninsula, Madagascar and eastern Indian Ocean Islands. It is valued by people at many economic scales but verifiable data, with which to quantify the role of Aloe in local livelihoods and commercial trade, are scarce. For a speciose genus of appreciable ethnological value, few taxa have been known in formal and international trade. mesophyll and exudate from certain Aloe species support sizeable commercial industries that differ markedly in geographical focus, supply chain and taxa used. Leaf mesophyll is primarily sourced from plantations of the well-known A. vera in Mexico, the United States and parts of South America, and is generally used in products made in the same region. By contrast, leaf exudate is principally wild-harvested from A. ferox in and A. secundiflora in Kenya for export to Europe and Asia. To a much lesser extent, Aloe spp. are used commercially in foods and to produce honey. It is unclear to what degree Aloe spp. are traded as medicinal for traditional use throughout their range. Their popularity in as decorative and/or collectable ornamentals sustains a considerable international trade. Besides habitat loss, wild populationsof many species of Aloe are threatened by exploitation for the succulent trade and a few species by over-utilisation for natural products, making rare, endemic and utility taxa an obvious priority for conservation. With the exception of , all species of Aloe are protected by the Convention on International Trade in Endangered Species (CITES). There is, nevertheless, considerable potential for commercially-valuable species of Aloe to be employed for rural development and poverty alleviation. The success of the expanded Aloe-based industries will depend on sustainable harvesting and other practices compliant with the Convention on Biological Diversity. © 2011 SAAB. Published by Elsevier B.V. All rights reserved.

Keywords: Aloe; Conservation; Exudate; Horticulture; Mesophyll; Natural products; Ornamental; Sustainable use; Trade

1. Introduction “big” genera of more than 500 species (Frodin, 2004), fully comprehensive studies of the and biology of Aloe are The leaf-succulent genus Aloe L. (Xanthorrhoeaceae) is a difficult and research to date has largely focused on geographical familiar floristic element throughout its distribution in Africa, the or taxonomic subsets. The genus is represented in several Arabian Peninsula, Madagascar and the eastern Indian Ocean biodiversity hotspots, including the Horn of Africa, Madagascar Islands (Reynolds, 1950) and, as such, inherently contributes to and Indian Ocean Islands, Maputaland-Pondoland-Albany, Cape regional biocultural diversity (Cocks, 2006). Aloe comprises over Floristic Region and Succulent Karoo (Mittermeier et al., 2004; 500 species, ranging from diminutive to large -like Myers et al., 2000) and includes many taxa that are naturally rare forms, with new taxa still being described regularly. Like other and geographically restricted (Oldfield, 2004). Besides habitat loss and other threats to biodiversity in general, specific concerns have been raised for certain Aloe species due to exploitation for ⁎ Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey TW9 3AB, United the trade and natural products industry. Aloe Kingdom. presents a textbook conservation challenge, requiring the E-mail address: [email protected]. protection of taxa that are rare, endemic and/or exploited, and

0254-6299/$ - see front matter © 2011 SAAB. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.sajb.2011.07.002 O.M. Grace / South African Journal Of Botany 77 (2011) 980–987) 981 management to ensure their availability as natural resources BCE (Morton, 1961), and resulted in the species' movement important in livelihood security. along trade routes from the Arabian Peninsula to the Numerical values of “worth” can be persuasive in the Mediterranean, Indian subcontinent, Americas and Caribbean, argument for species-level conservation. Quantifying the biocul- where it has become naturalised. Dried leaf exudate prepara- tural value of individual taxa, however, is difficult, since folk uses tions from a small number of other species have been known in and cultural significance rarely attract a monetary value, although formal trade since the late sixteenth century. These include A. the benefits to wellbeing and livelihood security may be obvious. perryi Baker on Socotra, A. arborescens Mill. and A. ferox in On the other hand, quantitative data, describing the volume and South Africa, and records of uncertain validity for A. africana market value of plants and plant-derived products passing through Mill. and A. marlothii A.Berger,alsoinSouthAfrica trade channels, are useful for understanding the economic value of (Reynolds, 1950; Hodge, 1953; Bruce, 1975; Smith et al., plants, if not their cultural significance. A variety of indicators 2008). Explanations for the few Aloe spp. entering international attest to the cultural and economic value of Aloe,suchasthe trade may lie in the selection of taxa with desirable medicinal numerous vernacular names and uses recorded for the genus properties as much as abundant supply and the proximity of (Grace et al., 2008, 2009, 2011). A recent search for “aloe” on plant populations to transport hubs and ports. The leaf Google.com returned no fewer than 30.8 million results, mesophyll and exudate of Aloe spp. probably share an equally compared with 206000 for neighbouring genus (search long use history, yet the mesophyll has been known only in term “gasteria”) and 88600 for (“xanthorrhoea”), contemporary trade. This may have begun in the 1920s with a both of which are also popular horticultural subjects. The single producer in the United States distributing fresh leaf contemporary value of Aloe has been preceded by many centuries mesophyll from farmed A. vera by mail (Morton, 1961). of people–plant relationships. It is one of the few identifiable Commercial interest in the leaf mesophyll emerged in the 1930s plant taxa depicted in the rock art of the southern African San in the United States (Grindlay and Reynolds, 1986) and people (Reynolds, 1950) and at least one species, A. vera (L.) expanded as technologies were developed to process and Burm.f., has been traded between the Arabian Peninsula and prolong the shelf-life of the . Today, the use of leaf Mediterranean for at least two thousand years (Morton, 1961). exudate is waning in the United States and Europe due to The of Aloe is described in a considerable body of concerns for safety (Jellin and Gregory, 2009). In contrast, there literature, analysis of which suggests most species are valued in appears to be an increasing demand for the leaf mesophyll as an some way and used on a local scale (Grace et al., 2008, 2009). ingredient in a broad range of manufactured products such as For a speciose genus of appreciable ethnological value, patent remedies, foods and food supplements, toiletries, beauty surprisingly few species of Aloe have been known in formal products and household commodities. trade. The market profiles of species such as A. ferox Mill. and A. The industries based on Aloe leaf exudate and mesophyll differ vera appear to be expanding, yet the trade in aloe-derived markedly in geographical focus, supply chain and species used. products remains poorly understood and relevant information Leaf exudate is principally wild-harvested from populations of A. unavailable. This paper reviews the economic botany of the genus ferox on communal or privately-owned land in South Africa and, Aloe and its role in livelihood security. In keeping with the theme in East Africa, wild-harvested or cultivated A. marsabitensis of this issue, the discussion is focused on South Africa, one of the Verdoorn & Christian, A. ngongnensis Christian, A. rabaiensis centres of diversity in the genus with over 120 species (Glen and Rendle, A. secundiflora Engl. and A. scabrifolia Newton & Hardy, 2000). Information from the literature is combined with Lavranos (sometimes confused with A. turkanensis Christian anecdotal evidence of the contemporary economic uses and trade (Newton, 1994)). The main importers of leaf exudate are countries in Aloe spp., highlighting their importance across a range of socio- in Europe and Asia (Melin, 2009; Newton, 1994; Newton and economic scales. Conservation concerns and the potential for Vaughan, 1996; Oldfield, 2004). In contrast, leaf mesophyll is to support sustainable industries compliant with the primarily sourced from plantations of A. vera located in Mexico, Convention on Biological Diversity, are considered. the United States and several South American countries, and is generally traded in semi-processed forms within the same region 2. Aloes in trade (International Aloe Science Council, 2011). Mill. is cultivated on a lesser scale in Asia, South America and 2.1. Natural products Italy for both leaf exudate and mesophyll (Bosch, 2006a). This species is also wild-harvested in South Africa for export, notably The commercial trade in Aloe-derived natural products is to Japan, where the species is a popular medicinal plant (Newton based mainly on two materials obtained from the of and Chan, 1998; Smith et al., 2008). Leaf mesophyll from certain Aloe species: leaf exudate, used in laxatives, and leaf predominantly wild-harvested A. ferox in South Africa (Newton mesophyll, used in products applied topically for skin ailments and Vaughan, 1996), A. macroclada Baker in Madagascar (S. or taken internally for digestive complaints and general Rakotoarisoa, pers. comm.) and several species in Tanzania wellbeing. The remarkable history of aloes in commerce has (Sachedina and Bodeker, 1999) are used in expanding local been documented in a substantial and varied body of literature industries that seem to mirror the use of A. vera in cosmetics, (see, for example, Morton, 1961) and warrants only a brief toiletries and non-scheduled remedies. It is conceivable that other account here. The formal trade in leaf exudate of at least one species of Aloe enter the trade on a limited scale from time to time. species, A. vera, has been recorded since the fourth century Phytochemical characterisation of the leaf mesophyll of A. 982 O.M. Grace / South African Journal Of Botany 77 (2011) 980–987) davyana Schönland (= A. greatheadii var. davyana (Schönland) At that time, collectors in some rural villages were reportedly paid Glen & D.S.Hardy) (Botes et al., 2008b)suggeststhisspecies KSh 20 (about R5.50 or US$0.8) per litre of exudate which may may be targeted for commercial development in South Africa. have taken several days to gather (L. Newton, pers. comm.). In Although the genus has been the subject of numerous South Africa, the rural industry supported by wild-harvested A. phytochemical studies (Reynolds, 1985, 2004; Dagne et al., ferox was estimated to be worth R4 million (US$569000) per 2000), differences between the species in commercial trade are annum in the late 1990s (Newton and Vaughan, 1996), projected not clearly documented and a comparative study of these would to R15 million (NUS$2 million) per annum a decade later be useful to highlight potential in the trade. (Shackleton and Gambiza, 2007). Estimates of the larger Besides the use of synonyms in the literature, notably A. industry-taking into account the retail chain-have varied widely barbadensis Mill. for A. vera, a multitude of descriptive terms and from R150 million per annum (US$20 million) to US$90 million names are applied to Aloe-derived products. Alternative terms per annum (NR600 million) (Shackleton and Gambiza, 2007). The commonly used for the leaf exudate include , juice or latex. The industry yields some 400 tonnes of dried leaf exudate per annum, exudate arises from enlarged inner bundle sheath parenchyma of which the bulk is exported (the major importers being Germany, cells and is released as a wounding response (Beaumont et al., Japan and Argentina), and the remainder used in non-scheduled 1985; Liao et al., 2006). The dried product prepared from boiled medicines or placed in stored reserves (Newton and Vaughan, leaf exudate, sometimes incorrectly termed resin or extract, is 1996). Production is necessarily confined to the species' natural variously known as drug-, bitter-, crystalline- or powdered aloes, distribution in the Western and Eastern Cape Provinces; it was aloe lump or -brick. Trade names for leaf exudate preparations historically centred in small towns east of Cape Town and were historically intended to indicate the provenance (and, extended to the Karoo and Eastern Cape Province, where it has therefore, superior quality) of the product, such as “Cape aloes” recently become the subject of rural development initiatives prepared from A. ferox. The convention was frequently misapplied (Melin, 2009; Newton and Vaughan, 1996). However, opportu- and resulted in much confusion (see Hodge (1953) and Robertson nities are unclear for African producers (particularly of leaf (1979)). Nevertheless, the practice has persisted; for example, mesophyll) to compete on global markets, which have been “Mossel Bay prime aloe” exported from South Africa does not criticised for their impenetrability due to the influence of major necessarily contain leaf exudate collected from plants at Mossel producers in the United States (Sachedina and Bodeker, 1999). Bay (Newton and Vaughan, 1996). Terminology referring to the The socio-economic benefits of the A. ferox industry in South leaf mesophyll, commonly known as aloe gel, fillet or pulp, is less Africa are spread widely (Newton and Vaughan, 1996), from the complex, reflecting the relatively recent and largely industrial poorest people whose only source of income is derived from Aloe market for it. Processed derivatives of the leaf mesophyll are sold tapping, to itinerant agricultural workers and other part-time aloe under names such as gel fillet, concentrated- and crude gel, tappers, their families and communities. In the Western Cape, the decolourised- and/or pasteurised gel, freeze- or spray-dried potential annual income for a full-time tapper was estimated to be powdered gel (Waller et al., 2004). Similar products are made R10000 (US$1400) in 1992 but, due to a complex debt cycle and using whole leaves. Although it shares some of the characteristics lack of empowerment, this was seldom, if ever, realised (Newton of , such as high polysaccharide content, the leaf and Vaughan, 1996). In towns central to the A. ferox industry, leaf mesophyll is a tissue rather than secretory product (Beaumont exudate has been used as a currency for obtaining credit and et al., 1985). offsetting debt in local stores, or to purchase food (Newton and TheglobalmarketforA. vera, the major source of leaf Vaughan, 1996). Historical records show that the trade in leaf mesophyll, was reportedly worth US$125 million in 2004 exudate from Aloe spp. is characteristically vulnerable to (R878 million, using exchange rates at the time of writing of fluctuations in demand, driven by export markets and economic R7 to the dollar) with a projected growth margin of 35% per conditions, and in supply, influenced by factors such as annum (Bosch, 2006c) and, hence, US$300 million (R2, and plant pests, despite the storability of dried exudate preparation 1 billion) today. Statistics given by the International Aloe Science (Newton and Vaughan, 1996; Robertson, 1979; Sachedina and Council (2011) indicate that some 24000 ha of A. vera are Bodeker, 1999). Factories extracting leaf exudate and mesophyll cultivated globally, with 300 ha in Africa which may include from wild-harvested A. ferox, which employ a limited workforce plantations in Nigeria supplying local markets (Bosch, 2006c). of skilled and semi-skilled workers and operate year-round, have Despite the industrial interest in A. vera as a source of natural been seen to challenge the livelihood security of the majority of the products—described by Grindlay and Reynolds (1986) as the workforce (Newton and Vaughan, 1996). On the other hand, a “Aloe vera phenomenon”—authoritative data in the literature processing factory was central to the business model of an A. ferox describing the production volumes, trade figures and socio- cooperative established in the Eastern Cape in 2004 (Melin, 2009). economic benefits of the industry are scarce. The Aloe Tappers Association was established in South Africa in The significant economic impacts of wild-harvested Aloe, the 1980s (Newton and Vaughan, 1996)andtheKenyaAloe specifically in Kenya and South Africa, are clearer. The Aloe Working Group in the 1990s (L. Newton, pers. comm.) to promote exudate industry in Kenya is centred in Rift Valley Province and fair conditions for workers and sustainable harvesting. Imple- based upon five or more species used somewhat interchangeably mentation of national legislature compliant with the Convention (Oldfield, 2005). During the 1990s, exports of wild-harvested on Biological Diversity (CBD) (1992) is expected to serve the exudate from Kenya sometimes exceeded 80 tonnes per annum, interests of Aloe harvesters and other stakeholders, notably by the principal importers being China and Thailand (Oldfield, 2004). endorsing the rights to equitable benefits (see Section 3. O.M. Grace / South African Journal Of Botany 77 (2011) 980–987) 983

Sustainable use and conservation, below). Traditional medicinal monly known as gasteraloes and alworthias, respectively. A great uses of A. ferox in South Africa, transfer of knowledge to diversity of names have been published, many of which Europeans at the Cape of Good Hope, and the species' have been registered with the South African Aloe Breeders introduction to European materia medica in the 18th century, Association (Newton, 2004). have been documented in considerable detail (see Hodge, 1953 Not surprisingly, the most sought-after aloes among succulent and references therein). Traditional exudate harvesting and collectors include rare, morphologically distinctive and difficult preparation methods continue to be practised with few contem- to grow taxa, and desirability is reflected in the price of living porary adjustments, and have been comprehensively recorded by, plants in trade. Prized taxa include the rare Lesotho endemic A. among others, Hodge (1953), Newton and Vaughan (1996), polyphylla Schönland ex Pillans, tree aloes such as the Western Sachedina and Bodeker (1999), Shackleton and Gambiza (2007) Cape endemic A. plicatilis (L.) Mill., and the charming A. and Melin (2009). The comprehensive literature would, therefore, haemanthifolia A.Berger & Marloth (J. Bertelsen, pers. comm.). be useful in identifying the holders of intellectual property relevant The latter are favoured for their atypical distichous and barely- to the A. ferox industry. succulent leaves with rounded apices. Aloe haemanthifolia is a has not been recorded in the wild beyond the particularly difficult subject in cultivation (Van Wyk and Smith, of region, but is likely to have been introduced 2005), and plantlets (ca. N10 cm in diameter) may retail for up to elsewhere (Bosch, 2006b). It is reportedly used as far afield as R650 (US$95). Newton and Chan (1998) recorded specimens Kinshasa (Democratic Republic of Congo): topical preparations sold for over R1 500 (NUS$200) in the 1990s. , for haemorrhoids and skin complaints containing the leaves are one of the best-known aloes, is appreciated for its distinctive spiral prepared and dispensed by at least one health centre in the city (P. phylotaxis and natural tolerance to frost and snow, which makes Latham, pers. comm.). Aloe spp. are traded in medicinal plant the species suitable for outdoor cultivation in the northern markets throughout Africa; whole plants of species such as A. hemisphere (Reynolds, 1950). The difficulty of maintaining A. aristata in South Africa and A. sinkatana in Sudan have been polyphylla in cultivation is evident in the difference in price noted to attract particularly high prices (Marshall, 1998). Other between young plants (ca. 10 cm in diameter, up to US$21 or species recorded in market surveys in South Africa include A. R140) and mature specimens (ca. 30 cm in diameter, US$100 or ferox, A. maculata, A. marlothii, A. micrantha and A. tenuior R680). The relatively low cost of immature plants of some Aloe (Dold and Cocks, 2001; Williams et al., 2001). About 60 species spp. is, furthermore, a reflection of abundant supply yielded by of Aloe have been recorded in traditional medicine in southern micropropagation, even if the species is threatened with extinction Africa (Grace et al., 2008) and it is likely that some of these may in the wild, such as A. boweia Schult. & Schult.f. and A. be sold for medicine, albeit infrequently. The lack of references to polyphylla (Newton and Chan, 1998). Tissue culture protocols local and small-scale trade in aloes, both historical and using a variety of explants have been published for A. arborescens contemporary, agrees with the general trend towards opportunis- (Kawai et al., 1993), A. calcairophila Reynolds (Sarasan et al., tic use of local species and poor market demands. A detailed study 2006), A. polyphylla (Ramsay and Gratton, 2000; Abrie and Van is necessary to more fully evaluate Aloe spp. in the medicinal plant Staden, 2001), A. pretoriensis Pole-Evans (Groenewald et al., trade and their contribution to livelihood security. 1975), and A. vera (e.g. Hashem and Kaviani, 2010,among others). The range of taxa available to purchase as plantlets would 2.2. Horticulture indicate, however, that in vitro multiplication techniques have been far more widely optimised for Aloe. Retail prices in the Aloes are both decorative and highly collectable. They have specialist trade are frequently considerably higher become common in the general horticultural trade servicing than those of commercial nurseries and private vendors selling gardeners and landscapers, particularly in the regions where the live Aloe plants in the markets and roadside nurseries of African genus occurs naturally, as well as the specialist ornamental plant towns and cities for decorative purposes. For instance, a single trade. The horticultural challenges presented by the morpholog- plantlet (ca. 5 cm in diameter) of the critically endangered tree ical and taxonomic diversity of the genus appeal to succulent plant aloe A. pillansii L.Guthrie, native to South Africa and Namibia, enthusiasts. Aloe features prominently among the subjects of was recently sold for more than US$150 (N R1000) at auction on succulent plant collectors' societies; indeed, a stylised short- Ebay.com, yet plantlets of similar size retail for a tenth of the stemmed Aloe (based on A. peglerae Schönland) appears in the amount in nurseries in South Africa. logo of the Succulent Society of South Africa, and the Society's Aloe spp. are immensely popular subjects for landscaping, journal is named for the genus. Although A. vera and perhaps a due to their characteristic architectural form and the diversity of few other species were already in cultivation, lesser-known aloes birds and insects attracted to the . Within their natural from the African continent entered the ornamental plant trade range, some large, single-stemmed species (e.g. A. africana when succulent plants became fashionable in Europe in the Mill.) are suitable for street plantings, as they have rather sixteenth century and seventeenth centuries (Pole-Evans, 1919; shallow systems and rarely drop leaves. The majority of Reynolds, 1950). Today, the major importers of living specimens Aloe spp. in winter, thus providing vibrant colour of Aloe spp. are Japan, the United States and United Kingdom displays in gardens and parks, as well as in their natural habitat, (Newton and Chan, 1998). Artificially-bred Aloe hybrids during the dry season. An early example of spectacular massed considerably expand the diversity of collectable taxa (De Wet, plantings of aloes was “the largest collection of South African 2004); Aloe×Gasteria and Aloe× crosses are com- Aloes [sic] in existence” established at the Union Buildings in 984 O.M. Grace / South African Journal Of Botany 77 (2011) 980–987)

1912 (Pole-Evans, 1919). However, the popularity of the genus On a commercial scale, at least one beekeeper in Kenya, near as a garden subject has waned at times, and one of the great Nairobi, produces quality honey from a locally abundant scholars of Aloe, G.W. Reynolds, was moved to endorse their species of Aloe (P. Latham, pers. comm.). use in rockery plantings (Reynolds, 1938). Aloe spp. are readily propagated and large numbers of plants can be amassed from 2.4. Food minimal stock. Nevertheless, it is important to note that artificial plantings are prone to infection and infestation unless carefully The literature includes references to several species of edible maintained (Smith and Van Wyk, 2008). In South Africa, this aloes, their uses including snack foods, famine foods, as a has proved particularly problematic in the ex situ conservation cooked vegetable and as an ingredient in preserves. It should be of Aloe specimens transplanted to gardens and public spaces noted that not all species of Aloe are edible: some contain toxic from areas earmarked for development. alkaloids (Dring et al., 1984) and certain species, including A. Besides representation in impressive private growers' vera, may cause adverse reactions (Steenkamp and Stewart, collections, living collections of aloes are maintained in 2007). The cultivated species A. arborescens and A. vera have publicly-accessible botanic gardens around the world. Expan- been used on a large scale in foodstuffs, especially in dairy sive collections are held, for instance, at the Städtische products such as yoghurt and ice cream, in Asia and the United Sukkulentensammlung Zürich (Municipal Succulent Plant States for some years. In South Africa, a perceptible increase in Collection) in Switzerland, the Huntington Botanical Gardens the variety of manufactured food products containing A. ferox, in the United States, the Royal Botanic Gardens, Kew in the such as confectionary and juice blends, apparently mirrors United Kingdom, and, in South Africa, the Karoo the global rise in popularity of A. vera leaf mesophyll in foods. National Botanic Garden. These collections serve the purposes The use of A. ferox leaves in commercially manufactured of providing repositories of genetic diversity for ex situ preserves and condiments follows a centuries-old tradition of conservation, and facilities for public engagement and educa- use in the Western Cape (Watt and Breyer-Brandwijk, 1962). tion. Collections of living plants are useful for research, allowing intensive study of a diversity of plants. The excellent 3. Sustainable use and conservation infrageneric classification of Aloe by A. Berger (1908), famously compiled without the author seeing a single plant in The ways in which aloes are used and valued have implications the field, was based on observations of specimens in the private for their conservation and future utility. Specific threats affecting collection of Sir Thomas Hanbury in Italy (Pole-Evans, 1919)as individual species are not well understood, but general trends are well as of material. G.W. Reynolds' use of Berger's apparent across the genus. The threats and conservation status of (1908) classification as the basis for his treatments (Reynolds, Aloe spp. in South Africa are probably the most well studied (e.g. 1950, 1966), which were based on extensive travels to collect Smith et al., 2000; Van Jaarsveld and Smith, 1997). Full Red List and observe aloes in habitat, is a testament to its quality. More assessments have been made of 43 species of Aloe (N7%) (IUCN, recently, phylogenetic studies of Aloe using DNA-based 2011), from which it is clear that the prevailing threat to the genus characters (Treutlein et al., 2003; O. M. Grace unpublished is habitat loss caused by anthropogenic factors, notably land use data) have indicated that elements in the existing classification change (e.g. agriculture, mining, urban expansion), clearance of are artificial. A future revision, taking molecular characters into vegetation for energy needs, overgrazing/trampling by livestock, account, will be necessary to accommodate the expanding and erosion. Collecting for the ornamental plant trade affects species diversity and infrageneric concepts in the genus. many more species of Aloe than wild-harvesting for natural products or traditional uses. Rare, endemic and utility taxa are the 2.3. Bee plants target of such activities and are, therefore, priorities for conservation. Aloes are well-known bee plants in Africa. Species in flower All species of Aloe are protected by the Convention on during the dry season afford an important source of for International Trade in Endangered Species (CITES), with the honey bees (Apis mellifera) and nectariferous birds (Bornman exception of A. vera. It was removed from the CITES Appendices and Hardy, 1971; Botes et al., 2008a, 2008b; Symes et al., in 1985, to reflect the species being widely cultivated (Oldfield, 2008). In South Africa, A. davyana is the most highly regarded: 1992 cited in Newton and Vaughan, 1996) despite possibly being extensive flowering stands of the species on the outskirts of extinct in the wild. The species originates from the Arabian Pretoria are used seasonally by beekeepers, who move their Peninsula but there are no records of the species being seen in its hives to these so-called “aloe fields” in order to build up natural habitat recently. Twenty-one species of Aloe threatened by colonies, rear queens and increase colony numbers, as well as extinction are listed on CITES Appendix I, prohibiting all for winter honey production (Human and Nicholson, 2006). international trade for commercial purposes (CITES, 2011). The Honey produced by bees foraging on A. davyana is pale in remainder are listed on Appendix II, to control the trade in species colour and free from any after-taste, except for with a slight hint of conservation concern and so-called “look-alike” taxa (CITES, of smokiness (Glen and Hardy, 2000). It is not clear from the 2011). This is typical of large, collectable and/or taxonomically literature whether hives supported by Aloe spp. are kept only for complex groups; succulent examples include subsistence, but it is likely that beekeepers may, at times, derive (), () and, at the family income from surplus honey and comb produced by their hives. level, Cactaceae. The case of Aloe was highlighted in a recent O.M. Grace / South African Journal Of Botany 77 (2011) 980–987) 985 evaluation of A. arborescens: although not currently threatened changes still required of the industry. South Africa is among a by the export of wild-harvested material from South Africa small proportion of CBD member countries to have ratified the (described by Newton and Chan, 1998), the species' removal agreement in national law (Crouch et al., 2008) and de- from CITES Appendices would raise conservation issues for velopments in the A. ferox industry will undoubtedly be relevant numerous species sometimes misidentified as A. arborescens to emerging Aloe-based industries elsewhere in the range of (Smith et al., 2008). An evaluation of A. ferox,includedin Aloe spp. Appendix II, has been recommended in light of increasing exports In Kenya, protocols for sustainable wild-harvesting on a of the leaf exudate (Melin, 2009). The level of national protection commercial scale, known as Aloe Management Units, have afforded to the genus varies widely, but permits are required for been developed for A. calidophila Reynolds, A. rivae Baker, A. collecting, research and commercial harvesting in most countries scabrifolia and A. secundiflora but have yet to be fully where Aloe spp. occur. In South Africa, illegal trade in Aloe spp. is implemented (Wabuyele and Kyalo, 2008). East African taxa relatively well characterized but almost impossible to quantify, identified as most suitable for the natural products industry and and necessitates closer trade controls (Newton and Chan, 1998). large-scale propagation include A. macrosiphon Baker and A. Effective policy is crucial to support conservation and ukambensis Reynolds (Newton, 1994). Wild-harvesting of Aloe optimise the use of natural resources. In the case of Aloe spp., spp. is illegal and therefore not reflected in export statistics for sustainable exploitation depends heavily upon the stakeholders Kenya, but is known to support a considerable trade in the leaf in the horticultural and natural products industries. The exudate; A. secundiflora, A. scabrifolia and possibly A. expansion of markets for Aloe products has obvious and turkanensis (a possible misidentification of A. scabrifolia compelling socio-economic potential and may also benefit in (Newton, 1994)) are of particular concern (Oldfield, 2004). situ conservation. One example of the positive effects of Given the volume of plant material involved in the trade, there commercial exploitation is the Kenya Aloe Working Group, are legitimate concerns regarding the sustainability of harvest- which aims to conserve natural populations of Aloe spp. by ing rates and species-specific impacts. The leaves of six to ten A. promoting the cultivation of species used for leaf exudate and ferox plants (with an average of 24 leaves each) are required to mesophyll for livelihood security, in areas of low or erratic obtain one litre of leaf exudate (Melin, 2009), and up to two tons rainfall, where growing conventional food crops is uncertain (L. of fresh leaves are required to yield a kilogram of powdered A. Newton, pers. comm.). It brings together stakeholders through- ferox gel (Newton and Vaughan, 1996). Risks of misidentifica- out the supply chain, and uses secure export markets as tion or substitution of A. ferox with related species are low incentives for nurserymen, farmers, and manufacturers to use (Newton and Vaughan, 1996) but are greater in East Africa propagated A. secundiflora and A. turkanensis as a profitable where several species are used, and the possibility of alternative to illegally wild-harvested material. Farmers who misidentification represents a significant threat to taxa with a can show that their plantations were established with Aloe restricted range (Oldfield, 2004). This would be of great seedlings from an approved nursery are able to register with the concern should wild-harvested A. davyana, a representative of national CITES authority – the Kenya Wildlife Service – to the taxonomically unresolved maculate species complex (Grace legally export their products. The export of semi-processed et al., 2009), become a source of commercial leaf mesophyll materials and products, rather than raw materials, is encouraged and/or exudate (Botes et al., 2008b). In general, traditional to promote local employment opportunities and avoid re- harvesting practices rarely result in plant death (Melin, 2009; importing the material in processed form at a later stage. For Newton and Vaughan, 1996), and damage to plant populations instance, in Province, A. rabaiensis is used for making is more likely to be the consequence of poor land management, soap, skin cream and other products for local markets (L. fire and pests. However, higher harvesting rates have been Newton, pers. comm.). In South Africa, the A. ferox industry is observed in regions where the traditional method of leaf exudate among the local bioresource industries covered by recent collection is not customarily practised and where plants are legislative developments in , access and benefit- wild-harvested from communal lands (Melin, 2009). sharing regulations within the National Environmental Man- Specialist succulent collectors have an important role to play agement Biodiversity Act (NEMBA). The new legal framework in the sustainable future of Aloe spp., not least in the ex situ aligns national laws with international agreements such as the conservation of species diversity and influence over market CBD and CITES (Crouch et al., 2008), with potentially positive trends. Conservation is a key objective of succulent plant outcomes for stakeholders at all levels in the A. ferox industry collectors' societies, such as the International Organization for by, for instance, protecting the holders of traditional knowledge, Succulent Plant Study, and Succulent Society of the equitable distribution of benefits, sustainable resource America, British Cactus and Succulent Society and, locally, management, and best practice in processing. Practical the Succulent Society of South Africa. These interest groups shortfalls in the implementation of the new legislature (see promote ethical as much as legal plant collecting practices that Crouch et al., 2008) have, however, affected at least one are compliant with both the CBD and legal requirements. development initiative based on A. ferox in the Eastern Cape CITES exports from different African countries indicate that (Melin, 2009). An appraisal within the context of the new laws many of the living plants in trade must be propagated outside will be necessary to measure successes thus far, with particular Africa, since the volume of living plant material exported falls attention to the differences between A. ferox wild-harvested far short of the volume of material advertised in trade (Newton from communal or privately-owned lands, and to identify and Vaughan, 1996; Newton and Chan, 1998) with little, if any, 986 O.M. Grace / South African Journal Of Botany 77 (2011) 980–987) returns to the source country. The scenario is not unique to Aloe Bosch, C.H., 2006a. Aloe arborescens Mill. Record from Protabase. In: (Crouch et al., 2008) yet influential parties are well placed to Schmelzer, G.H., Gurib-Fakim, A. (Eds.), PROTA (Plant Resources of Tropical Africa/Resources végétales de l'Afrique tropicale), Wageningen, continue fostering demands for plant specimens sourced in Netherlands. http://database.prota.org/search.htm. Accessed 20 March 2011. ways that uphold the objectives of the CBD. Bosch, C.H., 2006b. Aloe ferox Mill. Record from Protabase. In: Schmelzer, G.H., Gurib-Fakim, A. (Eds.), PROTA (Plant Resources of Tropical Africa/ Resources végétales de l'Afrique tropicale), Wageningen, Netherlands. 4. Conclusions http://database.prota.org/search.htm. Accessed 20 March 2011. Bosch, C.H., 2006c. Aloe vera L. Record from Protabase. In: Schmelzer, G.H., The economic scales at which Aloe is valued by people vary by Gurib-Fakim, A. (Eds.), PROTA (Plant Resources of Tropical Africa/ orders of magnitude, from the rural poor whose sole livelihood is Resources végétales de l'Afrique tropicale), Wageningen, Netherlands. based on a single species of Aloe growing on communal lands, to http://database.prota.org/search.htm. Accessed 20 March 2011. Botes, C., Johnson, S.D., Cowling, R.M., 2008a. Coexistence of succulent tree agricultural economies based on several species of cultivated aloes: partitioning of bird by floral traits and flowering Aloe, and the extraordinary global production of A. vera.The phenology. Oikos 117, 875–882. literature is notably lacking in verifiable data regarding the Botes, L., Van Der Westhuizen, F.H., Loots, D.T., 2008b. Phytochemical production and trade in all species used commercially; these data contents and antioxidant capacities of two Aloe greatheadii var. davyana – are necessary for more quantitatively assessing the impact of Aloe extracts. Molecules 13, 2169 2180. Bruce, W.G.G., 1975. Medicinal properties in the aloe. Excelsa 5, 57–68. spp. on livelihoods and concerns for their conservation. There is a CBD, 1992. Convention on Biological Diversity. United Nations Environment need for detailed study of the informal trade in Aloe spp. as Programme, Geneva. medicinal plants. The emergence of several national markets CITES, 2011. Convention on International Trade in Endangered Species of Wild supported by local species, mirroring the use of A. vera,may Fauna and Flora. www.cites.org Accessed 14 April 2011. significantly increase the biocultural value placed on species of Cocks, M., 2006. Biocultural diversity: moving beyond the realm of ‘indigenous’ and ‘local people’. Human Ecology 34, 185–189. Aloe throughout their distribution. 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