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At the Rio Summit, held in 1992 in the city of Rio de Janeiro, sustainable development was proposed as the strategy to ensure environmentally sound and long-term development. Therefore, the United Nations Convention on Biological Diversity established the following main objectives: (1) to conserve biological diversity, (2) to use its components in a sustainable way, and (3) to make a fair and equitable distribution of benefits derived from that use (United Nations 1992). Within this framework, in March 1992 the National Commission for the Knowledge and Use of Biodiversity (CONABIO) was created in Mexico, as a permanent inter-ministerial commission, with the purpose to coordinate and promote actions related to the knowledge and the sustainable use of our country’s biodiversity (Sarukhán et al. 2009, CONABIO 2012). The work carried out by CONABIO is unprecedented in Mexico and its contributions have benefited different areas of the country and abroad.
Since then, milestones of the outmost importance have been reached in terms of integrating and analyzing information from different disciplines such as taxonomy, ecology, physiology, agronomy, geography, climatology, edaphology, and even from the social sciences to define both general and particular approaches to the biological conservation, as well as the use of technologies that are necessary to support increasingly robust conservation proposals (e.g., Bojórquez-Tapia et al. 1995, Álvarez-Buylla et al. 1996, Heywood & Iriondo 2003, Heywood & Dulloo, 2005, Lascuráin et al. 2009, Costedoat et al. 2015, Brooks et al. 2016, Larkin et al. 2016, Hayano-Kanashiro et al. 2017, List et al. 2017, Pfaff et al. 2017).
In general, biodiversity conservation is carried out using both in situ and ex situ approaches. These two are complementary and ensure the conservation of the genetic diversity of species and their populations in the short and long terms. In situ conservation encompasses the maintenance and sustainable use of species and their viable populations in their natural habitats as well as the ecosystem diversity. In situ conservation also includes the diversity of species used in agriculture and their wild relatives as source of genetic diversity in the habitats where such diversity appeared and/or where it continues to evolve (Heywood & Dulloo 2005, Pisanty et al. 2009). On the other hand, ex situ conservation is the application of a wide variety of resources, techniques and specialized infrastructure that contribute to the recovery and survival of individuals or populations outside their habitats. A central objective of ex situ conservation is to reduce the extinction risk of species or populations, as well as to reintroduce populations into their natural habitats (Lascuráin et al. 2009). There are various methods and techniques for ex situ conservation, such as seeds, pollen and tissues cryopreservation, gene banks, botanical gardens, and arboreta (Lascuráin et al. 2009). To date, it is widely accepted that ex situ conservation activities can play a very relevant role and complementary to the in situ approach, which integrates some conservation procedures such as the recovery and reintroduction of species and ecological restoration (Heywood & Iriondo 2003, IUCN/SSC 2014, Dávila-Aranda et al. 2016, Heywood 2017).
In this context, the objective of this work was to gather and analyze the information available in scientific publications explicitly related to in situ and ex situ conservation of wild plants in Mexico during the 2000-2021 period, with the purpose of answering questions such as: how much has been published on the subject in the last twenty years?, what are the themes or objects of study (disciplines, plant groups, regions, species, etc.) of the publications?, what have been the approaches and methods used?, and how much is the scientific information generated on plant conservation taken into consideration in public policy instruments on environmental matters?
Methods
Compilation and review of scientific literature. To determine the main scientific contributions to plant conservation in Mexico, a systematic search was carried out in May 2021 using the Web of Science search engine for scientific papers published on the subject between 2000 and 2021. The search criteria consisted in including those papers published in scientific journals in which the database included the terms plant conservation + Mexico in their title. In addition, we also included those papers that included in their abstracts, the terms “in situ conservation” or “ex situ conservation”. After checking and avoiding duplicates, 207 documents remained as the result of the search (articles, books or chapters). The final number of documents was 103 after filtering out articles that lacked information that could be clearly related to in situ or ex situ conservation activities on wild plants in Mexico.
Analysis of the consideration of scientific literature in public policy instruments in environmental themes. In order to know the use of scientific information in plant conservation in Mexico in the public policy on environmental themes, a sample of public documents associated to various tourism development projects in coastal areas of the country ruled by the authority for the years 2002, 2004, 2006, 2008 and 2010 was reviewed, specifically the documents that correspond to the Regional Environmental Impact Statements (MIA-R by its Spanish acronym). In the review of this documentation, it was determined that a MIA-R was considered to use scientific information on plant conservation if it complied to the following bibliographic sources: (i) publications on Protected Natural Areas that refer to plants (e.g., the flora of the Sian Ka’an or El Triunfo Biosphere Reserve, etc.); (ii) publications that indicate or suggest in the title that they include conservation issues; (iii) references of any of the Priority Areas defined by CONABIO.
According to the main topics addressed by the publications retrieved from the bibliographic search, they were classified into six categories: (a) Regions or Ecoregions, (b) Communities or Ecosystems, (c) Taxonomic Groups, (d) Species and Populations, (e) Botanical Gardens, and (f) Seed Banks. For these categories, publications are presented under the headings “in situ conservation” (topics a-d) and “ex situ conservation” (topics e and f); additionally, the results of analysis of the tourism development projects MIA-R are described.
In situ conservation
The literature review revealed that there is a scarce production of papers specifically aiming to undertake in situ conservation activities of the Mexican flora during the period considered in this work. The retrieved papers include data from regions or ecoregions, communities or ecosystems, taxonomic groups (e.g., genera or families), as well as from species and populations (e.g., endemic, threatened or endangered).
Regions or Ecoregions. Conservation studies of regions or ecoregions are focused on relatively large geographic areas, with hundreds of plant species and dozens of natural communities included. The Natural Protected Areas of Mexico (ANP by its Spanish acronym) were initially established based on aesthetic and recreational criteria, but gradually the criteria evolved to support initiatives that aim to contribute to the in situ conservation of the regions’ or ecoregions’ biodiversity. In the last 20 years, the scientific community and Mexican institutions such as the above mentioned CONABIO and the National Commission for Protected Natural Areas (CONANP by its Spanish acronym), both entities belonging to the Secretariat of Environment and Natural Resources (SEMARNAT by its Spanish acronym), became aware of the need to review the operation, size and connectivity of the country’s protected areas. Currently, the Mexican territory has a total of 182 ANPs covering about 90,839,522 ha (Table 1; CONANP 2018). The monitoring of the operation in some ANP has shown the successes and the difficulties regarding the management and conservation of natural resources in regions such as the Yucatán Peninsula (García-Frapolli et al. 2009). In addition, other studies have focused on redesigning and delimiting the ANPs, using new criteria and additional information in order to explore alternative designs that maximize the conservation of habitats and natural resources (e.g., in the Mariposa Monarca [Monarch Butterfly] Biosphere Reserve, Bojórquez-Tapia et al. 2003, and the Sierra de San Pedro Mártir National Park, Bojórquez-Tapia et al. 2004).
Table 1 Protected Natural Areas of Mexico by categories.
| Category | Number | Total area (ha) | % Protected |
|---|---|---|---|
| Biosphere Reserve | 44 | 62,952,750.50 | 69.3 |
| Natural Park | 67 | 16,220,099.30 | 5.5 |
| Natural Monument | 5 | 16,269.11 | 0.1 |
| Natural Resources Protection Area | 8 | 4,503,345.22 | 17.6 |
| Flora and Fauna Protection Area | 40 | 6,996,864.17 | 26.5 |
| Santuaries | 18 | 150,193.29 | 0.6 |
| Total | 182 | 90,839,521.55 | 100 |
Moreover, some studies have aimed to identify regions of high concentration of endemic plant species in order to propose and prioritize areas for conservation, such as in the Baja California Peninsula (Riemann & Ezcurra 2007), the Sierra Madre Oriental (Salinas-Rodríguez et al. 2018) and the Sierra Norte of Oaxaca (Suárez-Mota et al. 2018). Finally, some studies have focused on evaluating the loss of species due to habitat modification and alteration by large-scale human activities, such as grazing (e.g., Isla Guadalupe, León de la Luz et al. 2003) and agriculture (e.g., Baja California, Vanderplank et al. 2014). In addition, spatial models of land cover and land use change have been used to estimate the impact of human activities on natural ecosystems. An example of this is the Mesoamerican Biological Corridor in Chiapas (Ramírez-Mejía et al. 2017) or other sites on the Costa Grande region of Guerrero state and in central Quintana Roo state (Durán-Medina et al. 2007).
Communities or Ecosystems. Some studies on community or ecosystem conservation in Mexico have focused on habitat fragmentation effects on species composition and the physiognomy of the dominant vegetation (e.g., Arroyo-Rodríguez & Mandujano 2006, Sánchez-Gallen et al. 2010). For instance, a well-documented example is the humid tropical forest of Los Tuxtlas, Veracruz which has been particularly affected by deforestation (Arroyo-Rodríguez & Mandujano 2006). Oher studies have aimed to establish specific conservation and restoration programs at the local level, by implementing sustainable management schemes for threatened ecosystems such as the cloud forest (Luna Vega et al. 2000, Toledo-Aceves et al. 2011).
Additionally, several studies have evaluated the spatial variation of the impact of climate change on biodiversity across different ecosystems or communities in Mexico (Trejo et al. 2011). For example, Estrada-Contreras et al. (2015) evaluated the effects of climate change on tropical evergreen, coniferous and mesophyllous montane (cloud) forests in the state of Veracruz; according to their results and under the conditions expected in 2050, for about 20 species of this vegetation type there will be considerable reductions in their distribution ranges and others will probably become extinct, as is the case of Dialium guianense (Caesalpinoideae: Fabaceae), Calophyllum brasiliense (Calophyllaceae), and Brosimum alicastrum (Moraceae), since this ecosystem will be reduced to 60 % of its current surface. Similarly, Gómez-Mendoza & Arriaga (2007) predicted the reduction of the distribution area of several species of Quercus (7-48 %), and Pinus (0.2-64 %); the most vulnerable species of the Pinus genus were P. rudis, P. chihuahuana, P. oocarpa and P. culminicola, and of Quercus were Q. crispipilis, Q. peduncularis, Q. acutifolia, and Q. sideroxyla. By contrast, Rehfeldt et al. (2012) predicted the expansion of the tropical deciduous forest and the xerophilous scrub to suitable climates in several regions of Mexico.
Likewise, other studies addressing climate change seek to identify geographic areas with the potential to host the largest number of species representative of a particular ecosystem, to prioritize conservation areas (e.g., the mesophyllous montane (cloud) forest, López-Arce et al. 2019), such as the work undertaken by Worthington et al. (2020), in which the authors proposed to include Mexico in mangrove restoration and conservation programs at a global level. Another good example is the recent study undertaken by Tellez et al. (2020) that analyzes the richness of native trees in Mexico, including 2,885 species (ca. 44 % endemic to Mexico) that belong to 612 genera and 128 families listed in the IUCN Red List, in SEMARNAT’s NOM-059, or in both. In addition, a total of 98 Mexican tree species are listed in CITES for their protection. Moreover, in terms of current conservation efforts, they also document that 19 % of the Mexican tree species have an ex situ protection in seed banks, and that most species richness peaks overlap in protected areas.
From an ethnoecological perspective, in recent years the studies undertaken on agroforestry systems have provided relevant information on the conservation of locally important plant communities. These studies focus on the complexity of original vegetation zones interspersed with cultivated areas that include management strategies for the original communities and populations, which favor the maintenance of biological and cultural diversity, while providing numerous resources and ecosystem services to rural human communities (Schroth et al. 2004, Perfecto & Vandermeer 2008). For instance, these systems have been studied in detail in the Tehuacán-Cuicatlán Valley, where approximately 1,600 plant species are used by humans in numerous ways (Casas et al. 2001, Lira et al. 2009a). Results of these studies leave no doubt that such traditional exploitation of original vegetation areas represents sustainable practices where conservation is possible. Also, in the Tehuacán-Cuicatlán Valley, Vallejo et al. (2014) analyzed the biodiversity conservation success of the agroforestry systems of the temperate zones, as well as the motivation of people to carry out these practices. In this study, 79 tree and shrub species were recorded, 86 % of which are native and represent 43 % of all trees and shrubs species recorded in natural forests. Likewise, the authors identified that motivations to conserve standing plants in these systems are associated to their use as fruit trees, firewood, shade, beauty, as well as their nature and other environmental services.
In the case of the Tehuacán-Cuicatlán Valley, it has been reported that agroforestry systems derived from columnar cactus forests conserve between 50 and 90 % of the plant species richness existing in wild systems and on average close to 93 % of the genetic diversity of wild populations of cacti species representative of the original forests (Moreno-Calles & Casas 2008). Additionally, Rendón-Sandoval et al. (2021), who studied these systems in Cuicatlán, at the southern end of the Tehuacán-Cuicatlán Valley, agree in that agroforestry systems can maintain biodiversity while helping to satisfy human needs, and that those that protect or sponsor a greater proportion of forest cover and species diversity can provide a broader spectrum of benefits to people; such benefits include not only those obtained directly from the use or marketing of plant products (food, medicine, etc.) but also those that are less tangible, but equally essential, such as providing shade, maintaining humidity or providing habitat for pollinators.
Taxonomic Groups. The existing publications on taxonomic groups of vascular plants are aimed at analyzing diversity patterns at different spatial scales to prioritize areas for conservation. Such is the case of the studies on Asteraceae (Redonda-Martínez et al. 2021), Cactaceae (Gómez-Hinostrosa & Hernández 2000, Ortega-Baes & Godínez-Alvarez 2006, Ortega-Baes et al. 2010, Hernández & Gómez-Hinostrosa 2011), and Cucurbitaceae (Lira et al. 2002), as well as those undertaken on species of the genus Dahlia (Asteraceae; Carrasco-Ortiz et al. 2019) and Lycianthes series Meiozonodontae (Solanaceae; Anguiano-Constante et al. 2018).
Species and Populations. With the purpose of evaluating the genetic status and long-term viability of threatened species, important contributions related to population genetics have been published. Several species of the genus Agave (Asparagaceae) have been particularly studied from this perspective, for example A. cupreata and A. potatorum (Martínez-Palacios et al. 2011, Aguirre-Dugua & Eguiarte 2013), and A. angustifolia and A. victoriae-reginae (Eguiarte et al. 2013). Other threatened or endangered species in the order Cycadales (Cycads sensu lato, Gymnospermae) have also been addressed, such as Dioon angustifolium (González-Astorga et al. 2005), Zamia loddigesii (González-Astorga et al. 2006), and Microcycas calocoma (Pinares et al. 2009), as well as flowering plants in the family Orchidaceae, such as Laelia speciosa (Ávila-Díaz & Oyama 2007). In addition, similar works have been published on species of Cactaceae, including Mammillaria crucigera (Solórzano & Dávila 2015) and M. pectinifera (Maya-García et al. 2017), and in the Magnoliaceae, for Magnolia pacifica (Muñiz-Castro et al. 2020), M. decastroi, M. lopezobradorii, M. mexicana, M. sinacacolinii, and M. zoquepopolucae (Aldaba-Núñez et al. 2021).
Moreover, spatial analyses using distance indices have been carried out for undertaking in situ management and conservation of threatened species from arid and semi-arid environments, as in the case of Ariocarpus kotschoubeyanus and Mammillaria mathildae (Cactaceae), as well as Agave americana and A. salmiana (Asparagaceae) (Suzán-Azpiri et al. 2011). Other studies have focused on describing demographic parameters of populations in order to design conservation strategies to reduce the extinction probability of threatened species, such as Resinanthus aromaticus (Palacios-Wassenaar et al. 2016), Zamia inermis (Octavio-Aguilar et al. 2017), and Magnolia vovidesii (Galván-Hernández et al. 2020).
Niche modeling studies with different climate change scenarios have been published, aiming to identify future environmental changes and species or populations at risk of disappearing. Among the species included in these studies are Fagus grandifolia (Téllez-Valdés et al. 2006), Echinocereus reichenbachii (Butler et al. 2012), Neobuxbaumia tetetzo (Dávila et al. 2013), Magnolia schiedeana (Vásquez-Morales et al. 2014), Coryphantha macromeris, Mammillaria lasiacantha, Echinocereus dasyacanthus, and Ferocactus wislizenii (Cortes et al. 2014), eight species and two varieties of Abies (A. concolor, A. durangensis var. duragensis, A. durangensis var. coahuilensis, A. fincki, A. guatemalensis, A. hickelii, A. jaliscana, A. religiosa, and A. vejari) (Martínez-Méndez et al. 2016), Arenaria bryoides, Castilleja tolucensis, Chionolaena lavandulifolia, Draba nivicola, and Plantago tolucensis (Ramírez-Amezcua et al. 2016), as well as Guadua inermis and Otatea acuminata (Ruiz-Sánchez 2013), Cedrela odorata (Manzanilla-Quijada et al. 2020), Laelia speciosa (Flores-Tolentino et al. 2020), and Pinus gregii (Martínez-Sifuentes et al. 2020). In addition, there are studies evaluating the effects of climate change on the diversity of economically important crops and their wild relatives, which have allowed identifying geographic regions and taxa potentially vulnerable to extinction (e.g., Cucurbitaceae, Lira et al. 2009b, and corn (Ureta et al. 2012). In this context, Goettsch et al. (2021) analyzed information from various sources and used the IUCN Red List to determine the conservation status of 224 wild taxa closely related to several crops (e.g., corn, potatoes, beans, squash, chili, vanilla, avocado, tomatillo, and cotton); this work showed that 35 % of these taxa are threatened due to conversion of natural habitats for human use, abandonment of traditional agricultural methods and their replacement by intensified practices (i.e., highly mechanized and with the use of herbicides and pesticides).
Moreover, studies on plant domestication have documented processes that not only contribute to the conservation of the diversity of perennial and annual plants, but also enhances such a diversity through artificial selection that has resulted in numerous variants of some of the traditionally managed species (Casas et al. 2007, 2016a, b, c). In this context, there are some paradigmatic case studies in various species of Agave used for the production of alcoholic beverages and other purposes in western Mexico (Colunga-GarcíaMarín & Zizumbo-Villarreal 2007, Vargas-Ponce et al. 2007, Valenzuela-Zapata et al. 2011, Zizumbo-Villarreal et al. 2013), southern Altiplano (High Plateau) of the central-northern region of Mexico (Mora-López et al. 2011), and the Tehuacán-Cuicatlán Valley (Casas et al. 2016b).
Other perennial useful plants whose incipient or more intense human management has also been studied in this century include several species of Opuntia (Reyes Agüero et al. 2005) in the Southern Altiplano of Mexico, some columnar cacti in the Valle de Tehuacán-Cuicatlán, such as Escontria chiotilla, Polaskia chichipe, P. chende, Stenocereus pruinosus, S. stellatus, Myrtillocactus schenkii (Cruz & Casas 2002, Arellano & Casas 2003, Otero-Arnaiz et al. 2003, Oaxaca-Villa et al. 2006, Parra et al. 2008, Blancas et al. 2009), some trees such as Leucaena esculenta ssp. esculenta (Fabaceae) in Guerrero (Zárate et al. 2005), Prunus serotina ssp. capuli in Tlaxcala (Avendaño-Gómez et al. 2015), Sideroxylon palmeri (Sapotaceae) and Ceiba aesculifolia ssp. parvifolia (Bombacaceae) in the Tehuacán-Cuicatlán Valley (González-Soberanis & Casas 2004, Avendaño-Gómez et al. 2006, 2009), and a palm species (Sabal yapa) in the Yucatán Peninsula (Martínez-Ballesté et al. 2005).
In the case of annual useful plants, although many of them are generally considered weeds, the value of several of them in the diet and/or health care in rural communities has been demonstrated (Vieyra-Odilon & Vibrans 2001, Blanckaert et al. 2007, Albino-García et al. 2011, Vibrans 2016). Among the most amply studied taxa in the last two decades, in terms of incipient domestication processes, are Anoda cristata (Malvaceae) in the State of Mexico, several species of Amaranthus in the state of Puebla, and Dysphania ambrosioides (Chenopodiaceae) in the Tehuacán-Cuicatlán Valley (Rendón et al. 2001, Rendón & Núñez-Farfán 2001, Blanckaert et al. 2012).
Ex situ conservation
Botanical Gardens. A botanical garden is an institution that preserves documented collections of living plants, both native and exotic, which are maintained with a specific arrangement, and duly identified and labeled. The purposes of these gardens are to develop scientific research projects that contribute to the conservation of biological diversity, and to carry out education activities. In Mexico there are 64 botanical gardens, arboreta or living plants collections, of which 40 are currently registered at the Asociación Mexicana de Jardines Botánicos, A.C. (AMJB, the Mexican Association of Botanical Gardens), founded in 1980, for promoting biological studies, conservation and sustainable use of the Mexican flora, along with the development of educational programs for public awareness on the relevance of plant diversity and its conservation (Herrera et al. 1993, Caballero 2012). Nonetheless, to date only 19 botanical gardens have available information on their living collections and their advances in their ex situ plant conservation activities, considering goals 1-10 of the Global Strategy for Plant Conservation (GSPC) (Sharrock 2020, CONABIO 2021).
Available information (CONABIO 2021) shows that progress in the GSPC goals is variable among botanical gardens, especially in goals 1, 2, 3, 7, and 8 (Figure 1). Villaseñor (2016) determined that in these 19 collections there are around 9,016 records of higher plants, corresponding to 4,900 species from 195 families, which only represents 25 % of the recorded vascular flora of Mexico. Moreover, among the seven most diverse families in Mexico, Villaseñor (2016) states that the Cactaceae family has the highest number of specimens, while Orchidaceae is the second-best represented family, with 16.9 % of its species in botanical garden collections (Table 2). The effort made by scientists working in botanical gardens to document species kept in their collection is very important, and so has been the increase of taxa in these collections during the past two decades. The transition from 3,275 species recorded by Coombes et al. (2003) early in the century to 4,900 currently represented in the 19 botanical gardens considered here represents a huge conservation step.
Figure 1 The 19 Mexican botanical gardens members of the Mexican Association of Botanical Gardens, with their advances in 9 of the 10 goals of the Global Strategy for Plant Conservation (GSPC): (M1) To compile the list of flora available on the Internet; (M2) To evaluate the conservation status of all species; (M3) To develop and share information; (M4) To ensure at least 15 % of each ecological region or vegetation type; (M5) To protect at least 75 % of the most important areas for the diversity of plant species; (M7) To conserve in situ at least 75 % of known threatened plant species; (M8) To conserve in ex situ collections at least 75 % of threatened plant species; (M9) To conserve 70 % of the genetic diversity of crops; (M10) To implement effective management plans to prevent further biological invasions.
Table 2 Plant families with the highest species richness in Mexico and their representation in 19 Mexican botanical gardens.
| Family | Total species in Mexico (Villaseñor 2016) |
Botanical Gardens | Collections | Species in collections |
|---|---|---|---|---|
| Asteraceae | 3,057 | 18 | 321 | 189 |
| Fabaceae | 1,903 | 16 | 191 | 105 |
| Orchidaceae | 1,213 | 15 | 328 | 205 |
| Poaceae | 1,047 | 13 | 57 | 47 |
| Euphorbiaceae | 714 | 17 | 194 | 104 |
| Rubiaceae | 707 | 15 | 65 | 36 |
| Cactaceae | 677 | 13 | 1,583 | 580 |
At the genus level, Quercus (Fagaceae), Mammillaria (Cactaceae) and Agave (Asparagaceae) have more than 50 % of their species represented in these 19 Mexican botanical gardens, while the rest have a modest representation (Table 3). According to CONABIO (2021), 12 of the 19 Mexican botanical gardens here considered keep species at risk in their collections. In this regard, it is remarkable that 48 % (458 species) of the species included in the list of the Mexican Official Norm of Threatened Species NOM-059-SEMARNAT-2010 (SEMARNAT 2010), are protected in botanical gardens. By contrast, the set of documented species in some of the IUCN risk categories is very low, since only 7.7 % (320 species) of the species included in the Red List are sheltered in Mexican botanical gardens.
Table 3 Plant genera with the greatest diversity in Mexico and their representation in 19 Mexican botanical gardens.
| Genera | Total species in Mexico (Villaseñor 2016) |
Botanical Gardens | Species in collections |
|---|---|---|---|
| Salvia | 328 | 11 | 27 |
| Euphorbia | 245 | 18 | 43 |
| Tillandsia | 237 | 8 | 31 |
| Quercus | 174 | 11 | 98 |
| Mammillaria | 169 | 15 | 178 |
| Ageratina | 165 | 3 | 4 |
| Verbesina | 165 | 8 | 12 |
| Agave | 160 | 18 | 102 |
Given the complexity and high maintenance costs of living collections, the AMJB adopted the concept of “national collection”, which consists of sheltering a living heritage of a family or lower taxonomic group or a relevant thematic plant group, with the responsibility of having a curator or group of academics who can take care of the collections (AMJB 1994, Vovides et al. 2013). At present, eight national collections exist, seven of which represent taxonomic groups and one is thematic. Some have allowed advances in their biological knowledge, such as the bamboo collection (Ruiz-Sanchez 2013), or they have served as a basic complement for various floristic studies, such as the Palm Collection of the Culiacán Botanical Garden (Equihua Zamora et al. 2020). Others have allowed the development of propagation protocols such as the Crassulaceae Collection (Reyes Santiago et al. 2014), or ex situ rescue and conservation strategies as it occurs in the Cycad Collection (Iglesias-Andreu et al. 2017). Additionally, the AMJB has promoted the creation of networks among its members at national and international levels (Lascuráin et al. 2009, Vovides et al. 2013), and among its most remarkable objectives is a proposal to create a regional collection of cacti in the botanical gardens of southern United States and northern Mexico, as they share common arid environments (Hultine et al. 2016).
Seed Banks. One of the most efficient and affordable approaches for ex situ conservation is, undoubtedly, the safeguarding of seeds in the so-called “seed banks,” which are ideal living species reservoirs with controlled humidity and temperature conditions that can be used to guarantee long term preservation of plant resources. The benefits of ex situ conservation of seeds are innumerable and go from those related to the survival of the human species, given the fact that agriculture depends on preserving plant biodiversity, to the conservation of wild species, as an insurance policy against extinction. Ex situ conservation allows the long-term preservation of thousands of plant seeds in a reduced space, at a much lower cost (about 1 %) than in situ protection strategies (Li & Pritchard 2009), and in many cases it guarantees a wide spectrum of genetic variation (Bacchetta et al. 2008).
In Mexico, there are more than 50 seed banks, most of which, unfortunately, protect only a few species, generally related to food or timber uses, and only 10 banks protect wild species native to the country (Table 4). In this latter group, the Seed Bank of the FES Iztacala (National Autonomous University of Mexico) stands out, whose main objective is to protect native wild species of Mexico. Since its inception, this bank has been directly linked to the Millennium Seed Bank of the Royal Botanical Gardens of Kew, United Kingdom and currently protects 4,950 accessions of native plants from 26 states of Mexico, of a total of 2,700 species, among which are many useful, threatened or narrowly distributed species (Dávila-Aranda et al. 2016, Rodríguez-Arévalo et al. 2017).
Table 4 Available information on germplasm collections in Mexico. CONAFOR reports 18 germplasm banks in the national territory but only one of them was found.
| Official Name | Location | State | Objectives | Collections Type | Duration and storage conditions | Accessions | Species |
|---|---|---|---|---|---|---|---|
| Banco de Semillas FESI-UNAM | Facultad de Estudios Superiores Iztacala, UNAM | State of México | Wild and native germplasm | Wild and native species | Long term; -20 °C/14 % HR |
4,948 | 2,692 |
| Banco de Germoplasma Vegetal Coahuila | Universidad Autónoma de Coahuila | Coahuila | Forest seeds for production, conservation and supply to nurseries of the Secretaría de Medio Ambiente de Coahuila | Cold climate, arid and urban species | Medium term; 4 °C/40-60 % HR |
90 | 30 |
| Banco de Germoplasma de Maíces | Universidad Agrícola, Agraria, Antonio Narro | Coahuila | Mexican corn collections | Cultivated species. Corn from the states of Mexico and Tlaxcala. Some species from arid zones are currently being stored | Medium term; 4 °C/40-60 % HR |
Unknown, but can hold up to 100,000 | - |
| Banco de Germoplasma-UAQ | Universidad Autónoma de Querétaro | Querétaro | Native flora with an emphasis on plant genetic resources for food, agriculture, research and reintroduction | Wild and cultivated species | Short term; -5 °C |
More than 800 | 336 |
| BG-CICY | Centro de Investigación Científica de Yucatán | Yucatán | Conservation, reproduction, and availability of plant germplasm from the Yucatan Peninsula, and plant species from the Mexican tropics with emphasis on species related to the Mayan culture | Wild and cultivated species useful for the Mayan culture, other species that are under some type of threat, as well as wild relatives of cultivars. Some exotic species are also conserved | Long term; 4 -20 °C |
560 | 208 |
| Banco Nacional de Germoplasma Vegetal | Universidad Autónoma de Chapingo (UACh) | State of Mexico | - | Wild species and for food, medicinal and fuel use | - | 8,337 | 295 |
| Banco de Semillas GUADA | Universidad de Guadalajara | Jalisco | - | - | - | - | - |
| Universidad Veracruzana | Veracruz | Safeguarding the best germplasm of vegetables, fruit trees and other homegarden plants | Cultivated species | - | - | 56 | |
| Centro Nacional de Recursos Genéticos | SINARGEN and INIFAP | Jalisco | Conservation, improvement and research for the rational use of Mexico’s genetic resources for the benefit of society, and in the event of a catastrophic event, prevention of the loss of genes and ensure the survival of useful species | Cultivated and forest species | -18 °C | 16,677 | - |
| Banco de Germoplasma de la CONAFOR, Estado de México* | - | State of Mexico | - | - | Ten years; 5 °C/10 % HR |
4,436 kg of seeds | 36 |
| Bancos de Semillas Comunitarios | SNICS and SINAREFI | Oaxaca, State of Mexico, Chiapas, Yucatán, Puebla Guanajuato, Mexico City, Coahuila, Chihuahua and Morelos | To preserve the diversity of wild species, as well as having the collection in case of a natural disaster, as well as conserving in situ the diversity of the area | - | - | - | - |
| CIMMYT | State of Mexico | Develop nutritious, sustainable and resilient food systems to improve health and livelihoods | Improved corn and wheat lines | - | - | - |
In the last 20 years, only seven research papers have been published addressing the conservation of Mexican plant species in seed banks. For instance, Ulloa et al. (2006) documented the collection and storage of the seeds of eight Gossypium species from western Mexico in the Cotton Collection of the US National Plant Germplasm System; Acosta-Diaz et al. (2015) carried out the collecting and characterization of 11 species of the genus Phaseolus from Nuevo León and Tamaulipas states in northeastern Mexico, which were deposited at the banks of the Western Region Conservation Center of the University of Guadalajara and the Northern Region Conservation Center of the Antonio Narro Autonomous Agrarian University in Saltillo, Coahuila. Moreover, Ramírez-Villegas et al. (2020) used spatial modeling and conservation gap analysis to achieve optimal representation of genetic variation in the collections of Phaseolus vulgaris varieties, while Toledo-Aceves (2017) analyzed the germination rate of some tree species at risk of extinction in Mexico, to assess their potential for ex situ propagation. Furthermore, León-Lobos et al. (2012) analyzed the role of seed banks in plant conservation, and Dávila-Aranda et al. (2016) and Rodríguez-Arévalo et al. (2017) described part of the FES Iztacala Seed Collection and proposed strategies for the sustainable management of the species.
Scientific literature in public policy instruments in environmental issues
In Mexico, one of the main public policy instruments that regulates human productive activities considering environmental protection and biodiversity conservation are the Environmental Impact Assessments (MIAs, by their Spanish acronym) that are issued by SEMARNAT through public consultation processes and expert reviewers of the proposed projects. In this work, a total of 782 resolutions on tourism development projects were examined and only 524 MIA documents were found to have been reviewed. The review of MIAs aimed to find evidence of the incorporation of scientific literature on conservation matters for the environmental diagnosis and the design of mitigation or damage repair measures. The results of the MIAs review showed that only 32 % of the examined documents included references of scientific literature on conservation. Also, it became evident that most of the literature considered does not have updated information on biodiversity, which strongly suggests that the impact of research, in terms of development decision making on biodiversity and its conservation, especially in recent years, is very limited. Furthermore, the scarcity and publication dates of the literature listed in the MIAs does not allow us to conclude that plant conservation studies have an actual impact in this regard, at least through public policy tools on environmental matters.
Discussion and conclusions
The first reflection derived from our work is that, despite the wide temporal range considered in this review (2000-2021), and the abundant existing work regarding biodiversity characterization in Mexico, the actual use of this information in the development of strategies or specific activities for plant conservation in Mexico is remarkably low. Additionally, it should be noted that even publications focused on conservation are limited to strictly disciplinary areas, lacking connection with other disciplines or sectors and, therefore, are disjointed from other complementary initiatives, as well as from environmental, social, and regulatory contexts. It is also possible to observe that, despite the clear feedback of information that could occur between different conservation approaches, in many cases it does not seem evident that this occurs in the design of conservation strategies. An example of this situation is the lack of integration of genetic considerations and spatial distribution of biodiversity in the design of protected natural areas and also in the ex situ conservation collections. According to our analysis, despite notable efforts and the relatively important advances achieved in both conservation strategies, they are still far from being successful.
The causes of the disarticulation of both conservation strategies, as well as the disconnection of efforts and information from the environmental, social, and regulatory spheres may be explained by the lack of professional teams capable of seeking these connections and establishing communication bridges between sectors that allow the best possible use of knowledge to make decisions and design effective strategies that lead to scenarios of sustainable development and biodiversity conservation. Such articulation should not only consist in the agglutination of multidisciplinary efforts around a specific problem; it has been demonstrated that there is a large gap between theory and practice regarding the collapse of ecosystems and the implementation of practices for their management, which results in the few existing capacities to predict which species are facing higher risk due to human activities (Valiente-Banuet & Verdú 2013).
A second reflection is related to the scope shown by the scientific publications that were reviewed. While it is true that several of these studies have made it possible to implement or at least propose strategies for sustainable use and conservation, particularly for species with small population sizes, others are still required to evaluate and integrate, for example, genetic data with information on demographic parameters, ecological niche modeling, phylogeographic patterns, and even social and economic aspects that more clearly suggest the causes of the extinction threat to species. These studies would provide a more complete ecological and evolutionary context to establish better planning and stronger biodiversity conservation actions (Bosch et al. 2019, Lin et al. 2021). Regarding the studies that analyze the possible effects of climate change, although it is true that they provide information that can be used by scientists to analyze climate variation over time and evaluate its effects on the distribution patterns of biodiversity, the fact is that they work in a highly reduced time window and their applications are also quite relative. Nevertheless, the projections of expansion or contraction of species’ distribution areas that can be derived from some of these studies could be important for Mexico. This type of information is fundamental to expand the sizes of protected natural areas, or to create new areas that conserve critical refuges (Michalak et al. 2018), and to seek the connection of habitats throughout the species’ migratory routes (Carroll et al. 2015). All of this could facilitate the ability of species to persist, adapt and migrate. Future work based on the climate analogous models could show such efforts by integrating more detailed information about the target species (e.g., dispersal distance), identifying important areas for their movement between protected natural areas (Littlefield et al. 2017) or critical refuges (Stralberg et al. 2018), considering habitat fragmentation impacts (Batllori et al. 2017). As a complementary effort, the fundamental role that botanical gardens and seed banks play in conserving the plant diversity not only of Mexico but worldwide is becoming increasingly evident. Nevertheless, there is still a very clear disconnection between those who work in these spaces and those that carry out in situ conservation and management, using different approaches and tools.
A final reflection is related to the fact that, even though the panorama shown from this review is inauspicious, it is encouraging that in various public educational institutions it is increasingly frequent to find study programs that pursue inter- and transdisciplinary training in sustainability matters. These programs are expected to contribute to solve, among other issues, the disarticulation of conservation strategies and plans. Given the enormous relevance and impact that biodiversity conservation at all scales has on the preservation of civilization, it is urgent to increase public investment in the training of professionals who can lead interdisciplinary research and professional work in conservation and sustainable development with a vision of knowledge-action. Similarly, it is essential to revise the regulatory processes in environmental matters and their correct and rigorous implementation. Often, MIAs are carried out in a purely administrative/bureaucratic manner, using outdated information, performing superficial analyses with poor technical-scientific rigor, and prioritizing in many cases the development of projects over their environmental impact.
Considering all the above, the following conclusions and perspectives are raised:
1.There are very few studies and works that really include conservation activities on wild plant species.
2. Little or no multidisciplinary or interdisciplinary work related to conservation activities is being carried out.
3. There is little interest from the environmental governmental sphere to consider the scientific works related to the knowledge and conservation of the wild flora of the country.
4. Many botanical gardens should join efforts to protect, study and propagate endemic or threatened wild species in the country.
5. A shift should be made in scientific work to become less descriptive and turn into a more analytical and proactive conservation approach.
6. The multi- and interdisciplinary work of scientists should be focused on contributing management programs and providing solutions for the conservation of plant germplasm in Mexico.
7. It is important that educational and research institutions include in their study programs and research projects theoretical and practical aspects related to the conservation of the Mexican flora.
8. Given its importance, ex situ conservation requires greater attention and support at the institutional and governmental levels. We need many Mexican scientists involved in the conservation of our country’s flora.
9. Connectivity bridges should be strengthened between those carrying out in situ conservation activities with those who are interested in ex situ projects. The complementarity of both approaches will surely enhance the scientific documentation and conservation of species.
10. The criteria for the declaration of new protected natural areas in the country should be reviewed within the framework of current conditions and the current knowledge on the many species of our flora, as well as the current and future data related to the changes on the distribution patterns of ecosystems and species due to climate change.
