Arid and Semi-Arid Zones of Mexico: A Comprehensive Exploration of Biodiversity, Ecology, and Conservation

The arid and semiarid zones of Mexico occupy more than half of the country’s territory, a characteristic that makes them extremely heterogeneous. It has been suggested that climate heterogeneity promotes biological diversity; consequently, different climatic factors are important for explaining species distribution patterns at different scales. Multiple studies have considered climate as a substitute for biodiversity; therefore, describing environmental characteristics is of great interest in understanding biological diversity. The objective of this chapter is to perform a climatic characterization of the arid and semiarid zones of Mexico through climatic domains to understand the climatic heterogeneity in these environments. We defined climate domains as geographic units with similar environments through nonhierarchical multivariate classification of a dataset comprising climate estimates for points along a 1-km grid throughout the study area. As a result, we defined 15 climatic domains that allowed us to recognize regional environmental variations. According to the row fusion dendrogram, three groups were identified according to their environmental characteristics, and two domains remained independent. In this chapter, we present a classification of climatic domains for the arid and semiarid zones of Mexico to show part of the variation within these zones and as a form of regionalization that allows us to make sense of the biological patterns that will be studied in other chapters. Consequently, a better understanding of climate heterogeneity within a region can support the selection of areas with distinct environmental attributes and biological patterns.

The geological, geomorphological, and pedological elements that provide the framework for the development of life and biological diversity on Earth come from nature through its physical and geographical environment. This constitutes the most widely accepted definition of the concept of geodiversity. Proposed in the 1990s, this concept has gained relevance in the last decade as it seeks to establish relationships and interactions with various factors (biotic and abiotic) at different spatial and temporal scales. The firm intention is to seek answers regarding ecological dynamics, anthropic activities, and social processes. In this chapter, we offer a broad and general view of the different elements that make up geodiversity, focusing on the arid and semi-arid zones of central Mexico. Additionally, we provide a current overview of the importance of incorporating the physical-geographical environment and its potential for understanding ecological and environmental studies at any scale of work. The actualization of the knowledge of these regions’ purposes is the understanding of their environmental dynamic, productive potential, diversity, strategies, and management proposals considering their fragility and susceptibility to climate change. Finally, we establish a physical-geographical comparison based on the similarities and differences between the Puebla-Oaxaca and Querétaro-Hidalgo regions, demonstrating that their different components and characteristics, based on geological history, provide valuable information for identifying numerous environmental services and social benefits that distinguish them from other regions. These studies are mainly based on abiotic factors and their direct relationships as the foundation for the development of the biotic environment.

Arid and semiarid zones are generally considered places that contain few species; however, a high diversity of ants has been recorded in these areas. These organisms exhibit morphological, physiological and behavioral adaptations in response to the extreme environmental conditions of these ecosystems. In this study, we focused on ants in the arid and semiarid zones of Mexico, where 286 species belonging to 54 genera and 8 subfamilies were identified. Analysis of an accumulation curve of the species that have been reported over the last 44 years in these areas indicates that we currently know approximately 50% of the expected species; therefore, there are still many unknown species because the species accumulation curve calculated by randomization is far from reaching an asymptote. Ant studies that have been carried out in Mexico cover different aspects, such as understanding the factors that affect the structure of ant communities, which are related to vegetation and soil variables. The activity patterns of some species as well as the interactions between ants and plants have been studied. Work has also been done on the registration and description of new species for these areas. Although the number of studies on ants in the arid and semiarid zones of Mexico has been increasing in recent years, there are still many gaps in the knowledge of these insects, especially in arid zones like the Northeast region of the country.

The arid and semiarid areas of Mexico are complex natural systems influenced by the transitions between desert vegetation and other more humid, warmer, or higher-altitude environments. To describe the species richness and faunistic relationships in Mexican arid zones, we analyzed bird data from the Global Biodiversity Information Facility (GBIF). These records document these ecosystems, spanning 12 orders and 43 families. Among these species, 158 are resident and 151 are migratory or transient species. The distribution of records and species richness helped identify information gaps and revealed that species richness is greater than that estimated by previous studies. Moreover, there was strong similarity (i.e., low species turnover) among the vegetation types, with no clear distinction among the chaparral, shrubland, and grassland bird communities. However, there were important differences when comparing records from polygons of the Important Bird Areas, revealing a clear distinction among the three regions. The first region corresponds to the northern half of the Baja California Peninsula and is distinguished mainly by species with restricted distributions. The second group includes systems in the southern half of the Baja California Peninsula, islands of the Gulf of California, and northwestern Mexico. The third comprises the environments of the Mexican Plateau and the Gulf of Mexico slope. This study highlights the importance of considering the complexity of interactions between vegetation and birds in the arid and semiarid regions of Mexico in the design of effective conservation strategies. It also identifies key areas for conservation in different regions of the country. 

Arid and semiarid regions cover a large part of the Mexican territory and are characterized by high temperatures and low precipitation. Several species of hummingbirds, including endemic species such as the Beautiful Hummingbird (Calothorax pulcher) and the Dusky Hummingbird (Phaeoptila sordida), inhabit these areas. Using citizen data from the GBIF, we estimated the taxonomic richness and abundance of hummingbirds in the Mexican arid zones. We created a grid with cells of 0.5° latitude by 0.5° longitude covering arid and semiarid areas. Subsequently, we calculated the richness and abundance for each grid. Additionally, we used the Jaccard dissimilarity index to estimate the hummingbird species turnover between adjacent cells along the grid. Finally, we estimated the degree of association between hummingbirds and arid and semiarid areas. To achieve this goal, we calculated the geographic area that each hummingbird species occupies within Mexico and subsequently calculated the proportion of this area that is found within the arid zones of the country. We found 22 species in arid and semiarid zones, with most records corresponding to the Broad-billed hummingbird (Cynanthus latirostris), while the Beautiful Hummingbird (Calothorax pulcher) was less abundant. The arid and semiarid zones of Mexico have a high species richness of resident and migratory hummingbirds that increases from north to south. The areas with the highest species richness were Guanajuato, Querétaro, Hidalgo, and Puebla. However, no information on hummingbird records was available for 25.9% of the cells. Within the arid and semiarid regions of the country, there is a great turnover of hummingbird species, which reflects the complexity and ecological heterogeneity of these regions. Finally, the degree of association between the hummingbird species and the arid zones presented a great amplitude. This association gradient includes species with total dependence and species that sporadically use these areas. These results highlight the biological relevance of these regions for the conservation of resident and migratory hummingbirds. However, some areas, particularly in northern Mexico, lack records. In these areas, it is important to implement strategies to promote research and citizen science focused on filling these knowledge gaps.

Cacti are the most ubiquitous plants in the arid regions of the American continent and Caribbean Isles. Nearly 1427 taxa of cacti, which mainly inhabit the southern USA, Mexico, and South America, have been recorded. Since Mexico has 700 cactus species, 517 of which are endemic, this country is considered to be globally rich in cacti. In this chapter, we analyzed the number and distribution of cactus genera and species in 15 climatic domains. All available records for cactus species were downloaded from the GBIF website and manually curated to create a derived database containing individual records with coordinates and the scientific names of native taxa. This curated database contained 124789 records, which were mapped onto the 15 climatic domains to construct a binary matrix composed of genera and species. We estimated β diversity (βJ) to compare turnover in species composition among domains. We documented a total of 64 genera with 654 species, 78.6% of which were distributed in some of the 15 climatic domains. The number of genera and species were positively correlated (r 2=0.92, p<0.05). Domain 15 contained the highest number of genera (40) and species (214), while the lowest numbers were documented in domains 1 (13 genera) and 18 (35 species). Among the 15 domains, the genera with the highest number of species were Mammillaria (129), Opuntia (62), Echinocereus (51), and Coryphantha (44). The mean value of βJ was 0.83, indicating high variation in species composition among the domains.

This chapter compiles ethnobotanical records of medicinal flora in arid and semiarid zones of Mexico, covering 18 Mexican states. Phytochemical studies have been conducted on specialized metabolites of some species that, in some cases, attribute their medicinal properties. The flora compilation includes the scientific name, botanical family, popular name, and medicinal use. This review identified 691 records corresponding to 331 registered species, 219 genera, and 72 families. The five families with the highest numbers were Asteraceae (103), Fabaceae (40), Cactaceae (28), Euphorbiaceae (26), and Solanaceae (24). Popular nomenclature is recognized in 371 names in Spanish and/or indigenous languages. The plant most commonly mentioned is árnica (Grindelia inuloides), and some of its variants include árnica amarilla (Haplopappus spinulosus), árnica morada (Xanthisma gymnocephalum), and árnica silvestre (Adenophyllum aurantium). It is common for popular names to be related to the colors, chemical compounds, and/or biological forms of plants. The record of herbal resources associated with the illnesses grouped into systems shows that 122 species are used to treat digestive system conditions, whereas 61 species cure dermatological conditions. The states with the highest numbers of records were Aguascalientes, Puebla, and Sonora. Regarding specialized metabolites, studies have focused on phenolic compounds and terpenes in organic extracts. Mono- and sesquiterpenes are present in essential oils. Some species also have notable alkaloid contents. This chapter provides valuable information about the bioactive principles of plant-based medicinal resources in arid and semi-arid regions and demonstrates the therapeutic potential of Mexico’s resources.

Owing to its privileged biogeographical location, Mexico has an incomparable wealth with other regions of the world. This location has allowed for the development of various ecosystems, and drylands have been particularly important for plant diversity. Within this taxonomic richness, the family Euphorbiaceae has been highlighted due to its ecological and medicinal importance. This chapter explores the antibacterial properties of eugenol. It has been reported that this compound is present in some Euphorbia species, focusing on its antimicrobial activity in performed experiments. Comprehensive research has been conducted on this compound regarding its antimicrobial, anti-inflammatory, antioxidant, and anticancer properties. In this study, eugenol showed potential activity against microbial infections; it also showed activity for avoiding the development of biofilms and an increase in antimicrobial resistance when used in combination with antibiotics. In this case, the tested antibiotics were cefuroxime and cefepime. Previous studies have shown that eugenol, when combined with antibiotics, can produce sensitivity in Staphylococcus aureus-resistant strains, producing a significant reduction of the minimum inhibitory concentration (MIC). The MIC value was found to be between 125 and 1000 μg/mL. Eugenol can also initiate the apoptosis process and stop the cellular cycle process; in this regard, it was also found that eugenol at relatively low concentrations can inhibit the synthesis of biofilms in the evaluated microorganisms. This chapter details the characteristics and plant diversity of arid areas in Mexico, examines the traditional uses of Euphorbia in medicine, and highlights the potential medical benefits of its extracts and secondary metabolites, as well as some pharmacological properties of eugenol. More research is needed to understand the safety and efficacy of Euphorbia products given their diversity and endemism in Mexico.

This chapter examines participatory land use planning as a knowledge management tool for socioecological analysis in arid zones. It underscores the deep interdependence of social and ecological systems, advocating for an integrated management approach to tackle the complex challenges inherent in these environments. This approach is especially critical in Mexico's arid and semiarid regions, where the convergence of ecological fragility and social vulnerability makes sustainable management a pressing necessity. The Knowledge Management (KM) model is operationalized through the establishment of Citizen Science Nodes, which serve as platforms for collaboration among local stakeholders, academic researchers, and government agencies. These nodes enable a more inclusive and informed decisionmaking process by integrating diverse perspectives and various knowledge systems. The KM model uniquely merges traditional, locally rooted knowledge with contemporary scientific insights, fostering a comprehensive approach to community territorial planning to ensure thorough analysis and planning. Participatory methodologies, such as social mapping and community workshops, are employed. Accordingly, in this chapter, the construction process of an analytical model is derived from three case studies carried out in the Mixteca Poblana region and the accumulated field experience during the past nineteen years. In this model, traditional agricultural practices and ancestral knowledge are key factors in achieving ecological sustainability. Additionally, this chapter addresses modern challenges such as urbanization and globalization, which have a significant impact on the resilience of complex socioecological systems. The main findings suggest that integrating a socioecological approach with effective knowledge management not only strengthens community participation but also enhances resilience, offering a highly adaptable framework for sustainable natural resource management in arid zones.

State and transition models are proposed to explain changes in vegetation in deserts and semideserts. These models provide a framework for organizing complex ideas about the multiple ecological processes and management practices that drive vegetation change. However, these models have not been used to study vegetation change in the Mexican deserts and semideserts, although these ecosystems occupy approximately 50% of the country’s land area. The aim of this chapter was to describe the use of state and transition models for studying vegetation change in the Mexican deserts and semideserts. To achieve this goal, we first provide an overview of state and transition models. We then describe the use of state and transition models for different deserts and semideserts around the world. Finally, we use empirical evidence to illustrate the use of state and transition models to study vegetation change in the fluvial terraces of the Zapotitlán Salinas Valley, a semidesert located within the Tehuacán-Cuicatlán Valley. The state and transition models for fluvial terraces had different states: abandoned crop fields with weeds, abandoned crop fields with mesquite, closed mesquite shrubland, open mesquite shrubland, and badlands. The transitions between these states were related to the decrease in canopy cover and visual obstruction caused mainly by rained agriculture and firewood extraction. We hope that this chapter encourages the use of state and transition models to elucidate vegetation changes in Mexican deserts and semideserts.

Facilitation by nurse plants is one of the most commonly reported interactions and is considered a crucial factor in structuring plant communities, especially in arid and semi-arid ecosystems. This study is based on a comprehensive review of articles published between 1996 and 2023, aiming to select the main morphological characteristics of nurse species in these environments that are deemed most important in the beneficiary-protected interaction. From this review, we analyze this relationship from a functional perspective. This perspective allows taxonomically different species to be classified into groups that respond similarly to environmental conditions. Our hypothesis suggests that some species share morphological traits that can modify environmental conditions in various ways, potentially reducing the dimensionality of the study of interactions between pairs of species in these ecosystems. The most relevant characteristics are related to the improvement of microclimatic conditions, the decrease in herbivory, and the increase in nutrient availability in soil. Understanding these dynamics is essential because these studies help identify the main limitations of species regeneration and establishment in arid and semi-arid environments. Additionally, this information can be crucial for the conservation and restoration of these vulnerable ecosystems and provides a solid foundation for future research and environmental management strategies. 

La Comarca Lagunera is a region in the states of Coahuila and Durango within the Chihuahuan Desert in Mexico. It is one of the regions with the greatest industrial and economic development in the country, mainly due to agricultural activities and the mining industry. The development of La Comarca Lagunera is associated with the deterioration of natural resources, mainly due to the filtration of various pollutants in the wells where the population obtains water for drinking, in addition to the contaminants that accumulate in the soil. An evaluation and analysis of the data available in the literature, including its own results and the data from 2012–2022 published by CONAGUA, allowed us to determine the levels of the main pollutants in the region and their relationships with the limits recommended by Norma Oficial Mexicana NOM-127-SSA1-2021 (NOM-127), as well as the main effects on human health. The results show that the concentrations of the main water contaminants are above the values of the NOM-127, and many of the water wells with high levels of contaminants are still in use; thus, the deterioration in health has increased. On the other hand, the results of the evaluation of contaminants in the soil, mainly the compounds used as pesticides, are an important source of contamination and health problems, mainly in children. However, there is a lack of recent studies on these health problems, so collaboration between various organizations is imperative to update the data. 

In situ, species conservation demands that natural habitats be preserved, however, in a world characterized by pervasive human impact, the identification of pivotal regions harboring crucial species becomes imperative. Cactaceae species, prevalent and conspicuous in arid and semiarid areas, are predominantly included in national or international Red List categories. The primary aim of this chapter was to pinpoint the optimal selection of priority zones for the conservation of Cactaceae, focusing on levels of richness and endemism. The application of Possingham's algorithm and the principles of complementarity and irreplaceability were employed to determine these priority areas. The database utilized in Chapter 6 of this book was employed, housing 124,789 entries pertaining to 519 species of cacti. An area covering arid and semiarid regions was encompassed within a polygon that was partitioned into cells measuring 50x50 km. The geographical coordinates of each taxon were overlaid onto these cells. The risk classification documented in the Mexican Red List (NOM-059-SEMARNAT-2010) and the presence within a Protected Natural Area (PNA) were acquired for all 519 species. We identified 80 cells as priority areas for cactus conservation, and most of them were outside of some PNAs. Of the 519 species, 30.44% and 13%, are listed in risk categories and outside of PNAs, respectively. We concluded that arid and semiarid regions lack PNAs, and consequently, a large number of cacti as well as many other diverse taxonomic groups are not protected. 

The flora of the arid zones of Mexico is characterized by the high degree of diversity and endemism. Unfortunately, because it faces many threats, its study and conservation should be prioritized. One of the most efficient ex-situ conservation alternatives is the storage of germplasm in seed banks. The FESI-UNAM Seed Bank (SB) has the most extensive and diverse collection of species from the arid regions of Mexico, with more than 5,200 accessions of approximately 2,500 species. The objective of this chapter is to report the number of accessions and the floristic diversity for the five groups or 15 climatic domains into which the arid regions of Mexico are classified. Moreover, this chapter aims to identify regions with low representation in the SB and propose potential collection areas for future projects. The SB stores 2,135 accessions from arid zones, comprising 1,182 species from 547 genera and 108 families. Regions such as the center of the country and the Tehuacán-Cuicatlán Valley have the highest number of accessions, and families such as Asteraceae, Fabaceae, and Cactaceae account for approximately 45% of the collection. The need to strengthen the collection of seeds in arid zones is evident, and future projects should focus on the protection of endemic species and species under categories of risk, especially in regions not yet represented in the SB, whose role is essential for the conservation of the arid flora of Mexico.