Ficus is a genus of about 850 species of woody trees, vines and hemiepiphytes in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone; the common fig is a temperate species native to southwest Asia and the Mediterranean region, cultivated from ancient times for its fruit referred to as figs. The fruit of most other species are edible though they are of only local economic importance or eaten as bushfood. However, they are important food resources for wildlife. Figs are of considerable cultural importance throughout the tropics, both as objects of worship and for their many practical uses. Ficus is a pan-tropical genus of trees and vines occupying a wide variety of ecological niches. Fig species are characterized by their unique inflorescence and distinctive pollination syndrome, which utilizes wasp species belonging to the family Agaonidae for pollination; the specific identification of many of the species can be difficult, but figs as a group are easy to recognize.
Many have aerial roots and a distinctive shape or habit, their fruits distinguish them from other plants. The fig fruit is an enclosed inflorescence, sometimes referred to as a syconium, an urn-like structure lined on the inside with the fig's tiny flowers; the unique fig pollination system, involving tiny specific wasps, known as fig wasps that enter via ostiole these sub-closed inflorescences to both pollinate and lay their own eggs, has been a constant source of inspiration and wonder to biologists. There are three vegetative traits that together are unique to figs. All figs possess some in copious quantities. There are no unambiguous older fossils of Ficus. However, current molecular clock estimates indicate that Ficus is a ancient genus being at least 60 million years old, as old as 80 million years; the main radiation of extant species, may have taken place more between 20 and 40 million years ago. Some better-known species that represent the diversity of the genus include the common fig, a small temperate deciduous tree whose fingered fig leaf is well known in art and iconography.
Moreover, figs with different plant habits have undergone adaptive radiation in different biogeographic regions, leading to high levels of alpha diversity. In the tropics, it is quite common to find that Ficus is the most species-rich plant genus in a particular forest. In Asia as many as 70 or more species can co-exist. Ficus species richness declines with an increase in latitude in both hemispheres. Figs are keystone species in many tropical forest ecosystems, their fruit are a key resource for some frugivores including fruit bats, primates including: capuchin monkeys, langurs and mangabeys. They are more important for birds such as Asian barbets, hornbills, fig-parrots and bulbuls, which may entirely subsist on figs when these are in plenty. Many Lepidoptera caterpillars feed on fig leaves, for example several Euploea species, the plain tiger, the giant swallowtail, the brown awl, Chrysodeixis eriosoma and Copromorphidae moths; the citrus long-horned beetle, for example, has larvae that feed on wood, including that of fig trees.
The sweet potato whitefly is found as a pest on figs grown as potted plants and is spread through the export of these plants to other localities. For a list of other diseases common to fig trees, see List of foliage plant diseases; the wood of fig trees is soft and the latex precludes its use for many purposes. It was used to make mummy caskets in Ancient Egypt. Certain fig species are traditionally used in Mesoamerica to produce papel amate. Mutuba is used to produce barkcloth in Uganda. Pou leaves' shape inspired one of the standard kbach rachana, decorative elements in Cambodian architecture. Indian banyan and the Indian rubber plant, as well as other species, have use in herbalism. Figs have figured prominently in some human cultures. There is evidence that figs the common fig and sycamore fig, were among the first – if not the first – plant species that were deliberately bred for agriculture in the Middle East, starting more than 11,000 years ago. Nine subfossil F. carica figs dated to about 9400–9200 BCE were found in the early Neolithic village Gilgal I.
These were a parthenogenetic type and thus an early cultivar. This find predates the first known cultivation of grain in the Middle East by many hundreds of years; the 1889 book'The Useful Native Plants of Australia’ records that Ficus aspera had the common names "Rough-leaved Fi
The Arecaceae are a botanical family of perennial plants. Their growth form can be climbers, shrubs and stemless plants, all known as palms; those having a tree form are colloquially called palm trees. They are flowering a family in the monocot order Arecales. 181 genera with around 2600 species are known, most of them restricted to tropical and subtropical climates. Most palms are distinguished by their large, evergreen leaves, known as fronds, arranged at the top of an unbranched stem. However, palms exhibit an enormous diversity in physical characteristics and inhabit nearly every type of habitat within their range, from rainforests to deserts. Palms are among the most extensively cultivated plant families, they have been important to humans throughout much of history. Many common products and foods are derived from palms. In contemporary times, palms are widely used in landscaping, making them one of the most economically important plants. In many historical cultures, because of their importance as food, palms were symbols for such ideas as victory and fertility.
For inhabitants of cooler climates today, palms symbolize the vacations. Whether as shrubs, trees, or vines, palms have two methods of growth: solitary or clustered; the common representation is that of a solitary shoot ending in a crown of leaves. This monopodial character may be exhibited by prostrate and trunk-forming members; some common palms restricted to solitary growth include Roystonea. Palms may instead grow in sparse though dense clusters; the trunk develops an axillary bud at a leaf node near the base, from which a new shoot emerges. The new shoot, in turn, produces a clustering habit results. Sympodial genera include many of the rattans and Rhapis. Several palm genera have both solitary and clustering members. Palms which are solitary may grow in clusters and vice versa; these aberrations suggest. Palms have large, evergreen leaves that are either palmately or pinnately compound and spirally arranged at the top of the stem; the leaves have a tubular sheath at the base that splits open on one side at maturity.
The inflorescence is a spadix or spike surrounded by one or more bracts or spathes that become woody at maturity. The flowers are small and white, radially symmetric, can be either uni- or bisexual; the sepals and petals number three each, may be distinct or joined at the base. The stamens number six, with filaments that may be separate, attached to each other, or attached to the pistil at the base; the fruit is a single-seeded drupe but some genera may contain two or more seeds in each fruit. Like all monocots, palms do not have the ability to increase the width of a stem via the same kind of vascular cambium found in non-monocot woody plants; this explains the cylindrical shape of the trunk, seen in palms, unlike in ring-forming trees. However, many palms, like some other monocots, do have secondary growth, although because it does not arise from a single vascular cambium producing xylem inwards and phloem outwards, it is called "anomalous secondary growth"; the Arecaceae are notable among monocots for their height and for the size of their seeds and inflorescences.
Ceroxylon quindiuense, Colombia's national tree, is the tallest monocot in the world, reaching up to 60 m tall. The coco de mer has the largest seeds of 40 -- 50 cm in diameter and weighing 15 -- 30 kg each. Raffia palms have the largest leaves of any plant, up to 25 m long and 3 m wide; the Corypha species have the largest inflorescence of any plant, up to 7.5 m tall and containing millions of small flowers. Calamus stems. Most palms are native to subtropical climates. Palms can be found in a variety of different habitats, their diversity is highest in lowland forests. South America, the Caribbean, areas of the south Pacific and southern Asia are regions of concentration. Colombia may have the highest number of palm species in one country. There are some palms that are native to desert areas such as the Arabian peninsula and parts of northwestern Mexico. Only about 130 palm species grow beyond the tropics in humid lowland subtropical climates, in highlands in southern Asia, along the rim lands of the Mediterranean Sea.
The northernmost native palm is Chamaerops humilis, which reaches 44°N latitude along the coast of southern France. In the southern hemisphere, the southernmost palm is the Rhopalostylis sapida, which reaches 44°S on the Chatham Islands where an oceanic climate prevails. Cultivation of palms is possible north of subtropical climates, some higher latitude locals such as Ireland, Scotland and the Pacific Northwest feature a few palms in protected locations. Palms inhabit a variety of ecosystems. More than two-thirds of palm species live in humid moist forests, where some species grow tall enough to form part of the canopy and shorter ones form part of the understory; some species form pure stands in areas with poor drainage or regular flooding, including Raphia hookeri, common in coastal freshwater swamps in West Africa. Other palms live in tropical mountain habitats above 1000 m, such as those in the genus Ceroxylon native to the Andes. Palms may live in grasslands and scrublands associated with a water source, in desert oases such as the date palm.
A few palms are adapted to basic lime soils, while others are ada
A pupa is the life stage of some insects undergoing transformation between immature and mature stages. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, with four life stages: egg, larva and imago; the processes of entering and completing the pupal stage are controlled by the insect's hormones juvenile hormone, prothoracicotropic hormone, ecdysone. The pupae of different groups of insects have different names such as chrysalis for the pupae of butterflies and tumbler for those of the mosquito family. Pupae may further be enclosed in other structures such as nests, or shells; the pupal stage follows the larval stage and precedes adulthood in insects with complete metamorphosis. The pupa is a non-feeding sessile stage, or active as in mosquitoes, it is during pupation that the adult structures of the insect are formed while the larval structures are broken down. The adult structures grow from imaginal discs. Pupation may last weeks, months, or years, depending on temperature and the species of insect.
For example, pupation lasts eight to fifteen days in monarch butterflies. The pupa may diapause until the appropriate season to emerge as an adult insect. In temperate climates pupae stay dormant during winter, while in the tropics pupae do so during the dry season. Insects emerge from pupae by splitting the pupal case. Most butterflies emerge in the morning. In mosquitoes the emergence is in the night. In fleas the process is triggered by vibrations that indicate the possible presence of a suitable host. Prior to emergence, the adult inside the pupal exoskeleton is termed pharate. Once the pharate adult has eclosed from the pupa, the empty pupal exoskeleton is called an exuvia. In a few taxa of the Lepidoptera Heliconius, pupal mating is an extreme form of reproductive strategy in which the adult male mates with a female pupa about to emerge, or with the newly moulted female. Pupae are immobile and are defenseless. To overcome this, a common strategy is concealed placement. There are some species of Lycaenid butterflies.
Another means of defense by pupae of other species is the capability of making sounds or vibrations to scare potential predators. A few species use chemical defenses including toxic secretions; the pupae of social hymenopterans are protected by adult members of the hive. Based on the presence or absence of articulated mandibles that are employed in emerging from a cocoon or pupal case, the pupae can be classified in to two types: Decticous pupa – pupae with articulated mandibles. Examples are pupae of the orders Neuroptera, Mecoptera and few Lepidoptera families. Adecticous pupa – pupae without articulated mandibles. Examples include orders Strepsiptera, Hymenoptera and Siphonaptera. Based on whether the pupal appendages are free or attached to the body, the pupae can be classified in three types: Exarate pupa – appendages are free and are not encapsulated within a cocoon. All decticous pupa and some adecticous pupa are always exarate.. Obtect pupa – appendages are attached to the body and are encapsulated within a cocoon.
Some adecticous pupa are obtect forms. Coarctate pupa – enclosed in a hardened cuticle of the penultimate larval instar called puparium. However, the pupa itself is of exarate adecticous pupa forms.. A chrysalis or nympha is the pupal stage of butterflies; the term is derived from the metallic gold-coloration found in the pupae of many butterflies, referred to by the Greek term χρυσός for gold. When the caterpillar is grown, it makes a button of silk which it uses to fasten its body to a leaf or a twig; the caterpillar's skin comes off for the final time. Under this old skin is a hard skin called a chrysalis; because chrysalises are showy and are formed in the open, they are the most familiar examples of pupae. Most chrysalides are attached to a surface by a Velcro-like arrangement of a silken pad spun by the caterpillar cemented to the underside of a perch, the cremastral hook or hooks protruding from the rear of the chrysalis or cremaster at the tip of the pupal abdomen by which the caterpillar fixes itself to the pad of silk.
Like other types of pupae, the chrysalis stage in most butterflies is one in which there is little movement. However, some butterfly pupae are capable of moving the abdominal segments to produce sounds or to scare away potential predators. Within the chrysalis and differentiation occur; the adult butterfly emerges from this and expands its wings by pumping haemolymph into the wing veins. Although this sudden and rapid change from pupa to imago is called metamorphosis, metamorphosis is the whole series of changes that an insect undergoes from egg to adult; when emerging, the butterfly uses a liquid, sometimes called cocoonase, which softens the shell of the chrysalis. Additionally, it uses two sharp claws located on the th
Chihuahua the Free and Sovereign State of Chihuahua, is one of the 31 states of Mexico. It is located in Northwestern Mexico and is bordered by the states of Sonora to the west, Sinaloa to the southwest, Durango to the south, Coahuila to the east. To the north and northeast, it has a long border with the U. S. adjacent to the U. S. states of New Texas. Its capital city is Chihuahua City. Although Chihuahua is identified with the Chihuahuan Desert for namesake, it has more forests than any other state in Mexico, with the exception of Durango. Due to its variant climate, the state has a large variety of flora; the state is characterized by rugged mountainous terrain and wide river valleys. The Sierra Madre Occidental mountain range, part of the continental spine that includes the Rocky Mountains, dominates the state's terrain and is home to the state's greatest attraction, Las Barrancas del Cobre, or Copper Canyon, a canyon system larger and deeper than the Grand Canyon. On the slope of the Sierra Madre Occidental mountains, there are vast prairies of short yellow grass, the source of the bulk of the state's agricultural production.
Most of the inhabitants live along the Conchos River Valley. The etymology of the name Chihuahua has long been disputed by linguists; the most accepted theory explains that the name was derived from the Nahuatl language meaning "The place where the water of the rivers meet". Chihuahua is the largest state in Mexico by area, with an area of 247,455 square kilometres, it is larger than the United Kingdom and smaller than Wyoming, tenth US state in area; the state is known under the nickname El Estado Grande. Chihuahua has a diversified state economy; the three most important economic centers in the state are: Ciudad Juárez, an international manufacturing center. Today Chihuahua serves as an important commercial route prospering from billions of dollars from international trade as a result of NAFTA. On the other hand the state suffers the fallout of illicit trade and activities at the border; the earliest evidence of human inhabitants of modern day Chihuahua was discovered in the area of Samalayuca and Rancho Colorado.
Clovis points have been found in northeastern Chihuahua that have been dated from 12,000 BC to 7000 BC. It is thought. Inhabitants of the state developed farming with the domestication of corn. An archeological site in northern Chihuahua known as Cerro Juanaqueña revealed squash cultivation, irrigation techniques, ceramic artifacts dating to around 2000 BC. Between AD 300 and 1300 in the northern part of the state along the wide, fertile valley on the San Miguel River the Casas Grandes culture developed into an advanced civilization; the Casas Grandes civilization is part of a major prehistoric archaeological culture known as Mogollon, related to the Ancestral Pueblo culture. Paquime was the center of the Casas Grandes civilization. Extensive archaeological evidence shows commerce and hunting at Paquime and Cuarenta Casas. La Cueva De Las Ventanas, a series of cliff dwellings along an important trade route, Las Jarillas Cave scrambled along the canyons of the Sierra Madre in Northwestern Chihuahua date between AD 1205 and 1260 and belong to the Paquimé culture.
Cuarenta Casas is thought to have been a branch settlement from Paquime to protect the trade route from attack. Archaeologists believe the civilization began to decline during the 13th century and by the 15th century the inhabitants of Paquime sought refuge in the Sierra Madre Occidental while others are thought to have emigrated north and joined the Ancestral Pueblo peoples. According to anthropologist current natives tribes are descendants of the Casas Grandes culture. During the 14th century in the northeastern part of the state nomad tribes by the name of Jornado hunted bison along the Rio Grande; when the Spanish explorers reached this area they found their descendants and Manso tribes. In the southern part of the state, in a region known as Aridoamerica, Chichimeca people survived by hunting and farming between AD 300 and 1300; the Chichimeca are the ancestors of the Tepehuan people. Nueva Vizcaya was the first province of northern New Spain to be explored and settled by the Spanish. Around 1528, a group of Spaniard explorers, led by Álvar Núñez Cabeza de Vaca, first entered the territory of what is now Chihuahua.
The conquest of the territory lasted nearly one century and encountered fierce resistance from the Conchos tribe, but the desire of the Spanish Crown to transform the region into a bustling mining center led to a strong strategy to control the area. In 1562 Francisco de Ibarra headed a personal expedition in search of the mythical cities of Cibola and Quivira. Francisco de Ibarra is thought to have been the first European to see the ruins of Paquime. In 1564 Rodrigo de Río de Loza, a lieutenant under Francisco de Ibarra, stayed behind after the expedition and found gold at the foot of the mountains of the Sierra Madre Occidental.
An old-growth forest — termed primary forest or late seral forest — is a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community. Old-growth features include diverse tree-related structures that provide diverse wildlife habitat that increases the biodiversity of the forested ecosystem; the concept of diverse tree structure includes multi-layered canopies and canopy gaps varying tree heights and diameters, diverse tree species and classes and sizes of woody debris. Old-growth forests are valuable for economic reasons and for the ecosystem services they provide; this can be a point of contention when some in the logging industry may desire to cut down the forests to obtain valuable timber, while environmentalists seek to preserve the forests for benefits such as maintenance of biodiversity, water regulation, nutrient cycling. Old-growth forests tend to have large trees and standing dead trees, multilayered canopies with gaps that result from the deaths of individual trees, coarse woody debris on the forest floor.
Forest regenerated after a severe disturbance, such as wildfire, insect infestation, or harvesting, is called second-growth or'regeneration' until enough time passes for the effects of the disturbance to be no longer evident. Depending on the forest, this may take from a century to several millennia. Hardwood forests of the eastern United States can develop old-growth characteristics in 150–500 years. In British Columbia, old growth is defined as 120 to 140 years of age in the interior of the province where fire is a frequent and natural occurrence. In British Columbia’s coastal rainforests, old growth is defined as trees more than 250 years, with some trees reaching more than 1,000 years of age. In Australia, eucalypt trees exceed 350 years of age due to frequent fire disturbance. Forest types have different development patterns, natural disturbances and appearances. A Douglas-fir stand may grow for centuries without disturbance while an old-growth ponderosa pine forest requires frequent surface fires to reduce the shade-tolerant species and regenerate the canopy species.
In the Boreal-West Forest Region, catastrophic disturbances like wildfires minimize opportunities for major accumulations of dead and downed woody material and other structural legacies associated with old growth conditions. Typical characteristics of old-growth forest include presence of older trees, minimal signs of human disturbance, mixed-age stands, presence of canopy openings due to tree falls, pit-and-mound topography, down wood in various stages of decay, standing snags, multilayered canopies, intact soils, a healthy fungal ecosystem, presence of indicator species. Old-growth forests are biologically diverse, home to many rare species, threatened species, endangered species of plants and animals, such as the northern spotted owl, marbled murrelet and fisher, making them ecologically significant. Levels of biodiversity may be higher or lower in old-growth forests compared to that in second-growth forests, depending on specific circumstances, environmental variables, geographic variables.
Logging in old-growth forests is a contentious issue in many parts of the world. Excessive logging reduces biodiversity, affecting not only the old-growth forest itself, but indigenous species that rely upon old-growth forest habitat. A forest in old-growth stage has a mix of tree ages, due to a distinct regeneration pattern for this stage. New trees regenerate at different times from each other, because each one of them has different spatial location relative to the main canopy, hence each one receives a different amount of light; the mixed age of the forest is an important criterion in ensuring that the forest is a stable ecosystem in the long term. A climax stand, uniformly aged becomes senescent and degrades within a short time to result in a new cycle of forest succession. Thus, uniformly aged stands are less stable ecosystems. Forest canopy gaps are essential in maintaining mixed-age stands; some herbaceous plants only become established in canopy openings, but persist beneath an understory.
Openings are a result of tree death due to small impact disturbances such as wind, low-intensity fires, tree diseases. Old-growth forests are unique having multiple horizontal layers of vegetation representing a variety of tree species, age classes, sizes, as well as "pit and mound" soil shape with well-established fungal nets; because old-growth forest is structurally diverse, it provides higher-diversity habitat than forests in other stages. Thus, sometimes higher biological diversity can be sustained in old-growth forest, or at least a biodiversity, different from other forest stages; the characteristic topography of much old-growth forest consists of mounds. Mounds are caused by decaying fallen trees, pits by the roots pulled out of the ground when trees fall due to natural causes, including being pushed over by animals. Pits expose humus-poor, mineral-rich soil and collect moisture and fallen leaves, forming a thick organic layer, able to nurture certain types of organisms. Mounds provide a place free of leaf inundation and saturation, where other types of organisms thrive.
Standing snags provide food sources and habitat for many types of organisms. In particular, many species of dead-wood predators such as woodpeckers must have standing snags available for feeding. In North America, the spotted owl is well known for needing standing snags for nesting habitat. Fallen timber, or coarse woody debris, contributes carbon-rich organic matter directly to the soil, providing a substrate for mosses and seedlings, cr
The Americas comprise the totality of the continents of North and South America. Together, they comprise the New World. Along with their associated islands, they cover 8% of Earth's total surface area and 28.4% of its land area. The topography is dominated by the American Cordillera, a long chain of mountains that runs the length of the west coast; the flatter eastern side of the Americas is dominated by large river basins, such as the Amazon, St. Lawrence River / Great Lakes basin, La Plata. Since the Americas extend 14,000 km from north to south, the climate and ecology vary from the arctic tundra of Northern Canada and Alaska, to the tropical rain forests in Central America and South America. Humans first settled the Americas from Asia between 17,000 years ago. A second migration of Na-Dene speakers followed from Asia; the subsequent migration of the Inuit into the neoarctic around 3500 BCE completed what is regarded as the settlement by the indigenous peoples of the Americas. The first known European settlement in the Americas was by the Norse explorer Leif Erikson.
However, the colonization never became permanent and was abandoned. The Spanish voyages of Christopher Columbus from 1492 to 1502 resulted in permanent contact with European powers, which led to the Columbian exchange and inaugurated a period of exploration and colonization whose effects and consequences persist to the present. Diseases introduced from Europe and West Africa devastated the indigenous peoples, the European powers colonized the Americas. Mass emigration from Europe, including large numbers of indentured servants, importation of African slaves replaced the indigenous peoples. Decolonization of the Americas began with the American Revolution in the 1770s and ended with the Spanish–American War in the late 1890s. All of the population of the Americas resides in independent countries; the Americas are home to over a billion inhabitants, two-thirds of which reside in the United States, Brazil, or Mexico. It is home to eight megacities: New York City, Mexico City, São Paulo, Los Angeles, Buenos Aires, Rio de Janeiro, Bogotá, Lima.
The name America was first recorded in 1507. Christie's auction house says a two-dimensional globe created by Martin Waldseemüller was the earliest recorded use of the term; the name was used in the Cosmographiae Introductio written by Matthias Ringmann, in reference to South America. It was applied to both North and South America by Gerardus Mercator in 1538. America derives from the Latin version of Italian explorer Amerigo Vespucci's first name; the feminine form America accorded with the feminine names of Asia and Europa. In modern English and South America are considered separate continents, taken together are called America or the Americas in the plural; when conceived as a unitary continent, the form is the continent of America in the singular. However, without a clarifying context, singular America in English refers to the United States of America. In the English-speaking world, the term America used to refer to a single continent until the 1950s: According to historians Kären Wigen and Martin W. Lewis, While it might seem surprising to find North and South America still joined into a single continent in a book published in the United States in 1937, such a notion remained common until World War II.
By the 1950s, however all American geographers had come to insist that the visually distinct landmasses of North and South America deserved separate designations. This shift did not seem to happen in Romance-speaking countries, where America is still considered a continent encompassing the North America and South America subcontinents, as well as Central America; the first inhabitants migrated into the Americas from Asia. Habitation sites are known in Alaska and the Yukon from at least 20,000 years ago, with suggested ages of up to 40,000 years. Beyond that, the specifics of the Paleo-Indian migration to and throughout the Americas, including the dates and routes traveled, are subject to ongoing research and discussion. Widespread habitation of the Americas occurred during the late glacial maximum, from 16,000 to 13,000 years ago; the traditional theory has been that these early migrants moved into the Beringia land bridge between eastern Siberia and present-day Alaska around 40,000–17,000 years ago, when sea levels were lowered during the Quaternary glaciation.
These people are believed to have followed herds of now-extinct pleistocene megafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets. Another route proposed is that, either on foot or using primitive boats, they migrated down the Pacific coast to South America. Evidence of the latter would since have been covered by a sea level rise of hundreds of meters following the last ice age. Both routes may have
Sierra Madre Occidental
The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, along the Gulf of California. The Sierra Madre is part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of mountain ranges that form the western'backbone' of North America, Central America, South America and West Antarctica; the Spanish name sierra madre means "mother mountains" in English, occidental means "western", these thus being the "Western Mother Mountains". To the east, from the Spanish oriental meaning "eastern" in English, the Sierra Madre Oriental range or "Eastern Mother Mountains" runs parallel to the Sierra Madre Occidental along eastern Mexico and the Gulf of Mexico; the range extends from northern Sonora state near the Mexico-U. S. Border at Arizona, southeastwards to the Trans-Mexican Volcanic Belt and Sierra Madre del Sur ranges; the high plateau, formed by the range is cut by deep river valleys.
This plateau is formed from volcanic rock overlying a basement of metamorphic rock. This uplift has caused changes in weather patterns; this water source forms watersheds that provide the arid surroundings with water that makes it possible to irrigate and farm crops. The wet ecosystems are islands of biodiversity, differing from what would otherwise be a desert landscape. Oak forests are the predominant plant life, extend into the lowland deserts; this forest and canyon land provided a place for a variety of indigenous people to live, until Spanish settlers with associated mestizos came into the area to found towns for the silver mines in the area. The major industries in the area now are agriculture and forestry, which have become contentious because of land degradation and the native population's opposition to these practices; the range trends from the north to southeast. Canyons cut by the rivers of the wet western slopes exist in addition to those of the northeast slopes, notably the Copper Canyon.
The range runs parallel to the Pacific coast of Mexico, from just south of the Arizona-Sonora border southeast through eastern Sonora, western Chihuahua, Durango, Nayarit, Aguascalientes to Guanajuato, where it joins with the Sierra Madre del Sur and the Eje Volcánico Transversal of central Mexico after crossing 1,250 km. The mountains range from 300 km from the Gulf of California in the north, but begin to approach within 50 km of the Pacific in the south; these mountains are considered to be part of the much larger American cordillera, the mountains extending from Alaska down to these across western North America. Sierra Tarahumara or Tarahumara is the name for the region of the Sierra Madre beginning at the Durango border and extending north; this name comes from the Tarahumara natives. This is a dramatic landscape of steep mountains formed by a high plateau, cut through with canyons including Copper Canyon, larger and, in places, deeper than the Grand Canyon; this plateau has an average elevation of 2,250 m with most of the more eroded canyons on the western slope, due to the higher moisture content.
The highest elevations occur in the Tarahumara range. The exact elevations of the highest peaks are not known within accurate enough ranges to determine their relative elevation; the highest point is Cerro Mohinora, located at 25°57′N 107°03′W. Estimates for the height of the mountain start around 3,040 m and go up to 3,300 m. However, Cerro Barajas, at 26°24′N 106°5′W, may be as high as 3,300 m although other sources give 3,170 m as the elevation. Cerro Gordo, at 23°12′N 104°57′W, may have an elevation between 3,350 m and 3,340 m; the southern end of the mountains may be referred to as the Sierra Huichola. In this area, the Sierra Madre begins to give way to the range province. Subranges of this area include the Sierra Pajaritos, both in Nayarit; the mountains act as a source of water, in an otherwise arid environment from the increased precipitation from the mountain range. As such, rivers that have headwaters in the mountains provide water for irrigation in the surrounding lands; the need for water to irrigate prompted the construction of dams, the source of several environmental concerns in the area.
The northern end of the range is more arid. The Yaqui drains into the Gulf of California, as do the Humaya River in Sinaloa and the Fuerte River further south; the Río Grande de Santiago drains 100,000 km2 from the southern slopes of the Sierra Madre. Along the more arid eastern slopes of the mountains, the Nazas River and Aguanaval River drain the mountains into a closed basin; these mountains supply 90% of the water used for irrigation within the watershed. North of this system is the Conchos River. Along many rivers the arid conditions have caused courses to be dammed to provide water for irrigation; these dams have caused concerns along with those caused by other activities. The Yaqui has been dammed with three large reservoirs along its course; the Río Grande de Santiago has been dammed, including the Aguamilpa dam begun in 1991 and the El Cajón Dam upstream from it. To provide irrigation water for farming the dry basin, the Nazas river was dammed in the 1930s and 1940s; this has led to the former drainage lakes in the area drying up, soil depletion from the eliminat