Himalayas

The Himalayas, or Himalaya (/ˌhɪməˈleɪ.ə, hɪˈmɑːləjə/ HIM-ə-LAY-ə, hih-MAH-lə-yə) is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than 100 peaks exceeding elevations of 7,200 m (23,600 ft) above sea level lie in the Himalayas.
The Himalayas abut on or cross territories of six countries: Nepal, China, Pakistan, Bhutan, India and Afghanistan. The sovereignty of the range in the Kashmir region is disputed among India, Pakistan, and China. The Himalayan range is bordered on the northwest by the Karakoram and Hindu Kush ranges, on the north by the Tibetan Plateau, and on the south by the Indo-Gangetic Plain. Some of the world's major rivers, the Indus, the Ganges, and the Tsangpo–Brahmaputra, rise in the vicinity of the Himalayas, and their combined drainage basin is home to some 600 million people; 53 million people live in the Himalayas. The Himalayas have profoundly shaped the cultures of South Asia and Tibet. Many Himalayan peaks are sacred in Hinduism and Buddhism. The summits of several—Kangchenjunga (from the Indian side), Gangkhar Puensum, Machapuchare, Nanda Devi, and Kailash in the Tibetan Transhimalaya—are off-limits to climbers.
The Himalayas were uplifted after the collision of the Indian tectonic plate with the Eurasian plate, specifically, by the folding, or nappe-formation of the uppermost Indian crust, even as a lower layer continued to push on into Tibet and add thickness to its plateau; the still lower crust, along with the mantle, however, subducted under Eurasia. The Himalayan mountain range runs west-northwest to east-southeast in an arc 2,400 km (1,500 mi) long. Its western anchor, Nanga Parbat, lies just south of the northernmost bend of the Indus river. Its eastern anchor, Namcha Barwa, lies immediately west of the great bend of the Yarlung Tsangpo River. The Indus-Yarlung suture zone, along which the headwaters of these two rivers flow, separates the Himalayas from the Tibetan plateau; the rivers also separate the Himalayas from the Karakorams, the Hindu Kush, and the Transhimalaya. The range varies in width from 350 km (220 mi) in the west to 150 km (93 mi) in the east.
The name of the range hails from the Sanskrit Himālaya (हिमालय 'abode of snow'), from hima (हिम 'frost/cold') and ālaya (आलय 'dwelling/house'). They are now known as "the Himalaya Mountains", usually shortened to "the Himalayas".
The mountains are known as the Himālaya in Nepali and Hindi (both written हिमालय), Hinvāl (हिंवाळ) in Garhwali, Himāl (हिमाल) in Kumaoni, the Himalaya (ཧི་མ་ལ་ཡ་) or 'The Land of Snow' (གངས་ཅན་ལྗོངས་) in Tibetan, also known as Himālaya in Sinhala (written as හිමාලය), the Himāliya Mountain Range (سلسلہ کوہ ہمالیہ) in Urdu, the Himaloy Parvatmala (হিমালয় পর্বতমালা) in Bengali, and the Ximalaya Mountain Range (simplified Chinese: 喜马拉雅山脉; traditional Chinese: 喜馬拉雅山脉; pinyin: Xǐmǎlāyǎ Shānmài) in Chinese.
The name of the range is sometimes also given as Himavan in older writings, including the Sanskrit epic Mahabharata. Himavat (Sanskrit: हिमवत्) or Himavan Himavān (Sanskrit: हिमवान्) is a Hindu deity who is the personification of the Himalayan Mountain Range. Other epithets include Himaraja (Sanskrit: हिमराज, lit. 'king of snow') or Parvateshwara (Sanskrit: पर्वतेश्वर, lit. 'lord of mountains').
In western literature, some writers refer to it as the Himalaya. This was also previously transcribed as Himmaleh, as in Emily Dickinson's poetry and Henry David Thoreau's essays.
The Himalayas consists of four parallel mountain ranges from south to north: the Sivalik Hills on the south; the Lower Himalayan Range; the Great Himalayas, which is the highest and central range; and the Tibetan Himalayas on the north. The Karakoram are generally considered separate from the Himalayas.
In the middle of the great curve of the Himalayan mountains lie the 8,000 m (26,000 ft) peaks of Dhaulagiri and Annapurna in Nepal, separated by the Kali Gandaki Gorge. The gorge splits the Himalayas into Western and Eastern sections, both ecologically and orographically – the pass at the head of the Kali Gandaki, the Kora La, is the lowest point on the ridgeline between Everest and K2 (the highest peak of the Karakoram range). To the east of Annapurna are the 8,000 m (5.0 miles) peaks of Manaslu and across the border in Tibet, Shishapangma. To the south of these lies Kathmandu, the capital of Nepal and the largest city in the Himalayas. East of the Kathmandu Valley lies the valley of the Bhote/Sun Kosi river which rises in Tibet and provides the main overland route between Nepal and China – the Araniko Highway/China National Highway 318. Further east is the Mahalangur Himal with four of the world's six highest mountains, including the highest: Cho Oyu, Everest, Lhotse, and Makalu. The Khumbu region, popular for trekking, is found here on the south-western approaches to Everest. The Arun river drains the northern slopes of these mountains, before turning south and flowing to the range to the east of Makalu.
In the far east of Nepal, the Himalayas rise to the Kangchenjunga massif on the border with India, the third-highest mountain in the world, the most easterly 8,000 m (26,000 ft) summit and the highest point of India. The eastern side of Kangchenjunga is in the Indian state of Sikkim. Formerly an independent Kingdom, it lies on the main route from India to Lhasa, Tibet, which passes over the Nathu La pass into Tibet. East of Sikkim lies the ancient Buddhist Kingdom of Bhutan. The highest mountain in Bhutan is Gangkhar Puensum, which is also a strong candidate for the highest unclimbed mountain in the world. The Himalayas here are becoming increasingly rugged, with heavily forested steep valleys. The Himalayas continue, turning slightly northeast, through the Indian State of Arunachal Pradesh as well as Tibet, before reaching their easterly conclusion in the peak of Namche Barwa, situated in Tibet, inside the great bend of the Yarlang Tsangpo river. On the other side of the Tsangpo, to the east, are the Kangri Garpo mountains. The high mountains to the north of the Tsangpo, including Gyala Peri, however, are also sometimes included in the Himalayas.
Going west from Dhaulagiri, Western Nepal is somewhat remote and lacks major high mountains, but is home to Rara Lake, the largest lake in Nepal. The Karnali River rises in Tibet but cuts through the centre of the region. Further west, the border with India follows the Sarda River and provides a trade route into China, where on the Tibetan plateau lies the high peak of Gurla Mandhata. Just across Lake Manasarovar from this lies the sacred Mount Kailash in the Kailash Ranges, which stands close to the source of the four main rivers of Himalayas and is revered in Hinduism, Jainism, Buddhism, Sufism and Bonpo. In Uttarakhand, the Himalayas are regionally divided into the Kumaon and Garhwal Himalayas with the high peaks of Nanda Devi and Kamet. The state is also home to the important pilgrimage destinations of Chota Chaar Dhaam, with Gangotri, the source of the holy river Ganges, Yamunotri, the source of the river Yamuna, and the temples at Badrinath and Kedarnath.
The next Himalayan Indian state, Himachal Pradesh, is noted for its hill stations, particularly Shimla, the summer capital of the British Raj, and Dharamsala, the centre of the Tibetan community and government in exile in India. This area marks the start of the Punjab Himalaya and the Sutlej river, the most easterly of the five tributaries of the Indus, cuts through the range here. Further west, the Himalayas form much of the disputed Indian-administered union territory of Jammu and Kashmir where lie the mountainous Jammu region and the renowned Kashmir Valley with the town and lakes of Srinagar. The Himalayas form most of the south-west portion of the disputed Indian-administered union territory of Ladakh. The twin peaks of Nun Kun are the only mountains over 7,000 m (4.3 miles) in this part of the Himalayas. Finally, the Himalayas reach their western end in the dramatic 8000 m peak of Nanga Parbat, which rises over 8,000 m (26,000 ft) above the Indus valley and is the most westerly of the 8000 m summits. The western end terminates at a magnificent point near Nanga Parbat where the Himalayas intersect with the Karakoram and Hindu Kush ranges, in the disputed Pakistani-administered territory of Gilgit-Baltistan. Some portion of the Himalayas, such as the Kaghan Valley, Margalla Hills, and Galyat tract, extend into the Pakistani provinces of Khyber Pakhtunkhwa and Punjab.
Tectonics, the recurring physical changes that affect the arrangement of the Earth's crust, and plate tectonics, the movement of large regions of the Earth's crust in the manner of planar rigid bodies, are key to understanding the formation of the Himalayas. The Earth's crust rests directly on its mantle. Tectonic plates, comprising the crust and the upper portions of their underlying mantle, are moved around by convection in the asthenosphere. The oceanic crust, found beneath oceans, is, on average, 7 km thick. It is created from upwelling magma at mid-ocean ridges and predominantly consists of basalt, the principal igneous rock on Earth. In contrast, the continental crust underlying dry land has an average thickness of 35 km and is rich in silica, which is less dense than basalt. It makes the continental tectonic plates more buoyant than the oceanic.
India's defining geologic processes, which began 70 million years ago, had involved India rifting, or splitting away, from Gondwana, and the Indian continental plate along with the Neo-Tethys oceanic plate above it jointly moving northward. As these eventually reached the Eurasian plate, the less buoyant oceanic plate subducted, or slid under Eurasia and was carried into the deeper asthenosphere. In contrast, the Indian continental plate was obstructed because of its thickness and buoyancy. The lateral compression generated by the obstruction caused the plate to be sheared horizontally. Its lower crust and mantle slid under, but one layer of the upper crust piled up in sheets (called nappes) ahead of the subduction zone. Geophysicist Peter Molnar noted that most of the Himalayas are "slices of rock that once were the top part of India's crust." This is the process of mountain building, or orogeny, in the Himalayas.
Before the orogeny, the Eurasian coastline had been similar to today's Central Andes. Along such coastlines, the adjoining oceanic plate subducts and erupts as volcanoes. Magma, which eventually crystallizes into granite, rises into the Earth's crust below the active volcanoes but not to the surface. When India's continental plate pushed against Eurasia, not only did a part of the upper crust fold in nappes, but another stiffer part began to push against (or drag) Eurasia's ancient volcanic mountains farther north. As a result, the crust of this formerly coastal region shortened under compression and thickened to become what is today the Tibetan Plateau. Isostatic equilibrium, or the balance between the gravitational force pulling down on the crust and the force of buoyancy pushing up from the mantle, gives the Tibetan Plateau its notable thickness and altitude.
The Indian plate was not the only landmass that had rifted from Gondwana and drifted northward toward Eurasia. Before the India-Eurasia collision in Middle Paleocene (60 Mya) and subsequent Himalayan orogeny, two other landmasses, the Qiangtang terrane and Lhasa terrane, had drifted up from Gondwana. Qiangtang, a geological region in what is today northern Tibet, had done so in Late Triassic (237–201 Mya). The Lhasa terrane collided with the southern boundary of the Qiangtang in the Early Cretaceous (145–100 Mya). The collision caused the lithospheric mantle of the Lhasa terrane to thicken and shorten, forming a barrier that later prevented the Indian lithosphere from fully subducting under Tibet and leading to further thickening of the Tibetan plateau. The suture zones, or remains of the subduction zone and the terranes that are joined, are found in the Tibetan plateau. The Qiantang and Lhasa terranes were part of the string of microcontinents Cimmeria, today constituting parts of Turkey, Iran, Pakistan, China, Myanmar, Thailand and Malaysia, which had rifted from Gondwana earlier, closing the Paleo-Tethys Ocean above them and opening the Neo-Tethys Ocean between them and Gondwana, eventually colliding with Eurasia, and creating the Cimmerian Orogeny.
After the Lhasa terrane had adjoined Eurasia, an active continental margin opened along its southern flank, below which the Neo-Tethys oceanic plate had begun to subduct. Magmatic activity along this flank produced the Gangdese batholith in what is today the Tibetan trans-Himalaya. Another subduction zone opened to the west, in the ocean basin above the Kohistan-Ladakh island arc. This island arc—formed by one oceanic plate subducting beneath another, its magma rising and creating continental crust—drifted north, closed its ocean basin and collided with Eurasia.
The collision of India with Eurasia closed the Neo-Tethys Ocean. The suture zone (in this instance, the remnants of the Neo-Tethys subduction zone pinched between the two continental crusts), which marks India's welding to Eurasia, is called the Indus-Yarlung suture zone. It lies north of the Himalayas. The headwaters of the Indus River and the Yarlung Tsangpo (later in its course, the Brahmaputra) flow along this suture zone. These two Eurasian rivers, whose courses were continually diverted by the rising Himalayas, define the western and eastern limits, respectively, of the Himalayan mountain range.
During the India-Eurasia collision, two elongated protrusions located on either side of the northern border of the Indian continent generated areas of extreme deformation. A point where mountain ranges with different directions of extension, and thus formed by tectonic forces at varying angles, converge is called a syntaxis (Greek: convergence). The two syntaxes, Nanga Parbat and Namche Barwa, on the northwestern and northeastern corners of the Indian continent, respectively, are characterized by the quick upward movement of land or rocks that were once deeply buried and significantly altered by extreme heat and pressure. Geologists have estimated the rate of uplift of these rocks to be 7 millimetres (0.28 in) per year, or 7 kilometres (4.3 mi) per million years. The protruding regions have some of the highest mountain peaks at 8,125 metres (26,657 ft) and 7,756 metres (25,446 ft), respectively. The regions also have the greatest topographical relief in the interior of a continent, approximately 7,000 metres (23,000 ft) over a horizontal distance of 20–30 kilometres (12–19 mi). Nanga Parbat has a narrow, anticline, or arch-shaped fold whose crest dips sharply to the north, perpendicular to the general direction along which the Himalayas extend. The Indus and Yarlung Tsangpo, which originally emptied into the New-Tethys, now bend around the Nanga Parbat and Namche Barwa, respectively, to eventually empty into the Indian Ocean.
Geologists Wolfgang Frisch, Martin Meschede, and Ronand Blakey write, "India rapidly marched northward towards Asia with a velocity of ca. 20 cm/yr, a plate velocity that exceeds any modern example. This velocity considerably slowed to ca. 5 cm/yr following the collision, yet India continued to protrude into Asia for more than 2000 km. ... The irregular northern margin of the Indian continental crust first came into contact with Eurasia along its northwestern corner, approximately 55 Ma. As a consequence, India underwent a counter-clockwise rotation to close the remaining part of the Neotethys in scissor-like fashion from west to east. The closure of the Neotethys was completed approximately 40 Ma."
Today, the Indian plate continues to be driven horizontally at the Tibetan Plateau, which forces the plateau to continue to move upwards. The Indian plate is moving at 67 mm (2.6 in) per year, and over the next 10 million years, it will travel 1,500 km (930 mi) into Asia. Approximately 20 mm per year of the India-Asia convergence is absorbed by thrusting along the Himalaya southern front. This leads to the Himalayas rising by about 5 mm annually, making them geologically active. The movement of the Indian plate into the Asian plate also makes this region seismically active, leading to earthquakes from time to time.
The Himalayan mountain range consists of three sub-ranges: (1) the Higher- or "Tethys" Himalayas, (2) the Lesser Himalayas, and (3) the Siwaliks. The nappes—large, stacked sheets of rock—found in the Tethys Himalayan mountain range, are primarily composed of sedimentary rocks, such as limestone formed from the accumulation and compression of sediments like sand, mud, and shells deposited in the Neo-Tethys seabed during the Paleogene" (66 Mya–23 Mya). Below the sedimentary rocks in the Higher and Lesser Himalayas is a bottom layer, or basement, composed of metamorphic rock formed much earlier during the Pan-African-Cadomian orogeny between 650 Mya and 550 Mya. The lowest subrange, the Siwaliks, represents the sedimentary rock deposits washed off the rising Himalayas in a foreland basin, a low-lying crustal region, at their foot. It primarily consists of sandstones, shales, and conglomerates formed during the Neogene period (23 Mya to 2.6 Mya).
Geologists Wolfgang Frisch, Martin Meschede, and Ronand Blakey further write, "The Siwaliks are both underlain and overlain by thrusts; they have been overridden by the nappe stack of the Higher and Lesser Himalayas and, in turn, are thrust over more interior parts of the Indian continent. Each of the three mega-units is internally imbricated into several individual nappes. Fensters (windows) and klippen provide important structural information regarding the thrust belts and help document the existence of broad thrust sheets, some of which record thrust distances in excess of 100 km. A fenster or window is an erosional hole through a thrust sheet that exposes a tectonically lower unit framed by a higher unit; a klippe is detached by erosion and forms a remnant of a nappe or higher thrust sheet that rests on top of a lower unit."
Despite their scale, the Himalayas do not form a major continental divide, and a number of rivers cut through the range, particularly in the eastern part of the range. As a result, the main ridge of the Himalayas is not clearly defined, and mountain passes are not as significant for traversing the range as with other mountain ranges. Himalayas' rivers drain into two large systems:
The northern slopes of Gyala Peri and the peaks beyond the Tsangpo, sometimes included in the Himalayas, drain into the Irrawaddy River, which originates in eastern Tibet and flows south through Myanmar to drain into the Andaman Sea. The Salween, Mekong, Yangtze, and Yellow River all originate from parts of the Tibetan Plateau that are geologically distinct from the Himalaya mountains and are therefore not considered true Himalayan rivers. Some geologists refer to all the rivers collectively as the circum-Himalayan rivers.
The great ranges of central Asia, including the Himalayas, contain the third-largest deposit of ice and snow in the world, after Antarctica and the Arctic. Some even refer to this region as the "Third Pole". The Himalayan range encompasses about 15,000 glaciers, which store about 12,000 km (2,900 cu mi), or 3600–4400 Gt (10 kg) of fresh water. Its glaciers include the Gangotri and Yamunotri (Uttarakhand) and Khumbu glaciers (Mount Everest region), Langtang glacier (Langtang region), and Zemu (Sikkim).
Owing to the mountains' latitude near the Tropic of Cancer, the permanent snow line is among the highest in the world, at typically around 5,500 m (18,000 ft). In contrast, equatorial mountains in New Guinea, the Rwenzoris, and Colombia have a snow line some 900 m (2,950 ft) lower. The higher regions of the Himalayas are snowbound throughout the year, in spite of their proximity to the tropics, and they form the sources of several large perennial rivers.
In recent years, scientists have monitored a notable increase in the rate of glacier retreat across the region as a result of climate change. For example, glacial lakes have been forming rapidly on the surface of debris-covered glaciers in the Bhutan Himalaya during the last few decades. Studies have measured an approximately 13% overall decrease in glacial coverage in the Himalayas over the last 40–50 years. Local conditions play a large role in glacial retreat, however, and glacial loss can vary locally from a few m/yr to 61 m/yr. A marked acceleration in glacial mass loss has also been observed since 1975, from about 5–13 Gt/yr to 16–24 Gt/yr. Although the effect of this will not be known for many years, it potentially could mean disaster for the hundreds of millions of people who rely on the glaciers to feed the rivers during the dry seasons. The global climate change will affect the water resources and livelihoods of the Greater Himalayan region.
During the last ice age, there was a connected ice stream of glaciers between Kangchenjunga in the east and Nanga Parbat in the west. In the west, the glaciers joined with the ice stream network in the Karakoram, and in the north, they joined with the former Tibetan inland ice. To the south, outflow glaciers came to an end below an elevation of 1,000–2,000 m (3,300–6,600 ft). While the current valley glaciers of the Himalaya reach at most 20 to 32 km (12 to 20 mi) in length, several of the main valley glaciers were 60 to 112 km (37 to 70 mi) long during the ice age. The glacier snowline (the altitude where accumulation and ablation of a glacier are balanced) was about 1,400–1,660 m (4,590–5,450 ft) lower than it is today. Thus, the climate was at least 7.0 to 8.3 °C (12.6 to 14.9 °F) colder than it is today.
The Himalayan region is dotted with hundreds of lakes. Pangong Tso, which is spread across the border between India and China, at the far western end of Tibet, is among the largest with a surface area of 700 km (270 sq mi).
South of the main range, the lakes are smaller. Tilicho Lake in Nepal, in the Annapurna massif, is one of the highest lakes in the world. Other lakes include Rara Lake in western Nepal, She-Phoksundo Lake in the Shey Phoksundo National Park of Nepal, Gurudongmar Lake, in North Sikkim, Gokyo Lakes in Solukhumbu district of Nepal, and Lake Tsongmo, near the Indo-China border in Sikkim.
Some of the lakes present the danger of a glacial lake outburst flood. The Tsho Rolpa glacier lake in the Rowaling Valley, in the Dolakha District of Nepal, is rated as the most dangerous. The lake, which is located at an altitude of 4,580 m (15,030 ft), has grown considerably over the last 50 years due to glacial melting. The mountain lakes are known to geographers as tarns if they are caused by glacial activity. Tarns are found mostly in the upper reaches of the Himalaya, above 5,500 m (18,000 ft).
Temperate Himalayan wetlands provide important habitat and layover sites for migratory birds. Many mid and low altitude lakes remain poorly studied in terms of their hydrology and biodiversity, like Khecheopalri in the Sikkim Eastern Himalayas.
The physical factors determining the climate in any location in the Himalayas include latitude, altitude, and the relative motion of the Southwest monsoon. From north to south, the mountains cover more than eight degrees of latitude, spanning temperate to subtropical zones. The colder air of Central Asia is prevented from blowing down into South Asia by the physical configuration of the Himalayas. This causes the tropical zone to extend farther north in South Asia than anywhere else in the world. The evidence is unmistakable in the Brahmaputra valley as the warm air from the Bay of Bengal bottlenecks and rushes up past Namcha Barwa, the eastern anchor of the Himalayas, and into southeastern Tibet. Temperatures in the Himalayas cool by 2.0 degrees C (3.6 degrees F) for every 300 metres (980 ft) increase of altitude.
As the physical features of mountains are irregular, with broken jagged contours, there can be wide variations in temperature over short distances. Temperature at a location on a mountain depends on the season of the year, the bearing of the sun with respect to the face on which the location lies, and the mass of the mountain, i.e. the amount of matter in the mountain. As the temperature is directly proportional to received radiation from the sun, the faces that receive more direct sunlight also have a greater heat buildup. In narrow valleys—lying between steep mountain faces—there can be dramatically different weather along their two margins. The side to the north with a mountain above facing south can have an extra month of the growing season. The mass of the mountain also influences the temperature, as it acts as a heat island, in which more heat is absorbed and retained than the surroundings, and therefore influences the heat budget or the amount of heat needed to raise the temperature from the winter minimum to the summer maximum.
The immense scale of the Himalayas means that many summits can create their own weather, the temperature fluctuating from one summit to another, from one face to another, and all may be quite different from the weather in nearby plateaus or valleys.
The Himalayan hydroclimate is crucial for South Asia, where annual summer monsoon floods impact millions.
A critical influence on the Himalayan climate is the Southwest Monsoon. Variability in monsoon rainfall, influenced by local Hadley circulation and tropical sea surface temperatures, is the main factor behind wet and dry years. This is not so much the rain of the summer months as the wind that carries the rain. Different rates of heating and cooling between the Central Asian continent and the Indian Ocean create large differences in the atmospheric pressure prevailing above each. In the winter, a high-pressure system forms and remains suspended above Central Asia, forcing air to flow in the southerly direction over the Himalayas. But in Central Asia, as there is no substantial source for water to be diffused as vapour, the winter winds blowing across South Asia are dry. In the summer months, the Central Asian plateau heats up more than the ocean waters to its south. As a result, the air above it rises higher and higher, creating a thermal low. Off-shore high-pressure systems in the Indian Ocean push the moist summer air inland toward the low-pressure system. When the moist air meets mountains, it rises and upon subsequent cooling, its moisture condenses and is released as rain, typically heavy rain. The wet summer monsoon winds cause precipitation in India and all along the layered southern slopes of the Himalayas. This forced lifting of air is called the orographic effect.
The vast size, huge altitude range, and complex topography of the Himalayas mean they experience a wide range of climates, from humid subtropical in the foothills, to cold and dry desert conditions on the Tibetan side of the range. For much of the Himalayas—in the areas to the south of the high mountains, the monsoon is the most characteristic feature of the climate and causes most of the precipitation, while the western disturbance brings winter precipitation, especially in the west. Heavy rain arrives on the southwest monsoon in June and persists until September. The monsoon can seriously impact transport and cause major landslides. It restricts tourism – the trekking and mountaineering season is limited to either before the monsoon in April/May or after the monsoon in October/November (autumn). In Nepal and Sikkim, there are often considered to be five seasons: summer, monsoon, autumn, (or post-monsoon), winter, and spring.
Using the Köppen climate classification, the lower elevations of the Himalayas, reaching in mid-elevations in central Nepal (including the Kathmandu valley), are classified as Cwa, Humid subtropical climate with dry winters. Higher up, most of the Himalayas have a subtropical highland climate (Cwb).
The intensity of the southwest monsoon diminishes as it moves westward along the range, with as much as 2,030 mm (80 in) of rainfall in the monsoon season in Darjeeling in the east, compared to only 975 mm (38.4 in) during the same period in Shimla in the west.
The northern side of the Himalayas, also known as the Tibetan Himalaya, is dry, cold, and generally windswept, particularly in the west where it has a cold desert climate. The vegetation is sparse and stunted and the winters are severely cold. Most of the precipitation in the region is in the form of snow during the late winter and spring months.
Local impacts on climate are significant throughout the Himalayas. Temperatures fall by 0.2 to 1.2 °C for every 100 m (330 ft) rise in altitude. This gives rise to a variety of climates, from a nearly tropical climate in the foothills, to tundra and permanent snow and ice at higher elevations. Local climate is also affected by the topography: The leeward side of the mountains receive less rain while the well-exposed slopes get heavy rainfall and the rain shadow of large mountains can be significant, for example, leading to near desert conditions in the Upper Mustang, which is sheltered from the monsoon rains by the Annapurna and Dhaulagiri massifs and has annual precipitation of around 300 mm (12 in), while Pokhara on the southern side of the massifs has substantial rainfall (3,900 mm or 150 in a year). Thus, although annual precipitation is generally higher in the east than in the west, local variations are often more important.
The Himalayas have a profound effect on the climate of the Indian subcontinent and the Tibetan Plateau. They prevent frigid, dry winds from blowing south into the subcontinent, which keeps South Asia much warmer than corresponding temperate regions in the other continents. It also forms a barrier for the monsoon winds, keeping them from traveling northwards, and causing heavy rainfall in the Terai region. The Himalayas are also believed to play an important part in the formation of Central Asian deserts, such as the Taklamakan and Gobi.
The flora and fauna of the Himalayas vary with climate, rainfall, altitude, and soils. The climate ranges from tropical at the base of the mountains to permanent ice and snow at the highest elevations. The amount of yearly rainfall increases from west to east along the southern front of the range. This diversity of altitude, rainfall, and soil conditions, combined with the very high snow line, supports a variety of distinct plant and animal communities. The extremes of high altitude (low atmospheric pressure), combined with extreme cold, favor extremophile organisms.
At high altitudes, the elusive and previously endangered snow leopard is the main predator. Its prey includes members of the goat family grazing on the alpine pastures and living on the rocky terrain, notably the endemic bharal or Himalayan blue sheep. The Himalayan musk deer is also found at high altitudes. Hunted for its musk, it is now rare and endangered. Other endemic or near-endemic herbivores include the Himalayan tahr, the takin, the Himalayan serow, and the Himalayan goral. The critically endangered Himalayan subspecies of the brown bear is found sporadically across the range, as is the Asian black bear. In the mountainous mixed deciduous and conifer forests of the eastern Himalayas, red pandas feed in the dense understories of bamboo. Lower down, the forests of the foothills are inhabited by several different primates, including the endangered Gee's golden langur and the Kashmir gray langur, with highly restricted ranges in the east and west of the Himalayas, respectively.
The unique floral and faunal wealth of the Himalayas is undergoing structural and compositional changes due to climate change. Hydrangea hirta is an example of floral species that can be found in this area. The increase in temperature is shifting various species to higher elevations. The oak forest is being invaded by pine forests in the Garhwal Himalayan region. There are reports of early flowering and fruiting in some tree species, especially rhododendron, apple, and box myrtle. The highest known tree species in the Himalayas is Juniperus tibetica, located at 4,900 m (16,080 ft) in Southeastern Tibet.
Similar to the mountains, the communities living near the Himalayas are experiencing climate change and its negative impacts significantly more than other parts of the world. Some of the impacts that the communities are facing include erratic rainfall, flooding, rising temperatures, and landslides. These impacts can have extreme negative effects on the villages living in the area especially as the temperatures rise at higher rates than many other places in the world (Alexander et al., 2014). There are more than 1.9 million people who are highly vulnerable due to climate change with an additional 10 million people at risk in Nepal. Nepal is among the top ten most vulnerable Global South countries due to climate change in the world, standing at number 4 as of 2010 according to the climate change risk atlas. According to NAPA (National Adaptation Program of Action) of Nepal, many threats including floods, droughts, and landslides are an imminent threat to the glacial lake area. With this in consideration, climate change policy and framework for LAPA (Local Adaptation Plans of Action) were prepared in 2011 primarily focusing on addressing climatic hazards.
Local communities are suffering from food scarcity and malnutrition as well as an increasing risk to diseases such as malaria and dengue fever as temperatures rise and allow these diseases to migrate further north. There is also an increasing risk of water borne illnesses accompanied by an increasing lack of safe drinking water. Illness is not the only danger to the communities as temperatures sky rocket. With the climate changing weather patterns are also changing and more extreme weather events are occurring putting local communities more at risk to physical harm and death during erratic weather events. Marginalized groups including children and women are experiencing more severe impacts from climate change and are often more exposed to disease and injury. Over the last couple years these health impacts have gotten increasingly worse and more common. Recent studies have shown that dengue fever has had a consistent pattern of epidemic in Nepal in the years 2010, 2013, 2016, 2017, 2019, 2022 with the largest in terms of severity occurring in 2022. 54,784 reported cases were recorded from all 77 districts in seven provinces. These diseases are simply in addition to other diseases that can be seen with the rise of global temperatures and air pollution. Many vulnerable groups are experiencing an increase in respiratory illness, cardiac illnesses, and asthma. The heat can lead to issues such as a strain on respiratory illnesses, heat stroke, and fever. There is also the increased risk of cancer. Many lower income communities such as the himalayan villages suffer from exposure to more pollution or in some cases exposure to toxic chemicals which has led to an increased rate of cancer in these communities as well as an increased risk of death.
The increasing temperatures are also leading to a decrease in territory for local wildlife. This trend has decreased the prey populations of at-risk predators, such as snow leopards. Seeking alternative food sources, snow leopards and other predators attack local farmers' livestock. This livestock consists of yaks, oxen, horses, and goats. Snow leopards have killed about 2.6% of the local livestock per year in response to their shrinking habitat. The overall loss, about a quarter of the average income of local farmers, has had a major impact on the local economy. In retaliation, farmers have begun killing snow leopards, seeking to protect their livestock and their livelihoods.
Nepal is a part of the Paris agreement and thus is required to have a climate action plan and is being tracked by the Climate Action Tracker. According to the Climate Action Tracker, Nepal is "almost sufficient" on its track to reach the goals set by the Paris Agreement. There are two factors that hold Nepal back from reaching sufficient status and thus stand out. There is no Climate Finance Plan and emissions and temperature rising rate ranking at critically insufficient. Nepal has many goals, however, that are on track with the Paris Agreement. The first of note being a goal of net-zero emissions by 2045. To reach this goal Nepal submitted two separate plans to account for whatever future they experience the first being WAM (with additional measures) and the second being WEM (with existing measures). WEM is based primarily on already existing policies and highlights the energy sector as the main target for CO2 reduction. The WAM scenario introduces a far more ambitious strategy for reducing emissions. In this scenario the focus is primarily on an intervention method and disruption of the energy sector reducing the use of fossil fuels and the incorporation of renewable energy sources. This pathway heavily relies on reducing emissions from energy sources while preserving the carbon-absorbing capacity of the LULUCF (Land Use, Land-Use Change and Forestry) sector. Under this scenario, it is anticipated that net CO2 emissions will remain negative from 2020 to 2030, approach 'zero' between 2035 and 2045, and then revert to negative values by 2050. The goal of this scenario is to accelerate the journey toward achieving carbon neutrality before 2045. These policies along with many more have Nepal on track to stay beneath the 1.5 threshold set by the Paris Agreement.
In recent years many citizens of these Himalayan communities have started to notice the extreme effects of climate change by experiencing nature itself. They have noticed a decrease in precipitation especially in lowland districts, fluctuating temperatures during months of the year that are typically cooler, and changes in weather patterns even compared to early 2000s weather. Many local villagers have identified climate change simply through the availability of certain native plants decreasing or shifting seasons. The concept of climate change has now been aligned with the risk of natural disasters and has increased awareness in the local communities. These impacts of climate change have greatly affected agriculture in the area and has forced farmers to change crops and when they plant them. In response to this rather than push for policy change, citizens have begun to adapt to climate change. According to Dhungana, 91.94% of the respondents experienced drought as major climatic hazards then floods at 83.87%, landslides at 70.97%, and forest fires at 67.74%. In response to this citizens have begun adapting and adopting new practices. As a response to drought at the high altitudes, plantations are planting more protective trees, drought resistant plants, and have begun adopting irrigation practices drawing from nearby streams. In response to flooding, farmers have created more basins, dam construction, and small drainage canals.
The response to landslides includes plantation grasses in previously barren areas, Gabion wall construction, avoiding livestock grazing in landslide-prone areas, and a prohibition on tillage in areas at risk of landslides. To fight the increased rate of forest fires, citizens have begun beating the fires with green branches and mud, construction of fire lines, and are raising awareness about the wildfires. Fire lines are lines of varying width built through the leaf litter of a forest floor down to the soil and minerals to prevent a spread of fire past the line. The main reason for these adaptations is to decrease the risk that climate change poses over these marginalized communities while taking advantage of the moment and allowing for a positive change towards a more sustainable or adaptable future. Major barriers to these adaptations include a lack of funds, a lack of knowledge, a lack of technology, a lack of time, and lack of mandatory policy.
There are many cultural and mythological aspects associated with the Himalayas. In Jainism, Mount Ashtapada of the Himalayan mountain range is a sacred place where the first Jain tirthankara, Rishabhanatha, attained moksha. It is believed that after Rishabhanatha attained nirvana, his son, Bharata, had constructed three stupas and twenty four shrines of the 24 tirthankaras with their idols studded with precious stones over there and named it Sinhnishdha. For the Hindus, the Himalayas are personified as Himavat, the king of all mountains and the father of the goddess Parvati. The Himalayas are also considered to be the father of the goddess Ganga (the personification of river Ganges). Two of the most sacred places of pilgrimage for the Hindus are the temple complex in Pashupatinath and Muktinath, also known as Shaligrama because of the presence of the sacred black rocks called shaligrams.
The Buddhists also lay a great deal of importance on the Himalayas. Paro Taktsang is the holy place where Buddhism started in Bhutan. The Muktinath is also a place of pilgrimage for the Tibetan Buddhists. They believe that the trees in the poplar grove came from the walking sticks of eighty-four ancient Indian Buddhist magicians or mahasiddhas. They consider the saligrams to be representatives of the Tibetan serpent deity known as Gawo Jagpa. The Himalayan people's diversity shows in many different ways. It shows through their architecture, their languages, and dialects, their beliefs and rituals, as well as their clothing. The shapes and materials of the people's homes reflect their practical needs and beliefs. Another example of the diversity amongst the Himalayan peoples is that handwoven textiles display colors and patterns unique to their ethnic backgrounds. Finally, some people place great importance on jewelry. The Rai and Limbu women wear big gold earrings and nose rings to show their wealth through their jewelry. Several places in the Himalayas are of religious significance in, Buddhism, Jainism, Sikhism, Islam and Hinduism. A notable example of a religious site is Paro Taktsang, where Padmasambhava is said to have founded Buddhism in Bhutan.
A number of Vajrayana Buddhist sites are situated in the Himalayas, in Tibet, Bhutan, and in the Indian regions of Ladakh, Sikkim, Arunachal Pradesh, Spiti, and Darjeeling. There were over 6,000 monasteries in Tibet, including the residence of the Dalai Lama. Bhutan, Sikkim, and Ladakh are also dotted with numerous monasteries.
The Himalayas are home to a diversity of medicinal resources. Plants from the forests have been used for millennia to treat conditions ranging from simple coughs to snake bites. Different parts of the plants – root, flower, stem, leaves, and bark – are used as remedies for different ailments. For example, a bark extract from an Abies pindrow tree is used to treat coughs and bronchitis. Leaf and stem paste from an Andrachne cordifolia is used for wounds and as an antidote for snake bites. The bark of a Callicarpa arborea is used for skin ailments. Nearly a fifth of the gymnosperms, angiosperms, and pteridophytes in the Himalayas are found to have medicinal properties, and more are likely to be discovered.
Most of the population in some Asian and African countries depends on medicinal plants rather than prescriptions and such. Since so many people use medicinal plants as their only source of healing in the Himalayas, the plants are an important source of income. This contributes to economic and modern industrial development both inside and outside the region. The only problem is that locals are rapidly clearing the forests on the Himalayas for wood, often illegally.