7.1: Natural Environments and Climate Vulnerability

Learning Objectives

1. Describe the dynamics of plate tectonics in South Asia and the formation of the world's tallest mountains.
2. Explain the hydrology of the Hindu Kush Himalayan Region identify the disruptions brought by climate change.
3. Define carbon inequity and climate vulnerability in the context of South Asia.
4. Describe the unique characteristics and ecosystem values of the Sundarbans.

 

Plate Tectonics and the World's Highest Peaks

South Asia is a region well defined by physical geography. It is often referred to as the Indian Subcontinent because its landmass was once its own continent atop the Indian Plate. Over millions of years, the Indian Plate has carried this landmass north, forming a convergent plate boundary with the Eurasian Plate that began around 40-50 million years ago (See Figure 7.1.1). The pressure from the collision between the two continental plates has forced the Earth’s crust to fold, buckle, and rise, pushing bedrock upwards. This is the geologic force responsible for the formation of the tallest mountains in the world, the Himalayas. The Himalayas are a dramatic geographic feature, a natural barrier extending some 1,500 miles (about half the width of the United States) between India and China, also containing the highland countries of Nepal and Bhutan. Mount Everest (29,029ft), the world’s highest peak, is located between Nepal and China. Between Pakistan and Afghanistan, the Karakoram range extends through Kashmir and then meet up with the high ranges of the Himalayas. The Karakoram Range includes some of the world’s steepest peaks, including the world’s second tallest mountain, K2 (28,251 ft). There are only 14 mountain peaks in the world higher than 8,000 m (26, 247 ft) in elevation – all of them are in the Himalayan or Karakoram ranges (See Figure 7.1.2). Known as the “eight thousanders,” the world’s highest peaks continue to grow by as much about 5 millimeters (about 0.2 in) per year, since the Indian Plate continues to shove landmass towards the Eurasian Plate.

The tectonic collision between the Indian and Eurasian plates makes South Asia one of the most seismically active regions in the world. Some of the most devastating earthquakes in recent history happened in the region, including the 7.8 magnitude earthquake that hit Nepal on April 25, 2015. The earthquake caused widespread destruction in the capital city of Kathmandu as well as many other parts of the country, flattening hundreds of buildings, historic landmarks, and temples, and killing and injuring thousands and impacting millions of people. The Indian Plate is also in collision with Burma Plate in the east, causing tremendous tension in a subduction zone in the Indian Ocean. On December 26, 2004, the epicenter of a massive earthquake of 9.3 magnitude occurred at the bottom of the ocean releasing energy that triggered a tsunami that reached 30 meters in height, devastating many countries in the Indian Ocean, including Sri Lanka and the Maldives. It remains the deadliest tsunami in recorded history, with a total death toll estimated at 230,000.^[1] While these catastrophic seismic events are relatively infrequent, their consequences are devastating in terms of the loss of life and infrastructure damage. South Asia is a populous low-income region, qualities that make environmental disasters particularly calamitous. When catastrophic seismic events occur, it takes many years for countries and communities to recover. Reconstruction plans include establishing early warning and evacuation plans as well as building for resilience.

 

Figure \(\PageIndex{1}\): [left] This map illustrates the movement of the Indian Subcontinent. Over 70 million years, the Indian Plate has moved north towards the Eurasian Plate, eventually resulting in the contemporary collision zone (Public Domain; USGS). [right] The Indian Plate continues to push towards the Eurasian Plate creating a convergent plate boundary and a continental uplift that continues to build the world's tallest mountain ranges, the Himalayas (CC BY-SA 4.0; alataristarion via Wikimedia Commons).

 

Figure \(\PageIndex{2}\): [left] This satellite image shows the world's tallest mountains, labeling in red the 14 mountains that exceed 8,000 meters in elevation: Shisha Pangma, Gasherbrum II, Broad Peak, Gasherbrum I, Annapurna, Nanga Parbat, Manaslu, Dhaulagiri, Cho Oyu, Makalu, Lhotse, Kangchenjunga, K2, and Mount Everest. All of them are found in either the Karakoram or Himalayan mountain ranges (adapted from NASA; permitted use). [right] This picture shows the south face of Mount Everest, the world's tallest peak, and Gokyo Lake at the bottom (CC BY-SA 4.0; Zippy Monkey via Wikimedia Commons).

 

Hindu Kush Himalayan Hydrology

The Himalayas are part of a larger alpine system stretching across Eurasia known as the Hindu Kush Himalayan Region (HKH). It stretches 3500 kilometers across eight countries: Afghanistan, Bangladesh, Bhutan, China, India, Nepal, Myanmar, and Pakistan. The Hindu Kush Himalaya are arguably the world’s most important water tower. The ranges store the largest volume of ice and snow outside of the Arctic and Antarctica and are often referred to as “the third pole.” These glaciated mountains are the source of water for ten of Asia’s largest rivers. Together, they support the drinking water, irrigation, and energy for over 240 million people in the region and another 1.9 billion people living downstream.

All major rivers in South Asia originate in the Himalayas. The Indus River, which has been a center of human civilization for thousands of years, starts in the Tibetan Plateau and flows through the center of Pakistan. The basin stretches from the Himalayan mountains to the north to the dry, alluvial plains of Sindh province in Pakistan and flows out into the Arabian Sea. Pakistan’s food security relies heavily on the Indus River as it provides irrigation water for 80 percent of the country’s crops. Similarly, the Ganges River flows through northern India, providing a water lifeline for India’s food production. As the Ganges flows out of the Himalayas, it creates a narrow, rugged canyon. It then flows through the Indo-Gangetic plain, a vast fertile area that makes up most of the northern and eastern parts of India as well as parts of Pakistan, Nepal and Bangladesh. Today, the Ganges River basin is the most populated river basin in the world with about 400 million people. Many Hindus visit the Ganges River in Varanasi, which is considered the holiest of cities. The city’s culture is also closely tied to the river, as the Ganges is the most sacred river in Hinduism. In Bangladesh, the main branch of the Ganges is known as the Padma, then downstream as the Meghna. They represent the merging of waters with the Brahmaputra River, one of the three major rivers in South Asia. It flows through Tibet and enters India from the east where it meets up with the Ganges in Bangladesh to flow into the Bay of Bengal. The Ganges Delta is a vast and highly fertile area and the world’s largest delta. While the Indus, Ganges, and Brahmaputra rivers trace their origins to the glaciated landscapes of the Hindu Kush Himalaya, contributions of glacial meltwater to river basin run-off tends to decrease from west to east and are most important in the Upper Indus basin. In the Ganges and Brahmaputra, the tropical monsoon rains are the main source of water replenishment and stream flow.

The tropical monsoon is the prevailing climate in South Asia. It is distinguished by a seasonal reversal of winds that drive pronounced wet and dry season. The driving mechanism behind the seasonal shifts of the tropical monsoon is largely attributable to differential heating and cooling of the continent and the surrounding water bodies. In the summer, the continent heats up quickly warming the adjacent air that eventually begins to rise. The rising hot air creates a vacuum that pulls in warm moist airmasses from the Bay of Bengal and the Indian Ocean bringing moisture-laden clouds and abundant rain over land. The summer monsoon rains—usually falling between June and September—feed the rivers and streams of South Asia and provide the water needed for agriculture. Summer monsoons are anticipated events, and people in South Asia have tuned their agricultural cycles and celebrations in anticipation of the rains they bring. More than 70 percent of the annual precipitation of the region occurs during the summer monsoon months. By October, the rainy season is generally over. In the winter, the cold, dry air above the Asian continent blows to the south, and the winter monsoon is characterized by cool, dry winds coming from the north, a dry season.

South Asia’s mountains are rain-catchers of the moisture carrying airmasses that the summer monsoon brings, and much of the rain falls in the form of orographic precipitation. Orographic precipitation occurs when moisture carrying airmasses are pushed towards a mountain range and force to rise, cool, condense, and precipitate. The summer monsoon carries moist airmasses to the foot of the Himalayas, a formidable topographic barrier that forces the incoming air up. The resulting precipitation feeds the streams and basins that flow into the major rivers, such as the Brahmaputra, Ganges, and Indus. The topographic barrier also creates drastic landscapes in on its windward and leeward sides. On the south-facing side of the Himalayas, we find some of the wettest places on Earth. On the other side, the rain shadow from the mountains forms the arid Gobi Desert and Tibetan Plateau. A similar pattern can be noted in India’s Western Ghats, a mountain range on its western coast that causes orographic precipitation on its windward side.

 

Figure \(\PageIndex{3}\): This map illustrates the combined mechanisms contributing to the Hindu Kush Himalayan hydrology. The region holds the third largest glaciers in the world, only second to those in the poles. Seasonal ice melt is an important contributor to freshwater flows, especially in the Indus River. The three major river basins - especially the Ganges and Brahmaputra - rely on the rains of the tropical monsoon to replenish their streams. Most of the annual precipitation comes in the summer monsoon when moist maritime air rushes in to replace the warm rising continental air. The mountains trap these incoming air masses forcing them to rise and cool and precipitate. This orographic precipitation drenches the foothill landscapes of the south-facing Himalayas. The downpour makes the Ganges River the most voluminous river in South Asia. Visible here in this map is also the rainshadow effect, with the Tibetan Plateau in the north facing dry conditions as it sits on the leeward side of the Himalayas (CC BY-NC-SA 2.0; GRID Arendal via Flickr).

 

Climate Vulnerability in Pakistan and Bangladesh

Glacier Retreat in the Hindu Kush Himalayas

The Hindu Kush Himalaya is on the frontline of climate change. Over the past decades, there has been a strong and clear warming trend across the region. Higher altitude areas have warmed faster than lowland areas and faster than the global average. This temperature increase has led to most glaciers to retreat and lose mass. In the future, temperatures will increase by 1–2°C on average by 2050, even reaching 4–5°C in some mountainous and high-altitude areas under a high emissions scenario. Even in the best-case scenario of a 1.5°C in global warming, the average increase in the HKH is projected to be 1.8 ± 0.4°C. Glaciers are some of the most sensitive indicators of climate change, as they respond rapidly to changes in temperature and precipitation. The retreat of glaciers has wide-reaching impacts on natural ecosystems and human settlements through risking local water supplies. In the short-term, the rapid melting will add volume to rivers. However, as glaciers continue to melt, run-off will eventually decrease, especially in river basins that receive substantial amounts of water from glaciers, such as the Indus River basin. This continued melting of glaciers is also resulting in an increase of glacial lakes, some of which may experience outburst flows that put mountain and downstream communities at great risk.

 

Figure \(\PageIndex{4}\): This map shows in blue the glaciers of the Hindu Kush Himalayas and the overall trend of ice loss, illustrated by the size of the red bars. With the exception of a few glaciers in the Karakoram Range, Himalayan multi-year ice is experiencing an alarming retreat. This is a global trend. As the graph on the top right illustrates, the world's major glaciers are melting at an alarming rate as temperatures increase, especially drastically in high-altitude regions (see graph on the bottom right). Glaciers are some of the most sensitive indicators of climate change, as they respond rapidly to changes in temperature and precipitation. Glaciers can provide local water resources in the mountains as well as influence runoff in lowland rivers and recharge river-fed aquifers. The retreat and advance of glaciers has wide-reaching impacts and affects on natural ecosystems and human settlements through effects on water supply and water flow patterns, affecting the availability of water for hydropower generation, agriculture and ecosystems (CC BY-NC-SA 2.0; GRID Arendal via Flickr).

 

Catastrophic Floods in Pakistan and Bangladesh

The heavy rains the monsoon brings every summer already pose great risks of floods and landslides in the region, and climate change is affecting the predictability and intensity of the monsoons. In Pakistan, the combination of record-breaking summer temperatures, rapid glacial melting, and a historically intense monsoon downpours culminated into a tragic flood event in July-August 2022. Glacial lakes overflowed and rivers expanded beyond their floodplains, affecting some 33 million people, and causing more than 1,400 deaths. The worst flooding occurred along the Indus River where some provinces received five to six times more monsoon rain than the 30-year average. Across the country, about 150 bridges and 2,200 miles of roads have been destroyed, and more than 700,000 livestock and 2 million acres of crops and orchards were lost.^[2] It was a devastating monsoon season for Pakistan, a place where floods are the most frequent and costly hazard, and likely to worsen due to climate change.

Coastal Bangladesh is also at the frontline of climate change related risks. Home to over 40 million people, the coastal zone of Bangladesh is located downstream of the Himalayas where over 400 rivers and tributaries flow and eventually discharge through the Ganges Delta into the Bay of Bengal. One of the great natural hazards of coastal Bangladesh is the occurrence of tropical cyclones, a tropical storm that forms over warm oceans (about 80°F) and reach wind speeds of at least 74mph. Cyclones, which are accompanied by powerful winds and heavy rainfall, are a regular phenomenon and pose a serious threat to coastal communities along the entire coastline. On average, about one cyclone makes landfall every year, striking the funnel-shaped and shallow northern portion of the Bay of Bengal—a perfect natural amplifier— at times raising waters more than 10 meters above the sea level. Tropical cyclones are extreme weather events likely to increase in frequency and intensity due to climate change. With 62 percent of the coastal land having an elevation of less than three meters above sea level, much of coastal Bangladesh is at risk of catastrophic floods from cyclones and intensified monsoons. This susceptibility is only exacerbated by sea-level rise, caused by an expanding warmer ocean and ice melt. Sea level rise will further increase coastal flooding, push salt water into tidal channels, and threaten drinking water supplies.^[3]

As we explored here, a combination of factors like the thawing of glaciers, intensified monsoons and cyclones, and sea-level rise are climate regional expressions of climate change that pose high threats to large populations in Pakistan and Bangladesh. According to the Intergovernmental Panel on Climate Change (IPCC), climate vulnerability refers to the predisposition to be adversely affected by climate impacts and lack of ability to cope and adapt. Human mortality from floods, droughts, and storms is much higher in regions identified to have high climate vulnerability. The latest IPCC Report (2022) rendered countries in South Asia as highly vulnerable countries in comparison to other countries in the world.^[4] Both Pakistan and Bangladesh are populous countries with densely populated floodplains and coastal areas where tens of millions of rural and poor people face higher exposure and vulnerability to floods, and are less capable of preparing for, dealing with, and recovering from floods.

For decades, scientists warned that burning fossil fuels results in an accumulation of greenhouse gases in the atmosphere that disrupts global climate systems. Reflecting on the adverse impacts of climate change in places like Pakistan and Bangladesh gives us another opportunity to examine carbon inequity, the disproportionate greenhouse gas emissions of a handful of wealthy countries that have imposed a climate burden on other countries. Since the Industrial Revolution, South Asian countries contributed a negligible share of CO² emissions while the United States, countries of the European Union, and China account for most of the CO2 emissions to date.[5] Even though India has drastically increased its total CO2 emissions in recent years, it has a large population, and the per person figures are still small in relation to wealthy countries. The disastrous effects of the climate crisis are costly – they cost human lives, livelihoods, cultural ways, and billions of dollars worth of damage. This is a burden for countries with already struggling economies. In a worst case scenario, the World Bank projects that climate change could worsen the living conditions of as many as 800 million people in South Asia and potentially displace 36 (about 1.6% percent of its population), all by 2050.^{[6] [7]}

 

Figure \(\PageIndex{5}\): These satellite images depict the catastrophic floods of 2022 along the Brahmaputra River in Bangladesh (left) and the Indus River in Pakistan (right). These false-color images, acquired with NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) satellite, combine infrared and visible light to make it easier to see the boundary between water and land. Water appears navy blue and black; clouds are white or cyan; and vegetation is bright green. [left] In mid-June 2022, Bangladesh was pummeled by intense torrential monsoon rains. After weeks of downpours, flooding swamped millions of homes and displaced hundreds of thousands of people in India and Bangladesh. Officials have called the floods the worst to hit the area in more than a century. The map on the top left shows the Brahmaputra before the monsoons (May 8, 2022) and the bottom shows the floods induced by the downpours (June 26, 2022) (NASA; permitted use). [right] In early September 2022, floods in Pakistan were the worst in a decade. Accelerated glacial melt and monsoon rains had pummeled the region for several weeks and floodwaters inundated large areas. This map series depict a progression from June 24th before the monsoon, to floods around August 31, and receding waters in October 13th, 2022. It was a historical episode that affected over 33 million people (NASA; permitted use).

 

Ecosystem Valuation in the Sundarbans

The Sundarbans is the world’s largest remaining mangrove forest in the Ganges Delta spanning between India and (mostly) Bangladesh along the Bay of Bengal. Mangroves are a unique biome that exist along tropical coastlines as buffer zones between land and sea. They are typically made up of trees and shrubs that have unique adaptations to cope with the harsh conditions of high salinity, warm temperatures, extreme tides, muddy waters, and oxygen-depleted soils. The Sundarbans is of global importance for its exceptional biodiversity, including numerous threatened species such as the emblematic Royal Bengal tiger, the Ganges river dolphin, the estuarine crocodile, and the Indian python. It contains 35 of the 50 known global mangrove plant species.^[8] The significance of Sundarbans is acknowledged by UNESCO, which declared the Indian and Bangladeshi sections of the mangrove World Heritage Sites in 1987 and 1997, respectively.

The Sundarbans provide a range of ways for us to conceptualize ecosystem valuation, or the different ways value can be ascribed to ecosystems. Mangroves are widely recognized for their valuable services, especially amidst a global climate crisis. They are a powerful natural barrier that serves as a first line of defense against hurricanes by dissipating wave and wind energy and reducing erosion. The Sundarbans protects roughly 14 million inhabitants in India’s Kolkata Metropolitan Region’s and other areas from cyclones, rising sea tides, and other adverse natural events that have the potential to take a large toll on human life and property. In addition, mangrove forests are considered carbon sinks because they absorb and retain carbon from the atmosphere. During their growth, trees use the carbon from carbon dioxide to form their leaves, roots, and branches. When these parts eventually die, the carbon becomes buried in the mangrove waterlogged soils. Known as blue carbon, the carbon from submerged vegetation can be stored underwater for millennia, if left undisturbed. Although mangroves cover much less territory than forests, it is estimated that they can store more carbon than forests, largely because of their underground biomass.^[9]

The lives of traditional communities are intertwined with the Sundarbans. The inhabited areas consist of 54 islands populated by over 4.4 million people, where poverty is prevalent and economic opportunities are limited. Thus, the Sundarbans have a local economic value, and many communities depend on the mangrove forest for wood, fish, crabs, shrimp, honey, and fruits as a source of livelihood. The hostile living conditions have also formed and shaped inhabitants’ religious beliefs and cultural values about the natural environment for hundreds of years. The Bengal tiger, for example, is a feared and revered animal with many myths and legends surrounding this native and endangered species. The worship of nature is a customary practice in the area, and hundreds of cultural legends have emanated from the mangrove forest. The local people perceive the Sundarbans as a key part of their identity and sense of place. It is an important cultural and natural heritage site that connects them to their history and ancestral roots. The interconnected human and nonhuman lives in the Sundarbans (and beyond) also have intrinsic value, the right and worth to continue to exist and manifest their biocultural legacies.

As the disruption of the global climate was initiated from the excesses and ways of life from afar peoples, the biocultural communities in the Sunderbans face an existential threat as sea levels continues to rise and inundate mangroves beyond their adaptive capabilities. Discussions about these impacts are incomplete without the moral consideration of the intrinsic worth of peoples and environments endangered by our current planetary havoc.

 

Figure \(\PageIndex{6}\): [top left] Bengal tigers are tiger sub-species native to South Asia. The picture above shows a Bengal tiger in the Sundarbans, home to the largest population of Bengal tigers in the world. They have adapted to living in a unique environment. They have larger paws and webbed feet to help them swim and move through the muddy terrain to hunt. They are endangered and revered (and feared) animals by local peoples who hold many traditional myths and legends surrounding them (CC BY-SA 4.0; Nandy via Wikimedia Commons). [bottom left] Mangrove trees have some unique adaptations to the salty, muddy, and flooded mangrove environment. Many trees in the Sundarbans have prop roots that grow out from the trunk and help to anchor the tree in the soft, muddy soil and increase root access to oxygen. The trees pictured here are in the Sundarbans National Park (CC BY-SA 4.0; Oo91 via Wikimedia Commons). [right] The Sundarbans mangrove forest is not only a critical ecosystem for the world's biodiversity, but it is also of immense significance to the people living in the region. It is an important source of livelihood, culture, identity, and sense of place. Depicted here is a local navigating the streams of Sundarbans National Park at dawn (CC BY-SA 2.0; bk via Flickr).

 

 

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References:

[1] Suppasri, A., Goto, K., Muhari, A., Ranasinghe, P., Riyaz, M., Affan, M., ... & Imamura, F. (2015). A decade after the 2004 Indian Ocean tsunami: the progress in disaster preparedness and future challenges in Indonesia, Sri Lanka, Thailand and the Maldives. Pure and Applied Geophysics, 172, 3313-3341.

[2] Earth Observatory, NASA. (Sep 1, 2022). Devastating Floods in Pakistan.

[3] Kazi, Swarna; Urrutia, Ignacio; van Ledden, Mathijs; Laboyrie, Jean Henry; Verschuur, Jasper; Haque Khan, Zahir-ul; Jongejan, Ruben; Lendering, Kasper; Mancheño, Alejandra Gijón. 2022. Bangladesh: Enhancing Coastal Resilience in a Changing Climate. World Bank, Washington, DC. © World Bank.

[4] IPCC, 2022: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, pp76. [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press. Cambridge University Press, Cambridge, UK and New York, NY, USA.

[5] Our World in Data. (2021). Share of global cumulative CO₂ emissions.

[6] Sengupta, S. and Popovich, N. (June 28, 2018). Global warming in South Asia: 800 million at risk. The New York Times.

[7] Zandt, F. (Nov 4, 2021). Climate Change, the Great Displacer. Statista.

[8] Titumir, R. A. M., Paran, M. S., & Pasha, M. W. (2019). The Sundarbans is our mind: An exploration into multiple values of nature in conversation with traditional resource users. Understanding the multiple values associated with sustainable use in socio-ecological production landscapes and seascapes (SEPLS), 5, 97-117.

[9] NOAA. What is blue carbon?

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Attributions:

“Hindu Kush Himalaya” and “Climate Vulnerability” is adapted from Alfthan, B. et al. (2018). Outlook on climate change adaptation in the Hindu Kush Himalaya. Mountain Adaptation Outlook Series. United Nations Environment Programme, GRID-Arendal and the International Centre for Integrated Mountain Development, Vienna, Arendal and Kathmandu. CC BY-NC-SA 3.0.

“Climate Vulnerability” is adapted from Hamidi, A. R. et al. (2022). Flood Exposure and Social Vulnerability Analysis in Rural Areas of Developing Countries: An Empirical Study of Charsadda District, Pakistan. Water, 14(7), 1176. MDPI AG, CC BY 4.0; and Kazi, S. et al. 2022. Bangladesh: Enhancing Coastal Resilience in a Changing Climate. World Bank, Washington, DC. © World Bank, CC BY 3.0 IGO; and NASA (2022). Devastating Floods in Pakistan. Permitted use.

"Ecosystem Valuation in the Sundarbans" is adapted from World Bank. 2014. Building Resilience for Sustainable Development of the Sundarbans: Strategy Report. Washington, DC. © World Bank. CC BY 3.0 IGO.