Changing Climate, Changing Himalaya and the Consequences for Human Health

George Rodway

Introduction

Humans have experienced a difficult introduction to the start of the third decade of the 21st century. A world-wide pandemic has forced us into rethinking routine ways of life. However, we are becoming increasingly aware of a far more pernicious impact of our daily lives than that provided by the relatively sudden emergence of Covid-19 seen in late 2019. The seemingly inexorable effects of what we have come to term 'climate change' has touched us all, and will, without doubt, continue to touch our lives in major ways into the future.

Himalayan peoples, and those whose lives are influenced by the Himalaya, will not escape the consequences brought by a changing climate. Significant climate-related problems will need to be reckoned with for the foreseeable future. This essay provides a very brief overview of the general Himalayan environment, examines how it has and will continue to be impacted by a changing climate, and explores some of the major health-related challenges humans who are resident in the Himalayan regions will need to face. A substantial factor, however, must be considered in what might seem an otherwise outwardly dreary expectation. Himalayan peoples have historically proven themselves exceptionally hardy and adaptable—a necessity borne of life in an often-extreme environment that reaches to the roots of their culture and genetic code.

The environment

The combination of rainfall and elevation in the Himalaya is reflected in the immense river systems that drain the mountains. It is not the mountains that frame human activity in the Himalaya: it is the rivers.¹ The three great rivers of East Asia—the Salween, the Mekong and Asia’s longest, the Yangtze—all rise close together on the eastern end of the Tibetan plateau. Other great rivers predate the Himalaya’s rise, including the Indus and the Yarlung Tsangpo-Brahmaputra. Others began with the mountains, including the Ganges and the great river systems of Nepal.

It is no overstatement to assert, as Ed Douglas does in his recent comprehensive opus titled Himalaya: A Human History, that the combination of altitude and climate is what makes the Himalaya so remarkable.¹ In approximately a hundred and fifty kilometres at its narrowest, the Himalaya is contained by the plains, or terai, to the south and the Tibetan plateau to the north. Within that distance the gain in altitude is as much as eight kilometres. This means that in a relatively brief distance you can move through an exceptionally wide range of ecosystems. For instance, we find subtropical broadleaf forests in the Siwalik foothills, mixed temperate forests of oak and rhododendron in the middle hills, firs and pines at higher altitudes. Pastureland above the tree line can extend well over five thousand metres. Above that, you are in an ecosystem like that which is found in the the Arctic.

The natural hazards associated with such a rapid rise in elevation are complicated and erratic: e.g., floods, earthquakes and landslides. But less obvious dangers abound, such as glacial lakes draining incredibly rapidly and in catastrophic fashion. The most famous example of this is perhaps a lake of ten square kilometres near Mount Machhapuchhre in the Annapurna region, which collapsed in the mid sixteenth century, sending a wall of water and five cubic kilometres of debris into the Pokhara valley. These events, called Glacial Lake Outburst Floods, are of great concern today as climate change prompts glacial retreat.

Variations in climate and environment can be little short of astounding as one moves across the Himalaya. While the monsoon is the region’s major weather system, local climate, even from one side of a valley to the other, can be surprisingly different. This variety is also manifested in the number of languages spoken across the Himalaya. Yet despite this provincialism, the residents of the Himalaya have always been travellers. Across the ranges, traders exchanged Tibetan salt for Indian grain for millennia. The seasonal activity of herders taking animals to high pasture is another practice that has persisted. But population growth and urbanization are also evident in the Himalayan regions—as is the case over so much of the planet. And, perhaps most importantly, climate change is having a greater impact throughout the Himalaya than practically anywhere else on earth.

A changing climate

Paleoclimatology uses physical and chemical evidence from the geological record to deduce changes in the earth’s climate over time. We have exquisitely detailed knowledge of how climate has varied over the last few million years. In just the past three million years, earth’s climate has swung between mild states and periods of massive glaciation. What explains these changes? Ice cores in Greenland and Antarctica provide intriguing clues about the great glacial cycles of the past. It is known now that ice-age cycles of the past several million years were almost certainly caused by periodic oscillations of the earth’s rotation and orbit that primarily affect the orientation of its axis, changing the distribution of sunlight with latitude. Iceages thus occur when arctic regions receive relatively little summer sunlight as a result of orbital variations, causing ice and snow not to melt as much as would otherwise occur.²

But what of the opposite end of the climate continuum? Clearly the earth is now in a period of 'mild' climate. Mountain glaciers around the world are currently receding at an unprecedented rate and have been doing so since the start of the Industrial Revolution. The latest research identifies human-induced climate warming as almost entirely responsible.³ Another scientific paper published in 2021 provides the most detailed and complete picture to date of glacier wastage over the last two decades from over one million satellite images and shows how ice loss has been accelerating during this period for most of the 200,000 plus glaciers around the world.⁴

Increasing combustion of fossil fuels has led to carbon dioxide’s (CO2) seemingly relentless climb and now exceeds 400 parts per million, its highest level in at least three million years, according to the analysis of gases trapped in ice cores. Sea level continues to rise and, absent serious measures to curtail greenhouse gas emissions, is projected to increase by another 1-3 feet by the end of this century.2 The present-day temperature increases lags behind the CO2 increase as the climate responds to the unprecedented CO2 rise. The sad fact is that even if we stopped burning fossil fuels tomorrow, the global temperature increase would continue,⁵ as it takes hundreds to thousands of years for CO2 concentrations to adjust naturally. Interestingly, in 1897, the Swedish chemist and Nobel laureate Svante Arrhenius had realized that increasing combustion of fossil fuels would eventually raise atmospheric CO2 concentrations. His reasoning was that this would inevitably occur because human emissions were far too large for the natural system to deal with on human time scales. By 1906, without modern computers and relying only on principles of basic physics that had been quantified at this time in history, he had calculated that doubling the concentration of CO2 would raise the earth’s surface temperature by about 4 degrees centigrade, a number well within contemporary estimates of 2-4.5 degrees centigrade per doubling of CO2.²

Projections based on climate models suggest that the globe will continue to warm another several degrees over the next century. Civilization developed during a period of exceptional climatic stability over the last 7,000 years.² Therein lies the heart of the problem. While our distant ancestors had to cope with a sea level rise of about 400 feet over a mere 8,000 years or so leading up to the development of civilization, human society has since become finely adapted to the current climate, so much so that a mere three-foot increase in sea level (small by the standards of geologically recent changes) would displace around 100 million people.² Agriculture and animal husbandry are also tuned to the present climate, so that comparatively small shifts in precipitation and temperature can exert considerable pressure on governments and social systems whose failure to respond could lead to famine, disease, mass emigrations, political instability, and armed conflict.

Basic climate theory and models suggest another result of a few degrees of warming: more floods and more droughts occurring on earth. When the amount of water vapor in the air increases as a result of a rise in air temperature (a 7-degree F increase in air temperature increases the concentration of water vapour by 25 %), we might expect a consistent proportional increase in the amount of precipitation that falls. While climate models show this does in fact tend to happen in the spots on earth that are already receiving above average rain and snowfall, they also show that the intensity, duration, and geographical extent of droughts will become more frequent in the earth’s historically drier areas. And recent climate records suggest these twin perils of flood and drought across the globe are already on the rise.⁶

Effects on human health and security

Given that 60 percent of the world’s population lives in water basins shared by two or more nations, many historians, scientists, and political experts have speculated that the twenty-first century will be one of worldwide conflicts over water. In addition, overpopulation and industrial development are increasing water scarcity worldwide. Water sources in locales with a history of border warfare, such as the mountainous regions separating India and China, risk both new and further exacerbation of current conflicts.⁶ A short summary table of climate change effects and impacts on water security is included here, adapted from the Intergovernmental Panel on Climate Change: Climate Change and Water

Adapted from Intergovernmental Panel on Climate Change: Climate Change and Water, https://archive.ipcc.ch/pdf/technical-papers/climate-change-water-en.pdf

A warmer world will create newly hospitable habitats for tropical and sub-tropical insect vectors and the diseases they carry. Historically, disease-free areas have been protected from becoming hazardous by cold environmental temperatures. In other words, with the extreme low temperatures of winter, insect (and in particular, mosquito) populations are decimated. However, as the average global temperature increases, mosquitos will thrive longer and reproduce more successfully at higher latitudes and altitudes. In the Northern hemisphere, they are spreading northward and increasing their natural habitat.⁶ Vector-borne diseases (diseases carried by other species, such as mosquitos, ticks, and fleas) take an enormous toll on human health. Malaria, dengue, West Nile virus disease, Lyme disease, and Zika virus infection now and increasingly will account for much of the global burden of disease. The World Health Organization estimates that every year more than one billion cases of vector-borne disease result in more than one million deaths.⁷

In the jungles of northern India, colder seasonal temperatures have historically helped to put an end to the deadly malaria season. Known as aul in Nepal, malaria did not just affect the plains. Ed Douglas quotes the British resident Brian Hodgson’s writing from the mid nineteenth century: “No elevation short of 3,000 to 4,000 feet above the sea suffices to rid the atmosphere of the low Himalaya from malaria.¹” Villagers would typically build their farmhouses above this line so they could escape the mosquitos, walking down to their lower fields in the morning. Climate change will likely continue raise the mosquito’s ceiling, creating new problems in remote villages.

Changes in environment at the global, regional, and local levels are often reflected in changes in human health.⁸ The human health impacts of climate change are not yet systematically documented. Based on available data on communicable diseases, their control, and spread along with simulated climate change scenarios developed through modeling, it is possible to draw some broad conclusions on the health impacts of climate change. Such conclusions, derived from studies conducted in many parts of the world and reported in the scientific literature, can be briefly summarized. Although based on limited data sets, these deductions from Pant et al. in 2018 are reasonable indicators for many health-related issues that will be encountered in the Himalaya (with dominating local influences and factors) in the not-too-distant future.⁸

1. A warmer environment would lead to increased deaths due to heightened number of heat waves and lack of nighttime cooling.
2. Infectious diseases such as cholera would increase as emerging and reemerging infections take root.
3. Malaria risk would increase in higher altitude mountain and mid-latitude regions.
4. Humidity and temperature range increases with higher frequency of extreme weather variations will produce an undesirable effect on human health
5. These climate changes are projected to make other mosquito-borne diseases like dengue and Japanese encephalitis more prevalent and widespread.
6. Increased flooding and periods of drought that are anticipated will affect the availability of freshwater and food making the population more vulnerable to infection because of water-borne diseases and malnutrition.

As we witness a greater number and intensity of extreme weather events, we can expect similar outcomes correlated to socioeconomic conditions. As is commonly the case with certain diseases, the most vulnerable – the poor, the sick, and elderly – will bear the brunt of the impacts of climate change with respect to adverse health effects. But as mentioned in the Introduction of this article, the hardiness and adaptability of the people of the Himalayan regions has served them well for countless generations. What remains to be seen is whether the resilience of subsequent generations will match that of their ancestors in the face of the environmental alterations that climate change will invariably bring. But a long, inspiring, and remarkable history is on their side.

References

1. Douglas E. Himalaya: A human history. London: The Bodley Head; 2020.
2. Emanuel K. What we know about climate change. Cambridge, Massachusetts: The Massachusetts Institute of Technology Press; 2018.
3. Roe GH, et al. On the attribution of industrial-era glacier mass loss to anthropogenic climate change. Cryosphere. 2021;15:1889-1905.
4. Hugonnet R, et al. Accelerated global glacier mass loss in the early twentyfirst century. Nature. 2021;592:726-731.
5. Bamber J. What does the future hold for the glaciated and high mountain world? Alpine Club Newsletter. 2022;Winter:3-5.
6. Lemery J, Auerbach P. Enviromedics: The impact of climate change on human health. Lanham, Maryland: Rowman & Littlefield; 2017.
7. WHO. A global brief on vector-borne diseases. 2014; WHO_DCO_WHD_2014.2011_eng.pdf. Available at. Accessed August 12, 2022.
8. Pant GB, Kumar PP, Revadekar JV, Singh N. Climate change in the Himalayas. Cham, Switzerland: Springer International Publishing; 2018.

Summary

George Rodway discusses the impact of climate change on the Himalaya: how changes in temperature will impact the landscape and nature, and ways in which these will challenge Himalayan peoples.

 

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