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The thick haze from forest fires that smarted the eyes of many in March and April turned air pollution into a trending topic in Nepal. But the share of forest fires in annual air pollution is very small. Bigger contributions are made by biomass, garbage burning, factories and the transport sector. The black carbon emitted by these sources is not only putting Nepalis' health at risk but accelerating melting of glaciers, which feed many of the rivers. Rapid loss of water from rivers can hit irrigation, thereby reducing food production, and diminish hydroelectricity generation.


In the first week of April, Community Eye Hospital in Hetauda suddenly started seeing a surge in the number of patients. The hospital, which used to handle around 100 to 150 patients a day, was receiving around 300 visitors on a daily basis, with almost all of them complaining about irritation in their eyes.

Around 100 km further in Kathmandu complaints of stinging eyes were growing as well. The same problem also gripped other urban centers. Rinsing eyes did provide some relief. But it was temporary as the burning sensation would come back minutes later.

This was the impact of forest fires that led to formation of thick haze, which engulfed much of the country in the last week of March and first three weeks of April.

Forest fires generally occur during the months of March, April and May in Nepal. In the past, rain used to work as a natural antidote and douse fires. But this year the country witnessed very little precipitation during the months of March and April, leaving the forests dry. This problem was compounded by farmers who deliberately burnt dry forested land, hoping to grow more grass to feed the livestock. It is also speculated that grasses in some of the forests may have grown a lot taller, as prolonged lockdown restricted movement of people. This may have helped wildfires to rage for a longer period of time.

Nepal reported over 6,000 wildfires from mid-November to mid-April, according to Nepal Disaster Risk Reduction Portal. The number of fires during the period was 10 times more than a year ago. "Each of the 77 districts in the country has reported at least one incident of forest fire," says Prakash Lamsal, joint secretary of the Environment Ministry. Districts like Lamjung, Manang, Gorkha, Taplejung and Bajhang witnessed wildfires for more than a month. "The last time we had forest fire of such magnitude was in 2009 when almost 1.3 million hectares of forests were on fire," says Lamsal.

When wildfires rage, they release nitrogen oxides and volatile organic compounds. In the presence of sunlight, these gases produce ozone close to the Earth's surface. But do not mistake this ozone with the ozone layer in Earth’s upper atmosphere.

The ozone layer in Earth’s upper atmosphere absorbs sun's harmful ultraviolet rays. It is thus referred to as the good ozone. But the ozone that forms near the Earth's surface is not good for human health, as it is highly reactive and is a toxic gas. This ozone is often referred to as the bad ozone.

"This year also, surface ozone (bad ozone) concentration increased in late March and early April, as many forests caught fire. This elevated ozone concentration could also have increased the problem of eye and throat irritation," says Bhupesh Adhikary, senior air quality specialist at the International Center for Integrated Mountain Development (ICIMOD), a Nepal-based intergovernmental organisation.

Smoke and ashes emitted by wildfires, coupled with seasonal surge in ground-level ozone concentration, pollutants discharged by vehicles and brick kilns, open garbage burning, biomass used to cook food, dust particles from construction sites, and smoke that travels from the Indo-Gangetic Plain, are making Nepal's air quality hazardous. This kind of dirty air contains carbon monoxide, nitrogen oxides, dust and other tiny particles. These particles make people susceptible to various kinds of allergies, heart diseases and respiratory problems, such as asthma and bronchitis.

"A third of deaths from stroke, lung cancer and heart disease are due to air pollution, as the effects are equivalent to that of smoking tobacco," says Dr Rabindra Khunjeli, a respiratory specialist. Daily exposure to air pollution can also impact brain cells and trigger neurodegenerative disorders, such as Parkinson's and Alzheimer's, according to Dr Khunjeli.

If Nepal fails to tackle this issue, Nepalis may have to deal with an array of health issues, hitting productivity and affecting longevity. This will eventually inflate public health spending, which can have a knock-on effect on infrastructure and human capital development, as more financial resources will have to be diverted to the health sector. This will exert pressure on public revenue and may stifle economic growth.

Dirty air
Nepal is home to majestic mountains, pristine hills, forested lands and mighty rivers. Anyone who has visited hill stations and villages here would be thrilled with the setting and the quality of air. These hill stations and villages are located in the proximity of many urban centres, and city residents visit these places from time to time just to get a dose of fresh air. Yet entire Nepal has been continuously labeled as a country with one of the highest levels of air pollution in the world.

Nepal was ranked as the eighth worst country in the world in terms of air pollution in 2018 by IQAir, which compiles global data on air pollution. Its ranking remained the same in 2019, before improving to 12th in 2020.

These ranks were allotted on the basis of atmospheric concentration of fine particulate matters that are 2.5 micrometers or smaller in diameter. These particulate matters are referred to as PM2.5. If you want to know how small 2.5 micrometers is, pluck a hair, which measures 60 micrometers in diameter. Since these particulate matters are very tiny, they can be inhaled just by breathing the air in the surrounding.

Nepal's PM2.5 level stood at 54.10 micrograms per cubic meter in 2018 and fell to 44.50 micrograms per cubic meter in 2019, according to IQAir. This level further dropped to 39.20 micrograms per cubic meter in 2020, perhaps because of the lockdown. These data show slight improvement in Nepal’s air quality in the last three years. Yet the PM2.5 level has not fallen below 35.5 micrograms per cubic meter. When the concentration of PM2.5 hovers between the band of 35.5-55.4 micrograms per cubic meter, such air is deemed 'unhealthy for sensitive groups'. This type of air causes irritation and respiratory problems in children and people with medical conditions.

Nepal's air has become pretty dirty, thanks to pollutants emitted by households, factories and the transport sector. This may come as a surprise to many, but one of biggest drivers of air pollution in Nepal is households. Residential sector contributes to 87 percent of PM2.5 emission originating in Nepal, followed by industries (nine percent), transport sector (two percent) and forest fires (one percent), as per the data provided by ICIMOD. The share of pollutants changes slightly in March and April when forest fires occur. In these two months, households make a contribution of about 82 percent to PM2.5 emission originating in Nepal, followed by industries (about nine percent), transport sector (about two percent) and forest fires (about eight percent). This year the contribution of forest fires in PM2.5 emission is likely to go up because prolonged dry spell helped the flames to spread quickly. This type of weather event, according to experts, has occurred only four times in the last 20 years. "Yet the contribution of forest fires in total PM2.5 emission of this year is expected to go up by only five to 10 percent because wildfires occur only in a particular time of the year," says Siva Praveen Puppala, senior aerosol scientist at ICIMOD, adding, "People tend to jump to conclusion that the main source of air pollution is forest fires because they can see and smell the haze, but there are other factors that are making our air dirty."

The residential sector is the biggest source of air pollution in Nepal because many households, especially in rural areas, use firewood and animal dung to cook food, as biomass is the source of almost 70 percent of energy in the country. These households also burn agricultural residue in the fields to make the soil more fertile, while leaves that litter the grounds and weeds that are plucked are also openly burnt. Households everywhere in Nepal also burn garbage frequently. In fact, open garbage burning is one of the biggest sources of air pollution in urban centers like Kathmandu, where PM2.5 level is worse than the national average.

The fastest way to reduce air pollution in urban centres, especially Kathmandu valley, according to Puppala, is to stop garbage burning. Of course, diesel-powered vehicles and factories are also worsening the air quality of Kathmandu valley, which is home to over four million people. But it is not easy to immediately replace all diesel-powered vehicles with electric vehicles or rampantly cut down on emission of factories, as they may have economic consequences. This is not the case with garbage burning, which does not make any economic contribution. "So, if the garbage burning is brought to zero, air pollution level can come down by 30 percent in Kathmandu," says Puppala.

If Kathmandu wants to further improve its air quality it should reduce road traffic congestion. Traffic congestion makes a big contribution to air pollution because vehicles consume more fuel when they are stuck in a gridlock. If Kathmandu can deal with the problem of traffic congestion, improve road conditions, and completely stop garbage burning, it can easily reduce air pollution by 50 percent, says Puppala.


Loss of balance
Everyone agrees that air quality in Kathmandu as well as other urban centers needs to be improved. But these places represent only a small fraction of Nepal. Vast areas of the country located in hills and mountains, which are not densely populated and from where blue skies and stars could be seen throughout the year, appear much cleaner. What's more, Nepal is not as industrialised as its neighbouring countries, India and China. Nepal also has a lot less cars and trucks than its neighbouring countries. Yet Nepal is listed as one of the top countries with high levels of air pollution in the world. Why? This is the question asked by many.

The answer lies in the proximity of large parts of the country to the Indo-Gangetic Plain, which spreads across 2.5 million sq km, covering southern Nepal, northern and eastern India, eastern Pakistan, and most of Bangladesh. The number of people who live on this belt exceeds the combined population of the US, Canada and Australia. Many of these people depend on biomass for fuel. This area also houses lots of factories that spew dirty air. These reasons have made the Indo-Gangetic Plain one of the most polluted in the world.

Satellite images clearly show pollutants stagnating in this area. The presence of tall mountains in the Himalaya has further complicated the problem, as they work as walls, preventing pollutants from flushing out. When these pollutants travel to Nepal, they get stuck in mountain valleys. This means the hills and mountains, which are Nepal's assets, also trap particulate matters. When large amounts of particulate matters are present in the atmosphere, they form haze.

“Haze generally reaches an altitude of less than three km over southern Nepal. But in northern Nepal, it can reach five km above sea level, especially when there are high altitude forest fires,” says Arnico Panday, an atmospheric scientist, who is also CEO of Ullens Education Foundation.

Haze generally absorbs some of the sunlight that would normally reach the surface below. That is why hazy days feel colder in low altitude valleys and in the plains, explains Panday, who is also a senior research fellow at the Institute for Integrated Development Studies (IIDS), one of the oldest think-tanks in Nepal. But near or above the top layer of haze, where there is sunlight, the air temperature gets warmer than usual. “A hike in air temperature at higher altitudes--where temperatures are generally below freezing point--leads to increased melting of the lower parts of glaciers. This loss is in addition to glacial melt caused by sunlight-absorbing deposits of black carbon and other dark particles present on the snow,” says Panday. “As glaciers recede, their ice volume goes down. This affects the volume of stored water that glaciers release into the rivers during the dry season, hitting irrigation and hydropower. So haze and black carbon have impacts beyond air quality.”

Brewing crisis
Glaciers are one of the big sources of river water in Nepal. Nepal has 3,808 glaciers spread in an area of 4,212 sq km. These glaciers are located in four major river basins: Koshi, Gandaki, Karnali and Mahakali. The water generated by glaciers, which flow through rivers, has not only helped Nepalis to irrigate their fields but has enabled hundreds of millions of farmers as far as in India and Bangladesh to get good yields. If water levels recede faster in rivers, food production may come under undue pressure, creating even bigger problems for countries like Nepal where malnutrition and stunting still pose a big challenge.

River water has also helped Nepal to generate hydroelectricity. Over 6,000 rivers and rivulets in Nepal have the potential to generate 83,000 megawatts of electricity, of which 42,000 MW is commercially exploitable. If Nepal can harness this hydro potential, it can play a crucial role in lighting many parts of South Asia and earn massive foreign currency to bridge its ballooning trade deficit, which stands at around 40 percent of the gross domestic product. But to reap this benefit rapid melting of glaciers must be curbed, because if their stock evaporates, rain water alone cannot help the country generate adequate electricity throughout the year.

Studies conducted so far on glacial melt have produced grim results. An assessment done by ICIMOD in 2019 showed that 650 glaciers in the Hindu Kush-Himalaya region—which contains the world’s largest volume of glacier ice outside the polar regions—are losing 8 billion tonnes of snow every year and are not being replenished. This loss triggered the glacier surface to shrink by an average of 43 cm a year from 2000 to 2016, as against 22 cm a year from 1975 to 2000. Glaciers at lower levels, on the other hand, are losing their thickness by five meters per year. There is now a growing sense of alarm over the prospect of glaciers receding faster in Nepal, as studies have shown that sheets of snow and ice on the stretch of Himalaya that falls in the country are melting faster than glaciers in the western part of Himalaya, where Pakistan's Karakoram range is situated.

The major reason for glacial melt is rise in temperature on the Earth, which is referred to as global warming. Global warming is not unnecessary per se, as it keeps the Earth warm, which is necessary for life to grow on this planet. Otherwise, the Earth would be covered with ice and become uninhabitable. The only problem is it is heating a lot faster.

The globe basically warms when gases in the atmosphere trap heat from the sun that would otherwise be reflected before escaping into space. This process of trapping the sunlight is referred to as the greenhouse effect.

For most of the past 800,000 years, the concentration of carbon dioxide--which is a dominant greenhouse gas--in the atmosphere stood at 200 to 280 parts per million. This means there were 200 to 280 molecules of the carbon dioxide per million molecules of air. By 1960, the concentration jumped to 317 parts per million. Since then, the number has surged past 400 parts per million, driven up by human activities such as burning of fossil fuels and deforestation, according to the US-based Natural Resources Defense Council. The higher concentration of greenhouse gases, particularly carbon dioxide, is causing extra heat to be trapped, pushing up global temperatures.

The average global temperature on Earth has gone up by a little more than one degree Celsius since 1880. Two-thirds of that warming has occurred since 1975, at a rate of around 0.15 to 0.20 degree Celsius per decade. If the global temperature goes up by only 1.5 degree Celcius from the pre-industrial period, 36 percent of glaciers on Hindu Kush and Himalaya range will disappear by 2100, says the 2019 ICIMOD report. If that temperature rises by two degree Celcius, half of the glaciers would be lost.

Lately, altitudes ranging from 5,000 to 6,000 meters in Nepal are witnessing rise in temperature. In the next couple of decades, temperature at those altitudes is expected to remain at above zero degree Celcius for more number of days in a year. That's the condition in which glaciers melt faster.

This situation may be aggravated by deposits of black carbon generated by burning of biomass, fossil fuel, garbage and forests. So, while climate change is the most important factor for glacial melt, air pollution works as a catalyst to worsen the problem. An analysis conducted in 2017-18 showed that meteorological factors, especially climate change, command a share of 70 percent in glacial melt, with air pollution induced by black carbon making the remaining 30 percent of contribution. To put it simply, if climate change reduces the height of a glacier by 1 meter, pollution elevates the loss to up to 1.3 m.

Deeper costs
When black carbon settles on glaciers, they absorb more sunlight because dark colours trap more heat. This intensifies glacial melt. A study conducted by a team led by ICIMOD scientist Puppala in the area surrounding Yala glacier in Langtang region showed that anthropogenic sources, such as emission from vehicles, factories, households and garbage burning, helped generate 77 percent of the atmospheric black carbon mass, while open-burning sources, such as forest fires and open agricultural burning, made a contribution of another 14 percent. The biggest portion of black carbon in the Yala region came from Nepal and India (69 percent), followed by China (22 percent), Bangladesh (three percent), Pakistan (two percent), Bhutan (one percent), and nearby regions. If this kind of emission is not reduced, two-thirds of glaciers in Hindu-Kush and Himalaya range would be gone by 2100, warns the ICIMOD report.

Glaciers are like frozen rivers. They start moving when the ice on its lower part starts melting. The melting occurs because the lower part of the glacier is relatively warmer than the topmost part, which is exposed to lower temperature. The ice lost to melting must be replenished with fresh snow. But that balance has been lost, as fresh snow has not been able to make up for the losses caused by melting. When glaciers lose ice, they flow more quickly.

When glaciers move they wear away land beneath them, accumulating aggregates like pebbles, stones, rocks and boulders. As glaciers recede, they leave behind depressions, usually in the shape of a bowl that get filled with liquid water, while pebbles, stones, rocks and boulders form the walls, leading to formation of glacial lakes. Nepal has 1,466 glacial lakes spread over 64.8 sq km. These lakes have emerged as potential threats, as the boundaries of the glacial lakes, made of pebbles, stones, rocks and boulders, are not robust. So, excessive amounts and force of water may cause the lake to burst, triggering massive floods. This is referred to as the glacial lake outburst flood. This kind of incident occurs once every several years in Nepal. Namche Small Hydropower Project located in the Khumbu region, which was being built at a cost of USD 1.5 million, fell victim to Dig Tsho glacial lake outburst flood, which swept away the entire plant. Bhotekoshi-Sunkoshi glacial lake outburst flood of 1981, on the other hand, damaged the Arniko Highway, the only road link to China at that time. The torrent of water and debris that glacial lake outburst floods discharge can sweep away or drown entire villages. For instance, if Imja Tsho glacial lake near Mount Everest outbursts, areas near Chhukhung, Sylkyo, Dinboche, Thyanboche, Namche Bazar, Manjo and Phakding are likely to be inundated and face devastation. Surveys have shown that many glacial lakes in Nepal are expanding rapidly as more and more snow and ice are melting, posing greater threat to hydropower dams, irrigation projects and, above all, human lives.

The dynamics of how glaciers will change in the future and what will happen to the quantity of water they release, however, are still unknown. Models have been developed to understand this phenomenon. But most of the models capture the entire Himalaya region as a single entity and extrapolate the patterns, even though topography, geology, and terrain in this belt are not uniform. This calls for assessment of potential impacts in smaller catchments where the conditions can be modeled more precisely. One such study has been conducted in the Koshi river basin, which is the source of Tamor, Arun, Dudhkoshi, Likhu, Tamakoshi, Sunkoshi and Indrawati rivers.

Snow and glacier melt contributes to 34 percent of annual discharge in the Koshi river basin, according to the study. The contribution from glacial melt in the basin is particularly significant during the pre-monsoon season from March to May, providing 63 percent of stream-flow, says the 2016 paper titled 'Impacts of Climate Change on the Hydrological Regime of the Koshi River Basin in the Himalayan Region'. These are the months when water is scarce, as rainwater is virtually absent. This shows glaciers are the dominant source of water for Koshi river basin during the dry season. The share of glacial melt in the basin, however, drops to 10 percent during the winter season from November to February when air temperature plunges, and stands at around 39 percent in the monsoon season from June to September. The water generated by glaciers is most important for hydropower and irrigation projects in the pre-monsoon season, when the weather is very dry. But that may change in the second half of this century. Glacier melt in the Koshi river basin is expected to accelerate up to 2046 by 1.78 mm per year on average, increasing the discharge of water in rivers, mostly in monsoon. This may be good news for farmers, but the surge in flow of water also heightens the risk of floods, landslides, and erosion of fertile topsoil. This could exert pressure on hydropower dams and flood swathes of land in Nepal and India. After 2046, snowmelt will fall to 0.68 mm per year on average in Koshi river basin due to a drop in stock of glaciers, which might reduce the flow of water in rivers, especially in pre- and post-monsoon seasons. The 2019 ICIMOD study on Hindu Kush-Himalaya region also showed that glacial melt will increase river flows till 2060, after which they will shrink, hitting the Indus River and other rivers in central Asia the most.

Going forward, the biggest challenge would be to prevent disputes related to sharing of water, which will gradually become one of the most precious natural resources in the world. Chances of two nuclear powers in South Asia, India and Pakistan, engaging in a bitter fight cannot be ruled out, as disputes between the two are deepening over use of water in Indus River, which falls under the domain of India (39 percent), Pakistan (47 percent), Tibet in China and Afghanistan. This might further affect the regional integration process, which is already facing headwinds due to rivalry between India and Pakistan.

"Air pollution, glacial melt and reduction in river water discharge are regional as well as international issues, which Nepal alone cannot settle. So, this problem must be raised frequently in regional and international platforms," says atmospheric scientist Panday. "As a responsible nation, Nepal should strive to reduce the level of air pollution by curbing its domestic emissions, including black carbon, which are also accelerating the glacial melt."

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