Nepal’s mountains, forests and rivers make it rich in nature, but they also make the country very sensitive to pollution and climate change. Questions on the environment appear in almost every Lok Sewa general knowledge and science paper. This note explains the basic ideas in simple words and lists the dates and agreements that are asked most often.
1. Ecosystem and food chain
An ecosystem is a natural unit in which living things interact with each other and with their non-living surroundings. A pond, a forest and a grassland are all ecosystems.
- Biotic components: the living parts, such as plants, animals and microbes.
- Abiotic components: the non-living parts, such as sunlight, air, water, soil and temperature.
Living things in an ecosystem play three roles:
| Role | What it does | Examples |
|---|---|---|
| Producers | Make their own food by photosynthesis | Green plants, algae |
| Consumers | Eat other living things | Deer (herbivore), tiger (carnivore), human (omnivore) |
| Decomposers | Break down dead bodies and return nutrients to the soil | Bacteria, fungi |
A food chain shows who eats whom, for example: grass → deer → tiger. Each step is a trophic level. Many food chains joined together form a food web.
The Sun is the main source of energy for almost every ecosystem. Energy flows in one direction and only about 10 percent of it passes from one trophic level to the next (the ten percent law); the rest is used up or lost as heat.
2. Biodiversity
Biodiversity means the variety of life on Earth. It is studied at three levels:
- Genetic diversity: variety within one species, such as the many local types of rice.
- Species diversity: the number of different species in an area.
- Ecosystem diversity: the variety of habitats, such as forests, wetlands and grasslands.
Nepal is rich in biodiversity because its altitude ranges from the low Terai to the highest peaks. Main threats include habitat loss, deforestation, poaching, pollution, climate change and invasive species such as banmara (Mikania). Biodiversity is protected in situ (in natural homes such as national parks) and ex situ (outside them, such as zoos and seed banks). Chitwan National Park, established in 1973, is Nepal’s first national park.
3. Pollution: air, water, soil and noise
Pollution is the addition of harmful substances or energy to the environment. The harmful agents are called pollutants.
| Type | Main causes | Main effects |
|---|---|---|
| Air | Vehicle smoke, brick kilns, factories, burning waste and forest fires | Asthma and lung disease, acid rain, smog |
| Water | Sewage, factory waste, fertilizers and pesticides washing into rivers | Cholera, typhoid, diarrhoea, death of fish |
| Soil | Too much chemical fertilizer and pesticide, plastic, industrial waste | Loss of soil fertility, poisons in food |
| Noise | Vehicle horns, loudspeakers, machines, aircraft | Hearing loss, stress, poor sleep, high blood pressure |
Important terms:
- The bowl shape of the Kathmandu Valley traps polluted air, especially in winter.
- Acid rain forms when sulphur dioxide and nitrogen oxides from burning fuel mix with rainwater; it harms plants, soil, lakes and buildings.
- Eutrophication happens when fertilizer and sewage add too many nutrients to a lake, causing a heavy growth of algae that uses up oxygen and kills fish.
- Arsenic in groundwater is a serious problem in some parts of the Terai.
- Noise is measured in decibels (dB).
4. The ozone layer and CFCs
Ozone (O₃) is a form of oxygen with three atoms. Most of it is found in the stratosphere, roughly 15 to 35 km above the Earth, forming the ozone layer. This layer absorbs most of the harmful ultraviolet (UV) rays of the Sun, which cause skin cancer and eye cataracts. Ozone thickness is measured in Dobson units.
Chlorofluorocarbons (CFCs), once widely used in refrigerators, air conditioners and spray cans, rise to the stratosphere, where sunlight breaks them and releases chlorine. One chlorine atom can destroy a very large number of ozone molecules. The thinning of the ozone layer, called the ozone hole, is most severe over Antarctica.
5. Greenhouse effect and global warming
The greenhouse effect is the trapping of the Sun’s heat by certain gases in the atmosphere, like the glass of a greenhouse. Sunlight warms the Earth, and the Earth gives off heat; greenhouse gases absorb part of this heat and keep the planet warm. Without this natural effect, the Earth would be far too cold for most life.
Main greenhouse gases and their sources (nitrogen and oxygen, the two main gases of air, are not greenhouse gases):
| Gas | Main human sources |
|---|---|
| Carbon dioxide (CO₂) | Burning coal, petrol, diesel and wood; cutting forests |
| Methane (CH₄) | Paddy fields, cattle, rubbish dumps |
| Nitrous oxide (N₂O) | Chemical fertilizers |
| CFCs and HFCs | Refrigerators, air conditioners |
Carbon dioxide is the most important greenhouse gas released by human activity. When people add more of these gases, more heat is trapped and the average temperature of the Earth rises. This is global warming. The long-term change in temperature, rainfall and weather patterns that follows is called climate change.
6. Climate change and Nepal
Nepal adds very little to global greenhouse gases but is among the countries most at risk. Studies show that the Himalaya is warming faster than the global average. Major effects are:
- Glacier melt: glaciers are shrinking and snowlines are moving higher, threatening the long-term flow of rivers.
- Glacial lakes and GLOF: meltwater collects in lakes held back by loose rock and ice (moraine). If the wall breaks, a sudden Glacial Lake Outburst Flood (GLOF) rushes down the valley. The Dig Tsho GLOF of 1985 in the Khumbu area destroyed a nearly completed hydropower plant, bridges and farmland. Tsho Rolpa in Dolakha is one of the most dangerous glacial lakes; its level was lowered by about 3 metres in 2000 to reduce the risk.
- Erratic rainfall: more droughts, floods and landslides; changes in the monsoon.
- Health: mosquito-borne diseases such as malaria and dengue spreading into hill areas.
To draw world attention, the Government of Nepal held a cabinet meeting at Kalapatthar, near Mount Everest base camp, in December 2009, just before the Copenhagen climate conference.
7. Sustainable development
Sustainable development is development that meets the needs of the present without harming the ability of future generations to meet their own needs. This definition comes from the Brundtland Report, “Our Common Future”, published in 1987.
- The Earth Summit in Rio de Janeiro in 1992 adopted Agenda 21, a plan for sustainable development.
- The United Nations adopted the Sustainable Development Goals (SDGs) in 2015: 17 goals to be met by 2030. Goal 13 is climate action.
8. Key international agreements
| Agreement | Year | Main purpose |
|---|---|---|
| Ramsar Convention | 1971 | Protection of wetlands |
| Vienna Convention | 1985 | Framework to protect the ozone layer |
| Montreal Protocol | 1987 | Phasing out CFCs and other ozone-depleting substances |
| UNFCCC (UN Framework Convention on Climate Change) | 1992 | Basic global treaty on climate change, opened for signature at the Rio Earth Summit |
| Convention on Biological Diversity | 1992 | Conservation of biodiversity, also opened for signature at Rio |
| Kyoto Protocol | 1997 | Legally binding cuts in greenhouse gas emissions for developed countries; came into force in 2005 |
| Paris Agreement | 2015 | Keep warming well below 2 °C and try to limit it to 1.5 °C; every country sets its own targets |
The countries that have joined the UNFCCC meet every year at the Conference of the Parties (COP). The Paris Agreement was adopted at COP21.
9. Important environment days
| Date | Day |
|---|---|
| 2 February | World Wetlands Day |
| 22 March | World Water Day |
| 22 April | Earth Day |
| 22 May | International Day for Biological Diversity |
| 5 June | World Environment Day |
| 16 September | International Day for the Preservation of the Ozone Layer (World Ozone Day) |
World Environment Day marks the opening of the UN Conference on the Human Environment in Stockholm in 1972. World Ozone Day marks the signing of the Montreal Protocol on 16 September 1987.
📌 Key points to remember
- Producers make food, consumers eat others and decomposers recycle nutrients.
- Energy flows one way in a food chain; only about 10 percent passes to the next level.
- Biodiversity has genetic, species and ecosystem levels; Chitwan is Nepal’s first national park.
- Sulphur dioxide and nitrogen oxides cause acid rain; noise is measured in decibels.
- The ozone layer in the stratosphere blocks UV rays; CFCs destroy it.
- Carbon dioxide, methane and nitrous oxide are major greenhouse gases.
- GLOF means Glacial Lake Outburst Flood; Tsho Rolpa is in Dolakha.
- Nepal’s cabinet met at Kalapatthar in December 2009 to highlight climate change.
- Brundtland Report 1987 defined sustainable development; SDGs are 17 goals for 2030.
- Montreal 1987 (ozone), UNFCCC 1992, Kyoto 1997, Paris 2015.
- World Environment Day is 5 June; World Ozone Day is 16 September; Earth Day is 22 April.
Test yourself: Environment, Pollution and Climate Change
50 questions check what you read about Ecosystem and food chain, Greenhouse effect and global warming and Important environment days. Each attempt picks 25 at random.