This section includes information adapted from Mera Publications’ book, Natural History of the Wild Side of Everest. We thank Mera Publications for their work and permission.

The Environment of the Nepal Eastern Himalaya and Khumbu Valley

1. Geography and Landscape

• Khumbu Valley features breathtaking mountains, glaciers, and deep valleys, dominated by Mount Everest (8,848 m), the world’s highest peak.
• Sagarmatha National Park is a World Heritage Site, preserving the region’s natural beauty and biodiversity.
• Encompasses the Dudh Kosi and Bhotekoshi rivers and Gokyo Lakes.
• Elevation ranges from 2,845 m (Monjo) to 8,848 m (Everest’s summit).
• Various climatic zones include:
  • Temperate (below 3,000 m)
  • Subalpine (3,000 – 4,000 m)
  • Alpine (above 4,000 m)
  • Nival (above 5,000 m)

2. Flora and Fauna

• Over 1,000 floral species found in Sagarmatha National Park.
• Vegetation zones:
  • Subalpine (3,000 – 4,000 m): Fir, birch, rhododendron.
  • Alpine (4,000 – 5,000 m): Juniper, rhododendron, mosses, lichens.
  • Above 5,000 m: Barren land, only limited plant life.
• Wildlife diversity:
  • 208 bird species, including Impeyan pheasant, bearded vulture, snowcock, and alpine chough.
  • Ungulates (hoofed mammals): Himalayan tahr, Himalayan serow, musk deer.
  • Big cats: Snow leopard (above 3,500 m), Indian leopard (lower forests).

3. Climate and Elevation Effects

Temperature and Altitude

• Temperature drops by 2°C per 300 m ascent.
• Growing season decreases by 6 days per 100 m ascent.

Moisture and Altitude

• Moisture increases with altitude up to 4,000 m, then decreases.
• Treeline at 4,000 m, beyond which dryness limits tree growth.

Latitude Influence

• Nepal is near the equator, making lower elevations warmer than similar elevations in more northern regions.
• The Himalaya blocks cold air from Central Asia, keeping Nepal warmer than expected at its latitude.

Monsoon Influence

• Most rain falls during the monsoon (originating from the Bay of Bengal).
• Eastern Nepal is wetter than the west.
• Upper Arun River Valley is one of Nepal’s wettest places.
• Higher moisture in the east fosters greater biodiversity.

4. Bio-Climatic Zones

1. Tropical (below 1,000 m)

• Found along major rivers like Arun River.
• Year-round warm temperatures.

2. Subtropical (1,000 – 2,000 m)

• Forests of chilaune, chestnut, alder.
• Warm/hot climate, distinct wet and dry seasons.

3. Temperate (2,000 – 3,000 m)

• Broad-leaved trees, cool winters, heavy moisture.
• Cloud forests prevent solar radiation, limiting crop cultivation.
• Growing season: 9 months.

4. Subalpine (3,000 – 4,000 m)

• Fir, birch, and rhododendron forests.
• Cold winters, heavy snow.
• Growing season: 6 months.

5. Alpine (4,000 – 5,000 m)

• Tundra-like vegetation (low shrubs, mosses, lichens).
• Strong winds, cold conditions, short growing season (<3 months).

6. Nival/Snow & Ice (above 5,000 m)

• Too harsh for most plants and animals.
• Few flowering plants at 6,000 m.
• Surviving species: Spiders, invertebrates.

5. Effects of Landscape on Biodiversity

Microclimates and Their Impact

• South-facing slopes: Sunnier, drier, and warmer.
• North-facing slopes: Cooler, moister, richer in vegetation.
• Ridgetops: Less moisture, more wind and sunlight.
• Basins and hollows: Moist, shaded, often damp environments.
• Rain Shadow Effect:
  • Mountains force clouds to rise, leading to rainfall on the windward side.
  • Leeward valleys remain dry.

Geological Impact

• Cliffs and rocky outcrops: Prevent normal plant growth.
• Landslides: Destroy vegetation, slow regeneration.

6. Environmental Changes Over Time

Factors Driving Change

• Glacial retreat due to climate change.
• Landslides, avalanches, and floods reshape vegetation.
• Silt deposition in lakes allows new plant growth.
• Slash-and-burn agriculture and wildfires alter landscapes.
• Warmer, drier conditions have increased the frequency of fires.

Stages of Ecological Succession

1. Bare Rock: Lichens and mosses begin breaking down rock.
2. First Green Plants: Grasses and sedges establish.
3. Shrub Growth: Willow, alder begin taking root.
4. Tree Growth: Forest matures with diverse vegetation.

7. Ecological Communities

Forests with Warm Summers & Cool Winters (2,000 – 3,000 m)

• Temperate Forests: Oak, chestnut, maple, walnut.
• Evergreen Oak Forests: Lower temperate, two types:
  • Oak-laurel forests (moist areas)
  • Oak-rhododendron forests (dry areas)
• Broad-leaved Deciduous Forests: Upper temperate, dominated by maple, magnolia, birch.
• Bamboo Groves: Thrive in disturbed areas.
• Alder Forests: Found in ravines and shaded sites.
• Rhododendron Forests: Steep ridge-tops in heavy rainfall areas.

Subalpine Forests (3,000 – 4,000 m)

• Silver fir, birch, rhododendron forests dominate.
• Vegetation types:
  • Fir Forest (3,000 – 4,000 m): Dense, misty conditions.
  • Fir-Birch-Rhododendron (3,500 – 4,000 m): Mix of species.
  • Birch-Rhododendron (3,300 – 3,700 m): Moist conditions encourage mixed vegetation.
• Pasturelands: Result from deforestation and livestock grazing.

Tree-Line (4,000 m)

• Boundary between subalpine and alpine zones.
• Harsh conditions prevent tree growth.
• Vegetation:
  • Rhododendron scrub (3,700 – 4,200 m).
  • Rhododendron-Juniper shrubland (3,700 – 4,100 m).

Alpine Zone (4,000 – 5,000 m)

• Extreme climate, 6+ months of winter.
• Dwarf Rhododendron, Juniper shrubs dominate.
• Grasslands in moist areas.
• Willow shrubs grow along streams.
• Juniper-Rhododendron scrublands are widespread but often burnt for grazing.

Conclusion

The Nepal Eastern Himalaya and Khumbu Valley exhibit a unique ecological diversity due to variations in altitude, moisture, temperature, and geography. This dynamic environment supports a rich biodiversity and continues to evolve due to climate change and natural processes. Preserving this fragile ecosystem is crucial for sustaining its rich flora and fauna.