Terrestrial Ecosystems or Biomes

First, understand the core idea —
The biosphere (the life-supporting zone of the Earth) can be divided into two broad parts:

1. Terrestrial – land-based ecosystems
2. Aquatic – water-based ecosystems

Now, the terrestrial portion is divided into large natural regions called Biomes.

Think of a biome as a “continent-scale ecosystem” — a massive natural zone where climate, vegetation, soil, and animal life show a particular pattern.

👉 No two biomes are alike — because each has a distinct climate, soil type, vegetation, and animal community.

So, if someone asks, “Why are there pine trees in Canada but not in Africa?” — the answer lies in their different biomes.

🗺️ Major Terrestrial Biomes

Biomes are classified mainly on climate, especially temperature and precipitation.
Here are the major ones you should remember:

Major Biome Type	Examples
Tundra	Arctic & Alpine Tundra
Forest	Taiga, Temperate Deciduous, Temperate Rainforest, Sub-tropical Deciduous, Mediterranean, Tropical Deciduous, Tropical Rainforest
Grassland	Steppe (Temperate Grassland), Savanna (Tropical Wet & Dry)
Desert	Tropical & Mid-latitude Deserts

Now, let’s explore each biome — from the coldest to the warmest.

❄️ Tundra Biome

“Tundra” means treeless plain.
It’s found in the Arctic regions and on high mountain tops (Alpine Tundra).

📍Location:

• Arctic Tundra – Near the North Pole
• Alpine Tundra – Above the tree line in high mountains like the Himalayas, Andes, Alps

🧊 Key Feature: Permafrost

• The ground here remains permanently frozen (below 0°C for at least two consecutive years).
• Because of this, trees cannot grow — roots can’t penetrate frozen soil.

🌿 Vegetation:

• Only mosses, lichens, and small shrubs like Arctic willow survive.
• On coastal lowlands, you’ll find reindeer moss — food for reindeer.

🐻 Animal Life:

• Adapted to extreme cold — thick fur, small ears/tails to minimize heat loss.
• Examples: Reindeer, Arctic fox, Musk ox, Polar bear, Arctic hare.
• Insects have very short life cycles — active only during short summers.
• Reptiles and amphibians are absent — they can’t tolerate freezing.

🧬 Lifespan:

Some species like Arctic willow can live for 150–300 years — growth is slow, but survival is long.

Read More about Tundra Climate here

🌲 Taiga or Boreal Biome

As you move slightly south from the tundra, temperature rises just enough for trees to grow — but still harsh.
This gives us the Taiga, also known as the Boreal forest.

🌍 Location:

• Sub-Arctic regions — e.g., Canada, Russia, Scandinavia.

🌿 Vegetation:

• Evergreen coniferous forests — pine, spruce, fir.
• Conifers have needle-like leaves and waxy coatings to prevent water loss.

🌱 Productivity:

• Lowest among all forests — because:
  • Weather is too cold.
  • Soils are thin and nutrient-poor, called Podzols.
  • Decomposition is slow, so humus content is low and soil becomes acidic.

🧪 Podzols — Soil of Boreal Forests

Let’s understand this technically.

• Thin topsoil, over a sandy or loamy base.
• Leaching (downward movement of nutrients) is heavy → nutrients lost to lower layers.
• Soil is acidic (low pH) because basic elements are washed away.
• Hence, poor for agriculture — mostly used for grazing or forestry.

🦊 Animals:

• Siberian tiger, bear, wolf, lynx, red fox, wolverine.
• Amphibians like Rana and Hyla also exist but are few.

Read More About Taiga Climate here

🌳 Temperate Deciduous Biome (North-Western Europe – British Type)

Now, as we move to milder regions (moderate temperature + adequate rainfall) — we get deciduous forests.

🌿 Vegetation:

• Trees shed leaves in winter to protect from frost — this is an adaptation.
• Species: Oak, Elm, Ash, Beech, Birch, Poplar.
• Shedding begins in autumn, regrowth starts in spring.

🌱 Soil:

• Podzolic but deeper than taiga — more fertile due to faster decomposition.

🌧️ Temperate Rainforest Biome

📍 Location:

• Found in small patches — mainly along the northwestern coast of North America (from Northern California to Southern Alaska).
• Also in Southern Chile, New Zealand, Australia.

🌿 Vegetation:

• Large conifers: Douglas fir, Western red cedar, Sitka spruce, Mountain hemlock.
• Mosses and lichens are abundant, often growing as epiphytes (plants growing harmlessly on other plants).

🌴 Sub-Tropical Deciduous Biome (Eastern China, SE USA)

• Climate supports luxuriant vegetation — both evergreen broad-leaved and deciduous trees.
• On highlands, pines and cypresses dominate.
• Growth is perennial (year-round) since there’s no extreme dry or cold season.

🌾 Steppe or Temperate Grassland Biome

📍 Location:

• Interiors of continents — e.g., Eurasian steppes, North American prairies.

🌿 Features:

• Treeless plains dominated by short, nutritious grasses.
• As rainfall increases northward, wooded steppes emerge.
• Animal diversity is limited but includes grazing herbivores.

Read more about Steppe Climate here

🌿 Temperate Deciduous Biome (Mediterranean Climate)

☀️ Climate:

• Hot, dry summers and mild, wet winters.
• Plants must tolerate drought, heat, and fire.

🌿 Vegetation:

• Xerophytic (drought-tolerant) plants.
• Small, broad leaves; short, widely spaced trees (often evergreen oaks).
• Fire-resistant species — regenerate quickly after burns.

Read More about Mediterranean Climate here.

🌳 Tropical Deciduous Biome (Monsoon Climate)

📍 Location:

• India, parts of Africa, Southeast Asia.

🌿 Vegetation:

• Also called Dry Deciduous or Drought-Deciduous Forests.
• Dominant species: Teak, Sal, Neem, Bamboo, Shisham, Sandalwood, Khair, Mulberry.
• Trees shed leaves in dry season to conserve water.

Read more about this climate here.

🐘 Savanna or Tropical Wet and Dry Biome

🌍 Location:

• Found between tropical rainforests and deserts — e.g., Africa, Brazil, India (some parts).

🌿 Features:

• Tall grasses with scattered trees like Acacia.
• Trees are deciduous and umbrella-shaped — to reduce transpiration and withstand wind.
• Some trees have thick trunks that store water.

🦓 Fauna:

• Extremely rich in wildlife — lions, elephants, giraffes, zebras, antelopes, birds, reptiles.

Read more about this here.

🔥 Managed Fires and the Savanna

Interestingly, fire is not always destructive here.

• Controlled burning rejuvenates grasslands — promotes fresh, nutritious regrowth.
• Helps control ticks and thorny shrubs.
• Ecologically, such fires are carbon-neutral —
  the CO₂ released during burning is reabsorbed by new grass in the next growth cycle.

🌴 Tropical Rainforest Biome — The Lungs of the Earth

Let’s begin with an image in your mind:
Imagine standing in a forest so dense that sunlight struggles to touch the ground. It’s hot, humid, and alive — filled with insects, birds, animals, and the sound of constant rain.
That’s your Tropical Rainforest Biome — the most productive and biodiverse ecosystem on Earth.

🌦️ Climate and Vegetation

• These forests grow in regions where temperature is high throughout the year (around 25–27°C) and rainfall is abundant (200–400 cm annually).
• Because of this warm and wet climate, trees remain evergreen — they never shed all leaves together.
• Common trees: Mahogany, Ebony, Dyewoods, and many other hardwood species.
• In brackish waters (mix of sea and river water), Mangrove forests thrive — they are crucial for coastal protection

🌿 Layered Vegetation — The Canopy System

Now, a fascinating feature:
Since sunlight is limited near the forest floor, all plants compete to reach it.
This creates a multi-layered structure:

1. Emergent Layer – tallest trees rising above the rest.
2. Canopy Layer – dense roof formed by the majority of trees; blocks sunlight.
3. Understory Layer – smaller trees and shrubs growing in filtered light.
4. Forest Floor – dark, damp, with little vegetation but rich in decomposing matter.

Among these, you’ll find epiphytes — plants like orchids or ferns that grow harmlessly on other trees to reach sunlight.
They don’t steal nutrients from the host; instead, they absorb moisture and minerals from air and rain.
This relationship is a form of commensalism — the epiphyte benefits while the host remains unaffected.

🌍 Significance of Tropical Rainforests

Let’s understand why these forests are literally the heartbeat of our planet:

🫁 Oxygen Factory
They produce about 20% of Earth’s oxygen, earning them the title “Lungs of the Earth.”

🌳 Carbon Sink
They absorb nearly 2 billion tonnes of CO₂ annually, helping to slow global warming.

☔ Rain Makers
Through evapotranspiration, they recycle 50–75% of their own rainfall.
So, the rainforest makes its own rain!

🏞️ Source of Rivers
The great rivers — Amazon, Congo, Mekong — all originate from these forests.

🧬 Biodiversity Hotspot
Home to over 30 million species — half of the world’s wildlife and two-thirds of its plants.

☕ Commercial Importance
Ideal for crops like coffee, cocoa, palm oil, rubber — all need 100–200 cm rainfall.

👥 Indigenous Communities
Several tribal groups have lived here for millennia, practicing slash-and-burn (shifting) cultivation and using forest resources for food, shelter, and medicine.

🌦️ Rainforest and Climate Regulation

• These forests constantly exchange water and energy with the atmosphere, influencing local and regional climates.
• Moisture released by rivers into oceans helps regulate ocean currents, which in turn affect global weather patterns.

🇧🇷 The Amazon Rainforest — A Global Treasure

🌊 The Amazon Basin:

• Produces 20% of the world’s fresh water that flows into oceans.
• Returns 75% of moisture to the moving air masses — thus, most of South America (except Chile, blocked by the Andes) gets rainfall because of the Amazon!

🔥 Threats to the Amazon Rainforest

Let’s now understand the crisis part of the story — how humans and climate change are pushing this vital ecosystem towards collapse.

(a) Frequent Fires and Droughts

• Normally, rainforests are too moist to catch fire.
• But mega-droughts (linked to El Niño and Atlantic Ocean warming) have made the forest fire-prone.
• These fires dry out the forest, destroy the canopy, and make the ecosystem vulnerable.

(b) Slash and Burn Agriculture

• Farmers cut vegetation, let it dry, and burn it to clear land for farming.
• This process repeats for years — each time reducing forest fertility.

(c) Political and Economic Factors

• In Brazil, policies under Jair Bolsonaro weakened forest protection agencies.
• Illegal land grabbers burn forests for timber, cattle ranching, palm oil, and soybean cultivation.

🌎 Global Consequences of Amazon Fires

(a) Carbon Sink to Carbon Source

• The Amazon usually absorbs 2 billion tonnes of CO₂ annually.
• Due to fires, it now releases CO₂, worsening global warming.

(b) Prolonged Droughts

• Fewer trees → less evapotranspiration → fewer clouds → longer dry seasons.
  A deadly cycle begins.

(c) Pollution

• Forest fires produce:
  • 15% of global greenhouse gas (GHG) emissions
  • 30% of carbon monoxide (CO)
  • 10% of methane (CH₄)
  • 85% of soot emissions

These further heats the planet, making forests drier and weaker.

(d) Transformation into Grasslands

• When fires and droughts persist, nutrient-poor soils cannot support trees.
• Gradually, the forest turns into tropical savanna — a lower-productivity ecosystem.

This point is critical — scientists warn that once a tipping point is reached, the forest will die back, losing its capacity to recover.

🔥 Fires: Destructive for Some, Essential for Others

Here’s an interesting contrast.

While tropical rainforests are fire-sensitive, many other ecosystems depend on fire for renewal:

• Taiga forests of Siberia and Canada
• African savannas
• Australian eucalyptus forests
• Californian coniferous forests
• Mediterranean scrublands

Here, periodic small fires:

• Clear dead vegetation
• Trigger germination of seeds
• Maintain open landscapes

Examples:

• Douglas fir survives due to thick bark.
• Lodgepole pine cones open only in fire’s heat.
• Australian grass tree seeds open with smoke.

So, controlled fires = natural rejuvenation,
but uncontrolled mega-fires = ecological collapse.

⚠️ Other Human Threats

🏭 Plantations and Resource Extraction

• Palm oil, coffee, cocoa, sugarcane, and rubber plantations have cleared nearly half of equatorial forests.
• Oil extraction in countries like Ecuador and Venezuela has caused massive destruction.

💀 Effects of Destroying Rainforests

(a) Soil Degradation

• Rainforest soil is poor in nutrients — most nutrients are stored in vegetation itself.
• Once trees are cut, nutrient cycling stops, and heavy rains wash away the topsoil.

(b) Droughts and Famine

• Less vegetation → less rainfall → prolonged droughts → food scarcity.

(c) Commercial Crop Failure

• Crops like coffee and cocoa depend on rainforest humidity — once the forest goes, even these crops will fail.

(d) Loss of Indigenous Communities

• Logging and oil companies often displace local tribes, bringing diseases and violence.
• Centuries-old cultures vanish with the forests.

🏜️ Desert Biome — The Land of Extremes

After lush rainforests, let’s move to the other extreme of nature — the Desert Biome.
It’s the exact opposite of the rainforest — little water, sparse vegetation, and extreme temperatures.

🌡️ Climate

• Rainfall: less than 25 cm per year
• Temperature: can be extremely hot during the day and cold at night due to absence of clouds.

🌵 Vegetation

The vegetation is xerophytic — meaning drought-resistant.
Plants are adapted to save water and survive heat.

🌿 Characteristics:

• Cacti, thorny bushes, dwarf acacias, and wiry grasses dominate.
• Seeds have thick coverings — they remain dormant until rain arrives.
• Roots are long and spread widely — to absorb every drop of moisture.
• Leaves are reduced to spines or are waxy, hairy, or needle-like — reducing transpiration (water loss).
• Plants are widely spaced — to reduce competition for water.

🦎 Fauna and Adaptations

• Animals are nocturnal — active at night to escape heat.
• Many get water from metabolic processes or food.
• Common examples: camels, jerboas, snakes, lizards, scorpions.

Summary Table

Biome	Climate (Temp & Rainfall)	Soil	Vegetation (Flora)	Fauna	Key Features
Tundra	Very cold, dry; <25 cm rain	Permafrost	Mosses, lichens, dwarf shrubs	Reindeer, Arctic fox, polar bear	Treeless plain; short summer; low biodiversity
Taiga (Boreal)	Cold, sub-Arctic; moderate rain	Podzols (acidic, poor)	Conifers – pine, spruce, fir	Bear, wolf, lynx, tiger	Evergreen forest; slow decomposition; poor soils
Temperate Deciduous	Moderate temp & rainfall	Podzolic, fertile	Broad-leaved trees – oak, beech, elm	Deer, fox, birds	Trees shed leaves in winter; rich humus
Temperate Rainforest	Cool, very wet	Moist deep soil	Tall conifers, mosses, lichens (epiphytes)	Elk, black bear	Small global extent; lush evergreen forest
Sub-Tropical Deciduous	Warm, humid year-round	Fertile	Mixed evergreen & deciduous; pines, cypress	Diverse species	No distinct dry/cold season; luxuriant growth
Steppe (Temperate Grassland)	Semi-arid; 25–75 cm rain	Chernozem, rich humus	Short nutritious grasses	Bison, antelope	Treeless plains; grazing lands; continental interiors
Mediterranean	Hot dry summers, mild wet winters	Thin, rocky	Xerophytes, olive, evergreen oak	Goat, sheep	Fire-prone; drought-tolerant shrubs
Tropical Deciduous (Monsoon)	Hot summers, distinct wet/dry	Red/black soils	Teak, sal, neem, bamboo	Elephant, tiger, deer	Trees shed in dry season; most widespread in India
Savanna (Tropical Wet & Dry)	Wet & dry seasons; 75–125 cm rain	Lateritic	Tall grasses, acacia, baobab	Lion, zebra, giraffe	Grassland with scattered trees; fire-tolerant; rich wildlife
Tropical Rainforest	Hot, humid; 200–400 cm rain	Lateritic, leached	Dense evergreen; mahogany, ebony; layered canopy	Insects, monkeys, jaguar	Highest biodiversity; “Lungs of Earth”; carbon sink
Desert	<25 cm rain; extreme temps	Sandy, saline	Cacti, thorny bushes, acacia	Camel, lizard, snake	Xerophytic plants; nocturnal animals; water scarcity