Biomes and where they are

A biome is a large-scale global ecosystem, defined mainly by its climate (temperature and rainfall). Their distribution follows the global atmospheric circulation:

• Tropical rainforest — near the Equator, where rising air brings hot, wet conditions all year.
• Hot desert — around 30° N and S, where sinking air makes it hot and dry.
• Taiga (boreal / coniferous forest) — in the cold high latitudes of the northern hemisphere.
• Tundra, temperate forest, grassland — in between, set by their own climates.

Key idea: climate is the master control on biomes — but soils, altitude and drainage cause local variation too.

The tropical rainforest

The rainforest is hot (~27 °C all year) and very wet (over 2000 mm rain a year). It has a layered structure and clever adaptations:

Nutrients cycle fast: dead leaves rot quickly in the heat and are taken straight back up by the trees, so most nutrients are stored in the living plants, not the soil.

Rainforest nutrients

The taiga (boreal forest)

The taiga is the cold coniferous forest of the far north (Canada, Scandinavia, Russia). It contrasts sharply with the rainforest:

• Climate — long, freezing winters and short, cool summers; low rainfall.
• Plants — coniferous evergreens (pine, spruce, fir) with needle leaves and a conical shape that sheds snow; evergreen so they photosynthesise as soon as it's warm enough.
• Biodiversity — much lower than the rainforest; few tree species.
• Nutrients — cycle slowly: cold slows decomposition, so nutrients build up in the soil and leaf litter as acidic podsol soils.

Compare: rainforest = hot, wet, hugely biodiverse, fast nutrient cycling. Taiga = cold, low biodiversity, slow nutrient cycling.

Match the feature to the biome

Tap a feature on the left, then tap the biome it belongs to on the right.

Why biodiversity matters

Biodiversity is the variety of living things in an ecosystem. Forests provide vital goods (things we use) and services (things they do for us):

• Goods — timber, food, fuel, medicines (many drugs come from rainforest plants).
• Services — storing carbon (regulating climate), producing oxygen, cycling water and nutrients, and protecting soils.
• High biodiversity makes an ecosystem more resilient and is a genetic library we can't replace.

Threats to forests

Forests, especially the rainforest, are under pressure from:

• Deforestation for cattle ranching, soya and palm-oil farming, logging (timber) and mining.
• Roads and settlement opening up remote forest.
• Climate change, which brings more drought and fires; and in the taiga, logging and oil/gas extraction.

Why it matters: deforestation releases stored carbon (worsening climate change), destroys habitats and biodiversity, and — because rainforest soils are thin — quickly leaves infertile, eroded land.

Your turn — impacts of deforestation

Managing forests sustainably

Sustainable management meets today's needs without stopping future generations meeting theirs. Strategies include:

• Selective logging — only mature trees are felled, leaving the forest to recover.
• Ecotourism — small-scale, low-impact tourism that gives locals income from a living forest.
• Agro-forestry and replanting; protected areas / national parks.
• International agreements and consumer schemes (e.g. FSC-certified timber, debt-for-nature swaps, REDD+).

Sustainable or unsustainable?

Tap an action, then tap the box it belongs in.

Comparing the biomes

The key ideas to know

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