Biomes and Climate Zones: How Earth's Major Ecosystems Are Distributed

Most of Earth's living systems organize into a small number of recurring ecological communities called biomes. The defining variables are temperature, precipitation, and seasonality. Eight to twelve major terrestrial biomes are commonly recognized: tropical rainforest, savanna, desert, temperate grassland, temperate deciduous forest, Mediterranean shrubland, boreal forest (taiga), and tundra. Some classifications add montane and chaparral as separate biomes.

Biomes form latitudinal bands because incoming solar energy varies systematically by latitude. Equatorial regions receive direct, year-round sunlight; polar regions receive low-angle sunlight that loses much of its energy passing through the atmosphere. The result is a temperature gradient from hot at the equator to cold at the poles. Precipitation, by contrast, depends on global air-circulation cells that produce rising air (and rain) at the equator and at mid-latitudes, and sinking air (and dryness) at roughly 30 degrees north and south — which is why most of Earth's great deserts cluster in those bands.

Beyond latitude, three other factors reshape climate locally: elevation (every 1,000 m of altitude gain drops the temperature roughly 6.5 °C), ocean currents (warm currents like the Gulf Stream make Western Europe far milder than Labrador at the same latitude), and distance from a coast (continental interiors swing more between summer heat and winter cold than coastal regions).

Geographers and climatologists use the Köppen climate classification to assign every place on Earth a code that captures its temperature and precipitation pattern. The system uses up to three letters: a major group (A tropical, B dry, C temperate, D continental, E polar), a precipitation sub-type, and a temperature variation. Brazil's Manaus is "Af" (tropical rainforest); Riyadh is "BWh" (hot desert); London is "Cfb" (oceanic temperate). Köppen codes appear on virtually every climate atlas and in most country reference data.

The chart below shows the approximate share of Earth's land surface covered by each major biome. Hover any segment to see the percentage and a short description.

Four countries that illustrate how a dominant biome shapes economy, culture, and settlement.

Brazil

Tropical rainforest · Af

The Amazon basin holds the world's largest contiguous tropical rainforest, generating roughly 20 percent of Earth's atmospheric oxygen and storing massive amounts of carbon. Indigenous communities, agricultural frontiers, and conservation policy collide here.

Country page

Russia

Boreal forest (taiga) · Dfc

Russia hosts the largest single forest on Earth — the Siberian taiga, dominated by spruce, fir, larch, and pine. Cold continental winters and short summers shape settlement patterns, transportation, and energy demand across eleven time zones.

Country page

Saudi Arabia

Hot desert · BWh

Almost the entire country sits in the subtropical hot-desert belt centered on 25 degrees north. Permanent agriculture relies on fossil aquifers and desalinated water; cities are coastal or oasis-based, and air conditioning consumes roughly half of national electricity.

Country page

New Zealand

Temperate maritime · Cfb

Surrounded by ocean and crossed by westerly winds, New Zealand has mild temperatures year-round and abundant rainfall on its western coasts. Pasture-fed agriculture (dairy, sheep) thrives, and settlement clusters where the climate is least extreme.

Country page

Use these prompts for class discussion, journal entries, or short written responses (150-300 words each).

1. What is the difference between weather and climate, and why does the distinction matter when discussing climate change?
2. Why does the Amazon rainforest produce roughly 20 percent of Earth's oxygen but cover only about 0.5 percent of its surface?
3. Pick two countries from the case studies. Explain how their dominant biome shapes their economy, settlement pattern, and energy use.
4. Climate change is shifting biome boundaries poleward and upslope. What might happen to the boreal forests of Russia and Canada in 100 years?
5. Some countries (the United States, China, Australia) span four or more biomes. How does this affect their political and cultural diversity?

Draft alignment — pending educator review. National standards only; state-specific frameworks are not cited here.