Level: SL and HL core, with an HL extension noted below. Subtopic 2.4: Climate and biomes.
A biome is a group of comparable ecosystems that have developed under similar climatic conditions, wherever they occur. The global distribution of terrestrial biomes is determined mainly by abiotic factors, especially temperature and precipitation.
How Biome Distribution Is Determined
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Temperature affects photosynthesis, respiration, decomposition and the length of the growing season. Warm conditions generally support greater productivity if sufficient water is available.
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Precipitation determines water availability. High rainfall supports forests, moderate rainfall may support grasslands, and very low rainfall produces deserts.
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Latitude influences incoming solar radiation. The tricellular model of atmospheric circulation explains global belts of temperature and precipitation: rising moist air near the equator supports tropical rainforest, while descending dry air near approximately 30 degrees north and south contributes to desert formation.
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Local factors modify the broad climatic pattern.
| Determinant | Effect on biome distribution |
|---|---|
| Altitude | Temperature generally decreases with elevation, producing biome zonation on mountains. |
| Ocean currents | Redistribute heat and influence coastal temperature and precipitation. |
| Soil and geology | Affect drainage, nutrient availability and plant productivity. |
| Distance from the sea | Inland areas often experience more extreme temperatures and different rainfall patterns. |
| Human activity | Agriculture, deforestation, fire and urbanization may replace or alter the biome predicted by climate. |
For example, the Amazon Basin's high temperatures and year-round rainfall support tropical rainforest, whereas the Sahara's very low precipitation supports desert vegetation.
