Global warming shifts biome distributions by changing the temperature and precipitation conditions that determine where biomes can exist. As climatic zones move, biomes generally shift poleward, move to higher altitudes, contract, expand, or become replaced by different biomes.
Level: SL and HL: Subtopic 2.4 Climate and biomes.
The Mechanism
A biome is a group of comparable ecosystems that developed under similar climatic conditions. Its distribution is primarily controlled by abiotic limiting factors, especially temperature, precipitation, and their seasonality.
- Anthropogenic greenhouse gas emissions enhance the greenhouse effect and increase global temperatures.
- Temperature and precipitation patterns change, altering the climatic conditions associated with particular biomes.
- Species respond by migrating, adapting, or declining. Because species move at different rates, existing communities may break apart rather than relocate intact.
- A different community may establish, producing a shift in biome distribution. Where movement is blocked by mountains, coastlines, agriculture, or cities, the original biome may contract.
| Climatic or human change | Likely effect on biome distribution |
|---|---|
| Rising average temperature | Poleward and upslope movement of climatic zones |
| Altered precipitation | Expansion of drought-tolerant grassland or desert; contraction of moisture-dependent forest |
| Reduced snow and ice cover | Expansion of shrubs and boreal species into tundra |
| Habitat fragmentation | Prevents species migration and reduces ecosystem resilience |
| Longer fire seasons | Encourages replacement of forest by grassland or shrubland |
In the Arctic tundra, warming allows shrubs and boreal vegetation to expand northward. Darker vegetation absorbs more solar radiation than snow, reducing albedo and creating a positive feedback loop that amplifies warming.
A common misconception is that an entire biome simply moves as one unit. In reality, individual species respond differently, while soil development, migration barriers, competition, and human land use create time lags and fragmented transitions.
Exam Technique
For an explain question, link cause to effect: warming changes abiotic conditions, which changes species distributions and therefore biome boundaries. Add a named example, identify any feedback, and distinguish projected climatic suitability from the biome that actually develops.
