Climate change impacts ecosystems at local, regional, and global scales by altering abiotic conditions, species distributions, ecological interactions, and ecosystem resilience. These effects are interconnected: local disturbances can accumulate into regional change, while global warming drives impacts at every smaller scale.
This is core SL and HL content in IB ESS Subtopic 6.2, Climate changecauses and impacts.
The Mechanism
- Anthropogenic greenhouse gas emissions enhance the greenhouse effect, increasing average global temperatures.
- Temperature and precipitation patterns change, while extreme events such as droughts, floods, heatwaves, and wildfires may become more intense or frequent.
- These altered abiotic factors affect organisms' survival, reproduction, and distribution. Species may migrate, adapt, or experience population decline.
- Changes to individual populations alter food webs, competition, predation, and other ecological relationships. This can reduce ecosystem resilience, making systems less able to maintain stability after disturbance.
| Scale | Main ecosystem impacts | Named example |
|---|---|---|
| Local | Changed flowering times, heat stress, habitat loss, altered species abundance, or coral bleaching | Repeated marine heatwaves cause coral bleaching on Australia's Great Barrier Reef. |
| Regional | Biome shifts, changing water availability, disrupted migration routes, and increased wildfire risk | Rising temperatures and drought increase fire disturbance across the Amazon rainforest. |
| Global | Redistribution of biomes, biodiversity loss, ocean warming, sea-level rise, and disruption of carbon stores and sinks | Arctic sea-ice decline reduces habitat and strengthens the ice-albedo positive feedback loop. |
A key misconception is that ecosystems are affected only by higher temperatures. Climate change also alters precipitation, ocean chemistry, seasonality, disturbance regimes, and interactions between species. Impacts also affect societies by changing ecosystem services such as food production, water regulation, carbon sequestration, and coastal protection.
Exam Technique
For an explain question, give a linked causal chain: climatic change, altered abiotic factor, biological response, then ecosystem consequence. For higher-mark questions, distinguish scales, use named examples, and connect impacts to feedback, resilience, biome shifts, and ecosystem services rather than listing isolated effects.