- Climate change affects ecosystems at local, regional and global scales, altering their structure, functioning and long-term stability.
- Changes in temperature, precipitation, sea levels and extreme events disrupt species interactions, nutrient cycles, food webs and energy flows.
- Reduced ecosystem resilience and significant environmental stress may force entire ecosystems to reorganize, move or collapse, leading to biome shifts.
Biome shift
Biome shift refers to the movement of major vegetation and ecosystem types towards the poles or higher elevations due to long-term climate changes.
Local Impacts
Coral Bleaching
- Corals have a symbiotic relationship with zooxanthellae, which provide them with nutrients and colour.
- Increased sea temperature causes corals to expel these algae, resulting in bleaching.
- If stressful conditions persist, corals starve and die.
- Bleaching events have intensified globally due to warming oceans and increased frequency of marine heatwaves.
Great Barrier Reef, Australia
- The 2016, 2017 and 2020 bleaching events affected over 60% of shallow-water corals.
- Recovery is slowed by repeated thermal stress, cyclones, and outbreaks of crown-of-thorns starfish.
- Some reefs now show shifts from coral-dominated communities to algae-dominated ecosystems.
- Coral bleaching is a clear indicator of ecosystem vulnerability to climate change.
- It highlights the importance of maintaining stable environmental conditions for ecosystem resilience.
Desertification
- Desertification results from the spread of dry, degraded land into once-productive ecosystems.
- It is accelerated by reduced rainfall, increased evaporation, overgrazing, deforestation, soil erosion, and climate change.
- Loss of vegetation reduces soil stability, leading to dust storms, reduced carbon storage, and biodiversity decline.
Murray-Darling Basin, Australia
- Decades of reduced rainfall and higher temperatures have increased evaporation.
- In 2019, mass fish deaths occurred due to hypoxia in shallow, warming waters.
- The basin, supplying 40% of Australia’s agriculture, is experiencing long-term drying, pushing the region toward semi-desert conditions.
- Desertification is often mistaken for natural desert expansion.
- In reality, it is largely driven by human activities like deforestation and unsustainable farming.
Regional-Scale Impacts
Poleward and Altitudinal Migration
- Warmer temperatures shift biomes northward in the Northern Hemisphere and southward in the Southern Hemisphere.
- Species move higher in altitude, replacing cold-adapted species.
- Tundra and boreal forests are especially vulnerable due to limited room for migration.
- Shrubs and boreal trees are invading tundra landscapes.
- Caribou and arctic fox populations decline due to habitat loss.
Changes in Ecosystem Productivity
- Rising CO₂ can increase plant growth via the carbon fertilisation effect.
- However, nutrient limitations (especially nitrogen), drought and heat stress reduce long-term productivity.
- Increased pests, invasive species, and wildfires further reduce resilience.
- Summers are expected to become hotter and drier by 2050.
- Drought-tolerant trees like oak and ash may replace traditional beech woodlands.
Global Impacts
1. Sea-Level Rise
- Sea level increases from thermal expansion and melting glaciers/ice sheets.
- Current rates are the highest in at least 2800 years.
- Rising seas inundate wetlands, reduce coastal biodiversity and cause saltwater intrusion into aquifers.
- Large portions of the Ganges-Brahmaputra Delta face annual flooding.
- Maldives risks losing major inhabited islands by 2100.
2. Changes in Ocean Circulation
- The thermohaline circulation depends on temperature and salinity differences.
- Melting ice dilutes seawater, reducing density and slowing circulation.
- Disruption affects marine ecosystems, nutrient cycling and regional climates.
- Freshwater from melting Greenland ice may weaken the Gulf Stream.
- Northwestern Europe could cool despite global warming.
3. Ocean Acidification
- CO₂ dissolves in oceans, forming carbonic acid and lowering pH.
- Acidification weakens shells, corals and plankton, altering marine food webs.
- Reef tourism and fisheries decline.
Ecosystem Resilience and Factors Affecting It
- Biodiversity: High biodiversity increases resilience as species can substitute roles.
- Genetic diversity: Genetic variation enables adaptation to changing conditions.
- Large storages: Systems with large biomass or soil nutrient stores recover faster.
- Ecosystem complexity: More trophic interactions create stability and buffer disturbances.
- Human pressure: Logging, pollution and overfishing reduce resilience.
Always state that ecosystems with high biodiversity and large storages are more resilient to climate change.
Biome Shifts Due to Climate Change
- As temperatures increase, biomes shift toward the poles or to higher elevations.
- Tundra is invaded by shrubs and boreal forests during warming periods.
- Temperate forests may shift northward or experience major species loss.
Climate Change Impacts Human Societies and Affects Societal Resilience
Societal resilience
Societal resilience refers to the ability of communities to prepare for, absorb, recover from and adapt to climate-related hazards.
- Climate change affects societies differently depending on wealth, infrastructure, geography, and adaptive capacity.
- Impacts occur at local, national and global scales, influencing health, water resources, economic stability, agriculture, migration and infrastructure.
- Vulnerable populations, such as low-income communities and climate-exposed workers, bear the greatest burden.
Impacts on Water Supply
- Rising temperatures increase evaporation rates and reduce water availability.
- Glacial melt initially increases flow but eventually reduces long-term water supplies.
- Drought frequency increases in many regions.
- Water quality deteriorates during extreme weather events.
Cape Town, South Africa – “Day Zero” Crisis (2018): Severe drought brought the city within months of running out of water, illustrating urban vulnerability to climate extremes.
Impacts on Agriculture
- Temperature increases and rainfall variability reduce crop yields.
- Pests and pathogens spread into newly warm regions.
- Crop-growing zones shift toward the poles.
- Heat and water stress reduce labour productivity and food availability.
Impacts on Human Health
- Warmer temperatures expand the range of vector-borne diseases such as malaria and dengue.
- Heatwaves increase deaths due to dehydration, heat stroke and cardiovascular stress.
- Air pollution worsens as heat accelerates chemical reactions that produce smog.
Impacts on Infrastructure
- Roads buckle during heatwaves.
- Flooding damages coastal housing, railways and metro systems.
- Ports and airports near coastlines face increasing disruption.
- Wildfires destroy power lines, pipelines and settlements.


