Lesson 3 of 7 / Climate, biodiversity and disease ecology
Warming changes habitats and interactions
How does a physical change become a biological stress?
I can explain climate effects on water, ice, ecosystems, migration and niches.
I can explain environmental and ecosystem consequences of climate change.Syllabus
Syllabus 9477, Extension B(b). Explain environmental and ecosystem consequences of climate change.
I can discuss effects on habitats, food chains and ecological niches.Syllabus
Syllabus 9477, Extension B(f). Discuss effects on habitats, food chains and ecological niches.
About 8 min
Make a guess. You are not marked.
Warming thaws frozen Arctic soils. Could this make warming worse?
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Decomposers release stored carbon as greenhouse gases.
Thawed organic matter decomposes, releasing CO2 and methane. That is a positive feedback.
The key idea
Climate alters temperature, water and habitat conditions, with consequences for survival, species interactions and food chains.
Trace the biological links
Is the effect direct, indirect or a feedback?
Marine heat stress can disrupt coral-algal symbiosis and cause bleaching. Loss of photosynthetic partners reduces energy supply; a bleached coral is stressed, not automatically already dead.
Original conceptual comparisons with no quantitative climate projection. In the timing graph, peak heights are illustrative and the horizontal axis is seasonal time. Habitat loss, freshwater stress, storms and range shifts can interact with these mechanisms.
Explanation
Warming melts land ice and expands seawater, contributing to rising sea level. Loss of reflective ice also increases absorbed solar energy, reinforcing warming. Floating sea-ice melt does not directly add sea level in the same way as melting land ice. Thawing frozen organic matter can allow microbial decomposition and release CO2 or methane, another positive feedback.
Changing rainfall and evaporation can stress freshwater supplies, while sea-level rise can increase saltwater intrusion. Many kinds of extreme events, including heatwaves and heavy rainfall, become more frequent or intense with warming, though not every storm type changes identically in every region.
Fish and insects may shift ranges towards cooler latitudes or elevations where conditions permit. Barriers, habitat fragmentation and unequal movement abilities mean species do not all track climate together. A species' niche includes the conditions, resources and interactions that allow it to persist, not just the place where it lives.
Marine heat stress can disrupt coral-algal symbiosis and cause bleaching, reducing energy supply and survival if stress persists. Seagrasses and mangroves can be affected by heat, inundation, salinity changes and extreme events. Their loss removes habitat and nursery functions for other organisms.
Timing changes can break ecological matches: a consumer's breeding peak may no longer coincide with peak food availability. Reduced producer biomass or a missing prey species can propagate through food chains. Evaluate direct physiological effects and indirect interaction effects separately.
Rising carbon dioxide also changes ocean chemistry. Carbon dioxide dissolves in seawater and reacts with water to form carbonic acid, which releases hydrogen ions, so the pH of the ocean falls. This is ocean acidification. Many of the extra hydrogen ions combine with carbonate ions to form hydrogencarbonate ions, so less carbonate is available. Corals, molluscs and some plankton build skeletons and shells from calcium carbonate, so they calcify more slowly, and existing calcium carbonate structures can start to dissolve. A reef that is bleached by heat and calcifying slowly from acidification grows more slowly than it is worn away.
Step by step
- 1
State the physical driver
Temperature, water availability, salinity or timing.
- 2
Link to a biological process
Metabolism, photosynthesis, reproduction or survival.
- 3
Trace indirect effects
Follow habitat or food-chain consequences.
Worked example
Work through the evidence
A plankton bloom advances earlier, but fish larvae hatch at the previous time. Predict a consequence.
One way to explain it
Larvae may miss peak food availability, reducing growth or survival and potentially affecting recruitment and predators that depend on the fish.
Why this answer works
- The key is a mismatch between interacting species.
- A warmer environment does not improve every process equally.
Watch out for this
A student says: "All species can simply move together to a cooler place." What is wrong with this?
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Movement constraints and different responses can separate interacting species and leave some with no suitable habitat.
In the real world
The Great Barrier Reef, 2016
Record sea temperatures in 2015-2016 caused mass coral bleaching around the tropics. On the Great Barrier Reef, the 2016 bleaching was the most severe of the three events recorded since 1998, and the pattern of bleaching followed the pattern of hot water. Cleaner water and less fishing made little difference to how badly reefs bleached, so the researchers concluded that local protection gives little resistance to extreme heat.
Source: Hughes and others (2017), Global warming and recurrent mass bleaching of corals, Nature 543, 373-377
Check your understanding
Which is a climate positive feedback?
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Thaw permits decomposition that releases more greenhouse gases.
Additional greenhouse gases can reinforce the warming that caused thaw.
Quick recall
How does a physical change become a biological stress?