What this lesson teaches
I can explain how changes in climate and ecosystems affect people.
Syllabus 9173, Topic 3.2, 2. Possible Effects of Climate Change. How will contemporary climate change impact humans?
Make a guess
A marine heatwave bleaches a coral reef. How might a fishing family nearby lose income?
- Bleaching makes the sea too acidic to fish in.
- The heat directly cooks the fish in their nets.
- Fewer fish as reef habitat is lost.
- It cannot, because bleached coral recovers.
Show the answer
Fewer fish as reef habitat is lost.
Repeated heat stress can kill coral and destroy the habitat fish rely on. Fish may also move to cooler water, so catches fall.
Climate change alters ecosystems, and those changes reach people through food, water, income and protection.
An ecosystem is living things, including people, interacting with each other and with non-living things like water, soil and air. So a change in temperature or water chemistry affects organisms and the people who rely on them.
Warming changes both averages and extremes. Warmer air holds more water vapour, so heavy rain can get heavier. Shifting winds move rain around, and more evaporation worsens drought. Not everywhere gets wetter. Heavy rain needs available moisture and rising air, not just warmth.
Marine heatwaves can bleach coral. Stressed corals lose the algae that feed them. Long or repeated stress kills them and destroys reef habitat. Fish may move to cooler or deeper water, changing local catches. Bleaching is not instant death, but repeated stress can be.
Oceans absorb carbon dioxide, which lowers pH and leaves less carbonate for shells. This ocean acidification is separate from bleaching. Warmer water also holds less oxygen.
On land, plants and animals shift their ranges and the timing of flowering and breeding. Drought, fire and pests weaken forests. Rivers and lakes warm, flood or dry out. Some species cannot move through broken-up habitats fast enough.
People feel these changes. Reef loss hurts fishing, tourism and coastal protection. Forest loss cuts carbon storage and water supply. Crop and pollinator problems raise food costs. Some places gain opportunities, but species responses, other livelihoods and pressures such as overfishing change the result.
- Ecosystem
- Living things and their surroundings, including people.
- Coral bleaching
- Heat makes corals lose their algae.
- Acidification
- Absorbed carbon dioxide lowers ocean pH.
Step by step
Change the climate
Heat, rain, river flow or ocean chemistry.
Change the ecosystem
How organisms or habitats respond.
Change a human benefit
Food, income, water or protection.
Worked example: From reef heat to household risk
A fishing family may catch less after repeated bleaching damages a reef. Lower income makes it harder to repair a boat or find other work. Catches also depend on fishing pressure and management.
Watch out for this
Ocean acidification means the ocean's pH is below 7.
It means pH is falling. Seawater stays above pH 7 but becomes less alkaline.
Check your understanding
Which explanation gives the clearest link from climate to people?
- Repeated marine heat damages coral, threatening fishing incomes.
- A reef is beautiful, so every nearby family earns the same.
- A drop in fish catch proves the reef has been damaged by heat.
Show the answer
Repeated marine heat damages coral, threatening fishing incomes.
Yes. It traces each step from climate to people.