What this lesson teaches
I can explain the direct, indirect and uneven effects of climate change on people.
Syllabus K229, Topic 2.2, Key Question 4. How might climate change affect human systems?
Make a guess
A drought far away ruins wheat harvests. Can it affect a city that had no drought?
- No, because cities do not need farms.
- Not unless the drought spreads to the city.
- Yes. Food prices can rise through trade.
- No. A place without the hazard cannot be affected.
Show the answer
Yes. Food prices can rise through trade.
Losses spread through connected systems. Smaller harvests mean less food to sell, so prices may rise far from the drought.
Climate hazards harm people directly, then the losses spread through food, water, health, culture and money, hitting poorer people hardest.
Direct impacts happen when a hazard hits people or property. Heat waves cause illness and cut the time people can safely work outdoors. Floods and cyclones injure people, damage homes and cut transport or power. Droughts reduce water supplies. Wildfires bring flames and smoke. Evidence is needed to show how much climate change added to any single event.
Indirect impacts spread through connected systems. Damaged crops or fisheries reduce food and income; these are provisioning services. Flooded roads can stop deliveries even where farms are fine. Prices may then rise far from the original hazard.
Changes in regulating services can affect health. Temperature and water conditions affect where disease-carrying insects survive. Floods can disrupt sanitation and pollute water. But health services, housing, pest control and behaviour also matter, so warming does not increase every disease everywhere.
Cultural services suffer too. Shrinking Arctic sea ice affects the traditional travel, practices and connection to place of some Indigenous communities. Damaged reefs, glaciers and valued landscapes affect recreation, tourism, heritage and identity. Their value goes beyond a price.
Losses are unequal, because hazards, exposure and the ability to cope differ. Income, health, jobs, infrastructure and public support all matter. A flood may destroy a poor family's only tools, while an insured family can replace its belongings. One loss can trigger more: less income means less money for food, healthcare and recovery. This chain is an impact cascade.
- Direct impact
- A hazard hits people or property.
- Indirect impact
- Losses spread through food, water, health and trade.
- Impact cascade
- One loss triggers more losses.
Step by step
Direct harm
Heat, floods, drought or storms hit people and places.
Connected losses
Damage spreads through food, transport and markets.
Unequal recovery
Money, health and support decide who copes.
Real examples to use
Pakistan floods, 2022
Extreme monsoon rain flooded about a third of the country, killed about 1,700 people and affected 33 million.
European heatwave, 2003
An extreme summer heatwave caused tens of thousands of extra deaths, especially among older people.
Worked example: Same heat, different effects
Two neighbourhoods have the same heat wave. People with shade, air-conditioning and flexible work can stay safe. Outdoor workers and older people without cooling face more harm. Temperature alone does not decide the outcome.
Watch out for this
A place without the hazard cannot be affected.
Trade, transport and migration can carry impacts to places far from the hazard.
Check your understanding
A drought abroad cuts harvests and raises food prices in a city. How is the city affected?
- Indirectly, through food supply and trade.
- Directly, because the city's own water supply runs short.
- It is not, because the drought happened overseas.
Show the answer
Indirectly, through food supply and trade.
Yes. Trade carries the impact to the city.