IB ESS HL 4.1.5 Human Activity Impacts Question Bank
Evaluate how extraction, land use and pollution alter water stores and flows.
- Syllabus
- First assessment 2026
- Course
- ESS HL
- Level
- HL
Exam points
- identify the hydrological store, flow or water-management issue
- apply the relevant water-cycle or scarcity concept
- evaluate the consequence and trade-offs using evidence
4.1.5—Human activity impacts question 1
[Maximum number: 4]
| Mangrove | Seagrass | Coral reef |
|---|---|---|
| Nursery/habitat for fish and shellfish | Nursery/habitat for many species | Nursery/habitat supporting high biodiversity |
| Traps sediments and absorbs nutrients | Traps sediments and absorbs nutrients | Filters particulates, increasing water clarity |
| Absorbs CO2 and emits oxygen | Absorbs CO2 and emits oxygen | Provides fish and shellfish |
| Reduces coastal erosion/storm impacts | Stabilizes sediment | Supports tourism/fisheries |
Figure: Ecosystem goods and services in coastal marine habitats
- Figure: Threats to biodiversity and ecosystems within the Coral Triangle
- Coral reefs and mangroves in the Coral Triangle have declined by over 40% since the 1970s; over 85% of coral reefs are threatened by population growth and human activity.
- Threats include removal of mangroves, unsustainable/destructive fishing, demand for turtle products and shark fins, land-based pollution, tourism impacts and climate change.
- Tourism threats include sewage, plastic waste, coral trampling, boat-anchor damage, stress to wildlife and collection of wildlife souvenirs.
Explain how the following land-based activities could have a damaging effect on marine ecosystems within the Coral Triangle:
Question (a)
(a)
Explain how deforestation could have a damaging effect on marine ecosystems within the Coral Triangle.
[ 2 ]
identify problem [1]
its corresponding effect on marine ecosystems [1]
removal of mangroves results in loss of habitat/nursery area for young fish;
...reducing biodiversity/secondary productivity in coastal area; ...making species prone to extinction;
increase in soil/coastal erosion leading to more sediment entering the Coral Triangle;
...this blocks sunlight that coral/sea grasses/algae require;
loss of carbon sink that can lead to increase in global temperatures;
...increase in water temperatures can stress coral/reduce biodiversity;
increased carbon dioxide released into the atmosphere that contributes to ocean acidification/lowers pH;
...this adversely affects some species eg fish / reduces biodiversity; ...damages calcifying species/shellfish/corals;
without trees, runoff is no longer filtered and nutrients absorbed, thereby increasing nutrient loading within the marine ecosystem;
...this leads to eutrophication;
...this leads to algal blooms that can harm other species/reduce light to corals/seagrasses/algae; ...this leads to algal blooms that can lead to lower oxygen levels in the water (hypoxia/anoxic conditions);
removal of trees reduces water retention and increases risk of floods (overflow of freshwater) into the coastal/marine environment;
...the sudden high velocity of water could physically damage some species; ...sudden change in water salinity may kill some species;
Marking guidance:
Award [1] for identifying the problem, and [1] for explaining its effect on marine ecosystems.
Do not accept just "soil/coastal erosion" without link to increased sedimentation.
Question (b)
(b)
Explain how agricultural activity could have a damaging effect on marine ecosystems within the Coral Triangle.
[ 2 ]
identify problem [1]
its corresponding effect on marine ecosystems [1]
increase in nutrient/fertilizer/nitrate/phosphate pollution;
...this leads to eutrophication;
...this leads to algal blooms that can harm other species/reduce light to corals/seagrasses/algae; ...this leads to algal blooms that can lead to lower oxygen levels in the water (hypoxia/anoxic conditions);
increase in pesticide pollution;
...can harm/kill (non-target) organisms within the Coral Triangle;
increase in pollution from animal waste/manure/organic matter;
...that can block sunlight required by corals/seagrasses/algae; ...lower oxygen levels in the water;
overgrazing can increase soil erosion resulting in increased sedimentation in the reef/coastal environment;
...that can block sunlight required by corals/seagrasses/algae
Marking guidance:
Award [1] for identifying the problem, and [1] for explaining its effect on marine ecosystems.
Do not accept loss of mangroves and its associated effects.
Do not accept just "overgrazing causes soil erosion" without link to increased sedimentation.
All question bank results loaded