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4.11.7Additional lessons

Restoring Ecosystems — IB Biology HL Revision Notes & Topical Questions

5 min read 5 parts Lesson 98 of 101

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Part 1 of 5Restoration Approaches

4.11.7 Restoring Ecosystems

Restoration tries to repair damage so that the ecosystem can work naturally again.

Rewilding
  • Large areas are allowed to return to a more natural state, sometimes with reintroduction of missing species.
Reforestation
  • Native trees are planted or allowed to regenerate on cleared land to rebuild soil, habitat and carbon stores.
Remediation
  • Contaminated soil or water is cleaned, for example by removing toxins or planting species that take up metals.
Reintroduction
  • Species lost from an area are brought back, as with wolves to Yellowstone National Park in the 1990s.
MethodExamplePossible problem
ReintroductionWolves in YellowstoneConflict with farmers
ReplantingNative woodland after loggingSlow growth, cost
Wetland recreationReflooding drained landLoss of farmland
Natural regenerationFencing off cleared landNeeds nearby seed sources

Part 2 of 5Planning a Restoration Project

1
Survey the degraded site and identify what has been lost, such as species, soil quality or water flow.
2
Remove the cause of damage, for example stopping grazing, pollution or drainage.
3
Reintroduce native species and restore physical conditions to allow natural succession to resume.
4
Monitor biodiversity and ecosystem services for many years and adjust management if progress stalls.
5
Where the community has recovered and shows self-sustaining populations of key species, active management can be reduced or stopped altogether.

Part 3 of 5Judging Success

Judging Success
Biodiversity
  • Compare species richness and abundance at the restored site with a healthy reference ecosystem.
Function
  • Check that nutrient cycling, water retention and productivity have been re-established.
Time scale
  • Mature ecosystems take decades or centuries to rebuild, so early success may be only partial.
Local support
  • Projects last longer where communities benefit from jobs, tourism or improved resources.
Costs and benefits
  • Restoration is expensive but can bring benefits such as flood control, carbon storage, clean water and recreation.

Part 4 of 5Worked Example

Question

  • A restored wetland had 12 plant species before restoration and 30 species after ten years.
  • Calculate the percentage increase in species richness.

  1. Increase = 30 − 12 = 18 species.
  2. Percentage increase = 18 ÷ 12 × 100 = 150%.

Answer 150% increase

Part 5 of 5Exam Checklist & Tips

4.11.7 – Key Points for the Exam

  • Restoration Actions that help a degraded ecosystem recover.
  • Rewilding Restoring natural processes and species with minimal ongoing management.
  • Reintroduction Return of a species to an area from which it was lost.
  • Remediation Removal of pollutants from soil or water.
  • Reference ecosystem An undamaged ecosystem used as a standard for comparison.

Common Mistakes

  • Assuming that planting trees alone restores a whole ecosystem.
  • Ignoring that the original cause of damage must be stopped first.
  • Claiming restoration is quick, when ecosystems may need decades.
  • Using introduced non-native species when native species are needed.

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