4.11.4Additional lessons
Sustainability in Ecosystems and Agriculture — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 95 of 101
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5What Sustainable Means
Sustainable use keeps natural capital intact.
Definition
- Definition A practice is sustainable if it meets present needs without reducing the ability of future generations to meet theirs.
Renewal rate
- Renewal rate Resources such as fish or timber are sustainable only if harvesting is not faster than natural replacement.
Nutrient return
- Nutrient return Soil nutrients removed in crops must be replaced, by manure, compost or legume rotations, or yields fall.
Limiting damage
- Limiting damage Sustainable use avoids permanent loss of habitat, soil and water quality.
| Practice | Sustainable approach | Unsustainable approach |
|---|---|---|
| Fishing | Quotas and mesh size limits | Overfishing of breeding stock |
| Forestry | Selective cutting and replanting | Clear felling without replanting |
| Farming | Crop rotation and cover crops | Monoculture with heavy fertiliser |
Section 2 of 5Building a Sustainable Farm
1
Rotate crops, including nitrogen-fixing legumes, so that soil fertility is restored and pests do not build up.
2
Add organic matter such as compost to improve soil structure and reduce reliance on artificial fertiliser.
3
Use integrated pest management, with natural predators and targeted spraying, to reduce pesticide use.
4
Limit tillage and maintain ground cover to reduce erosion and carbon loss from soil.
5
Monitor yields and soil quality each year and adapt the plan accordingly.
Section 3 of 5Trade-offs and Evaluation
Trade-offs and Evaluation
Economic
- Economic Sustainable methods may give lower short-term yields or need more labour but protect long-term income.
Environmental
- Environmental They reduce eutrophication, soil erosion and damage to non-target species.
Social
- Social Local communities depend on resources, so fair access is part of sustainable planning.
Evidence
- Evidence Long-term monitoring data are required to judge whether a practice really is sustainable.
Section 4 of 5Worked Example
Question
- A fish stock is 50 000 tonnes and its natural regrowth is 8% each year.
- State the maximum sustainable catch in a year if the stock is to stay constant.
- Annual regrowth = 8% of 50 000 = 0.08 × 50 000 = 4 000 tonnes.
- Harvest equal to regrowth keeps the stock level constant.
Answer 4 000 tonnes per year
Section 5 of 5Exam Checklist & Tips
4.11.4 – Key Points for the Exam
- Sustainability Use of resources in a way that allows them to continue to be available.
- Crop rotation Growing different crops in sequence on the same land.
- Nitrogen fixation Conversion of atmospheric nitrogen into usable ammonium compounds by bacteria.
- Overexploitation Harvesting faster than the resource can be replaced.
- Integrated pest management Combining several control methods to keep pests below damaging levels.
Common Mistakes
- Saying that sustainable means no use at all of a resource.
- Ignoring that fertilisers can be recycled only if nutrients are returned to the same soil.
- Describing sustainability in economic terms only.
- Assuming that organic farming is always more sustainable without considering yield and land use.
Last updated:
\n