Human systems and resource use
Domain 9 examines population, consumption, resource use, waste and sustainability. The exam tests demographic transition, ecological footprints, IPAT, waste hierarchies and indicators of development.
Core rules
- Demographic transition moves from high birth and death rates to low birth and death rates; population growth is fastest during the middle transition when death rates fall first.
- Population pyramids reveal age structure and dependency ratios.
- IPAT: Impact = Population × Affluence × Technology. It is a simplifying model; affluence and technology can raise or lower impact depending on consumption patterns.
- Ecological footprint compares demand on productive land and water with biocapacity; it is expressed in global hectares.
- The waste hierarchy: prevent, reduce, reuse, recycle, recover energy, dispose. Prevention has the highest priority.
- Sustainability indicators include HDI, ecological footprint and genuine progress; no single indicator captures everything.
Worked example
A country has population 1.0 million, average affluence $10,000 per person and technology factor 0.5 kg CO₂ per dollar. IPAT impact = 1,000,000 × 10,000 × 0.5 = 5 × 10⁹ kg = 5 million tonnes CO₂. If technology improves by 20% (factor 0.4), impact falls to 4 million tonnes, with population and affluence unchanged. Reasoning: the multiplication shows why efficiency alone may not offset growth in population or consumption; the model is illustrative, not a precise forecast.
Traps
- Assuming population growth is driven mainly by birth rates; death-rate decline matters too.
- Treating the ecological footprint as only a carbon measure; it includes cropland, grazing, forest, built land and fishing grounds.
- Putting recycling above prevention in the waste hierarchy.
- Using GDP as a sustainability indicator without qualification.
- Assuming demographic transition follows the same path everywhere.