Biocapacity is the capacity of a biologically productive area to generate renewable resources and absorb the wastes produced. It is compared with an ecological footprint, which measures the biologically productive area required to support a population's resource consumption and waste generation.
This is core SL and HL content in IB ESS Subtopic 1.3: Sustainability. Both measures are commonly expressed in global hectares (gha), allowing areas with different biological productivity to be compared using a standardized unit.
| Measure | What it represents |
|---|---|
| Biocapacity | The renewable resources and waste-absorption capacity that ecosystems can supply |
| Ecological footprint | The ecosystem area demanded by a person or population's consumption and waste |
| Ecological reserve | Biocapacity is greater than the ecological footprint |
| Ecological deficit | The ecological footprint is greater than biocapacity |
For example, suppose a population has an ecological footprint of 6 gha per person but access to only 4 gha of biocapacity per person. It has an ecological deficit of 2 gha per person. The deficit may be supported temporarily by importing resources, depleting natural capital, or allowing wastes such as carbon dioxide to accumulate.
The common misconception is that biocapacity measures how much land physically exists. It actually measures the productivity of biologically productive land and water, so two areas of equal size may have different biocapacities.
The relationship is a sustainability indicator, but it is a simplified model. National footprints can hide unequal consumption within a country, while imports may shift environmental pressure onto other societies. This creates an environmental justice issue when high-consuming populations use resources or waste-absorption capacity located elsewhere. Global Footprint Network's Earth Overshoot Day applies this relationship at the global scale.
Exam technique: If asked to explain the relationship, define both terms, compare demand with supply, and state whether the result is an ecological reserve or deficit. For an evaluation, add limitations, unequal consumption, trade, and environmental justice.