Ecological Footprint measures how much biologically productive land and sea a population needs to produce what it consumes and absorb its waste — mostly carbon emissions, usually the largest single slice. Biocapacity is how much productive land Earth actually has. When a country's footprint exceeds the planet's biocapacity share, the gap is filled by importing resources or drawing down shared global stocks — an ecological deficit.
- Earths needed = country footprint per person ÷ world biocapacity per person (≈1.6 global hectares/person) — the real Global Footprint Network metric.
- Country Overshoot Day = the calendar day by which humanity would use up a full year of biocapacity if everyone on Earth consumed like this country's average resident.
- World Overshoot Day has drifted from late December in 1970 to early August today — humanity now spends roughly five months a year in ecological deficit.
Real-world relevance: this accounting (Global Footprint Network, since 1990s) underlies national sustainability policy, trade debates about "embedded" resource use, and the annual Earth Overshoot Day campaign.