What is a global hectare (gha)?
A global hectare is one hectare of biologically productive space with world-average productivity. In 2002 the biosphere had 11.4 billion hectares of biologically productive space corresponding to roughly one quarter of the planet's surface. This includes 2.0 billion hectares of ocean and 9.4 billion hectares of land. 1 global hectare is a hectare representing the average capacity of one of these 11.4 billion hectares.
Global hectares allow the meaningful comparison of the ecological footprints of different countries, which use different qualities and mixes of cropland, grazing land, and forest. For comparative purposes an ecological footprint is usually expressed in gha per person. Once all global hectares of bioprucdtive land and sea are divided by the total global population, we end up with our fair earth share - 1.8 gha