A global hectare (gha) is a way of
expressing productive capacity in a common unit. It is defined as a hectare
with the world-average productivity of all biologically productive land and
water in a given year (Kitzes et al., 2007). Ecological Footprint accounting
normalises different types of areas to account for differences in land and sea
productivity. Actual areas, in hectares, are converted into global hectares
using equivalence factors, which account for productivity differences between
land types (e.g., cropland versus forest product), and yield factors, which
account for differences within land types between countries.
In 2010, Earth’s bio capacity was approximately 12 billion global hectares (gha) – which amounts to about 1.7 gha for every person on the planet. This biologically productive land must also support the 10 million or more wild species with which we share the planet.
THE ABC FOR SUSTAINABLE CITIES
UNEP / UN HABITAT / FIDIC / GI-REC
