The global hectare (gha) is a common unit that quantifies the biocapacity of the earth. One global hectare measures the average productivity of all biologically productive areas (measured in hectares) on earth in a given year. Examples of biologically productive areas include cropland, forests, and fishing grounds; they do not include deserts, glaciers, and the open ocean. "Global hectare per person" refers to the amount of biologically productive land and water available per person on the planet. e.g., in 2005 there were 13.4 billion hectares of biologically productive land and water available and 6.5 billion people on the planet. This is an average of 2.1 global hectares per person. Due to rapid population growth, this figure is decreasing.
The global hectare is a useful measure of biocapacity as it can convert things like human dietary requirements into a physical area, which can show how many people a certain region on earth can sustain, assuming current technologies and agricultural methods. It can be used as a way of determining the relative carrying capacity of the earth.
A given hectare of land may be measured in equivalent global hectares. For example, a hectare of lush area with high rainfall would be scale higher in global hectares than would a hectare of desert.
It can also be used to show that consuming different foods may increase the earth's ability to support larger populations. To illustrate, producing meat generally requires more land and energy than what producing vegetables requires; sustaining a meat-based diet would require a less populated planet.
The average global hectare would occupy the area of a standard hectare. A hectare (//; symbol ha) is a unit of area equal to 10,000 square metres (107,639 sq ft) (a square 100 metres on each side, or, a square 328.08 feet on each side), 2.471 acre, 0.00386102 square miles, or one square hectometre (100 metres squared).
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