Which climate zone system was developed by Leslie Holdridge?

The climate-zone system developed by Leslie Holdridge is the Holdridge life zones system.

Holdridge proposed a global bioclimatic framework that links climate to likely natural vegetation. Rather than relying only on latitude or broad temperature bands, it uses three principal variables: annual precipitation, mean annual biotemperature, and the ratio of potential evapotranspiration to precipitation. These variables are arranged in a diagram of life zones, often shown as hexagonal regions within a triangular framework.

The system was first published in 1947 and updated in 1967. Holdridge defined biotemperature in a biologically motivated way: temperatures below freezing and above 30°C are adjusted because plant growth is greatly limited at those extremes. The scheme was initially especially useful in tropical and subtropical regions but was later applied globally.

It is not the same as the Köppen classification, which groups climates using temperature and precipitation thresholds, or the Trewartha system, another climate classification. Holdridge’s framework is especially valuable for ecological mapping and for studying how vegetation zones may shift with climate change.