Ecological Zones (Holdridge Lifezones)

The data set shows the Holdridge Life Zones of the World, a combination of climate and vegetation (ecological) types, under current, so-called "normal" climate conditions, as well as under a presumed doubling of atmospheric CO2. The Life Zones were devised using three indicators: biotemperature (based on the growing season length and temperature); mean annual precipitation; and a potential evapotranspiration ratio, linking biotemperature with annual precipitation to define humidity provinces.

The data set has a spatial resolution of one-half degree latitude/longitude, and a total of 38 life-zone classes which are listed on the accompanying legend sheet. The Holdridge Life Zones data set includes a total of four data files. The first (HOLDNORM) is as described in the paragraph above; the second (HOLDDOUB) shows how the Life Zones would change given an assumed doubling of atmospheric CO2 (according to a General Circulation Model from the U.K. Office of Meteorology).