The Earth's land area, the solid ground underfoot, is divided into seven land regions largely by convenience: Asia, Africa, North America, South America, Antarctica, Europe, and Australia (largest to smallest).
The World Wide Fund for Nature (WWF), the world's largest independent conservation organization, has divided Earth's land area into eight ecozones or zones of life: Palearctic (most of Eurasia and North Africa), Nearctic ( most of North America), Afrotropic (Sub-Saharan Africa), Neotropic (South America and the Caribbean), Australasia (Australia, New Guinea and surrounding islands), Indomalaya (Southeast Asia and the Indian subcontinent), Oceania (Australia, New Zealand, Polynesia, Melanesia, and Micronesia), and Antarctic (Antarctica.)
Ecozones are defined by the evolutionary history of the biolife they contain, rather than by the locational convenience in the continential listing scheme. The distribution of life forms in these ecozones was originally determined by the early continential drift driven by the plate tectonics process.
One climate-change warning sign, is the degree to which plant and animal migrations between ecozones is occurring. These migrations can be expected, for example, in ecozones undergoing persistent warming or drought conditions. In a study done by Kelly and Goulden, "Rapid shifts in plant distribution with recent climate change", (Proceedings of the National Academy of Sciences), clear evidence of climate warming driving dominant plant species of one area to move about 65m up in elevation to inhabit a cooler environment was detected by comparing the results of two surveys done about 30 years a part, in the Santa Rosa Mountains of Southern California.