Tropical / subtropical Trockengebiete - Tropisch / subtropische Trockengebiete
The zone of tropical / subtropical arid areas is one of the nine global eco-zones according to J. Schultz.  Today it occupies about 20.8% of the earth's land surface.  At the beginning of the 21st century, around 60% of them are still largely near-natural . 
It lies mainly on the borders of the subtropical and tropical climatic zones . According to the predominant vegetation, it can be further subdivided into the landscape types subtropical steppe , highland steppe , subtropical dry forest , hot semi-desert and semi-desert .
The boundaries of the tropical / subtropical arid areas are in reality fluid, so that an exact extent - as shown on the map - cannot in fact be determined. This fact becomes understandable if one uses comparable geozonal models , e.g. T. have significant deviations. For example, consider the comparable zonobiom of the hot semi-deserts and deserts on the map of the zonobiome according to Walter and Breckle or the FAO Ecozones .
The arid tropics are the part of the tropics where no more than three of the twelve months of the year are humid . In the remaining nine or more months, the (potential) evaporation exceeds the amount of precipitation . Therefore, semi-deserts and deserts are mainly found in these areas .
- Schultz, J. (2008): The Earth's Eco Zones . Stuttgart: Ulmer. ISBN 978-3-8252-1514-9
- Values from J. Schultz (Schultz, J. (2008): Die Ökozone der Erde. Stuttgart) without Antarctica and Greenland converted to the entire land surface. See the article Ecozone # The individual ecozones . (See also tabular overview of various landscape zone models and their proportions. PDF; 114 kB)
- data for the studies "Last of the wild", "Intact forest landscapes" and "Review of status and conservation of wild land in Europe", summarized in the source description for the "Wilderness World Map" on Wikimedia Commons
- J. Schultz: The Earth's Eco Zones. 5th edition. Ulmer, Stuttgart 2016. ISBN 978-3-8252-4628-0 .
- J. Pfadenhauer, F. Kötzli: Vegetation of the earth. Springer Spectrum, Heidelberg 2014. ISBN 978-3-642-41949-2 .
- W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the world. 2nd Edition. Springer Spectrum, Heidelberg 2014. ISBN 978-3-642-36574-4 .