desertness

Desertness is the degree to which an environment exhibits desert-like conditions. It is best understood as a continuous property rather than a strict category, driven primarily by aridity, the imbalance between precipitation and evaporation. A widely used framework employs the aridity index, defined as precipitation divided by potential evapotranspiration; values near 0.05–0.20 indicate hyperarid regions, 0.20–0.50 arid, and 0.50–0.65 semiarid, with higher values describing drier subhumid areas. Temperature regime, seasonal rainfall, wind, and soil properties also influence desertness and its perception.

Desert environments share common ecological traits, including low and unpredictable rainfall, extreme temperatures, and nutrient-poor soils. Soils are often aridisols or pedogenic crusts with limited organic matter and varying salinity. Vegetation is sparse and highly adapted to drought, with deep roots, reduced leaves, or succulent tissues. Animal communities consist of drought-tolerant species and species with small populations that rely on brief moisture pulses. Primary productivity is low, but deserts can support diverse microhabitats after rain events.

Desertification refers to the expansion of desert-like conditions into previously non-desert areas, typically driven by climate trends, overuse of resources, and land management practices. Desertness also declines toward the peripheries of deserts and increases in arid and hyperarid zones, but can fluctuate seasonally and with climate change.

Prominent deserts include the Sahara, Arabian, Gobi, Atacama, and the Australian deserts. Researchers measure desertness with climatic indices, soil characteristics, and long-term ecological data to distinguish climate-driven aridity from human-induced degradation.