Semiárida

Semiárida is a term used to describe climatic and ecological zones characterized by low to moderate rainfall, high evapotranspiration, and marked variability in precipitation. These regions lie between arid deserts and more humid zones and are often drought-prone due to irregular rainfall.

Climate and hydrology: annual precipitation typically ranges from about 250 to 600 millimeters, with most rainfall concentrated in a brief wet season. Evapotranspiration exceeds precipitation for much of the year. Soils are frequently shallow, nutrient-poor, and susceptible to erosion. Temperature is usually warm to hot, with large diurnal or seasonal fluctuations.

Geography and extent: The semiárida climate occurs in several regions worldwide, including parts of Africa, the Americas, and Australia. In Brazil, the semiárido brasileiro refers to a large area of the Northeast characterized by water scarcity and a distinctive vegetation known as caatinga. In other regions, semiáridos support savanna or shrubland ecosystems and can host agriculture under drought-tolerant practices.

Ecology and human activities: Vegetation tends to be xerophytic or thorny, adapted to water scarcity. Land use often relies on crops such as millet, sorghum, and beans, as well as livestock. Water management, rainwater harvesting, and soil conservation are common adaptation strategies. Desertification and climate variability pose ongoing challenges, while climate change may alter rainfall patterns and increase drought frequency.