Dry forests are ecosystems defined by distinct wet and dry seasons. Unlike continuously lush rainforests, they experience alternating periods of abundant rainfall and prolonged dry spells. This climatic rhythm shapes their flora and fauna, leading to biodiversity adapted to cyclical water availability.
Defining Characteristics
Dry forests are defined by distinct wet and dry seasons, which profoundly influence their ecology. They receive 250 to 2,000 millimeters of annual precipitation, mostly during a short wet season. The dry season can last three to ten months, creating water scarcity. Temperatures remain consistently warm, averaging above 17°C (63°F).
Dry forest vegetation is dominated by deciduous trees, which shed leaves during the dry season to conserve water. This creates an open canopy, allowing sunlight to reach the forest floor and support underbrush growth. Some evergreen trees are also present. Soils vary, with some being fertile and attractive for agriculture, while others are nutrient-poor from heavy rains.
Global Distribution
Tropical and subtropical dry forests occur in bands between 10° and 20° north and south latitudes, often bordering rainforests or subtropical deserts. They cover about 42% of the planet’s tropical and subtropical forest area.
Prominent regions include Central and South America, such as western and southern Mexico, the Bolivian lowlands, and Brazil’s Caatinga. They are also found across Africa, including the miombo forests from Angola to Tanzania, and on tropical islands like Madagascar. In Asia, dry forest areas exist in India, Southeast Asia, and Indochina. Smaller tracts are in the rainshadows of some tropical islands and parts of Australia.
Life in Dry Forests
Life in dry forests exhibits adaptations to cope with seasonal water scarcity. Many plants, like teak and mountain ebony, are deciduous, shedding leaves to minimize water loss. Some species, such as the Ecuadorian ceibo tree, develop green bark for photosynthesis when leafless. Other plant strategies include succulence, storing water in tissues, and deep root systems to access groundwater.
Animals also display adaptations to survive the dry season. Some species enter dormancy (estivation), burrowing into damp soil to reduce metabolism and conserve water. Others migrate to humid refugia like riparian zones. Behavioral adaptations, such as nocturnal activity, help animals avoid intense heat and reduce water loss. Many animals also derive moisture directly from their food sources.
Conservation Challenges
Dry forests face threats, making their conservation important. Deforestation, driven by agricultural expansion, logging, and charcoal production, is a challenge, as these forests are often cleared more easily than rainforests. Fertile soils in many dry forest regions attract farming for export crops and livestock, leading to extensive land conversion. Human population growth and demand for resources intensify these pressures.
Climate change also poses a threat, potentially leading to increased aridity and altered rainfall patterns that stress dry forest ecosystems. Despite their biodiversity and resources for millions, dry forests have historically received less conservation attention than rainforests. Conservation efforts include establishing protected areas, reforestation programs, and promoting sustainable land management practices to restore and preserve these ecosystems.