Tropical and subtropical dry broadleaf forests

Tropical and subtropical dry broadleaf forests
Name	Tropical and subtropical dry broadleaf forests
Biome	Tropical and subtropical dry broadleaf forests
Continents	Africa, Asia, Australia, North America, South America
Countries	Brazil, India, Mexico, Madagascar, Thailand, Australia, Kenya, Ethiopia, Myanmar, Colombia
Area km2	2000000
Conservation status	Vulnerable

Tropical and subtropical dry broadleaf forests are a biome characterized by seasonally dry climates and deciduous or semi-deciduous broadleaf trees that shed leaves during prolonged dry periods. These forests occur in regions with marked wet and dry seasons and support distinctive assemblages of plants and animals adapted to water stress. Human societies across regions such as the Maya civilization, Mughal Empire, Portuguese Empire, Spanish Empire, and British Raj have historically altered and depended upon these landscapes.

Overview

Tropical and subtropical dry broadleaf forests span biogeographic realms including the Neotropical realm, Afrotropical realm, Indomalayan realm, and Australasian realm, and are recognized by conservation bodies such as the World Wildlife Fund and frameworks used by the International Union for Conservation of Nature. Major ecoregions include the Chiquitano dry forest, Caatinga, Chaco, Madhya Pradesh deciduous forests, Sri Lanka dry-zone, Miombo woodlands, Eastern Ghats, Northern Thornscrub, Dry Andes, and Madagascar spiny forests. Scientific study of these systems has been advanced by institutions such as the Smithsonian Institution, Kew Gardens, Royal Botanic Gardens, Kew, International Center for Tropical Agriculture, and universities including University of Oxford, Harvard University, University of São Paulo, University of Melbourne, and University of California, Berkeley.

Geography and Distribution

These forests occur on multiple continents: extensive areas in central and eastern Brazil, central India, central and eastern Madagascar, the Yucatán Peninsula, parts of Mexico, the Horn of Africa including Ethiopia and Kenya, peninsular Southeast Asia including Thailand and Myanmar, and northern Australia. Ecoregion boundaries often abut other biomes such as the tropical and subtropical moist broadleaf forests, dry shrublands and grasslands, montane ecosystems like the Andes, and coastal systems influenced by islands such as Sri Lanka and the Philippines. Biogeographic patterns reflect historical processes involving plate tectonics linked to events like the breakup of Gondwana and dispersal routes studied by scholars at the National Geographic Society.

Climate and Seasonality

Climate in these forests is marked by pronounced dry seasons associated with monsoon systems like the South Asian monsoon and climatic phenomena such as the El Niño–Southern Oscillation. Annual precipitation varies widely, often between 500 and 1500 mm, with prolonged droughts that drive deciduousness. Temperature regimes range from warm tropical conditions influenced by proximity to the Equator to subtropical climates affected by seasonal shifts related to the Intertropical Convergence Zone. Fire regimes, windstorms, and episodic floods interact with human land use in regions influenced by policies and agencies including the United Nations Environment Programme and national ministries such as the Ministry of Environment and Forests (India).

Flora and Fauna

Vegetation is dominated by drought-deciduous trees such as species in the genera Prosopis, Acacia, Dalbergia, Terminalia, and Bactris, with understories of grasses and shrubs including economically important species cultivated historically by civilizations like the Inca and Aztec. Faunal assemblages include endemic and threatened species such as the jaguar in the Neotropics, Bengal tiger in Indian dry forests, African elephant in Miombo, lemurs in Madagascar, and diverse bird communities including those studied by organizations like the Audubon Society and BirdLife International. Pollinators and seed dispersers such as bats, primates, and ungulates—including taxa documented by the Zoological Society of London—play vital roles in regeneration. Floristic composition shows affinities with neighboring moist forests and xeric biomes documented in floras curated at institutions like the Royal Botanic Gardens, Kew.

Ecology and Ecosystem Services

These forests provide ecosystem services recognized by multilateral initiatives such as the Convention on Biological Diversity and the United Nations Framework Convention on Climate Change. They store carbon in woody biomass and soils important for climate mitigation efforts like those coordinated under REDD+ and national contributions reported to the United Nations Framework Convention on Climate Change. Services include watershed protection for major river basins such as the Ganges, Amazon River, and Zambezi, provision of non-timber forest products used in traditional systems like those studied by the World Health Organization and Food and Agriculture Organization, and cultural services central to indigenous groups including the Maya, Guarani, and Adivasi communities. Ecological dynamics involve succession after disturbance, nutrient cycling, and interactions with large herbivores and predators monitored by conservation projects led by organizations like the Wildlife Conservation Society.

Threats and Conservation

Primary threats include agricultural expansion by actors linked to commodities such as soy and cattle in Brazil and cash crops in India and Mexico, infrastructure development including projects funded by entities like the World Bank and Asian Development Bank, illegal logging tied to international markets regulated through mechanisms like the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and fragmentation from urbanization in metropolitan regions such as São Paulo and Mumbai. Invasive species, altered fire regimes, and climate change driven by greenhouse gas emissions negotiated at conferences like the Conference of the Parties exacerbate vulnerability. Conservation responses include establishment of protected areas under national agencies like Brazil’s Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis and community-based programs supported by NGOs such as Conservation International, The Nature Conservancy, World Wildlife Fund, and bilateral donors including USAID.

Human Use and Management

People manage these forests through a mix of traditional systems including agroforestry practiced by groups such as the Maya and Guarani, state-managed forestry programs exemplified by policies in India and Australia, and market-driven land conversion for plantations and ranching endorsed by trade agreements involving the European Union and Mercosur. Sustainable management approaches promoted by multilateral initiatives include payment for ecosystem services piloted in Costa Rica and governance reforms influenced by the Nagoya Protocol and Ramsar Convention where wetlands intersect with dry forests. Restoration efforts rely on native species selection based on research from institutions like the International Union for Conservation of Nature and regional botanic gardens, while landscape-scale planning integrates stakeholders from local communities to international organizations such as the World Bank and United Nations Development Programme.

Category:Forests