Tropical dry forests are scattered across every major tropical landmass, but more than half of what remains sits in South America, with the rest spread across Mexico, Central America, the Caribbean, sub-Saharan Africa, South and Southeast Asia, and a handful of Pacific islands. An estimated one million square kilometers of tropical dry forest still stands worldwide, though the biome once covered far more ground. These forests occupy a climatic niche that gets far less attention than rainforests, despite covering roughly half of the seasonally dry tropics and supporting unique communities of plants and animals adapted to months-long droughts.
Global Extent and Continental Breakdown
How much tropical dry forest the world holds depends on which bioclimatic definition you use. Broad definitions based on aridity and seasonal rainfall patterns put the total biome extent at roughly 15 million square kilometers, while narrower definitions focused on the forests themselves estimate closer to 10 million square kilometers.1PLOS ONE. Global tropical dry forest extent and cover: A comparative study of bioclimatic definitions using two climatic data sets Those numbers include the broader climate envelope where dry forest can grow, not just the forest that actually exists today. The remaining actual forest cover is far smaller.
A widely cited global assessment estimated that about 1,048,700 square kilometers of tropical dry forest remains, distributed unevenly across three broad tropical regions. South America holds the majority, at roughly 54 percent of the total. North and Central America and the African-Eurasian tropics each hold a roughly equal share of most of the rest, while Australasia and Southeast Asia account for a small fraction, under 4 percent.2Journal of Biogeography. A global overview of the conservation status of tropical dry forests That lopsided distribution makes South America the geographic center of gravity for the biome, though it hardly tells the whole story.
The Americas Hold the Largest Remnants
Within the Western Hemisphere, tropical dry forests stretch for roughly 520,000 square kilometers across North and South America. Mexico contains the single largest national extent at about 181,000 square kilometers, accounting for nearly 38 percent of dry forest in the Americas. Brazil and Bolivia follow, harboring the largest continuous and best-preserved fragments.3Biological Conservation. Extent and conservation of tropical dry forests in the Americas The pattern is not a smooth belt of forest but a patchwork of isolated fragments, some of them enormous, others reduced to small pockets surrounded by farmland and pasture.
Five individual ecoregions account for more than half of this total. The Chiquitano dry forests straddling Bolivia and Brazil make up the largest single block at about 27.5 percent. The Atlantic dry forests of eastern Brazil, the Sinaloan and Bajío dry forests in western and central Mexico, and the Cuban dry forests round out the top five.3Biological Conservation. Extent and conservation of tropical dry forests in the Americas These forests generally grow on relatively fertile soils, have a closed canopy dominated by legume and trumpet-vine family trees, and support a sparse ground layer with few grasses, setting them apart from the open, grassy savannas found in similar climates.4Journal of Biogeography. Neotropical seasonally dry forests and Quaternary vegetation changes
The Caribbean deserves special mention. The islands cover only a small fraction of total Neotropical land area but hold a disproportionate share of the region’s dry forest. Caribbean nations have already lost about two-thirds of their original dry forest, and over 80 percent of what remains is highly fragmented, squeezed between coastal settlements and agriculture on these small, densely populated islands.
Africa’s Sudanian and Zambezian Woodlands
Africa’s tropical dry forests and woodlands form two massive belts running east to west across the continent, sandwiched between the humid equatorial rainforests and the semi-arid zones. The Sudanian belt stretches across West Africa south of the Sahel, from Senegal through Nigeria and into Sudan. The Zambezian belt covers a huge swath of southern and eastern Africa, including parts of Tanzania, Zambia, Mozambique, Zimbabwe, and the Democratic Republic of Congo.5PubMed Central. Continental estimates of forest cover and forest cover changes in the dry ecosystems of Africa between 1990 and 2000 Together these regions cover an enormous area, though much of what researchers classify as “dry ecosystem” here includes open woodlands and tree-dotted savannas rather than closed-canopy forest.
African dry forests and woodlands have received considerably less research attention than their Neotropical counterparts, which makes their conservation status harder to pin down. Many of the active and emerging deforestation frontiers identified in recent global analyses are concentrated in African and Asian dry woodlands, where monitoring has historically been thinnest.6Nature Sustainability. Uncovering major types of deforestation frontiers across the world’s tropical dry woodlands The result is a knowledge gap that leaves some of the world’s most threatened dry forests essentially invisible in global conservation planning.
South and Southeast Asia
Across South and Southeast Asia, tropical dry forests are found in India, Myanmar, Thailand, Cambodia, Laos, Vietnam, and parts of Indonesia. India’s dry deciduous forests are among the most widespread, stretching across the Deccan Plateau and parts of central and western India. In mainland Southeast Asia, dry dipterocarp forests and mixed deciduous forests occupy the interior lowlands, particularly in Thailand and Myanmar, where a pronounced dry season lasting several months strips trees of their leaves.
Southeast Asia has experienced some of the most rapid woodland losses globally. The region’s dry woodlands have been classified among “rampant” deforestation frontiers, characterized by severe forest loss and conditions favoring capital-intensive agriculture.6Nature Sustainability. Uncovering major types of deforestation frontiers across the world’s tropical dry woodlands Vietnam’s seasonal tropical forests, for instance, have seen fire frequency climb dramatically over the past century, with fires recorded in 90 percent of years after 1963 at one well-studied national park, up from just 9 percent of years before 1905.7Geophysical Research Letters. Human‐Driven Fire Regime Change in the Seasonal Tropical Forests of Central Vietnam That kind of shift reshapes what the forest looks like and what can survive in it.
Dry Forests on Pacific and Caribbean Islands
Some of the most ecologically distinctive tropical dry forests grow on oceanic islands. In the Pacific, New Caledonia and Fiji support the richest dry forests in terms of native species count, while New Caledonia and Hawaii stand out for their high proportions of endemic and threatened species.8Oryx. Prioritizing conservation of tropical dry forests in the Pacific These island dry forests tend to be small in area but packed with species found nowhere else on Earth. How species-rich a given island’s dry forest is depends more on how isolated the archipelago is than on the local climate, though rainfall does influence species richness at the individual-island level.9Diversity and Distributions. Scaling species richness and endemism of tropical dry forests on oceanic islands
In the Caribbean, large Greater Antillean islands like Cuba, Hispaniola, and Jamaica host dry forests with high levels of endemism, consistent with their complex geological histories.10Journal of Biogeography. Geographical ecology of dry forest tree communities in the West Indies Cuba alone harbors one of the five largest dry forest ecoregions in the Americas. These island forests face disproportionate pressure from human settlement and agriculture concentrated in the same coastal lowlands the forests occupy.
What Puts a Dry Forest Where It Is
Tropical dry forests do not form a continuous belt like the equatorial rainforests. They appear wherever rainfall is both seasonal and moderate, typically between 500 and 1,800 millimeters per year, with a dry season lasting several months during which most trees lose their leaves. That climate window exists in patches all over the tropics, and local topography often determines exactly where within a region the dry forest shows up.
Rain shadows are a major driver. When moisture-laden winds hit a mountain range, rain falls on the windward side and the leeward valleys receive far less. In the Andes, drier regions with less than 1,500 millimeters of annual rain are associated with slopes facing away from prevailing winds and areas of reduced cloud cover produced by local breezes.11Journal of Biogeography. Dry spots and wet spots in the Andean hotspot In the Brazilian Caatinga, the largest tropical dry forest and woodland block in South America, mountain ranges and inselbergs create rain shadows that structure the vegetation into distinct zones: wetter eastern slopes support semi-deciduous forests while drier western slopes host deciduous and thorn vegetation.12PLOS ONE. Aridity drives plant biogeographical sub regions in the Caatinga, the largest tropical dry forest and woodland block in South America So two valleys separated by a single ridge can host completely different forest types.
Where Dry Forests Meet Rainforests and Savannas
Tropical dry forests rarely have sharp borders. They grade into other vegetation types across transition zones that can stretch for hundreds of kilometers. In northeastern Brazil, evergreen Atlantic forest on the coast transitions inland to dry Caatinga forest, with a band of semi-deciduous forest lying in between. A similar gradient runs through the Chiquitania region of eastern Bolivia, where the transition from moist to dry forest unfolds over more than 200 kilometers of landscape covered by semi-deciduous forest.13Frontiers in Ecology and Evolution. Inserting Tropical Dry Forests Into the Discussion on Biome Transitions in the Tropics Water availability is the main mediator of these transitions, and intermediate moisture levels produce intermediate forest types rather than a clean boundary.
In Costa Rica, researchers have used satellite data to track the dry forest-to-rainforest boundary in real time. The transition zone, or ecotone, tends to sit at mid-elevations where topography channels moisture. In wet years the ecotone shifts upslope toward the dry side; in dry years it retreats downslope. The concern is that the dry-forest side of this boundary appears less resilient to future rainfall reductions, meaning that increased drought frequency could shrink it.14PubMed. Climate and topography control variation in the tropical dry forest-rainforest ecotone
The boundary between dry forest and savanna is a different story. Both exist in seasonally dry climates, but savannas are open, grassy, and shaped by regular fire, while dry forests have a closed canopy and little grass. Fire tends to maintain savannas, and where fire is suppressed, dry forest can encroach on savanna. Where fire intensifies, forest retreats. This fire-mediated boundary makes the two biomes surprisingly sensitive to human land management.
How the Map Has Shifted Over Deep Time
Today’s scattered fragments of tropical dry forest were not always so isolated. Modeling work using a specialist dry-forest plant suggests that during the Last Interglacial, roughly 120,000 years ago, climate conditions would have supported a much larger and more connected expanse of dry forest across South America, potentially linking the Caatinga forests of northeastern Brazil with the dry forests of Bolivia. During the Last Glacial Maximum, around 20,000 years ago, suitable habitat contracted to something closer to the current patchy distribution.15Flora. Were Dry Forests widespread in the Pleistocene and what is their fate under climate change? A modelling approach using a specialist plant That finding is interesting because researchers had previously assumed dry forests expanded during glacial periods when the climate was cooler and drier. Instead, the broadest distribution may have occurred during the warmer, wetter interglacial, with drier corridors still connecting forest patches.
This historical connectivity helps explain a biogeographic puzzle. Over a hundred plant species show up in two or more of the widely separated dry forest fragments across the Neotropics, a pattern hard to account for given how far apart some fragments are today.4Journal of Biogeography. Neotropical seasonally dry forests and Quaternary vegetation changes Past periods of connection, however brief in geological terms, allowed plants to migrate between now-isolated patches. The forests we see today are remnants of a once larger, more connected system.
The Deforestation Picture
Tropical dry forests and woodlands have lost enormous ground in recent decades. Over 71 million hectares of tropical dry woodland have been cleared since 2000, and roughly a third of all remaining wooded areas sit inside active deforestation frontiers. The most dramatic losses are in what researchers call “rampant frontiers,” areas with severe woodland loss driven by capital-intensive agriculture. The South American Chaco and parts of Southeast Asia are the clearest examples.6Nature Sustainability. Uncovering major types of deforestation frontiers across the world’s tropical dry woodlands About 59 percent of all identified frontiers are classified as active or emerging, and most of those are in African and Asian dry woodlands where monitoring infrastructure is weakest.
The practical consequence is that the map of tropical dry forests is shrinking and fragmenting in real time. Less than a third of the original extent of tropical and subtropical dry broadleaf forests is currently forested, and over 80 percent of what remains is exposed to edge effects, meaning that even the surviving patches are ecologically degraded by their proximity to cleared land. Fewer than 1 percent of remaining forest patches are larger than 10 square kilometers.16Biological Conservation. Widespread degradation and limited protection of forests in global tropical dry ecosystems For a biome that depends on large, connected patches for long-term species survival, those numbers are bleak.
Protection Gaps and Where Conservation Stands
Protected areas cover a strikingly small fraction of tropical dry forests. Globally, less than a quarter of remaining dry broadleaf forests fall within conservation or protection zones, with coverage sitting at about 16 percent for the dry broadleaf forest biome specifically.16Biological Conservation. Widespread degradation and limited protection of forests in global tropical dry ecosystems There is also a geographic bias: Southeast Asia has a disproportionately high share of protected dry forest relative to other regions, while Africa and the Americas lag behind.
In the Neotropics specifically, protected areas cover only about 8.4 percent of the remaining dry forest and represent roughly 10 percent of the total range of bird species that depend on these forests. About 19 percent of dry-forest bird species have less than 5 percent of their range inside any protected area. Strategic expansion of the protected area network, particularly in Peru, Brazil, Ecuador, and Bolivia, could roughly double coverage and dramatically improve the picture for the most threatened species.17Biological Conservation. Identifying priority conservation areas for birds associated to endangered Neotropical dry forests Mexico, despite holding the largest national extent of dry forest in the Americas, remains poorly represented under protected areas.3Biological Conservation. Extent and conservation of tropical dry forests in the Americas
Mapping Challenges and New Technology
One reason tropical dry forests have been overlooked in conservation is that they are genuinely hard to map. Unlike rainforests, which stay green year-round and are easy to distinguish in satellite images, dry forests look dramatically different between seasons. During the wet season they can resemble moist forests; during the dry season they can look like scrubland or even bare ground. They also grade into other vegetation types along fuzzy boundaries, making it difficult to draw clean lines on a map.
Recent work has started to address this. Researchers in Colombia developed a framework combining climate data, altitude, soil properties, and both optical and radar satellite imagery to map dry forests at 10-meter resolution in the Andes, where high environmental variability makes traditional mapping unreliable.18Ecological Indicators. Mapping Tropical Dry Forest Gradients in an Andean Region with High Environmental Variability Other teams have turned to deep learning algorithms that fuse optical and radar data to detect land-cover changes in dry forests with high accuracy.19PubMed Central. Tropical dry forest land use/land cover change detection using semi-supervised deep learning algorithms and remote sensing Radar is especially useful here because it penetrates clouds and is sensitive to the structure of vegetation rather than just its color, making it effective during the cloudy wet season when optical satellites struggle.
Better maps translate directly into better conservation decisions. When you can track exactly where dry forests are expanding, contracting, or degrading on a year-to-year basis, you can target protection efforts far more precisely than you could when the best available data was a coarse-resolution estimate of a biome boundary. For a forest type that has been consistently undervalued in global conservation planning, the ability to simply see it clearly may be the most consequential development of the past decade.