Generally found in large, discontinuous patches centered on the equatorial belt and between the Tropics of Cancer and Capricorn, Tropical and Subtropical Moist Forests (TSMF) are characterized by low variability in annual temperature and high levels of rainfall (>200 centimeter annually). Forest composition is dominated by semi-evergreen and evergreen deciduous tree species.
These trees number in the thousands and contribute to the highest levels of species diversity in any terrestrial major habitat type. In general, biodiversity is highest in the forest canopy which can be divided into five layers: overstory canopy with emergent crowns, a medium layer of canopy, lower canopy, shrub level, and finally understory.
These forests are home to more species than any other terrestrial ecosystem: Half of the world's species may live in these forests, where a square kilometer may be home to more than 1,000 tree species. These forests are found around the world, particularly in the Indo-Malayan Archipelagos, the Amazon Basin, and the African Congo. A perpetually warm, wet climate promotes more explosive plant growth than in any other environment on Earth.
A tree here may grow over 75 feet in height in just 5 years. From above, the forest appears as an unending sea of green, broken only by occassional, taller "emergent" trees. These towering emergents are the realm of hornbills, toucans, and the harpy eagle.
The canopy is home to many of the forest's animals, including apes and monkeys. Below the canopy, a lower understory hosts to snakes and big cats. The forest floor, relatively clear of undergrowth due to the thick canopy above, is prowled by other animals such as gorillas and deer.
All levels of these forests contain an unparalleled diversity of invertebrate species, including New Guinea’s unique stick insects and bird wing butterflies that can grow over one foot in length. These forests are under tremendous threat from man. Many forests are being cleared for farmland, while others are subject to large-scale commercial logging.
An area the size of Ireland is destroyed every few years, largely due to commercial logging and secondary impacts. Such activities threaten the future of these forests are the primary contributor to the extinction of 100-200 species a day on average over the next 40 years (exotics on islands and loss of island habitats are other major factors)
At the current rate of deforestation, more than 17,000 species will go extinct every year, which is more than 1,000 times the rate before man arrived on this planet.
Among the 13 terrestrial major habitat types, the largest number of ecoregions by far falls within the TSMF (50 ecoregions or 35% of all terrestrial ecoregions). The high number of ecoregions within this major habitat type reflects the biological richness and complexity of tropical moist forests.
Although there are more TSMF in the Indo-Malayan Biogeographic realm (17) than in the Neotropics (12), this is partly due to the archipelagic distributions of Asian tropical moist forests and their characteristic biotas. Four of the Asian TSMFs are small island systems, and the original extent of all of the Asian ecoregions fit easily within the area covered by western Amazonian moist forests.
The most diverse terrestrial ecoregions occur in the Western Arc forests of the Amazon Basin, with close rivals in the Atlantic Forest ecoregion of Brazil, the Chocó-Daríen ecoregion of northwestern South America, and Peninsular Malaysia and northern Borneo forest ecoregions. The montane forest biotas of the Northern Andes are remarkable for their globally high rates of beta-diversity and extraordinary local endemism.
The forests of the Guayanan region and Cuba are remarkable for their endemism and unusual biogeographic relationships. The Congolian coastal forests are likely the most diverse in the Afrotropics, although diversity information is scarce for several ecoregions in the central Congo Basin. The Guinean moist forests support many species not found in the Central African region.
The Albertine Rift montane forests are extremely rich for some taxa, such as birds, and have a high degree of endemism. The distinctiveness of the Eastern Arc Montane and East African Coastal Forests is attributable to their great age and isolation7). Madagascar forests and shrublands are also highly distinctive at global scales, even at higher taxonomic levels8). Tropical moist forests of New Guinea and New Caledonia are highly distinctive at global scales9), although Australian moist forests do share many affinities with New Guinea.
The forests of Sulawesi are noted for the regionally high degree of endemism in a range of taxa, a phenomenon also seen in the Philippines moist forests10) and in the Lesser Sundas Semi-evergreen Forests. The Western Ghats and southwestern Sri Lankan moist forests are distinctive due to their isolation and long history. Tropical moist forests on oceanic islands are often highly distinctive due to high rates of endemism, extraordinary radiations of taxa and adaptive radiation, and relictual or unique higher taxa.
These habitats may display high beta diversity, particularly between isolated montane areas and along altitudinal gradients; local and regional endemism can be pronounced in some regions.
Large natural landscapes required in some regions because larger vertebrates track widely distributed seasonal or patchy resources; water sources and riparian vegetation important for wildlife in drier regions.
Sensitivity to Disturbance
These fragile habitats are highly sensitive to plowing, overgrazing, and excessive burning due to their challenging climatic and soil conditions; larger vertebrates sensitive to even low levels of hunting.