Madagascar subhumid forests
Encyclopedia
The Madagascar subhumid forests are a tropical moist broadleaf forest
ecoregion
which originally covered most of the Central Highlands
of the island of Madagascar
.
, above approximately 800 meters elevation on the east and above 600 meters elevation on the west. The ecoregion has an area of approximately 199500 square kilometres (77,027.4 sq mi). The highlands catch the wet northeast trade wind
s, while the areas to the south, west, and north lie in the drier rain shadow
of the highlands. The subhumid forests are bounded by the humid Madagascar lowland forests
along the coastal strip to the east, by the Madagascar dry deciduous forests
to the north, northwest and west, and by the xeric
Madagascar succulent forests and Madagascar spiny thickets
to the southwest and south. In four areas above 1800–2000 meters elevation, the subhumid forests yield to the montane Madagascar ericoid thickets
. Amber Mountain (Montagne d’Ambre), which lies near the northern tip of the island, contains a significant pocket of subhumid forest, surrounded at lower elevations by dry deciduous forest. The subhumid forests ecoregion also includes the disjunct Analavelona and Isalo
massifs to the southwest, surrounded by succulent forests at lower elevations.
, grazing, and rice
cultivation, and some exotic species have been introduced. Pockets of closed-canopy evergreen forest still exist, as do open-canopy woodland
s. Large areas are now covered by grassland
, but the extent to which the grasslands are the result of human intervention is still subject to debate. Significant areas have become desertified
following extensive slash-and-burn activity primarily from 1970 onward, as population pressures led indigenous peoples to seek agricultural production in increasingly unsustainable
methods.
The subhumid forests shelter several species with origins in the temperate southern hemisphere Antarctic flora
, including several species of podocarps (Podocarpus
and Afrocarpus
), and Takhtajania
perrieri, from the magnoliid family Winteraceae
.
. Madagascar's long isolation from other continents resulted in a very limited land mammal fauna, and the endemic mammal lineages, in particular the lemur
s, adapted to fill certain niches. Giant lemurs, now extinct, were as large as adult gorillas. Several species of elephant bird
s (Aepyornis), giant flightless ratite
s related to the ostrich
, also became extinct since the arrival of humans approximately 2000 years ago, including Aepyornis maximus, the largest bird species ever to exist.
, presumably due to historically greater population density and proximity to the capital city of Antananarivo
; moreover, there has been extensive slash-and-burn activity by native peoples in the central highlands, eliminating most forest habitat
and applying pressure to some endangered species
. Slash-and-burn is a method sometimes used by shifting cultivators
to create short term yields from marginal soils. When practiced repeatedly over a large scale area, or without intervening fallow periods, the nutrient
poor soils may be exhausted or eroded to an unproductive state.
Tropical and subtropical moist broadleaf forests
Tropical and subtropical moist broadleaf forests , also known as tropical moist forests, are a tropical and subtropical forest biome....
ecoregion
Ecoregion
An ecoregion , sometimes called a bioregion, is an ecologically and geographically defined area that is smaller than an ecozone and larger than an ecosystem. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural...
which originally covered most of the Central Highlands
Central Highlands (Madagascar)
The Central Highlands, Central High Plateau, or Hauts-Plateaux are a mountainous biogeographical region in central Madagascar. They include the contiguous part of the island's interior above 800 m altitude...
of the island of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
.
Setting
The Madagascar subhumid forests historically covered most of Madagascar's Central HighlandsCentral Highlands (Madagascar)
The Central Highlands, Central High Plateau, or Hauts-Plateaux are a mountainous biogeographical region in central Madagascar. They include the contiguous part of the island's interior above 800 m altitude...
, above approximately 800 meters elevation on the east and above 600 meters elevation on the west. The ecoregion has an area of approximately 199500 square kilometres (77,027.4 sq mi). The highlands catch the wet northeast trade wind
Trade wind
The trade winds are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator...
s, while the areas to the south, west, and north lie in the drier rain shadow
Rain shadow
A rain shadow is a dry area on the lee side of a mountainous area. The mountains block the passage of rain-producing weather systems, casting a "shadow" of dryness behind them. As shown by the diagram to the right, the warm moist air is "pulled" by the prevailing winds over a mountain...
of the highlands. The subhumid forests are bounded by the humid Madagascar lowland forests
Madagascar lowland forests
The Madagascar lowland forests are a tropical moist broadleaf forest ecoregion, found on the eastern coast of the island of Madagascar.-Setting:...
along the coastal strip to the east, by the Madagascar dry deciduous forests
Madagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion generally situated in the western part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agriculture...
to the north, northwest and west, and by the xeric
Deserts and xeric shrublands
Deserts and xeric shrublands is a biome characterized by, relating to, or requiring only a small amount of moisture.-Definition and occurrence:...
Madagascar succulent forests and Madagascar spiny thickets
Madagascar spiny thickets
The Madagascar spiny thickets is an ecoregion in Madagascar. The vegetation type is found on poor substrates with low, erratic winter rainfall. An estimated 14,000 to is covered with this habitat, all in the southwest of the country...
to the southwest and south. In four areas above 1800–2000 meters elevation, the subhumid forests yield to the montane Madagascar ericoid thickets
Madagascar ericoid thickets
The Madagascar ericoid thickets is a montane shrubland ecoregion, found in the high mountains of Madagascar.The ecoregion covers the area above 1800 meters elevation in separate mountain areas of Madagascar, Tsaratanana , Marojejy , Ankaratra , and Andringitra...
. Amber Mountain (Montagne d’Ambre), which lies near the northern tip of the island, contains a significant pocket of subhumid forest, surrounded at lower elevations by dry deciduous forest. The subhumid forests ecoregion also includes the disjunct Analavelona and Isalo
Isalo
Isalo is a town and commune in Madagascar. It belongs to the district of Miandrivazo, which is a part of Menabe Region. The population of the commune was estimated to be approximately 8,000 in 2001 commune census....
massifs to the southwest, surrounded by succulent forests at lower elevations.
Flora
The original flora of ecoregion has been much altered by human use; extensive areas have been cleared for agricultureAgriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
, grazing, and rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
cultivation, and some exotic species have been introduced. Pockets of closed-canopy evergreen forest still exist, as do open-canopy woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
s. Large areas are now covered by grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
, but the extent to which the grasslands are the result of human intervention is still subject to debate. Significant areas have become desertified
Desertification
Desertification is the degradation of land in drylands. Caused by a variety of factors, such as climate change and human activities, desertification is one of the most significant global environmental problems.-Definitions:...
following extensive slash-and-burn activity primarily from 1970 onward, as population pressures led indigenous peoples to seek agricultural production in increasingly unsustainable
Sustainable agriculture
Sustainable agriculture is the practice of farming using principles of ecology, the study of relationships between organisms and their environment...
methods.
The subhumid forests shelter several species with origins in the temperate southern hemisphere Antarctic flora
Antarctic flora
The Antarctic flora is a distinct community of vascular plants which evolved millions of years ago on the supercontinent of Gondwana, and is now found on several separate areas of the Southern Hemisphere, including southern South America, southernmost Africa, New Zealand, Australia and New Caledonia...
, including several species of podocarps (Podocarpus
Podocarpus
Podocarpus is a genus of conifers, the most numerous and widely distributed of the podocarp family Podocarpaceae. The 105 species of Podocarpus are evergreen shrubs or trees from 1-25 m in height...
and Afrocarpus
Afrocarpus
Afrocarpus is a genus of conifers belonging to the podocarp family Podocarpaceae. Afrocarpus was designated a genus in 1989, when several species formerly classified in Podocarpus and Nageia were reclassified. Two to six species are recognized.As the name intimates, Afrocarpus is native to Africa...
), and Takhtajania
Takhtajania
Takhtajania is a genus of flowering plants of the family Winteraceae, which contains a single species, T. perrieri. It is native to the Southern Hemisphere....
perrieri, from the magnoliid family Winteraceae
Winteraceae
The Winteraceae are a family of flowering plants. The family includes 120 species of trees and shrubs in 9 genera.The Winteraceae are a mostly southern-hemisphere family associated with the Antarctic flora, found in tropical to temperate climate regions of Malesia, Oceania, eastern Australia, New...
.
Fauna
The subhumid forests were formerly home to the island's distinct megafaunaMegafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...
. Madagascar's long isolation from other continents resulted in a very limited land mammal fauna, and the endemic mammal lineages, in particular the lemur
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...
s, adapted to fill certain niches. Giant lemurs, now extinct, were as large as adult gorillas. Several species of elephant bird
Elephant bird
Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.-Description:...
s (Aepyornis), giant flightless ratite
Ratite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
s related to the ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
, also became extinct since the arrival of humans approximately 2000 years ago, including Aepyornis maximus, the largest bird species ever to exist.
History, conservation, and threats
Madagascar's high plateau forests have been altered more than the eastern rainforests or the western dry forestsMadagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion generally situated in the western part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agriculture...
, presumably due to historically greater population density and proximity to the capital city of Antananarivo
Antananarivo
Antananarivo , formerly Tananarive , is the capital and largest city in Madagascar. It is also known by its French colonial shorthand form Tana....
; moreover, there has been extensive slash-and-burn activity by native peoples in the central highlands, eliminating most forest habitat
Habitat (ecology)
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
and applying pressure to some endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
. Slash-and-burn is a method sometimes used by shifting cultivators
Shifting cultivation
Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned. This system often involves clearing of a piece of land followed by several years of wood harvesting or farming, until the soil loses fertility...
to create short term yields from marginal soils. When practiced repeatedly over a large scale area, or without intervening fallow periods, the nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
poor soils may be exhausted or eroded to an unproductive state.