The Horombe Plateau, a prominent plateau in southern Madagascar, presents a striking landscape of vast savannas and open horizons. This ancient geological surface, largely preserved, is known for its rugged beauty. It showcases Madagascar’s unique natural heritage, supporting distinct plant and animal life adapted to its conditions. Its ecological importance makes it valuable for natural exploration and scientific study.
Location and Physical Characteristics
The Horombe Plateau is situated in the Ihorombe region, in south-central Madagascar. It lies near the towns of Ihosy and Ranohira, along the main RN7 route. This expansive tableland spans a large area, with elevations generally exceeding 1,000 meters above sea level. The terrain is flat, characterized by vast grassy plains. Isolated rocky outcrops and inselbergs are interspersed within this expanse. The underlying geology primarily consists of sandstone, creating iron and aluminum-rich soils, which give the landscape distinctive reddish hues. These soils are often acidic.
Ecology and Wildlife
The Horombe Plateau features characteristic savanna and grassland ecosystems. Predominant vegetation includes Loudetia simplex and palm species like Hyphaene shatan, Medemia nobilis, and Bismarckia nobilis, a fire-resistant palm. Though Madagascar has high plant endemism, the plateau’s grasslands have fewer unique species than other Malagasy habitats. However, the adjacent Isalo National Park hosts endemic plants such as Pachypodium rosulatum and Aloes isaloensis.
Diverse animal populations inhabit the plateau and its surrounding areas. Lemurs, with over 100 endemic species, are prominent in the region. The area also hosts numerous reptile species, including chameleons, and over 300 amphibian species. Birdlife is varied; Isalo National Park records 77 species, including the endemic Benson’s rock thrush. Invertebrates, such as dragonflies, grasshoppers, termites, praying mantises, and hissing cockroaches, also thrive.
Geological Formation and Climate
The Horombe Plateau is an ancient geological surface, primarily composed of sandstone formations. Its landscape, including the adjacent Isalo Massif, is a continental sandstone plateau from the Jurassic period. These formations, part of the Isalo Group, are thick layers of coarse-grained sandstone from the Triassic to early Jurassic eras. Rocky outcrops and canyons have been sculpted over millennia by wind and water erosion. Granite veins in some northern and eastern parts indicate the area’s geological history.
The Horombe Plateau experiences a tropical dry climate. The hot, rainy season extends from November to April, while a cooler, drier season is from May to October. Annual rainfall ranges between 800 to 1000 millimeters, with significantly lower rainfall during the dry season months. Temperatures across the Ihorombe region range from 22°C to 27°C, peaking in January and dropping in May.
Conservation Importance
The Horombe Plateau has significant conservation value due to its unique savanna ecosystem and its endemic species. Its grasslands, though impacted by historical land use, are a distinct habitat type in Madagascar. Isalo National Park, a protected area within the Ihorombe region, shares ecological features with the plateau. This park safeguards diverse flora and fauna and is one of Madagascar’s most visited protected areas.
Conservation efforts for the region are managed by Madagascar National Parks, which oversees areas like Isalo. However, the plateau faces challenges, including widespread wildfires from annual burning practices. Human encroachment, driven by the pastoral activities of the Bara people and their zebu herds, also threatens the natural landscape. Habitat destruction also threatens this unique environment. Preserving it is essential.