East African mangroves

The Central African mangroves form the largest area of mangrove swamp in Africa, fringing the Atlantic coast and river mouths from Ghana and Nigeria south through Cameroon, Equatorial Guinea, Gabon, the Democratic Republic of the Congo, and Angola, with its greatest extent on the Niger Delta. These tidal forests are dominated by red mangroves of the genus Rhizophora (including Rhizophora racemosa and Rhizophora harrisonii), the black mangrove Avicennia germinans, and the white mangrove Laguncularia racemosa, with trees reaching up to 45 meters tall in fertile rivermouths and lagoons. The climate is humid and tropical where warm seas and high tides flood into the rivers, grading toward cooler, more temperate conditions in the south, and rainfall spans a wide gradient from a mean of about 750 mm in Angola to roughly 6,000 mm in Cameroon. The mangroves shelter rich communities of oysters, crabs, fish, and birds and support the threatened African manatee and turtles such as the African softshell, with the Sclater's guenon recognized as the ecoregion's flagship species; however, decades of Niger Delta oil spills and clearing for urban and industrial development have heavily degraded the habitat. The introduced Asian palm Nypa fruticans has also spread here as an invasive.

The Guinean mangroves form a band of coastal mangrove swamp along the rivers and estuaries of West Africa, spanning the shorelines of Senegal, Gambia, Guinea-Bissau, Guinea, Sierra Leone, and Liberia (with stands reaching into Côte d'Ivoire). The forest is built from salt-tolerant mangrove trees in the genera Rhizophora and Avicennia alongside Laguncularia racemosa and Conocarpus erectus, with the tallest trees reaching about 40 meters to form gallery forests along the creeks while inland fringes give way to grasses, ferns, and other salt-loving plants. The climate is strongly seasonal, alternating wet and dry periods, and rainfall varies enormously across the range, from very dry conditions in the Senegal River delta to some of the wettest coastline in Africa near Sierra Leone. Its flagship animal is the West African manatee, and Guinea-Bissau holds one of the largest populations of this elusive sirenian on the continent. The mangroves are a vital nursery for fish, shrimp, oysters, and waterbirds such as herons, flamingos, and the African spoonbill, but they are increasingly cleared for rice farming, firewood, and coastal development.

The Madagascar mangroves are an Afrotropic coastal ecoregion that fringes the western side of the island nation of Madagascar, lining roughly 1,000 kilometers of the Mozambique Channel coast and reaching its greatest extent in sheltered river estuaries and bays such as Bombetoka Bay at the mouth of the Betsiboka River near Mahajanga. The tidal forests here are built from a familiar set of Indo-Pacific mangrove trees, chiefly Rhizophora mucronata, Bruguiera gymnorhiza, Ceriops tagal, Avicennia marina, Sonneratia alba, and Lumnitzera racemosa, anchored in silt delivered by the many rivers draining the western lowlands. The climate follows Madagascar's seasonal rhythm, with a cool dry season from May through October and a warm, humid season from November through April. Recognized on the WWF Global 200 list of outstanding ecoregions, these wetlands shelter dugongs, green and hawksbill turtles, and waterbirds including the endemic Madagascar fish-eagle, yet they are under pressure, with a notable share already cleared for timber, charcoal, and farmland.

The Red Sea mangroves are scattered coastal stands fringing the Red Sea across seven countries: Djibouti, Egypt, Eritrea, Saudi Arabia, Somalia, Sudan, and Yemen. The grey mangrove, Avicennia marina, dominates and typically forms nearly pure, monospecific stands, with Rhizophora mucronata, Bruguiera gymnorhiza, and Ceriops tagal appearing only in a few areas. Conditions are harsh: there are no permanent rivers or freshwater inputs, salinity is high, and summer sea-surface temperatures exceed 31 degrees Celsius, while iron-poor carbonate soils stunt the trees to roughly two to three metres tall. Despite the global decline of mangrove ecosystems, this one expanded between 1972 and 2013, notably along the Eritrean coast, and its tangled roots shelter migratory birds and serve as nursery grounds for fish, with the Goliath heron as the ecoregion's flagship species. For gardeners, Avicennia marina is the signature native woody plant of this saline, low-rainfall coastal habitat.

The Southern Africa mangroves fringe the Indian Ocean shoreline along Mozambique's southernmost coast and the eastern coast of South Africa, marking the most southerly occurrence of mangroves on the African continent. They grow chiefly in sheltered river mouths and estuaries, dominated by salt-tolerant trees such as white mangrove (Avicennia marina), red mangrove (Rhizophora mucronata), black mangrove (Bruguiera gymnorrhiza) and Ceriops tagal, with species diversity increasing northward toward Kosi Bay. The climate is subtropical, and these stands persist unusually far south because the warm Agulhas Current pushes mangrove distribution roughly twenty degrees farther south on Africa's eastern coast than on its western coast. The estuaries shelter rich wildlife, including loggerhead and leatherback sea turtles, fiddler and mud crabs, mudskippers, and the near-endemic mangrove kingfisher, with dozens of bird species breeding among the trees. Around a quarter of the ecoregion is formally protected, though clearing for timber and for urban, industrial and tourist development remains an ongoing threat.

The Amazon-Orinoco-Southern Caribbean mangroves form a vast coastal ecoregion in the Neotropics, fringing the Caribbean shores of Colombia and Venezuela and the Atlantic coasts of Venezuela, Guyana, Suriname, French Guiana, and northeastern Brazil, including the Brazilian states of Amapá, Pará, and Maranhão. Shaped by the outflow of the Amazon and Orinoco rivers, its tidal wetlands are dominated by salt-tolerant mangroves such as Rhizophora racemosa and Avicennia schaueriana, alongside green buttonwood and the familiar red, white, and black mangroves. The climate is equatorial and fully humid, with year-round warmth roughly between 22 and 31 degrees Celsius and abundant rainfall averaging around 2,500 millimetres annually. These constantly flooded forests shelter rich birdlife and wildlife, from the scarlet ibis and American flamingo to giant otters, manatees, and nesting sea turtles, and the ecoregion's flagship is the critically endangered sapphire-bellied hummingbird. Though much of it remains relatively intact, mangrove stands here face mounting pressure from urbanization, pollution, and timber extraction.