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Earth from Space

Betsiboka Estuary, Madagascar

IMAGE:  Betsiboka Estuary, Madagascar

High-resolution image (520 Kb)

The Betsiboka Estuary on the northwest coast of Madagascar is the mouth of Madagascar's largest river and one of the world's fast-changing coastlines. Nearly a century of extensive logging of Madagascar's rainforests and coastal mangroves has resulted in nearly complete clearing of the land and fantastic rates of erosion. After every heavy rain, the bright red soils are washed from the hillsides into the streams and rivers to the coast. Astronauts describe their view of Madagascar as "bleeding into the ocean". One impact of the extensive 20th century erosion is the filling and clogging of coastal waterways with sediment - a process that is well illustrated in the Betsiboka Estuary. In fact, ocean-going ships were once able to travel up the Betsiboka Estuary, but must now berth at the coast.

A bad situation is made worse when tropical storms bring severe rainfall, greatly accelerating the rates of erosion. As illustrated in the top image, astronauts aboard the International Space Station documented widespread flooding and a massive red sediment plume flowing into the Bestiboka Estuary and the ocean in the wake of Tropical Cyclone Gafilo that hit northern Madagascar on March 7-8, 2004. The bottom image, a comparative image taken in September 2003, shows normal water levels in the estuary.

Despite the heavy coastal flooding in the top image, new coastal developments can be seen. The Mahajanga Aquaculture Development Project, a joint venture between Madagascar and the Japan International Cooperative Agency, strings along the coastal region at the mouth of the estuary. This project is a shrimp farm and was developed in 1999. Successive images taken by astronauts show increasing numbers of ponds constructed between 2000 and the present. Coastal aquaculture projects are frequently controversial, pitting the protection and viability of coastal ecosystems, especially rapidly disappearing mangroves environments, against badly needed industry in developing countries.

Astronaut photographs ISS008-E-19233 and ISS008-E-19236 were provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth.

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