image (520 Kb)
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.
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.
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.