Betsiboka: Madagascar’s Red River

Dec 19, 2018 0 comments


This image of the Betsiboka River’s estuary in northwest Madagascar provides tantalizing evidence of catastrophic erosion that has been plaguing this small island country in the Indian Ocean for the past fifty years. The bright red color seen in the river’s jellyfish-like tentacles and the sandbars in between is the result of iron-rich sediments that gets washed from the hills during heavy rain and deposited in the river’s mouth. It is estimated that as many as 400 tons of soil per hectare is washed away every year during the rainy season turning the Betsiboka River blood red and leaving deep gorges, known as Lavaka, in the highlands. Astronauts who took this picture remarked that it looks as if Madagascar was “bleeding to death.”

Deforestation has long been an issue for Madagascar as it is one of the world’s top biodiversity conservation sites because of the large number of endemic species that live here and rely on the island’s forest cover, one that the island is rapidly losing. Madagascar’s isolation from the African continent for millions of years has preserved and produced thousands of species of plants and animals found nowhere else on Earth. Nine out of ever ten species of plants and animals found in Madagascar are endemic. This large number of unique species makes deforestation a great threat to global biodiversity.


Photo credit: oldedoe/Flickr

In the past two thousand years, Madagascar has lost more than 90 percent of its original forest. This forest loss is largely fueled by tavy, a traditional slash-and-burn agricultural practice imported to Madagascar by the earliest settlers. Typically, an area of the rainforest is cut and burned to turn it into rice fields. After a year or two of production the field is left unused for 4-6 years before the process is repeated. After a couple of such cycles, the soil is exhausted of nutrients and can’t grow any more rice. It is then abandoned and a new area of the rainforest is chosen. Tavy leaves the land barren colonized only by scrub vegetation or grass that cannot anchor the soil making it prone to erosion and landslides. The problem worsened after the 1950s as a result of increased coffee production for the island's economy.

In addition to traditional agricultural practice, illegal logging for timber and fuel have resulted in dramatic loss of rainforest.

“With a population of 14 million people and growing, Madagascar is under enormous pressure to meets the needs of its people and still preserve the natural environment,” observes NASA. “Scientists fear the rapid, additional clearing of the island’s forests for cash crops such as cotton and tobacco endangers the habitat of the many plant and animal species unique to the island while at the same time creating soil erosion problems that impact water quality and the future productivity of agricultural lands.”


Deep gorges left by erosion is a common feature in Madagascar. Photo credit: Frank Vassen/Wikimedia


Photo credit: NASA


Photo credit: Axelspace

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