The Okavango Delta: an African treasure
In the middle of the Kalahari Desert in the north-west corner of Botswana a unique ecosystem is home to over a thousand species of plants, hundreds of species of birds, dozens of mammals, fish and amphibians; about 150.000 Homo sapiens live here as well.
Unlike almost all of the other rivers in the world the Okavango does not reach any seas or oceans: along its path to the Indian Ocean it is trapped by two geological faults that created a very flat region from where over 97% of the water evaporates. Every year, from September to December, precipitations in the Angolan uplands give water to two rivers that join near the Botswana’s border in March/April to form the Okavango: here they more slowly continue flowing towards South-East. Local rainfalls contribute to rise the water level mostly in the North-West areas of the Delta from November to March and then (April onwards, the local autumn season) the “Angolan rain” comes enlarging this wonderful wetland (in the past it has expanded up to 28,000 km2). This fascinating phenomenon has been recently described by a BBC documentary (“The great flood”) and happens right when all organisms need water, in the local dry season: furthermore elephants, zebras and other mammals migrate for months from the Kalahari to reach this fundamental oasis.
Natural cycles of large and small floods alternate: from 1850 to 1880, from 1955 to the late ‘70s and from 2000 onwards wetter conditions occurred (causing higher water levels) while in the periods 1880-1955 and 1980-2000 drier conditions generated smaller floods. 2009 will probably become the year of one of the greatest floods because rainfalls in Angola as well as local precipitations during the wet season have been particularly abundant and prolonged. The question that rises is whether climate change is having (or is going to have) an impact on the Okavango delta, on its immense biodiversity and on the people living here. Many research projects are taking place in the region and new ones are being planned to answer to this and to other challenging questions on how this peculiar and extremely precious ecosystem works.
The challenges facing the Okavango delta regarding increasing population (meaning higher water demands in the basin, especially in Angola and Namibia) and climate change require large scientific and policy making efforts in order to preserve and sustainably manage this huge natural heritage. This delta in fact represents one of the last near pristine wetland in Africa and is a real masterpiece of evolution on our planet.
Written by Luca Marazzi on behalf of Responding to Climate Change
*A research department of the University of Botswana – www.orc.ub.bw.
To watch videos regarding Climate Change please visit:
www.climate-change.tv |
