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March 2006

Opinion

 

A River Ran Through It

Dr Garth Cambray

A large grove of eucalypts on the Kariega river dwarfs Garth Cambray's bakkie.

In 20 years I have watched a river die. The Kariega river in the Eastern Cape of South Africa is well known because famous private game reserves such as Kariega Park and the new Pumba Private Game Reserve are on its banks. This river has had its liquid soul sucked out by an encroachment of the Australian invader plants, Eucalyptus camuldulensis, Acacia pycnantha and Acacia cyclops (the red river gum, golden wattle and rooikrans, respectively).

The vegetation of Australia, evolved in an island ecosystem with similar conditions to South Africa, and certain big differences. Plants such as those invading the Kariega river are not compatible with the ecosystem that has evolved there naturally, although they are adapted to the climatic conditions that prevail. The Eucalyptus genus of trees are notorious for their thirsty nature. Large Eucalypts have been shown to consume anywhere between 1000 and 5000 litres of water per day.

A view down the river showing a chocked stream bed covered in giant trees.

A 15km stretch of the Kariega river, from its catchment to the lower regions of the river, is entirely overgrown with invaders. In the lower regions of the river the trees, some with diameters over 2 meters, are packed so densely that it is difficult to walk between the trunks. In a 100m stretch of river, a forest 120m wide covered the banks. This translates to approximately 420 trees and about 840 cubic meters of water consumed per day - roughly enough to support 1000 households.

Robert Moss, owner of Mosslands Citrus farm, employs 90 people on his farm, with 40 hectares of citrus under irrigation. The farm however no longer has water. An irrigation dam built by his father on the Kariega until now never ran dry and normally overflowed even in dry periods. But starting in the 1980s the invader plants dried the river, the dam, and now the business too. Despite relatively good rains in January, the dam is still dry, as it has been since July 2005.

A unique Eastern Cape citrus plant, the Moss seedless orange, bred at Mosslands, which has not been watered since October 2005 due to the death of the Kariega river.

What does the death of the Kariega mean to South Africa? Without water flowing down the Kariega the Kariega estuary will be damaged. Many marine fish and animals use estuaries as breeding grounds. Without the fresh water bringing nutrients and reduced salinity to the estuary, it becomes a bad breeding ground. The result - less fish, less tourism, less employment.

From a tourism perspective, rivers are very useful features. A dead river is the opposite and immediately reinforces in peoples minds just how much we have damaged our planet. A dead river not flowing through two major game reserves is bad for business.

The lack of water in the river itself means that the entire aquatic ecosystem has been destroyed - crabs, insects, fish, frogs and plants are all gone. 

What should we do about this problem?

The Kariega river bed at the Mosslands dam site.

The trees on the banks of the Kariega are a valuable timber resource. The red river gum is a prized timber species - although the wood is prone to warping and splitting if treat incorrectly, it makes excellent furniture if treat right. A carefully planned scheme to fell these trees and convert them into durable outdoor furniture would help rid the river of trees and create jobs at the same time.

In many parts of Australia the River Red gum is protected - to limit logging activities. A solution to the problem could simply be establishing the existing market in Australia for this wood, producing and exporting those products to Australia, thus saving the Australian ecosystem and ours at the same time. And then hopefully one day, we will be able to look at Pumba and Mosslands and say 'A river runs through it' again.


More information:

Please contact Dr Garth Cambray at editor@scienceinafrica.co.za

 

 

 

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