World Rainforest Movement

South Africa: Thirsty alien trees in a water scarce country

GeaSphere and EcoDoc have just launched a report by Liane Greeff of EcoDoc Africa, “Thirsty alien trees, no water left and climate confusion – what version of sustainable development are we leaving our children”. The paper highlights the dramatic contradiction of the expansion of water intensive industrial timber plantations in South Africa under planned development programmes, and the scarce water resources of the country. It is a thorough report that we highly recommend and which can be read at:Http:// 

Liane Greeff has produced the following summary in order to give WRM’s readers a brief view of the report.

There is not enough water for South Africa’s current and planned developmental approach, and therefore we need to re-examine the impossible nexus between our scarce water resources, potential climate change impacts, our decision to plant more water intensive timber plantations, and issues of long term food security. We need to weave these threads together in a way that links with the broader issues of a sustainable development that our planet is facing, and humanity’s current collision course with an unknown climatic crisis. The question we need to ask ourselves (as a species) is “Why isn’t our generation doing something whilst we still can, and why aren’t our leaders leading us?”

Southern Africa is the 30th driest country on the planet, and according to recent statistics South Africa is already using 98% of its available water and within the next few years will be having a water deficit.  Exacerbating this situation are the dire climate change predictions which indicate that Africa will be affected badly, and that South Africa in particular is likely to experience less rainfall over most of the region with longer dry periods and increased storm events. When you put these statements together they portray a very bleak picture of water availability in our future.

Our leaders, however, seem to be carrying on with their business as usual approach to macro-economic planning.  Most of the development projects planned, such as the 150 000 hectares of timber plantations in the drought prone Eastern Cape, are water intensive and seem to be taking place in complete isolation from the fact that South Africa is a water-scarce and arid country. Indeed, South Africa needs to take much greater cognisance of our natural resource constraints.

The history of timber plantations and water research: Since 1935 South Africa has been researching timber plantations and their water use due to complaints when rivers downstream of plantations starting running dry. This resulted in seventy years of hydrological research at Jonkershoek and other sites, using the paired-catchment approach, which showed that plantations result in significant streamflow reductions, which vary according to species. For pines, it was calculated that there was 30-40 mm streamflow reduction per 10% of catchment planted, at peak water use, and using about 400-450mm of rainfall equivalent.

Eucalypts use more water – approximately 600mm of rainfall equivalent – because of their ability to grow deep roots, which measure 30 to 50 metres, and therefore are able to “mine” soil water, or desiccate a catchment.  In a South African catchment with deep soils and afforested with eucalypts, the stream can dry up completely and only reappear 3-4 years after the trees are removed. The amount of water a tree uses is dependent on what species it is, what age, where it is in the landscape, its size, the size of its canopy, how close it is to a river and whether it is growing by itself or as part of a plantation.  Generally speaking a eucalyptus tree will use anything from 100 to one thousand litres of water per day and a pine from 50 to 600 litres of water per day.

Recent research has found that plantations use a much higher proportion of streamflow during periods of low rainfall and low stream flow, when compared to an average per annum reduction. For example, in South Africa the annual reduction to stream flow caused by plantations is about 3.2%. However, the impact is far worse in periods of low flow where plantations reduce the stream flow by 8%. This means that when there is a lot of water, plantations use a smaller proportion, but when there is limited water, plantations use a higher proportion. So when water is scarce, timber plantations uses a lot and uses it before other users get a chance.

How much water does timber use? The exact answer is difficult. According to Statistics South Africa, timber used 10 828 million m3 or 16% of South Africa’s water for 2000 whilst for the same year the National Water Resources Strategy indicates that the incremental water use of the timber plantations in excess of the natural vegetation amounted to 1 460 million m3 (3%) for South Africa as a whole. However, the word “incremental” is important as it gives the impression that plantations use less then they do. The difference between these two figures is because the Statistics SA Water Accounts reflect the evapotranspiration use of the plantation trees whilst the NWRS figure refers only to incremental use and the reduction in streamflow. Environmental organisation GeaSphere calculated plantations to use an amount equal to 30 times more water each day than the entire population’s free basic water allocation of 25 litres per person per day.  What makes timber very different is that the trees use the water before it gets into the stream flows, which means that once the trees are planted the water-use is committed.

Community experiences of water scarcity: Timber plantations have impacted on communities in a number of ways. Firstly, timber plantations cover 1.7 million hectares of land in the high rainfall belt, and about 40% of this land is claimed by communities as their ancestral land, and rightfully theirs. Secondly, communities living downstream of plantations find that their water supply often dries up and they have no water.

Timber plantations and other invasive alien plants: Many of the species used in plantations such as some pines, eucalyptus and black wattle, are highly invasive, and South Africa has a huge problem with invasive plants taking over our natural landscapes and using vast quantities of water resources.  Recent research indicate that under current conditions the amount of South Africa’s water being lost to the expansion of alien invasive species could rise from its current estimate of 3% to over 16%.

Climate Change Predictions for South Africa and the double burden of clean development mechanisms using plantations as carbon sinks: The clean development mechanism is one of the more controversial climate change mitigation strategies which enables trading based on carbon sequestration or the sink solution, whereby carbon emitting industries in the North can continue or expand if the equivalent amount of carbon is sunk somewhere else, for instance in a plantation. Using timber as carbon sinks have been described by some authors as trading water for carbon, whilst other studies conclude that where plantations could cause or intensify water shortages, that this factor should be explicitly addressed when considering carbon sequestration programs. Indeed many organisations complain that carbon sequestration programmes often result in people from developing countries “paying twice” for climate change – firstly, with the climate change itself, and secondly with the often devastating impacts that are associated with development projects such as tree plantations and large dams.

Pulp and paper industry: Another factor to be included in the consideration of timber and water use is the amount of water used and polluted through the pulp and paper processing mills. Linked to this is the wasteful use of paper around the world where global use has increased five times in 40 years.

The intention of the report is to share with you just how thirsty alien trees are and to try and give you an idea of how vast the plantations are in terms of land area, and the size of the problem with respect to the shortage of available water that this generation is facing. With respect to climate change, the paper has argued that the costs specifically in terms of water use and biodiversity are too great and that timber plantations should not be expanded further, and indeed where possible, removed, and that other forms of carbon sequestration, such as increasing organic soil concentrations and promoting grassland health, are preferable.

By Liane Greeff , EcoDoc Africa, e-mail:,

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