Can Baobabs provide insight on climate change?

Recorded in the chemistry of the wood and the growth span of the tree is a history of climate patterns over the years. More baobabs – thousands of years old – have fallen in Pafuri, Mapungubwe and in Botswana since, and the baobab climate record has expanded. For the last three years, researchers from the University of Pretoria, Swansea University, University of Cape Town have studied additional baobabs from as far as Madagascar and Namibia.

Through coring the trees with a borer, dowels of wood can be removed without damaging the trees. The chemistry revealed through carbon isotope analyses of different tree rings gives scientists access to information on age and growth.  These trees, found mostly in summer rainfall areas, make good study models as they can live for more than 1 000 years. The baobabs can also reveal periods of growth and water stress, and therefore related rainfall and drought periods over hundreds of years.

The emerging climate record is a highly resolved indication of how rainfall has varied across Namibia, Botswana, South Africa and Madagascar over the last 1000 years. The message that comes from the baobabs is being used in two ways. The first is a relatively simple exercise of seeing how the natural climate system varies. Revelations are that natural climate cycles vary drastically, owing to factors such as El Niño (la Nina) and regime shifts.

This research has shown that a mega-drought across the entire region was likely the reason for the downfall of the Kingdom of Mapungubwe in the 1300s. It also reveals the mega-drought that caused the social upheaval known as Difaqane or Mfecane in the period between 1815 and 1840.

Even before human activity started warming our world, climate variability in southern Africa  included these mega-droughts. It is doubtful that that the economy would survive such an occurrence today. Droughts are a clear part of the record, and they are always transient. Through history, and through climate research conducted on these baobabs, it is evident that conditions usually recover after drought.

But can that be said for future conditions in a world affected by climate change? The second research approach, done in collaboration with colleagues in Stockholm, is to compare the baobab records with climate simulations reflecting conditions over the past 1000 years.

The research reveals that the models based on these climate simulations have accurately captured the major modes of rainfall variability over the last millennium. These models can help predict how climate change may occur in the future. Model forecasts for southern Africa suggest that some areas may see temperature increases in excess of five degrees, and rainfalls reduce by up to 30%.

If the models are accurate in reflecting the past 1000 years, what is revealed for the next 50 years is concerning. A future for conservation as climate change kicks in will be challenging, and the sooner we grapple with this the better.

Did you know that the Mapungubwe National Park offers free entry from 22 – 24 September? A detailed programme of the activities lined up for the week will be posted on the SANParks website.

For enquiries e-mail or phone us on the following numbers:

Written by Dr Stephan Woodborne
National Research Foundation, iThemba LABS

Caxton Central

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