Using history to understand how natural rangelands in the Eastern Cape have changed

By Gina Arena, PDP* PhD Candidate, SAEON Arid Lands Node Tweet

Gina Arena spent an afternoon meeting with Dr Piet Roux at his home in Middelburg, Eastern Cape (Photo: Timm Hoffman)

South African scientists have a lot to be thankful for when considering the pioneering work of the country’s 20^th century botanists and agriculturalists.

Not only have the detailed botanical studies of these botanists and agriculturalists formed the foundation of the comprehensive species inventories and vegetation maps of which so much of the research relies heavily upon today, but so do their historical photographs and vegetation data sets continue to provide insightful snapshots of past vegetation condition.

These historical records create opportunities for researchers to return to the same sites to resurvey vegetation and take repeat photographs to assess the extent, rate and nature of change over time.

Pioneering vegetation surveys

Dr Piet Roux, an agriculturalist and avid botanist, spent the better part of his career traversing the Stormberg Plateau region in the Eastern Cape between the 1940s and 1970s. He spent years conducting vegetation surveys to track the distribution of a grass species, Tetrachne dregei; work which he eventually published in a PhD thesis in Botany.

Oom Piet (a term of endearment used by many) was also very interested in understanding the physiological intricacies of this grass, which is an indicator of veld degradation under various climatic and grazing scenarios. Of particular interest from these data are the measures of species composition and cover on approximately 70 different farms spaced across a rainfall gradient where the Nama-Karoo and the Grasslands biomes meet.

Left: Compiling a general species list of plants at the original site surveyed by Dr Roux at Boesmanskop, Grootfontein in 1960. Right: Working through the descending point method transect at Boesmanskop where Dr Roux surveyed vegetation in 1960. Gina was assisted by Helga van der Merwe (far left), Lisa Hebbelmann (second, left) and Justin du Toit (far right). (Photos: Timm Hoffman).

Oom Piet’s survey data and historical landscape photographs were collated and archived at the Grootfontein Agricultural Development Institute (GADI) in Middelburg in the Eastern Cape, and at the Plant Conservation Unit (PCU) in Cape Town, respectively. Eight of these sites were revisited and resurveyed by Timm Hoffman in 1989 and then again by past PCU student, Mmoto Masubelele, in 2009, but a large proportion of these sites are yet to be resurveyed.

Revisiting the sites

Following in the footsteps of Oom Piet, SAEON PDP PhD student Gina Arena will be revisiting as many as 68 sites to assess how these environments have changed over a 60-year period. Over 19 to 23 June 2017, Gina visited Middelburg in the Eastern Cape with her supervisors Timm Hoffman (University of Cape Town), Tim O’Connor (SAEON) and Helga van der Merwe (SAEON), to scout out a few of the sites she will be resurveying for her PhD.

The four held discussions around Gina’s main research questions on assessing long-term changes in rangeland vegetation in the Eastern Upper Karoo, which has been influenced by past and current climate and land-use patterns. A visit with Oom Piet himself inspired Gina as he delivered meticulous accounts of his research in the Karoo veld.

Reconnaissance

The reconnaissance involved visiting the Afrikaner and Boesmanskop camps at GADI, where Oom Piet took a number of historical photographs in the 1960s. Timm Hoffman guided Gina through the process of taking a repeat photograph of an original photo taken at the Boesmanskop site.

Gina also worked through her first vegetation resurvey at Boesmanskop, where Oom Piet used a wheel point to survey the vegetation 60 years ago.

Left: A photograph taken by Dr Roux in 1960 at Boesmanskop on the Grootfontein farm in Middelburg. Right: The repeat photo taken by Timm Hoffman in 2017. In the historical photo, grass cover was dominated by the grasses Digitaria argyrograpta in the foreground, Themeda triandra in the middle and Eragrostis bicolour in the background, with Tetrachne dregei sparsely scattered in this cover, and with Pteronia tricephala (dark shrubs) and Pentzia globose (grey shrubs). In the repeat photo, grass cover is denser and taller, with a shift in dominance of the grass species Digitaria eriantha and Sporobolus fimbriatus, and shrub Lycium cinereum.

Already, differences in the vegetation could be seen between the 1960 and 2017 photographs, such as a change in grass species composition and species abundance, and the instalment of a grazing exclosure experiment. Data collected from the vegetation surveys will provide the quantitative analysis of any species shifts and/or increases in grass cover between these time steps.

Social component

Gina’s research will also take on a social component through her interactions and interviews with farmers and landowners who are likely to possess valuable knowledge and/or records on historical land-use practices, climate and fire history on the farms to be surveyed. Without input from landowners, any changes in vegetation over this period may not be understood in the full land-use context.

Gina will also take this opportunity to provide feedback to landowners from her research at their farms to broaden the impact of her findings.

Visit these websites to find out more about research at the Plant Conservation Unit at UCT and rePhotoSA, their repeat photography citizen project.

^{* The Professional Development Programme of the Department of Science and Technology and the National Research Foundation aims to accelerate the development of scientists and research professionals in key research areas.}