Forty years of vegetation monitoring in Namaqualand yields promising results

By Dr Helga van der Merwe, Research Career Award Fellow, SAEON Arid Lands Node

A scientific article^* on a 40-year, long-term data set from Namaqualand has been published in the journal Applied Vegetation Science, in collaboration with the Department of Plant Science at the University of Pretoria, the Northern Cape Department of Environment and Nature Conservation (DENC) and CapeNature.

Results of 40 years of monitoring in the Goegap Nature Reserve in Namaqualand show that the effects of heavy grazing are reversible

The Hester Malan Nature Reserve (now known as the Goegap Nature Reserve) was proclaimed in 1966 and fenced in 1969, following the purchase of a farm in Namaqualand approximately 15 km from the town of Springbok in the Northern Cape. The land, which had previously been over-utilised by livestock, was stocked with wildlife after proclamation of the reserve.

Monitoring anticipated vegetation change

In 1974, the then Department of Agriculture initiated a long-term monitoring project to record anticipated vegetation changes following the removal of livestock and the introduction of game species. Vegetation change was monitored using two line transects, 1 km (1000 points) each in length, and has been surveyed annually by means of the descending point method for 40 years. This data set allowed for the analysis of trends indicating changes in the vegetation cover, species and life form composition, rangeland condition, species richness and diversity.

The long-term data set showed an increase in vegetation cover, species richness and diversity as rangeland condition improved with time. These positive changes could be related to the removal of the high numbers of livestock and replacement of these with low wildlife numbers in the first years of survey. Later a gradual decline in the rate of increase in some of these parameters could be seen, which can be attributed to higher grazing pressure by increasing wildlife numbers during the later years of monitoring.

Positive results

Results showed that the effects of heavy grazing were reversible. Overall, recovery took place very slowly over decades, and was primarily detected in the perennial component of the vegetation. The increase in wildlife numbers in the latter studied years and decline in perennial vegetation cover highlights the fact that the animal numbers on this reserve will have to be actively managed in order to avoid damage to the vegetation.

The Tierkloof 1-km line transect on Goegap Nature Reserve Goegap Nature Reserve’s Carolusberg line transect, one of two line transects surveyed annually since 1974

Perhaps most importantly, the publication of this long-term data set has highlighted the strong partnerships and collaboration between DENC (Reserve and Scientific Sections), the University of Pretoria, CapeNature and SAEON. This has not only resulted in a successful effort to collect data and publish a paper, but also provided a glimpse into what long-term partnerships and monitoring can lead to.

^* Van Rooyen, M.W., Le Roux, A., Geldenhuys, C., Van Rooyen, N., Broodryk, N. & Van der Merwe, H. (in press, early view). Long-term vegetation dynamics (40 yr) in the Succulent Karoo South Africa: effects of rainfall and grazing. Applied Vegetation Science. DOI: 10.1111/avsc.12150