The effect of long-term climate change on the vertebrate fauna of Mariepskop South Africa

Abstract

Climate change is leading to loss of global and local biodiversity through changes in the ecology of fauna and flora. Changes in environmental temperature influence species distributional ranges. They respond by either migrating along with the shift in ecological zones or adapting to the new environmental conditions within a habitat. If neither adaptation nor migration is possible, local extinction of the species can result. This study was performed at Mariepskop mountain which served as the ideal environment for quantifying species distribution along an altitudinal gradient within different vegetation types. The information collected was used to quantify the factors shaping species distribution and to predict the fate of these species at Mariepskop with future climate change scenarios. In this study I identified vertebrate taxa with restricted distribution along the altitudinal gradient representing low, high and generalist species. Regional geographical distribution and temperature data were analysed to create geographical distribution and temperature profiles for each species. Local distribution data and temperature profiles created from data recorded at automated weather stations within the study area and long-term interpolated data were compared to the geographical profiles for each species. Habitat requirements at a geographical scale were investigated for each species and related to the local habitat selection rationale at Mariepskop. Quantifying vegetation types and land types in the study area I predicted the possible shifts in vegetation zones with future climate change. Using this rationale we predicted which species at Mariepskop were most likely to be affected by future temperature increases and to what extent. A detailed study focussing on the factors shaping the local restricted altitudinal distribution of the Drakensberg crag lizard (Pseudocordylus melanotus melanotus) to the highest altitudinal site was also performed. Factors investigated were suitable shelter and prey availability, ambient temperature conditions and operative temperatures recorded with copper lizard models. A behaviour study on focal lizards at the highest altitudinal sites was also performed to create diurnal activity pattern profiles for crag lizards. Activity profiles were related to temperature data and diurnal activity time budgets were calculated. We established that the restriction provided by the upper thermal limit of this species is the factor most likely responsible for limiting it to the highest altitudinal site. A temperature simulation model based on laboratory experiments and field data was designed to simulate future increased temperature scenarios at Mariepskop. It revealed a reduction in the diurnal activity time budget for P. m. melanotus with increased temperature. In summation we predicted that future climate change could affect three vertebrate species at Mariepskop due to shifts in vegetation zones. The Drakensberg crag lizard is however unlikely to be affected by a future 2?C increase in environmental temperature.