VULNERABILITY OF SOUTH AFRICAN ANIMAL TAXA TO CLIMATE CHANGE
This is a short summary of an article by Erasmus et al. (2000) that deals with, as the title suggested, the vulnerability of South African animal taxa to climate change. Similar studies have been done to evaluate the possible effects of climate change on our flora (McDonald and Midgley 1996; Rutherford et al. 2000; Midgley et al. 2002), but this is the firsts study that deals with the possible effects of climate change on our fauna.
The authors selected 179 animal species across a wide taxonomic range, to be included in this study. 34 bird species, 19 mammals, 50 reptiles, 19 butterflies and 57 ‘other invertebrate’ species (including beetles, antlions and termites) were selected. Historic and predicted climate data (using the Hadley Centre Unified Model with no sulphates) were used which was provided by the Computing Centre for Water Research, University of Natal, Pietermaritzburg. The variables used in this study were the minimum of the 12 mean monthly minimum temperatures, the maximum of the 12 mean monthly maximum temperatures and the precipitation seasonality, using the February and August mean rainfall figures. The historic climate data were resampled to 15’x15’ grid cells to conform to the resolution of the species data.
Values of climate variables at known records were used to interpolate distributions and climate affected distributions were produced by using the predicted climate data. The changes in distribution patterns were then assessed by comparing the interpolated distribution with the climate affected distributions. These analyses were conducted separately for each taxonomic group, collectively across all species and also collectively for red data and vulnerable species.
The accuracy of the model was tested by comparing interpolated data with known records. Because of incomplete data for most species, only the bird data was used to evaluate the models accuracy. The Receiver Operating Characteristic (ROC) analyses showed that the model was a fairly good one and could be used for predicting future distributions. Although this can only be said for the birds, this is the best model the authors could come up with, with the limited data available.
The results were quite disconcerting. 25% of all species modelled showed a more than 90% shift in their range. For red data and vulnerable species this went up as high as 40%! That is 40% of red data and vulnerable species displayed a more than 90% range shift under the changed climate conditions. Of all the invertebrates about 40% showed range contraction under the 2050 scenario. 78 % (139 species) of all species modelled showed range contraction, 17 % (30 species) expanded their range, 3% (6 species) showed no response and 2% (4 species) became extinct. Thus the overall results showed that the majority of species could experience a major decline in range size and also substantial range displacement, mostly in a west to east direction. What is really concerning is that these predictions could actually be underestimates as landscape transformation has not been explicitly factored into the model! That means many species may actually never be able to migrate to more favourable habitat because of land transformation and fragmentation.
The authors did however superimpose areas of the country where more than 50% has already been transformed by human activity (Fairbanks et al. 2000) on the post climate change species richness map. This was done to see how much ‘pristine’ land would be available to accommodate the shifts in range of species. The results highlight the potential increase in conflicts between those who want to transform land and conservation advocates. It also highlights the need to incorporate such studies in regional conservation planning, which according to the authors is not routinely done!
The authors acknowledged that the model used cannot be said to be accurate across the taxa sampled, but should be seen as an estimate of the proportion of species that have distributions determined largely by climate. It should be seen as a “first take of the likely impacts of climate change on animal distributions in South Africa” (Erasmus et al. 2000, p 686).
In conclusion this study suggests that a change in climate will have a profound impact on South African terrestrial animal species. The results should also be seen as conservative as the currents population growth rate in South Africa will result in intense landscape transformation. According to the authors “mitigation of the impacts of climate change is ultimately a function of political will to confront difficult issues such as land-use and population planning” (Erasmus et al. 2000, p 688). Actions that must be taken by conservationist and researchers to improve the situation is to substantially improve the quality of information on animal taxa in South Africa including diversity and range, making sure that this information is integrated into land-use planning, researching the links between climate and animal distributions and most important of all conveying research findings to politicians!
Erasmus BFN, van Jaarsveld AS, Chown SL, Kshatriya M and Wessels KJ. 2002. Vulnerability of South African animal taxa to climate change. Global Change Biology 8: 679–693.
Fairbanks DHK et al. 2000. The South African land-cover characteristics database: a synopsis of the landscape. South African Journal of Science 96:69-82.
McDonald IAW and Midgley GF. 1996. Impacts and implications for nature conservation. In: Shackleton LY, Lennon SJ, Tosen GR editors. Global Climate Change and South Africa. Cleveland, South Africa: Environmental Scientific Association. p 83-86.
Midgley GF, Hannah L, Millar D, Rutherford MC and Powrie LW. 2002. Assessing the vulnerability of species richness to anthropogenic climate change in a biodiversity hotspot. Global Ecology & Biogeography 11:445-451.
Rutherford MC et al. 2000. Climate Change in conservation areas of South Africa and its potential impact on floristic composition: a first assessment. Diversity and Distributions 5: 253-262.
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BCB Hons NISL student
University of the Western Cape
Private Bag X17
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2. I have used the CSE/CBE convention for citation and referencing. Each significant contribution to, and quotation in this project from the work, or works, of other people has been attributed, and has been cited and referenced.
3. This assignment is my own work.
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