- Email: [email protected]
Climate change and its impacts in South Africa
Research Update
roughly 90 MYA in Gondwanaland (Machado and Herre). Subsequent evolution has produced a stunning diversity of figs, fig wasps and interactions, which was perhaps the defining theme of the conference. Adaptive correlation between fig and wasp traits, and hence evolutionary convergence, was another recurrent theme, adding to an already emerging picture that the many interactions in fig systems result in a web of different biotic selection pressures6. New insights into many issues are arriving from detailed taxonomic, ecological and behavioural studies, as well as from population genetics and molecular phylogenies. The long history of fig and fig wasp diversification is thus being steadily
TRENDS in Ecology & Evolution Vol.16 No.1 January 2001
unravelled by a selection of diverse approaches. Acknowledgements
We would like to thank Sally Power and Stuart West for helpful comments on this report and to Simon van Noort and the South African Museum Conference Team for organizing the conference and providing wonderful hospitality. References 1 Ramirez, W.B. (1970) Host specificity of a fig wasp (Agaonidae). Evolution 24, 680–691 2 Michaloud, G.S. et al. (1996) Exceptions to the one to one relationship between African fig trees and their fig wasp pollinators: possible evolutionary scenarios. J. Biogeog. 23, 513–520 3 Kerdelhué, C. et al. (1997) Active pollination of
13
Ficus sur by two sympatric fig wasp species in West Africa. Biotropica 29, 69–75 4 Galil, J. and Eiskowitch, D. (1968) On the pollination ecology of Ficus sycomorus in East Africa. Ecology 49, 259–269 5 Machado, C.A. et al. (1996) Molecular phylogenies of fig pollinating and non-pollinating wasps and the implications for the origin and evolution of the fig-fig wasp mutualism. J. Biogeog. 23, 531–542 6 Herre, E.A. (1996) An overview of studies on a community of Panamanian figs. J. Biogeog. 23, 593–607
James M. Cook* Carlos Lopez-Vaamonde Dept of Biology and NERC Centre for Population Biology, Imperial College, Silwood Park, London, UK SL5 7PY. *e-mail: [email protected]
Meeting Report
Climate change and its impacts in South Africa Albert S. van Jaarsveld and Steven L. Chown The South African Country Study on Climate Change was hosted by the South African National Research Foundation in Pretoria, Gauteng, South Africa, on 22 August 2000.
In keeping with the requirements of the Framework Convention on Climate Change (http://www.unfccc.int/), multisector, national evaluations of the likely impacts of global climate change1 are steadily becoming available. These evaluations are usually geared towards identifying those sectors of national economies most vulnerable to current and predicted future climate change. Following this trend, the South African National Department of Environmental Affairs and Tourism, in collaboration with the USA Country Studies Program, commissioned an overview of the likely effects of forecast climate change on sectors representative of the South African economy. This national, multisector review included: (1) vulnerability assessments of pivotal national production sectors, such as agriculture; (2) likely impacts on natural resource bases (for example, water and biodiversity); and (3) the implications for crucial service sectors such as human health services. The outcomes of these studies were recently presented at a workshop hosted by the South African National Research Foundation.
The principal aim of the workshop was to integrate results from across the targeted economic sectors and, in so doing, provide decision-makers in South Africa with a best estimate of impacts and the probable extent of mitigation measures required. Several disturbing cross-sector contrasts emerged, raising questions about the generality of the documented patterns as well as about their sensitivity to different modelling approaches. In particular, the natural resource sectors suggested that forecast climate change would be accompanied by significant impacts on, for example, water resources and biodiversity, whereas the production sectors were confident that there would either be limited effects, or that adaptation could be undertaken at limited cost to the respective production sectors. Commercial aspects of climate change
Climate change predictions were derived from scenarios generated by Bruce Hewitson’s group (University of Cape Town, South Africa) using up to three General Circulation Models (GCMs: Genesis, HadCM2 and CSM). Considering a scenario in which CO2 levels doubled, the GCMs predicted: (1) significant subcontinental warming (1–3°C), with greatest warming in the northern regions of the subcontinent; (2) extended summer season characteristics; and (3) a probable reduction of 5–10% in mean annual
precipitation. However, the rainfall predictions were less consistent than were those for temperature. The arid interior and moister north-eastern regions of South Africa are likely to be subjected to elevated evapotranspiration rates, increased stress, and more frequent flood events, whereas the south-western regions of the country are likely to experience increased early winter frontal and orographic rainfall. Bob Scholes (Council for Scientific and Industrial Research, Pretoria, South Africa) and co-workers suggested that the grassland component of rangelands would be least affected by these changes, with minor productivity declines likely to be offset by CO2 fertilization affects and reductions in frost prevalence. The savanna component of rangelands appear more sensitive and decreases of up to 20% in forage production are likely in savanna regions. However, it appears that the less productive savanna regions might encroach on existing grassland areas. In summary, livestock production would remain relatively unaffected with marginal impacts on cattle production. In reviewing the commercial forestry (Scholes and Dean Fairbanks, Council for Scientific and Industrial Research) and maize production sectors [Andre du Toit (Agricultural Research Council, Small Grains Institute, Potchefstroom, South Africa) and collaborators], it was suggested that declines in production in
http://tree.trends.com 0169–5347/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S0169-5347(00)02037-1
Research Update
14
these sectors, which are associated with elevated temperatures or reduced water availability, would probably be minimized by CO2 fertilization affects, or could be compensated for through the development of resistant cultivars. In the ensuing discussion, Scholes suggested that commercial afforestation, which has significant negative effects on biodiversity2, might represent an important negative opportunity cost because of the carbon sequestration benefits that could potentially be traded under the provisions of the Kyoto Protocol. By contrast, the forecasts from the natural resource and service sectors were more disconcerting. Roland Schulze’s team (University of Natal, Pietermaritzburg, South Africa) indicated that a 10% decrease in water runoff per quaternary catchment was likely by the year 2015 in the western half of the country, whereas this target would be reached by 2060 in the most eastern regions. Water resources are already strained in southern Africa3 and predicted population increases and much-needed increases in the quality of life of the majority of South Africans are likely to increase demand. Impacts on biodiversity
The most dramatic responses were, however, predicted for the biodiversity and human health sectors. Biodiversity resources (with the exception of marine biodiversity) were predicted to suffer extraordinary impacts, largely owing to range contractions, range shifts, or a combination of both. Mike Rutherford (National Botanical Institute, Cape Town, South Africa) and co-workers demonstrated that areas considered climatically suitable for South Africa’s seven existing terrestrial biomes could shrink by 40%. In addition, much of the area currently occupied by grasslands would be susceptible to invasion by savanna tree species, thus bringing about an increase in the extent of the savanna biome and most probably an increase in bush encroachment. More disconcertingly, the botanists argued that a doubling in CO2 would mean the complete loss of the Succulent Karoo biome, home to the world’s largest succulent flora and arguably the world’s most botanically diverse arid region4. Both our own group and Rutherford and colleagues suggested that 44% of plant and 80% of animal species would undergo some, http://tree.trends.com
TRENDS in Ecology & Evolution Vol.16 No.1 January 2001
usually marked, alteration to their geographic ranges. Animal range contractions are likely to mean enhanced extinction risk because of smaller ranges and reduced abundance: the double jeopardy problem discussed by Gaston5. The majority of range shifts in both plants and animals were predicted to take place in an easterly direction towards the eastern highlands, a pattern in keeping with the predictions of significant increases in aridity in the western parts of the country and less intense aridification towards the east. Intriguingly, these predicted range shifts suggest that species will move into the most transformed landscapes in South Africa. This is likely to further exacerbate the predicted impacts of climate change owing to substantial habitat fragmentation in these areas. The predicted alterations in the ranges of species also suggest that movements of species are likely to lead to marked changes in community structure and perhaps also in community function. For example, the botanical studies emphasized that more than half of the existing centres of plant endemism in the country are likely to experience novel climate conditions and will be susceptible to community transformation. Threats to human health
In their discussion of climate change impacts on health services, Marlies Craig and Brian Sharp (Medical Research Council, Durban, South Africa) emphasized the effects of two major parasitic diseases in South Africa, malaria and schistosomiasis. Under the proposed climate change scenarios, the proportion of the South African population at risk of contracting malaria, a disease presently expanding its incidence in the country owing to a combination of drug failures and insecticide resistance, is expected to double, unlike predictions for falciparum malaria elsewhere6. Similarly, schistosomiasis is expected to extend its geographical range westward. In the ensuing discussion, there was a broad consensus that the catastrophic HIV/AIDS pandemic in South Africa7 would exacerbate the effects of climate change on disease prevalence, and production and natural resource sectors, such as agriculture and conservation, through the diversion of national, financial and human resources. In summary, the workshop indicated
that South Africa is likely to experience substantial climate change in the next decades and that the effects of this change, especially on biodiversity, will be dramatic. In addition to highlighting progress towards more quantitative assessments of the likely impacts of climate change on a variety of economic sectors, the workshop demonstrated that numerous questions remain unanswered. Among these, inconsistencies that emerge from modelling variations will be the easiest to identify by assessing the outcomes using a variety of modelling approaches. By contrast, comparative parallel studies from other parts of the world might be required to identify general patterns in climate-related adaptation and mitigation, and to identify regional peculiarities. Acknowledgements
Financial support from the National Research Foundation, the USA Country Studies Program and the Department of Environmental Affairs and Tourism are gratefully acknowledged. M.A. McGeoch and B. Reyers commented on this article. References 1 Hulme, M. et al. (1999) Relative impacts of human-induced climate change and natural climate variability. Nature 397, 688–691 2 Allan, D.G. et al. (1997) The impact of commercial afforestation on bird populations in the Mpumalanga province – insights from Bird Atlas data. Conserv. Biol. 79, 173–185 3 Department of Water Affairs (1986) Management of the Water Resources of the Republic of South Africa, Department of Water Affairs, Pretoria 4 Cowling, R.M. et al. (1998) Extraordinary high regional-scale plant diversity in southern African arid lands: subcontinental and global comparisons. Divers. Distrib. 4, 27–36 5 Gaston, K.J. (1998) Rarity as double jeopardy. Nature 394, 229–230 6 Rogers, D.J. and Randolph, S.E. (2000) The global spread of malaria in a future, warmer world. Science 289, 1763–1766 7 Williams, B.G. et al. (2000) Where are we now? Where are we going? The demographic impact of HIV/AIDS in South Africa. South Afr. J. Sci. 96, 297–300
Albert van Jaarsveld* Conservation Planning Unit, Dept of Zoology and Entomology, and Centre for Environmental Studies, University of Pretoria, Pretoria 0002, South Africa. *e-mail: [email protected] Steven L. Chown Dept of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
roughly 90 MYA in Gondwanaland (Machado and Herre). Subsequent evolution has produced a stunning diversity of figs, fig wasps and interactions, which was perhaps the defining theme of the conference. Adaptive correlation between fig and wasp traits, and hence evolutionary convergence, was another recurrent theme, adding to an already emerging picture that the many interactions in fig systems result in a web of different biotic selection pressures6. New insights into many issues are arriving from detailed taxonomic, ecological and behavioural studies, as well as from population genetics and molecular phylogenies. The long history of fig and fig wasp diversification is thus being steadily
TRENDS in Ecology & Evolution Vol.16 No.1 January 2001
unravelled by a selection of diverse approaches. Acknowledgements
We would like to thank Sally Power and Stuart West for helpful comments on this report and to Simon van Noort and the South African Museum Conference Team for organizing the conference and providing wonderful hospitality. References 1 Ramirez, W.B. (1970) Host specificity of a fig wasp (Agaonidae). Evolution 24, 680–691 2 Michaloud, G.S. et al. (1996) Exceptions to the one to one relationship between African fig trees and their fig wasp pollinators: possible evolutionary scenarios. J. Biogeog. 23, 513–520 3 Kerdelhué, C. et al. (1997) Active pollination of
13
Ficus sur by two sympatric fig wasp species in West Africa. Biotropica 29, 69–75 4 Galil, J. and Eiskowitch, D. (1968) On the pollination ecology of Ficus sycomorus in East Africa. Ecology 49, 259–269 5 Machado, C.A. et al. (1996) Molecular phylogenies of fig pollinating and non-pollinating wasps and the implications for the origin and evolution of the fig-fig wasp mutualism. J. Biogeog. 23, 531–542 6 Herre, E.A. (1996) An overview of studies on a community of Panamanian figs. J. Biogeog. 23, 593–607
James M. Cook* Carlos Lopez-Vaamonde Dept of Biology and NERC Centre for Population Biology, Imperial College, Silwood Park, London, UK SL5 7PY. *e-mail: [email protected]
Meeting Report
Climate change and its impacts in South Africa Albert S. van Jaarsveld and Steven L. Chown The South African Country Study on Climate Change was hosted by the South African National Research Foundation in Pretoria, Gauteng, South Africa, on 22 August 2000.
In keeping with the requirements of the Framework Convention on Climate Change (http://www.unfccc.int/), multisector, national evaluations of the likely impacts of global climate change1 are steadily becoming available. These evaluations are usually geared towards identifying those sectors of national economies most vulnerable to current and predicted future climate change. Following this trend, the South African National Department of Environmental Affairs and Tourism, in collaboration with the USA Country Studies Program, commissioned an overview of the likely effects of forecast climate change on sectors representative of the South African economy. This national, multisector review included: (1) vulnerability assessments of pivotal national production sectors, such as agriculture; (2) likely impacts on natural resource bases (for example, water and biodiversity); and (3) the implications for crucial service sectors such as human health services. The outcomes of these studies were recently presented at a workshop hosted by the South African National Research Foundation.
The principal aim of the workshop was to integrate results from across the targeted economic sectors and, in so doing, provide decision-makers in South Africa with a best estimate of impacts and the probable extent of mitigation measures required. Several disturbing cross-sector contrasts emerged, raising questions about the generality of the documented patterns as well as about their sensitivity to different modelling approaches. In particular, the natural resource sectors suggested that forecast climate change would be accompanied by significant impacts on, for example, water resources and biodiversity, whereas the production sectors were confident that there would either be limited effects, or that adaptation could be undertaken at limited cost to the respective production sectors. Commercial aspects of climate change
Climate change predictions were derived from scenarios generated by Bruce Hewitson’s group (University of Cape Town, South Africa) using up to three General Circulation Models (GCMs: Genesis, HadCM2 and CSM). Considering a scenario in which CO2 levels doubled, the GCMs predicted: (1) significant subcontinental warming (1–3°C), with greatest warming in the northern regions of the subcontinent; (2) extended summer season characteristics; and (3) a probable reduction of 5–10% in mean annual
precipitation. However, the rainfall predictions were less consistent than were those for temperature. The arid interior and moister north-eastern regions of South Africa are likely to be subjected to elevated evapotranspiration rates, increased stress, and more frequent flood events, whereas the south-western regions of the country are likely to experience increased early winter frontal and orographic rainfall. Bob Scholes (Council for Scientific and Industrial Research, Pretoria, South Africa) and co-workers suggested that the grassland component of rangelands would be least affected by these changes, with minor productivity declines likely to be offset by CO2 fertilization affects and reductions in frost prevalence. The savanna component of rangelands appear more sensitive and decreases of up to 20% in forage production are likely in savanna regions. However, it appears that the less productive savanna regions might encroach on existing grassland areas. In summary, livestock production would remain relatively unaffected with marginal impacts on cattle production. In reviewing the commercial forestry (Scholes and Dean Fairbanks, Council for Scientific and Industrial Research) and maize production sectors [Andre du Toit (Agricultural Research Council, Small Grains Institute, Potchefstroom, South Africa) and collaborators], it was suggested that declines in production in
http://tree.trends.com 0169–5347/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S0169-5347(00)02037-1
Research Update
14
these sectors, which are associated with elevated temperatures or reduced water availability, would probably be minimized by CO2 fertilization affects, or could be compensated for through the development of resistant cultivars. In the ensuing discussion, Scholes suggested that commercial afforestation, which has significant negative effects on biodiversity2, might represent an important negative opportunity cost because of the carbon sequestration benefits that could potentially be traded under the provisions of the Kyoto Protocol. By contrast, the forecasts from the natural resource and service sectors were more disconcerting. Roland Schulze’s team (University of Natal, Pietermaritzburg, South Africa) indicated that a 10% decrease in water runoff per quaternary catchment was likely by the year 2015 in the western half of the country, whereas this target would be reached by 2060 in the most eastern regions. Water resources are already strained in southern Africa3 and predicted population increases and much-needed increases in the quality of life of the majority of South Africans are likely to increase demand. Impacts on biodiversity
The most dramatic responses were, however, predicted for the biodiversity and human health sectors. Biodiversity resources (with the exception of marine biodiversity) were predicted to suffer extraordinary impacts, largely owing to range contractions, range shifts, or a combination of both. Mike Rutherford (National Botanical Institute, Cape Town, South Africa) and co-workers demonstrated that areas considered climatically suitable for South Africa’s seven existing terrestrial biomes could shrink by 40%. In addition, much of the area currently occupied by grasslands would be susceptible to invasion by savanna tree species, thus bringing about an increase in the extent of the savanna biome and most probably an increase in bush encroachment. More disconcertingly, the botanists argued that a doubling in CO2 would mean the complete loss of the Succulent Karoo biome, home to the world’s largest succulent flora and arguably the world’s most botanically diverse arid region4. Both our own group and Rutherford and colleagues suggested that 44% of plant and 80% of animal species would undergo some, http://tree.trends.com
TRENDS in Ecology & Evolution Vol.16 No.1 January 2001
usually marked, alteration to their geographic ranges. Animal range contractions are likely to mean enhanced extinction risk because of smaller ranges and reduced abundance: the double jeopardy problem discussed by Gaston5. The majority of range shifts in both plants and animals were predicted to take place in an easterly direction towards the eastern highlands, a pattern in keeping with the predictions of significant increases in aridity in the western parts of the country and less intense aridification towards the east. Intriguingly, these predicted range shifts suggest that species will move into the most transformed landscapes in South Africa. This is likely to further exacerbate the predicted impacts of climate change owing to substantial habitat fragmentation in these areas. The predicted alterations in the ranges of species also suggest that movements of species are likely to lead to marked changes in community structure and perhaps also in community function. For example, the botanical studies emphasized that more than half of the existing centres of plant endemism in the country are likely to experience novel climate conditions and will be susceptible to community transformation. Threats to human health
In their discussion of climate change impacts on health services, Marlies Craig and Brian Sharp (Medical Research Council, Durban, South Africa) emphasized the effects of two major parasitic diseases in South Africa, malaria and schistosomiasis. Under the proposed climate change scenarios, the proportion of the South African population at risk of contracting malaria, a disease presently expanding its incidence in the country owing to a combination of drug failures and insecticide resistance, is expected to double, unlike predictions for falciparum malaria elsewhere6. Similarly, schistosomiasis is expected to extend its geographical range westward. In the ensuing discussion, there was a broad consensus that the catastrophic HIV/AIDS pandemic in South Africa7 would exacerbate the effects of climate change on disease prevalence, and production and natural resource sectors, such as agriculture and conservation, through the diversion of national, financial and human resources. In summary, the workshop indicated
that South Africa is likely to experience substantial climate change in the next decades and that the effects of this change, especially on biodiversity, will be dramatic. In addition to highlighting progress towards more quantitative assessments of the likely impacts of climate change on a variety of economic sectors, the workshop demonstrated that numerous questions remain unanswered. Among these, inconsistencies that emerge from modelling variations will be the easiest to identify by assessing the outcomes using a variety of modelling approaches. By contrast, comparative parallel studies from other parts of the world might be required to identify general patterns in climate-related adaptation and mitigation, and to identify regional peculiarities. Acknowledgements
Financial support from the National Research Foundation, the USA Country Studies Program and the Department of Environmental Affairs and Tourism are gratefully acknowledged. M.A. McGeoch and B. Reyers commented on this article. References 1 Hulme, M. et al. (1999) Relative impacts of human-induced climate change and natural climate variability. Nature 397, 688–691 2 Allan, D.G. et al. (1997) The impact of commercial afforestation on bird populations in the Mpumalanga province – insights from Bird Atlas data. Conserv. Biol. 79, 173–185 3 Department of Water Affairs (1986) Management of the Water Resources of the Republic of South Africa, Department of Water Affairs, Pretoria 4 Cowling, R.M. et al. (1998) Extraordinary high regional-scale plant diversity in southern African arid lands: subcontinental and global comparisons. Divers. Distrib. 4, 27–36 5 Gaston, K.J. (1998) Rarity as double jeopardy. Nature 394, 229–230 6 Rogers, D.J. and Randolph, S.E. (2000) The global spread of malaria in a future, warmer world. Science 289, 1763–1766 7 Williams, B.G. et al. (2000) Where are we now? Where are we going? The demographic impact of HIV/AIDS in South Africa. South Afr. J. Sci. 96, 297–300
Albert van Jaarsveld* Conservation Planning Unit, Dept of Zoology and Entomology, and Centre for Environmental Studies, University of Pretoria, Pretoria 0002, South Africa. *e-mail: [email protected] Steven L. Chown Dept of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.