- Email: [email protected]
Conserving tropical biodiversity: the arid end of the scale
Update
TRENDS in Ecology and Evolution
showed that divergence in sperm length and female spermathecal length can only be explained by the interaction of the two [5]. A lack of study of female properties has seriously hampered our development of a better understanding of genital evolution (e.g. the almost complete lack of knowledge of the innervation of female genitalia). Genital evolution often seems to be relatively rapid compared with that of other characters. Even in allopatry, divergent populations show remarkable differences in genital form and function [6]. To the extent that this pattern is general, we should then modify concepts that assume that genital traits are intraspecifically constant. Much insect taxonomy has based upon this assumption. We suggest that genital studies that are oriented to explain macroevolutionary patterns, such as speciation [7] and extinction [8], would be interesting future areas for research. To this aim, genital traits should be the cornerstone for testing such patterns.
Vol.19 No.5 May 2004
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References 1 Hosken, D.J. and Stockley, P. (2004) Sexual selection and genital evolution. Trends Ecol. Evol. 19, 87 – 93 2 Birkhead, T.R. and Møller, A.P. (1998) Sperm Competition and Sexual Selection, Academic Press 3 Simmons, L.W. (2001) Sperm Competition and its Evolutionary Consequences in the Insects, Princeton University Press 4 Arnqvist, G. (1998) Comparative evidence for the evolution of genitalia by sexual selection. Nature 393, 784 – 785 5 Miller, G.T. and Pitnick, S. (2002) Sperm-female coevolution in Drosophila. Science 298, 1230– 1233 6 Cordero Rivera, A. et al. Post – mating sexual selection: allopatric evolution of sperm competition mechanisms and genital morphology in calopterygid damselflies (Insecta: Odonata). Evolution (in press) 7 West-Eberhard, M.J. (1983) Sexual selection, social competition, and speciation. Q. Rev. Biol. 58, 155 – 183 8 Doherty, P.F. et al. (2003) Sexual selection affects local extinction and turnover in bird communities. Proc. Natl. Acad. Sci. U. S. A. 100, 5858– 5862 0169-5347/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.03.012
Conserving tropical biodiversity: the arid end of the scale Antje Burke EnviroScience, PO Box 90230, Windhoek, Namibia
Du Toit, Walker and Campbell’s recent spirited call in TREE for international assistance in the battle to preserve tropical nature [1] could not have met with a more open mind towards their suggestions. Yet, in the arid tropics, some of their conclusions require qualifying and, here, I offer further points for consideration in support of the argument for international assistance. In arid areas, natural resources are not sufficient to support sustainable development of an ever-increasing rural population [2]. The focus by many donor agents on rural development to curb the flight from rural to urban areas has therefore been only partially successful [3]. Alternatives to traditional subsistence farming for generating income are limited and can usually support only a few households. Hence, in areas where income from unsustainable land uses exceeds that available from sustainable activities, such as wildlife tourism, there is very little chance for conservation to be sustained without a heavy-handed approach from governments. However, there are examples of successful community-based conservation efforts. In Namibia, the success of such efforts in arid areas is supported by recovering populations of wildlife [4], including desert elephants and black rhinoceros. This success is also explained, in part, by the economic returns that wildlife tourism, compared with subsistence farming, offers to those Corresponding author: Antje Burke ([email protected]). www.sciencedirect.com
living in these arid areas [5]. The meager rainfall received in such areas cannot support the growth of commercially exploitable crops; thus, the income that subsistence farmers generate from alternative land uses is not matched by that received from subsistence agriculture [6,7]. Whether these efforts are ‘sustainable’ in the long-term requires careful monitoring, of not only wildlife populations, but also the status of their supporting habitats. Where higher rainfall facilitates more productive subsistence agriculture, there are no economic incentives available for conserving rather than exploiting the land to its economic full potential. It is here where international intervention is most urgently needed. To further direct global conservation efforts, it is most important to establish these economic-incentive relationships in all environments, from arid areas to tropical or humid ecosystems, because the incentives required will differ with the aridness of the environment. However, before embarking on a global support programme for direct support to land users, there are constraints to consider – a major one being African governments’ willingness or unwillingness to accept international assistance. References 1 du Toit, J.T. et al. (2004) Conserving tropical nature: current challenges for ecologists. Trends Ecol. Evol. 19, 12 – 17
Update
226
TRENDS in Ecology and Evolution
2 Werner, W. (2002) Access to Resources: Livelihoods Options and Strategies, Namibia Economic Research Unit/Desert Research Foundation of Namibia 3 Schneider, K-G. (1994) Nutzung peripherer Wirtschaftsra¨ume in ¨ berlebensstrategien in Afrika Namibia, Okavango und Caprivi. In U (Bollig, M. and Klees, F., eds), pp. 345 – 360, Colloquium Africanum 4 Davis, A. (2003) Community based natural resource management in Namibia – an undeniable success. Conservation 2003/4, 8–9 5 Ministry of Environment and Tourism, (2000) State of Environment
Vol.19 No.5 May 2004
Report on Parks, Tourism and Biodiversity, Directorate of Environmental Affairs, Government of the Republic of Namibia 6 Barnes, J.I. and de Jager, J.L.V. (1996) Economic and financial incentives for wildlife use on private land in Namibia and the implications for policy. S.A. J. Wildl. Res. 26, 37 – 46 7 Barnes et al. (2001) Economic analysis of community wildlife use initiatives in Namibia. DEA Research Discussion Paper 42. 0169-5347/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.03.011
| Letters Response
Response to Burke. Conserving tropical biodiversity: the arid end of the scale Johan T. du Toit Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
I thank Antje Burke for making a valid and important point that terrestrial ecosystems in the tropics range from deserts to rainforests, and that land-use options (sustainable or otherwise) increase along an arid– humid gradient [1]. When a local community weighs up the immediate benefits of conservation against the costs of foregoing alternative land uses, the net result becomes an increasingly large opportunity cost as primary productivity increases towards the humid end of the gradient. It is not surprising, therefore, that lucrative logging operations are destroying rainforests even in ostensibly ‘protected’ areas, such as Indonesian Borneo [2]. Local communities cannot bear the opportunity costs of conserving such areas, and I entirely agree with Burke that globally funded conservation interventions are most urgently needed in the humid tropics. Ironically, however, if we focus on Africa, we find that human population density and vertebrate species richness both increase with net primary productivity, before both decreasing again at the extreme end of the scale [3]. So, most of Africa’s biodiversity occurs in the higher rainfall
Corresponding author: Johan T. du Toit ([email protected]). www.sciencedirect.com
regions, where human population pressures are mounting and political corruption is most rampant [4]. This reaffirms our argument [5] that ecologists must interact more effectively with political scientists, economists and sociologists to increase the effectiveness with which global payments can be directed at scientifically formulated interventions to conserve tropical biodiversity. References 1 Burke. A. (2004) Conserving tropical biodiversity: the arid end of the scale. Trends Ecol. Evol. Doi: 10.1016/j.tree.2004.03.011 2 Curran, L.M. et al. (2004) Lowland forest loss in protected areas in Indonesian Borneo. Science 303, 1000– 1003 3 Balmford, A. et al. (2001) Conservation conflicts across Africa. Science 291, 2616 – 2619 4 Smith, R.J. et al. (2003) Governance and the loss of biodiversity. Nature 426, 67 – 70 5 du Toit, J.T. et al. (2004) Conserving tropical nature: current challenges for ecologists. Trends Ecol. Evol. 19, 12 – 17
0169-5347/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.03.014
TRENDS in Ecology and Evolution
showed that divergence in sperm length and female spermathecal length can only be explained by the interaction of the two [5]. A lack of study of female properties has seriously hampered our development of a better understanding of genital evolution (e.g. the almost complete lack of knowledge of the innervation of female genitalia). Genital evolution often seems to be relatively rapid compared with that of other characters. Even in allopatry, divergent populations show remarkable differences in genital form and function [6]. To the extent that this pattern is general, we should then modify concepts that assume that genital traits are intraspecifically constant. Much insect taxonomy has based upon this assumption. We suggest that genital studies that are oriented to explain macroevolutionary patterns, such as speciation [7] and extinction [8], would be interesting future areas for research. To this aim, genital traits should be the cornerstone for testing such patterns.
Vol.19 No.5 May 2004
225
References 1 Hosken, D.J. and Stockley, P. (2004) Sexual selection and genital evolution. Trends Ecol. Evol. 19, 87 – 93 2 Birkhead, T.R. and Møller, A.P. (1998) Sperm Competition and Sexual Selection, Academic Press 3 Simmons, L.W. (2001) Sperm Competition and its Evolutionary Consequences in the Insects, Princeton University Press 4 Arnqvist, G. (1998) Comparative evidence for the evolution of genitalia by sexual selection. Nature 393, 784 – 785 5 Miller, G.T. and Pitnick, S. (2002) Sperm-female coevolution in Drosophila. Science 298, 1230– 1233 6 Cordero Rivera, A. et al. Post – mating sexual selection: allopatric evolution of sperm competition mechanisms and genital morphology in calopterygid damselflies (Insecta: Odonata). Evolution (in press) 7 West-Eberhard, M.J. (1983) Sexual selection, social competition, and speciation. Q. Rev. Biol. 58, 155 – 183 8 Doherty, P.F. et al. (2003) Sexual selection affects local extinction and turnover in bird communities. Proc. Natl. Acad. Sci. U. S. A. 100, 5858– 5862 0169-5347/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.03.012
Conserving tropical biodiversity: the arid end of the scale Antje Burke EnviroScience, PO Box 90230, Windhoek, Namibia
Du Toit, Walker and Campbell’s recent spirited call in TREE for international assistance in the battle to preserve tropical nature [1] could not have met with a more open mind towards their suggestions. Yet, in the arid tropics, some of their conclusions require qualifying and, here, I offer further points for consideration in support of the argument for international assistance. In arid areas, natural resources are not sufficient to support sustainable development of an ever-increasing rural population [2]. The focus by many donor agents on rural development to curb the flight from rural to urban areas has therefore been only partially successful [3]. Alternatives to traditional subsistence farming for generating income are limited and can usually support only a few households. Hence, in areas where income from unsustainable land uses exceeds that available from sustainable activities, such as wildlife tourism, there is very little chance for conservation to be sustained without a heavy-handed approach from governments. However, there are examples of successful community-based conservation efforts. In Namibia, the success of such efforts in arid areas is supported by recovering populations of wildlife [4], including desert elephants and black rhinoceros. This success is also explained, in part, by the economic returns that wildlife tourism, compared with subsistence farming, offers to those Corresponding author: Antje Burke ([email protected]). www.sciencedirect.com
living in these arid areas [5]. The meager rainfall received in such areas cannot support the growth of commercially exploitable crops; thus, the income that subsistence farmers generate from alternative land uses is not matched by that received from subsistence agriculture [6,7]. Whether these efforts are ‘sustainable’ in the long-term requires careful monitoring, of not only wildlife populations, but also the status of their supporting habitats. Where higher rainfall facilitates more productive subsistence agriculture, there are no economic incentives available for conserving rather than exploiting the land to its economic full potential. It is here where international intervention is most urgently needed. To further direct global conservation efforts, it is most important to establish these economic-incentive relationships in all environments, from arid areas to tropical or humid ecosystems, because the incentives required will differ with the aridness of the environment. However, before embarking on a global support programme for direct support to land users, there are constraints to consider – a major one being African governments’ willingness or unwillingness to accept international assistance. References 1 du Toit, J.T. et al. (2004) Conserving tropical nature: current challenges for ecologists. Trends Ecol. Evol. 19, 12 – 17
Update
226
TRENDS in Ecology and Evolution
2 Werner, W. (2002) Access to Resources: Livelihoods Options and Strategies, Namibia Economic Research Unit/Desert Research Foundation of Namibia 3 Schneider, K-G. (1994) Nutzung peripherer Wirtschaftsra¨ume in ¨ berlebensstrategien in Afrika Namibia, Okavango und Caprivi. In U (Bollig, M. and Klees, F., eds), pp. 345 – 360, Colloquium Africanum 4 Davis, A. (2003) Community based natural resource management in Namibia – an undeniable success. Conservation 2003/4, 8–9 5 Ministry of Environment and Tourism, (2000) State of Environment
Vol.19 No.5 May 2004
Report on Parks, Tourism and Biodiversity, Directorate of Environmental Affairs, Government of the Republic of Namibia 6 Barnes, J.I. and de Jager, J.L.V. (1996) Economic and financial incentives for wildlife use on private land in Namibia and the implications for policy. S.A. J. Wildl. Res. 26, 37 – 46 7 Barnes et al. (2001) Economic analysis of community wildlife use initiatives in Namibia. DEA Research Discussion Paper 42. 0169-5347/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.03.011
| Letters Response
Response to Burke. Conserving tropical biodiversity: the arid end of the scale Johan T. du Toit Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
I thank Antje Burke for making a valid and important point that terrestrial ecosystems in the tropics range from deserts to rainforests, and that land-use options (sustainable or otherwise) increase along an arid– humid gradient [1]. When a local community weighs up the immediate benefits of conservation against the costs of foregoing alternative land uses, the net result becomes an increasingly large opportunity cost as primary productivity increases towards the humid end of the gradient. It is not surprising, therefore, that lucrative logging operations are destroying rainforests even in ostensibly ‘protected’ areas, such as Indonesian Borneo [2]. Local communities cannot bear the opportunity costs of conserving such areas, and I entirely agree with Burke that globally funded conservation interventions are most urgently needed in the humid tropics. Ironically, however, if we focus on Africa, we find that human population density and vertebrate species richness both increase with net primary productivity, before both decreasing again at the extreme end of the scale [3]. So, most of Africa’s biodiversity occurs in the higher rainfall
Corresponding author: Johan T. du Toit ([email protected]). www.sciencedirect.com
regions, where human population pressures are mounting and political corruption is most rampant [4]. This reaffirms our argument [5] that ecologists must interact more effectively with political scientists, economists and sociologists to increase the effectiveness with which global payments can be directed at scientifically formulated interventions to conserve tropical biodiversity. References 1 Burke. A. (2004) Conserving tropical biodiversity: the arid end of the scale. Trends Ecol. Evol. Doi: 10.1016/j.tree.2004.03.011 2 Curran, L.M. et al. (2004) Lowland forest loss in protected areas in Indonesian Borneo. Science 303, 1000– 1003 3 Balmford, A. et al. (2001) Conservation conflicts across Africa. Science 291, 2616 – 2619 4 Smith, R.J. et al. (2003) Governance and the loss of biodiversity. Nature 426, 67 – 70 5 du Toit, J.T. et al. (2004) Conserving tropical nature: current challenges for ecologists. Trends Ecol. Evol. 19, 12 – 17
0169-5347/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.03.014