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concerted evolution. Proc. Natl. Acad. Sci. U. S. A. 92, 6813–6817 Wendel, J.F. (2000) Genome evolution in polyploids. Plant Mol. Biol. 42, 225–249 Sang, T. and Zhang, D. (1999) Reconstructing hybrid speciation using sequences of low copy nuclear genes: hybrid origins of five Paeonia species based on Adh gene phylogenies. Syst. Bot. 24, 148–163 Grant, V. (1966) Origin of a new species of Gilia in a hybridization experiment. Genetics 54, 1189–1199 Rieseberg, L.H. (2000) Hybrid origins of plant species. Annu. Rev. Ecol. Syst. 28, 359–389 Ungerer, M.C. et al. (1998) Rapid hybrid speciation in wild sunflowers. Proc. Natl. Acad. Sci. U. S. A. 95, 11757–11762 Song, K. et al. (1995) Rapid genome change in
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synthetic polyploids of Brassica and its implications for polyploid evolution. Proc. Natl. Acad. Sci. U. S. A. 92, 7719–7723 Small, R.L. et al. (1998) The tortoise and the hare: choosing between noncoding plastome and nuclear Adh sequences for phylogeny reconstruction in a recently diverged plant group. Am. J. Bot. 85, 1301–1315 Iwata, H. et al. (2000) Triparental origin of damask roses. Gene 259, 53–59 Cronn, R.C. et al. (1999) Duplicated genes evolve independently after polyploid formation in cotton. Proc. Natl. Acad. Sci. U. S. A. 96, 14406–14411 Soltis, D.E. and Soltis, P.S. (1999) Polyploidy: recurrent formation and genome evolution. Trends Ecol. Evol. 14, 348–352 Barrier, M. et al. (2001) Accelerated regulatory
gene evolution in an adaptive radiation. Proc. Natl. Acad. Sci. U. S. A. 98, 10208–10213
Olivier Raymond* Florence Piola Claire Sanlaville-Boisson Laboratoire de Biologie Moleculaire et Phytochimie, Universite Claude Bernard, Lyon 1, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France. *e-mail:
[email protected]
Meeting Report
Dohumanscreate deserts? Roberto J. Fernández The88thDahlemworkshoponIntegrated Assessment of the Ecological, Meteorological and Human Dimensions of Global Desertification was held at Freie Universität, Berlin, Germany,from 10to15 June2001.
Drylands cover 40% of the land surface of the Earth and are home to 20% of the human population. Large expanses of drylands are experiencing desertification – or land degradation – caused by a complex mix of factors. In many areas, vegetation cover has been removed or severely reduced as a result of human activities, such as overgrazing and fuel gathering, and soils are being eroded at accelerated rates [1]. Many consider that such human-induced degradation has substantially reduced the capacity of the land to support humans, livestock and wild animals. Others contest this notion, suggesting that the changes do not affect humans materially, or that what is seen is the result of drought, possibly intensified in some areas by climate change. There have been several major conferences on desertification, motivated initially by international concern over the Sahelian droughts in the mid-1970s [2] and more recently by the UN Convention to Combat Desertification (CCD). However, the term ‘desertification’ is considered by many to be so encompassing as to render it useless, or worse, a trap [3], and it was with these controversies in mind that this most recent conference on desertification was convened. The goal http://tree.trends.com
was to produce a framework to integrate the three crucial, but still disconnected, aspects of desertification (i.e. its meteorological, ecological and human dimensions) and to recognize the simultaneous roles and complex feedbacks among each of these dimensions at different temporal and spatial scales (http://www.fu-berlin.de/dahlem). Given these ambitious goals and the diverse backgrounds of the delegates, a remarkable degree of consensus was reached, with conclusions compiled into a volume to be published in 2002 [4] including suggestions for research and policy implementation. What follows is a highly biased account for which I draw liberally from the 17 background papers to the workshop, and especially from the four collective reports, which each summarize discussions at one particular spatial scale (international scale, F. Lambin et al.; national scale, S.P.J. Batterbury et al.; community scale, P.F. Robbins et al.; and household and farm scale, R.J. Fernández et al.). Farmsandcommunities
At the most detailed scale, it was proposed that desertification is always the consequence of joint biophysical and socioeconomic deterioration. Regardless of which kind of factor triggers desertification (e.g. eroded soil or high debt), the end result always includes both biophysical and socioeconomic deterioration. It was agreed that, rather than short-term crisis responses, it is preferable (and possibly, in the long run,
less expensive) to be proactive, building adaptive capacity by expanding resilience along both the biophysical and socioeconomic dimensions. This is in line with a recent call for more studies combining social and ecological sciences (http://lsweb.la.asu.edu/akinsig/report.htm). Groups dealing with less-detailed scales, however, suggested that interactions between these two dimensions are not as common at their level of concern. A recurrent theme of the workshop was the value of the ‘stakeholder’ concept (i.e. groups with divergent interests) and the importance of taking into account the factors behind contrasting responses to a single policy measure. Environmental problems cannot be attributed to their proper causes until the existence of divided perceptions of environmental status and change is understood and taken seriously. Because of this diversity, however, human societies have a potential for action beyond that of the individuals or groups that form them. Moreover, peoples who are weakly integrated into the market economy may have particularly strong community links, which could serve to amplify or attenuate forces of degradation that originate outside the community (e.g. taxation policies or climate change). Countries and beyond
Two issues dominated the debate at the less-detailed scales of analysis: climate and international organizations. A crucial question is how climate change will affect
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved. PII: S0169-5347(01)02366-7
ResearchUpdate
the climate variability to which many drylands (especially those at transition zones or ‘ecotones’) are extremely sensitive. Unfortunately, climate models are not yet sufficiently advanced to answer this with confidence. There was consensus that the notion of devegetation inducing regional drought episodes mainly as a result of changes in the radiative properties of the soil surface no longer holds. Evidence now indicates that plant cover influences on the hydrological cycle, as a result of its tremendous impact on energy balance, might be at least as important. Some participants anticipated future conflict among international organizations, particularly between those concerned with environmental issues and those concerned with trade issues (e.g. Multilateral Environmental Agreements versus General Agreement on Tariffs and Trade). Others held that the CCD is the best specific tool that we have with which to combat desertification and, now that it has been ratified by more than 150 countries, it needs to be strengthened. For example, this could be accomplished by improving links with other conventions, such as the Biodiversity Convention and the Intergovernmental Panel on Climate Change. It was also stated that, if some of the causes of desertification were addressed properly at the country level, many of the supposed limitations of the CCD would disappear. Communication issues
It was argued that ‘…research…does not just hit a wall of policy makers ready to bounce it back to local people through swiftly designed land management projects’. One concrete proposal was to ensure that organizations leave enough institutional space at the local level so as to permit non-governmental organizations, state ministries, field staff and farmers to work together. Central governments should maintain a firm hold over economic, land tenure and taxation policies because of their cascading (‘cross-scale’) effects on lower level decision units. ‘It does matter what scientists say, but also the context in which it is said…’ and there is always the potential for misuse. Communication between scientists and decision makers must be improved at all levels, as indicated by the belief that governments and organizations often do not use the science that they pay for – improvements that could be implemented immediately abound. For example, in http://tree.trends.com
TRENDS in Ecology & Evolution Vol.17 No.1 January 2002
spite of great progress in the production and free distribution of global-scale data sets, there is still ‘an urgent need to liberalize access to weather data’. Another example: our current understanding of rangelands indicates that aid, such as the supply of fodder to livestock during droughts, if it becomes a routine practice, is likely to decouple herbivore herds from their resources and thus make them more vulnerable to weather vagaries. This does not mean that aid has to be restrained. It is obviously wise to concentrate available technical and financial resources on time and areas that need them. However, what follows from this is that efforts should not be spread evenly among areas, regions or activities, because, by not giving every year to everyone, resources are saved for when they will impact the most in terms of long-term sustained production. But of course not all the blame rests with governments and administrators: science does not always provide appropriate answers when confronted with management and policy issues. Still, one of the most important lessons from unsuccessful projects and assessments of the past 30 years is: do not by-pass scientific procedures. Urgency and importance should not be a reason to seek advice based on unreliable data. The scientific method and peer-review system are the fastest ways to gather the information that is needed to make the best decisions in the face of uncertainty. An appeal was made for scientists to become more involved in a kind of large-scale
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‘adaptive management’, and to take a more active role in the decision-making process (see also Ref. [5].) Interdisciplinary assessments are not the solution to every problem and might not even be a good idea if the need is to focus on rather technical matters, such as the assessment of soil erosion or climate change. However, such assessments clearly have the potential to link many areas of science to land management practice and poverty alleviation, thus providing better guidance to policy developments, including those related to the CCD. Adequate feedback from policy applications will strengthen our understanding of dryland issues and of ways to tackle the many associated problems without further delay. References 1 Reynolds, J.F. (2001) Desertification. In Encyclopedia of Biodiversity, Vol. II (Levin, S.A., ed.), pp. 61–78, Academic Press 2 Thomas, D.S.G. (1997) Science and the desertification debate. J. Arid Environ. 37, 599–608 3 Mainguet, M. (1994) Desertification: Natural Background and Mis-management (2nd edn), Springer 4 Reynolds, J.F. and Stafford Smith, M., eds Global Desertification: Do Humans Cause Deserts? Dahlem University Press (in press) 5 Bradshaw, G.A. and Bekoff, M. (2001) Ecology and social responsibility: the re-embodiment of science. Trends Ecol. Evol. 16, 460–465
RobertoJ.Fernández Universidad de Buenos Aires, IFEVA – Facultad de Agronomía/CONICET, Av. San Martín 4453, Buenos Aires C1417DSQ, Argentina. e-mail:
[email protected]
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