Directory UMM :Data Elmu:jurnal:P:PlantScience:ecology:21-40:

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NEWS & COMMENT

Dept of Psychology, Ridley Building, University of Newcastle, Newcastle upon Tyne, UK NE1 7RU

([email protected])

Tim Guilford

Dept of Zoology, University of Oxford, South Parks Road,

Oxford, UK OX1 3PS ([email protected])

References

1 Wallace, A.R. (1867) Proceedings of the Entomological Society of London, 4 March 1867, Ixxx–Ixxxi

2 Poulton, E.B. (1890) The Colours of Animals: Their Meaning and Use Especially Considered

in the Case of Insects, Keegan Paul, Trench, Trübner and Co

3 Guilford, T. (1992) Predator psychology and the evolution of prey colouration. In Natural Enemies: The Population Biology of Predators, Parasites and Diseases (Crawley, M.J., ed.), pp. 377–394, Blackwell

4 Mallet, J. and Joron, M. (1999) Evolution of diversity in warning colour and mimicry: polymorphisms, shifting balance, and speciation. Annu. Rev. Ecol. Syst. 30, 201–233

5 Lindström, L. et al. (1999) Can aposematic signals evolve by gradual change? Nature 397, 249–251

6 Gambarale, G. and Tullberg, B. (1996) Evidence for a peak-shift of predator generalization among aposematic prey. Proc. R. Soc. London Ser. B 263, 1329–1334

7 Wright, S. (1982) The shifting balance theory and macroevolution. Annu. Rev. Genet. 16, 1–19

8 Marples, N.M. et al. (1998) Response of wild birds to novel prey: evidence of dietary conservatism. Oikos 83, 161–165

9 Spence, K.W. (1937) The differential response to stimuli varying within a single dimension. Psychol. Rev. 44, 430–444

10 Guilford, T. and Dawkins, M.S. (1993) Receiver psychology and the design of animal signals. Trends Neurosci. 16, 430–436

11 Gagliardo, A. and Guilford, T. (1993) Why do aposematic prey live gregariously? Proc. R. Soc. London Ser. B 251, 69–74

12 Osorio, D. et al. (1999) Accurate memory for colour but not pattern contrast in chicks. Curr. Biol. 9, 199–202

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hat could Cambridge University ex-pect to achieve by organizing a con-ference on conservation biology* and,

moreover, making it a student confer-ence? The ability to party until a few hours before show time then present pol-ished talks that never ran over the time limit, illustrated with superior, and some-times dazzling, dexterity with Power-Point presentations, not only reminded the few invited senior scientists of incipi-ent senility but also of studincipi-ents’ superior skills – for which we would like to take credit for teaching. OK, so arenas for dis-plays of academic prowess are essential to size up one’s competitors for entry-level jobs, but there must be other motivations. One, obviously, is that unlike ecology-as-we-know-it, conservation biology is a crisis discipline. Within the lifespans of students, humanity will have decided how much – if any – of the world’s tropical forests it will retain, whether to alter global climate at a geologically unprec-edented rate and whether to eliminate a fraction of life on Earth not seen since the event that eliminated the dinosaurs. Did the students address these challenges?

Generally, papers reflected the inter-ests of academic advisors. Only half included science that had more than tenu-ous connections to practical issues. Ecolo-gists should not flatter themselves that all they do makes a difference. The defining meeting on conservation biology at the University of Michigan in 1985, which produced Soulé’s book Conservation

Biology1 _{in 1986, had several panels of}

managers who wondered whether any ecologist makes a difference. (‘Only’, one said, ‘if we give him a spade and have him dig holes for fence posts.’) Although con-servation science has grown since then, tying science to practical issues is diffi-cult. If so many students spent no more than a sentence or two thinking about what its consequences for management or policy would be, it is surely because academics determine their research. How many students have met a manager or a policy maker? For those that answered ‘no’, one assumes that their academic advisors haven’t either.

The geographical spread – students came from nearly 30 countries – provided an interesting contrast in this regard. Generally, those from biodiversity-rich countries outside Europe and the USA did address immediate conservation needs. For them, working with managers is unavoidable. For example, Abi Tamim (Wildlife Institute of India, Dehradun, Uttar Pradesh, India) had the task of radio-tracking tigers in a park of dry forest, the habitat that constitutes nearly half of the species’ range in India. In contrast to wet forest, range sizes in dry forests are huge – on the order of hundreds of square kilo-meters and nearly the size of the national park in which he worked. Clearly, some reserves are too small for viable popu-lations and those who protect tigers must rethink their strategy. Tamim’s colleague, Tanushree Biswas (Wildlife Institute of India), showed that active habitat man-agement is converting natural grasslands to plantation areas to benefit the Indian rhino, but to the detriment of other

species. Barend Erasmus (University of Pretoria, South Africa) modelled the ranges of well known taxa in South Africa and pre-dicted their future ranges under a probable scenario of climate change. Most species’ ranges will be smaller under warmer condi-tions and they will also need to move to places where there are few parks.

Finally, Joel Musaasizi (Institute of Tropical Forest Conservation, Bwindi Im-penetrable Forest, Uganda) studied prob-lems in Bwindi Impenetrable Forest. It holds half the world’s mountain gorillas, is surrounded by densely populated areas and has crops planted to the edge of the forest. Baboons and bush pigs from the forest raid the crops; therefore, Musaasizi’s mission was to find ways to reduce their impact. These species only venture about 150 meters from the forest but bushes grow up outside the forest providing corridors for raids. The farmers ask why the animals feed, while the people starve? They view the animals as the prop-erty of foreigners and researchers, creat-ing a tension further exacerbated by farm-ers being prohibited to enter the forest to hunt. Farmers don’t cooperate on remov-ing the bushes because they don’t own the land and thus will not necessarily reap the benefit of such work. They could plant buffer crops, such as tea, that will not be raided. And, if it were organized well, they could benefit from the revenue sharing that comes from ecotourism. We cannot expect the world’s poorest to take the bur-den for our passion for preserving gorillas, thus Musaasizi’s problem is acute and also complex. By demonstrating the inte-gration of ecology with the realities of soci-etal constraints Musaasizi won the confer-ence prize for practical conservation.

A different contrast involves the spe-cies and systems studied. Globally threat-ened species are not distributed uniformly and there was evidence of students seeking

Conservation connections

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NEWS & COMMENT

out the globally rare and threatened – birds in the Everglades and Mauritius, antelope in Kazakstan, mammal preda-tors in Madagascar, exploited top-preda-tory fish across the oceans, monkeys, Caribbean corals and cloud forests. Nonetheless, many papers involved com-mon species from Europe, despite the fact that most of its countries could dis-appear and, from a biodiversity point of view, none of them would be missed.

Obvious problems emerge when try-ing to understand war far from the front-line. At best, missing the experience of (say) trying to sleep in hot, saturated air under a mosquito net fails to build required character. At worst, one answers the wrong questions. The rapidly growing industry of computer-intensive conser-vation priority setting was the subject of several talks. Cutting edge exercises have massive data requirements on species’ ranges that will probably be filled only from well-studied European countries where the answers cannot possibly mat-ter. In many species-rich countries, the answers matter desperately; however, the habitats will go before we even glimpse what taxa they contain, let alone map them. The areas we save will be because we make choices that recognize what is economically practical, politically feas-ible, locally acceptable in a culture so dif-ferent from our own, and, if we are really lucky, because we guess correctly that they hold the important species.

Likewise, detailed studies of the popu-lation dynamics of common temperate species might simply be impossible on tropical species that are far too rare to afford the necessary sample sizes. Nonetheless, learning basic skills on com-mon species can be a good place to start. Students certainly sense the lure of exotic places and rare species. Envy greeted the talks by Maggy Nugues and Christiane Shelton (University of York, UK). This was not because of undeniable management importance of understanding how agricultural runoff harms their species, but rather because – poor things – their species were corals accessible only by SCUBA off the coast of St Lucia. The con-ference surely broadened students’ hori-zons as to what and where they can study.

The conference also demonstrated that well crafted studies can provide cru-cial management advice from first-rate sci-ence. Such was the theme of the confer-ence’s overall best paper by Mar Cabeza (University of Helsinki, Finland), who an-swered an explicit conservation problem with conceptually rich solutions. An endangered butterfly has declined to 10% of its original range within a decade. There is a critical need to know which habitat patches should be protected to prevent this species from going extinct in Finland. The problem is that patches differ in how long their local populations last depend-ing on how large and how isolated they are. Patches also differ in how much they

cost to purchase. Persistent, cheap solu-tions differ from those that simply min-imize costs or maxmin-imize current numbers. Although the cheapest solution might pick a few good sites, a slightly more expensive one might pick a much larger cluster of not so good individual sites but with excellent long-term prospects.

Students learn most from each other. Good talks motivate ever better presen-tations and the appreciation of what consti-tutes excellent science. Students needed no encouragement to mix socially. In doing so, long past the exhaustion of their seniors, they juxtaposed good science with globally important environmental problems. They probably absorbed the need to do both good science and yet sometimes chose different problems from those advisors who have trodden less relevant, if academically safer, paths. Both science and global problems will be aided as a consequence of this and by the future conservation conferences that Cambridge University is planning.

Stuart L. Pimm

Center for Environmental Research and Conservation, MC 5556, Columbia University, 1200 Amsterdam Avenue, New York, NY 10027, USA

([email protected])

Reference

1 Soulé, M.E., ed. (1986) Conservation Biology. The Science of Scarcity and Diversity, Sinauer

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ince the old lady swallowed a spider to deal with the fly, leading to a runaway trophic cascade of successively more desperate attempts to cope with previ-ous mistakes, the limits of classic biologi-cal control programmes have long been apparent. The propensity for some agents to swarm out of control is well docu-mented. The so called ‘indirect’ effects that follow some releases of biocontrol agents have received considerable atten-tion1_{. Well known examples include the} Cactoblastis moths released to control prickly pears, but which subsequently spread to several other naturally occur-ring nonweed hosts1_{. These releases are}

spectacular failures, in the sense that the agent runs out of control, thus becoming a problem itself and a threat to biodiver-sity. Although addressing such problems will always be a major task in a biocontrol programme, recent theoretical work2_has

begun to look at the opposite of this

problem, namely the failure of agents to establish at all and how this might affect the design of releases.

How should research programmes be designed to cope with such failures? The answer to this question requires an under-standing of the ecology of small popu-lations, as well as the use of modelling techniques that allow the process of in-troducing agents to be considered as a series of decisions set within an ongoing research programme.

Failure of biological control agents to establish

The fate of a large proportion of attempted releases is abject failure: 65% and 41% of agents released to control insect and weed pests, respectively, have never got off the ground, with the agent failing to establish a viable population immediately following release3,4_{. It could be that there are good}

biological reasons for such failures: the

weather might have been poor, the release site might have been poorly chosen or the agent could have been released at the wrong stage. However, there might be another reason: quite simply, too few agents were released. The basis for this can be simply a numbers issue; if there are too few individuals then, just by chance, all might die or fail to reproduce. So called depensatory dynamics, resulting from demographic stochasticity5,6_{, result in a}

net positive relationship between popu-lation establishment probability and the size of release. Alternatively, the existence of ‘Allee effects’7,8_{, resulting from positive}

effects of social interactions on population growth at low densities, might destabilize low-density populations and result in ultimate population extinction.