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Blackwell Science, LtdOxford, UKGEBGlobal Ecology and Biogeography1466-822XBlackwell Science, 20011052001173Library LettersLibrary Letters10.1046/j.1466-822X.2001.00173.xLIBRARY LETTERS100Graphicraft Limited, Hong Kong

CALLING ALL TIMID POTENTIAL MODELLERS

Clark, C.W. & Mangel, M. (2000)

Dynamic statevariable models in ecology: methods and applications

.Oxford Series in Ecology and Evolution. OxfordUniversity Press, Oxford. ix + 289 pp, tables,figs, index. Hardback: Price £45.00, ISBN 0-19-512266-6. Paperback: Price £22.50, ISBN 0-19-512267-4.

Clark and Mangel have been the leading pro-ponents of the use of dynamic programmingmodels to address ecological problems. They nowfeel that dynamic state variable models is a bettercollective name, but there is no doubt that, what-ever the technique is called, this has been a verysuccessful tool of behavioural ecologists for closeon two decades. Essentially, it facilitates thesearch for the optimal behaviour of individuals insituations where decision-making is influenced byeither the internal state of the individual or theexternal state of the environment. The book isdescribed as a ‘self-teaching introduction to thetechnique and application’ of this type of model.I would seem to be an ideal potential purchaserof the book: I’ve been using models to addressecological questions for 10 years, have read manypapers that use dynamics programming, but havenever used the technique itself.

The first two chapters describe how the tech-nique works. As well as the mechanics, the authorsare very clear on the type of questions for whichthis is a powerful tool, and the types of questionsfor which other approaches might be equally ormore appropriate. The writing is a little terse inplaces, but very clear and easy to read. The authorsare not shy of mathematical notation, and thereader must be comfortable with understandingmathematical equations. If you are comfortablereading 50% of the theoretical papers of the typethat are published in

Journal of Animal Ecology

or

American Naturalist

, then you’ll have no prob-lems following this book. By the end of these twochapters, I was fully confident that I couldattempt (admittedly with the book to hand) toformulate dynamic state variable models of my own.More importantly, I was certain that another 10

years modelling would not go by without meactually wanting to use this technique for real.

Throughout the book, there is great emphasison the empirical testing of models, and thisaspect is really given its head in chapter 3. Theauthors’ approach is very strong on common senseand is a very gentle (and sometimes humorous)mediation on the usefulness of models (of any sort)to ecologists. As well as good practical advice onmethods, there are many wise words in this chapterthat all modellers (and anyone who wants to talkto a modeller) should read.

After this, the next six chapters each describeapplication of dynamic state variable modelling tovarious questions in ecology. As these are ques-tions that I’m not directly involved with myself,I had the feeling that the first three chapters hadtold me all I needed to know, and these next sixwould be something of a dull trudge. I was verypleasantly surprised. Part of the reason for this isthat the examples are presented in an interestingand easily accessible way, but also because thereis strong emphasis on the general modelling issuesinvolved.

I’d always thought that one drawback todynamic modelling was that it could not be usedto tackle problems where the optimal behaviour ofone individual depends on the behaviour of others.Chapter 10 disabused me of this misunderstand-ing, although it does not gloss over the technicalcomplications required by such problems, andprovides a fair and informative consideration ofgenetic algorithms as an alternative approach tosuch problems. Chapter 11 tackles the interestingidea of modelling learning behaviour and con-sidering the information possessed by an indi-vidual as a state variable. The last chapter, onhow best to describe the fitness of individuals inmodels, I enjoyed least. There is no getting roundit, this is a complex issue, and the authors prob-ably do as well as they could have done to coverthis issue in a very concise way.

In summary, even if you have the earlier bookby these authors (Mangel & Clark 1988), youshould still buy this book. There is very littleoverlap, indeed most of the references in the newbook are to publications from the last five years,

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and I found the new book far more accessible:the design of scientific books has come a long wayin the last decade. There is a recent book with asimilar title by Houston & McNamara (1999),which I would also recommend. However, Isuggest that the two books do not overlap, butrather are complementary, and the tyro especiallywould benefit from reading Clark and Mangelbefore tackling Houston and McNamara. If youwant to use models to answer questions in behavi-oural ecology, or you want to understand suchmodels, or if you just like reading interestingaccounts of good science, then buy this book.

Dr Graeme D. Ruxton

Division of Environmental & Evolutionary Biology, Institute of Biomedical & Life Sciences, University of Glasgow UK

REFERENCES

Houston, A.I. & McNamara, J.M. (1999)

Models ofadaptive behaviour

. Cambridge University Press,Cambridge.

Mangel, M. & Clark, C.W. (1988)

Dynamic model-ling in behavioural ecology

. Princeton UniversityPress, Princeton.

1052001173Library LettersLibrary Letters10.1046/j.1466-822X.2001.00173.xLIBRARY LETTERS100Graphicraft Limited, Hong Kong

DEHORNING DEBATE

Cunningham, C. & Berger, J. (2000)

Horn of dark-ness: rhinos on the edge

. Oxford University Press,Oxford, UK. xiv + 246 pp, index. Hardback:Price £14.95, ISBN 0-19-511113-3. Paperback:Price £9.95. ISBN 0-19-513880-5.

Horn of darkness

takes you to the heart of wildestAfrica. It is written as an adventure story thatdocuments a 3-year study of black rhinos inNamibia. In the process, Cunningham andBerger place their story firmly in context, intro-ducing the complex issues surrounding conserva-tion policy, as well as documenting the feelingsevoked when encountering Africa for the firsttime.

Rhino conservation highlights the difficultiesinvolved in ensuring the sustainable use of resourcesthat are linked to global markets in an inequit-able world, awash with arms. Rhino horn is usedfor traditional dagger handles and Asian medi-cines, and can bring around $4000 to $16 000

per kilo on the black market. The poacher willonly get a fraction of this amount, but even thispaltry share represents a small fortune for theaverage African villager.

Conservation and the need to protect wildplaces arise in a crowded world with a high con-sumption of natural resources. The authors describe,for example, how the focus of much developmentin Namibia involves the exploitation of subterra-nean water which reduces vegetation downstream,thus reducing food, shade, and cover from pre-dators, and forcing rhinos into areas with morehumans, thus increasing their vulnerability.

The stakes are high. Black rhino populationshave declined rapidly from around 60 000 duringthe 1960s to fewer than 2700 today, and these areconfined to fenced reserves and game parks.

In desperation, a programme of dehorningrhinos was introduced in Namibia to render therhinos useless to poachers; however, there was noevidence as to the efficacy of this strategy. It wasnot known whether dehorning affected the abilitiesof mothers to defend their offspring, or theestablishment of dominance and defence of territ-ory. In addition, the rate of horn regrowth wasunknown, thus making it difficult to determinethe required frequency of recapture.

Berger and Cunningham describe their courage-ous attempt to collect the data required to answerthese questions, by comparing the well-protectedhorned rhinos of the Etosha National Park withthe dehorned rhinos of the widely dispersed desertpopulations. This depended on taking photo-graphs of individuals at close range to enabletheir identification, and their accounts of stalkingrhinos make entertaining reading, such as whenlurking at the edge of water-holes at night, dodg-ing hyenas, lions and elephants, and trying not tobe charged by an annoyed rhino.

As the book progresses it becomes clear thatall is not well. The authors acknowledge themethodological difficulties that accompany suchfield studies; however, they honestly felt that theirpreliminary findings, which suggested that dehorn-ing was detrimental, should be published togetherwith the necessary qualifications.

They were surprised to find hostility fromwithin the hard-pressed wildlife department, whohad been annoyed at the use of these findings(without qualifications) by animal rights’ groupsto campaign against dehorning. There was also


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hostility from within NGOs concerned withrhino preservation, who found it easier to raisemoney for tangible, proactive interventions suchas dehorning, rather than the more pedestriananti-poaching patrols.

This book is a candid account of a well-intentioned scientific study. Motivated by thebelief that the science is paramount, the authorsgo about their task with the rugged individualismthat is the norm in their own country. Perhapsunderstandably, they seem continually preoccupiedwith their task and somewhat less empatheticwith their surroundings, both human and natural.It would have been nice, for example, to get ‘underthe skin’ of the rhino and learn more about itsecology.

It also appears that they neglect to nurture theconnections with individuals within governmentand other communities in the country, and as aresult seem to be naively unaware of the sensitiv-ities or implications of their studies for otherparties. But, this makes the story all the morereal. I enjoyed this readable book and wouldrecommend it to students of ecology and con-servation as a demonstration of the complex inter-play of the myriad factors surrounding scienceand policy, as well as to the general public withinterests in Africa and conservation.

Susan Canney

Department of Zoology University of Oxford Oxford, UK


VERSATILE BRACKEN

Taylor, J.A. & Smith, R.T. (eds) (2000)

Brackenfern: toxicity, biology and control. Proceedings ofthe International Bracken Group Conference,Manchester 1999

. International Bracken Group,Aberystwyth. xiii + 218 pp, figs, tables. Paper-back: Price £40.00, ISBN 0-9525505-2-0.

The world traveller may be looking for theunknown, but he can be sure of one thing: onany continent he visits he may encounter brackenfern (

Pteridium aquilinum

). Moreover, when brackenis present in the local flora, there is no way ofmissing it since everywhere in the world brackenwill build dense swards that completely dominatethe vegetation. Bracken has caught the attention

of many scientists worldwide because of thefascinating biology and ecology of the species, andthe problems that bracken causes in the manage-ment of ecosystems and in human and animalhealth. Many ‘brackenologists’ have joined togetherin the International Bracken Group, and theyheld their fourth 5-yearly international brackenconference in Manchester, UK, in July 1999. Acollection of papers presented at the conferencehas been brought together by J.A. Taylor andR.T. Smith, and was published as

Bracken fern:toxicity, biology and control

.This is the fourth book in a row specifically

dealing with bracken. From the titles of previouseditions —

Bracken: ecology, land use and controltechnology

(1986),

Bracken biology and management

(1990), and

Bracken: an environmental issue

(1995)(all by the same editors) — it becomes clear thatthe major interest lies in the identity and controlof the bracken problem. The large-scale deforesta-tion in many parts of the world has releasedbracken from the previous growth suppression byshading of the forest canopy, and in humid oroceanic climates this leads to large-scale spreadand dominance of bracken in the landscape.Persistent bracken clones pose strong limitationsto the biodiversity of ecosystems, and additionallyglobal climate change and air pollution createnew opportunities for bracken, which may furtherincrease the bracken problem. Finally, recentstudies have pointed to the health risk associ-ated with bracken. All these subjects are dealtwith in the various contributions to the book.Unfortunately, however, some of the most inter-esting contributions to the conference, mainlydealing with the ecology of bracken, are notincluded in the book since they were publishedin a special issue of

Annals of Botany

85 (supple-ment B), 2000.

What remains in the book is a potpourri ofstudies on bracken and, unfortunately, only ahandful of contributions really expand our under-standing of this successful species. In my view, themost interesting paper in the book was presentedby John Thomson of the National Herbarium ofNew South Wales in Sydney, and deals with thetaxonomic relationships in the

Pteridium

genus.The taxonomy of bracken has been a hot issueover the last decades.

Pteridium

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use morphological characteristics of the plant tostudy the taxonomy of bracken. Given the veryhigh degree of plasticity and variability of thebracken plant, this has led to a myriad of proposedvarieties. With new DNA techniques that havebecome available, Thomson has evaluated thestatus of most of these varieties and concludesthat a number of varieties can best be regardedas separate species within the genus. In his con-tribution to

Annals of Botany

, this is furthercorroborated by morphological characteristics. Inthe future, this revision of the genus could betaken as a starting point to investigate whetherthese taxa also differentiate in their ecology andbiology.

The long evolutionary history of ferns, and inparticular bracken, has produced a chemicaldefence system that facilitates the persistence ofexisting bracken clones. Previous attention hasbeen focused on allelopathic interactions withother plant species, but this should, in my view, beseen as collateral damage from the anti-herbivorytoxin production. The book provides a numberof novel contributions to our understanding ofthe toxicity of

Pteridium

. Over the years, brackenhas been screened for specific secondary com-pounds that cause serious illness in livestock, andit may be the source of the high incidence ofstomach cancer in regions where bracken isconsumed as a vegetable. This is reviewed byB.L. Smith

et al

. and several studies are presentedon the toxicity of bracken parts or its com-pounds. Fortunately, Siman

et al

. put earlier warn-ings for the carcinogenic properties of spores ofbracken and some other fern species in perspective.They conclude that substantial exposure mayindeed cause health problems, but only at suchhigh spore densities as are likely to occur inhorticultural environments. The low density ofbracken spores in the air should not prevent usfrom passing through the many bracken-dominatedlandscapes in the world.

In conclusion, the book provides a good over-view of the current bracken issues. For in-deptharticles, the reader should refer to the studiespublished in the various scientific journals.

Dr Jan den Ouden

Department of Environmental Sciences Wageningen University The Netherlands


A MIXED BAG OF CONSERVATION BIOLOGY TOOLS

Ferson, S. & Burgman, M. (eds) (2000)

Quantit

-

ative methods for conservation biology

. Springer-Verlag, Heidelberg. xi + 322 pp, figs, tables, index.Hardback: Price £48.00, US$69.95. ISBN 3-540-94322-6.

Conservation biology is a field in which the theoryfrom ecology, genetics, biogeography, economicsand social sciences is combined with the moreapplied fields of wildlife management, forestryand fisheries to address issues in the conservationof natural resources. It emerged as a separatescientific field in the United States during the 1970sand 1980s. The First International Conference onConservation Biology was organized by MichaelSoulé in 1978 and the Society for ConservationBiology was founded in 1985. Courses in conser-vation biology are now offered in universities acrossthe world and there have been more than fivetextbooks on the subject published in the pastfive years.

This book is a collection of 17 independentpapers with a brief preface of a page and a half bythe editors. The chapters cover a range of methodsthat are either being applied to real world manage-ment problems or have the potential to be so.However, as is acknowledged in the preface, andunsurprisingly for a field as broad as conserva-tion biology, an equally wide range of methodsare not covered.

The first four chapters describe statisticalmethods for predicting the status or distributionof species from existing data. Two chaptersdescribe the application of probabilistic methodsfor assessing the risks posed by alien species. Arange of population modelling approaches aredescribed in seven chapters. Three chapters coverthe application of genetics in conservation bio-logy and the final chapter describes mathematicalmethods for designing reserve networks.

The preface identifies within conservation bio-logy a ‘lack of standardized methodologies andunambiguous criteria’, which limits its applica-tion in management decision-making.

Unfortunately, this book does not have anintroductory or synthesizing chapter and there isvery little cross-referencing between chapters.These would have allowed the different methodsto be compared and put into the context of each


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other. Without these the book tends towards adisparate series of case studies, which are lesslikely to lead towards the adoption of the stand-ardized methodologies called for in the preface.For example, three of the chapters in the bookuse relatively simple matrix models and point tothe problems of using complex simulation modelsthat can be difficult to analyse. In contrast, anotherchapter, sandwiched between these, argues for thebenefits of relatively complex individual-basedsimulation models. There is no cross-referencingbetween these four chapters that might help thereader to establish how the different methodsrelate to each other, and to assess which mightbe the more appropriate to address a particularmanagement problem.

The best chapters combine an accessible descrip-tion of quantitative methods, together withexamples of how these can be applied to realworld management problems. For example, DannyLee describes a relatively new tool termed Bayesianbelief networks, and shows how this can be usedto deal with the uncertainty associated with theeffect of management on the population para-meters conventionally used in models to assesspopulation viability. He then demonstrates howthis method can be used to assess the impact ofland use upon a fish species in western NorthAmerica, showing that the outputs are clearenough to be meaningful to managers while alsodisplaying the input probabilities on which they arebased, thus allowing model inputs to be criticallyassessed. Mark Boyce describes the modellingapproach adopted by the International WhalingCommission, putting this in a detailed historicalcontext and critically assessing its implications.Other good chapters investigate the applicationof different methods to the same problem. Forexample, Jane Elith applies five different statisticalmodelling methods to predict the spatial distri-bution of plants, and Hugh Possingham

et al

.compare different mathematical methods foridentifying representative reserve networks.

In contrast to these good chapters I found overhalf of the chapters disappointing. This waseither because the description of the quantitativemethods themselves was inadequate or becausethere was insufficient information given about howthe methods might be used to inform manage-ment decisions. I also found the large amount ofintroductory material, often repeated between

chapters, made it difficult to extract the importantinformation on the quantitative methods beingdescribed.

There is an almost bewildering complexity ofdifferent methods being developed in conserva-tion biology and already used to inform decisionsin the management of natural resources. Whilstparticular management problems may require anindividually tailored approach, the developmentof a standardized toolbox of accessible approacheswould be advantageous in allowing an increasedunderstanding and likelihood of application inthe management community. Some of the methodsdescribed in this volume may have a place in sucha toolbox. However, to facilitate the choice of themost appropriate method for a given manage-ment problem, a greater effort will be required inthe description and comparison of alternativeapproaches.

Andy South

Department of Zoology University of Oxford Oxford, UK


MEMOIRS OF A GREEN CENTURION

Laurance, W. (2000)

Stinging trees and wait-a-whiles:confessions of a rainforest biologist

. University ofChicago Press, Chicago. x + 196 pp, black andwhite and colour photographs. Hardback: price£16.00, US$25.00, ISBN 0-226-46896-8.

I must confess that I was hesitant about acceptingthe offer to

critically

review William Laurance’sbook

Stinging trees and wait-a-whiles

because itwas subtitled

confessions of a rainforest biologist

.Would there be embarrassing personal revelationsfrom a scientist whose work I much admire? Orwould the embroidering of the professional withthe personal be a ruse to make some post-modernpoint about the abject failure of the ecologicalproject? No, the book proved to be a well written,scientifically interesting and an entertaining ‘goodread’ describing experiences during a physicallydemanding field programme associated with aconservation biology PhD research project intothe effect of rainforest fragmentation on mammals.It is set in far north Queensland during anintense conservation–development conflict in whichLaurance become involved. The book is clearly

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pitched for the folks back home in the seat of theAmerican empire, with a narrative structure andendearing naivety akin to a Hollywood movie.

No doubt the text will stimulate some under-graduates to tunnel their way out of the academicprison so that they too can get first-hand experi-ence of the wonders of the tropical rainforests.No doubt, it will make older generations of fieldbiologists have pangs of nostalgia as they recallthose wonderful times before their lives becamecrowded with thankless responsibilities and theirbodies accumulated annoying defects like a second-hand car. It will also probably panic a few pro-fessors who, putting aside their own youthfulmisdemeanours, will pause to reflect on whattheir graduate students, drunk with youth, mightbe getting up to in the course of the tropical fieldprogrammes. However, one of the confusing thingsabout globalization is that such cultural products arenow much more likely to be read and interpretedby others with fundamentally different frames ofreference. For example, I suspect that the bookwill be of interest to philosophers of science, for herea first-world scientist gives us a behind-the-scenesglimpse of the production of tropical ecology.

Because the narrative tension hinges on theultimate triumph of particular cultural and envir-onmental values in a conservation–developmentconflict, the book raises a number of questionsconcerning the practice and ethical basis of eco-logical research. Who owns biodiversity? Shouldfield ecologists from foreign countries becomeactivity engaged in local political debates? Shouldresearchers become emotionally and sociallyinvolved with their host communities during theirsojourns? Should building community supportand thereby developing an appreciation of thelocal historical and cultural milieu be a criticalfirst-step of any research project? These ethicalquestions now dog anthropologists but have, todate, received little attention amongst ecologists.

Laurance and his enthusiastic team of, largelynon-Australian, volunteers felt they were ‘havinga positive role’ in the conservation debate becausethey ‘were right in the epicentre of the conflict’and were making a pro-conservation messageheard. Despite local opposition, and the fact theywere often working on private property, theydetermined that they wouldn’t ‘be badgered’ intostopping doing something they ‘really believedin’. Therefore, they decided to continued their

conservation activities and ‘damn the torpedoes’(p. 138). In some tropical countries, and possibleeven in rural America, this attitude would be farmore dangerous than the small town hostilitythey were subjected to in Anglo-northern Aus-tralia during the 1980s. Although I really enjoyedthis book, at a deeper level I was left feeling thatthe practice of tropical ecology is much morecomplex socially than youthful fun and games.

David Bowman

Key Centre for Tropical Wildlife Management Northern Territory University Australia


A BRAVE TRY

Tenhunen, J.D. & Kabat, P. (eds) (1999)

Integrat-ing hydrology, ecosystem dynamics, and biogeo-chemistry in complex landscapes

. John Wiley &Sons, Chichester, UK. xv + 367 pp, figs, tables,photos, subject and author indexes. Hardback:Price £80.00, ISBN 0-471-98474-4.

Covers and titles are not a good basis for judginga book. Sometimes though, such things seemdesigned to stoke up expectation for the potentialreader and so cannot be completely ignored. Here,both promise great things. The ‘cosmic’ cover imagemay well be familiar: it is a sixteenth-centuryGerman woodcut used by folk as various asnineteenth-century French astronomer CamilleFlammarion and 1970s rock group ‘The Strawbs’.The title is no less all-embracing. It begins withthe ‘I-word’, lists three distinct disciplines, andends with a nod to cutting-edge work on complexdynamic systems. Small wonder that I approachedthis review with excitement!

Sadly, however, I was disappointed. ‘Under-promise, but overdeliver’ is a widely used phrasein business; the editors and publishers of thisbook have contrived to do the reverse. To be fair,the odds were stacked against them, since it is noeasy thing to build convincing bridges betweenthe speciated islands of scientific endeavour.

This is a report in the Dahlem Workshop series,and summarizes a meeting held in 1998. In the 17chapters by 39 authors from 11 countries, issues ofscale-crossing (as one might expect) loom large.Indeed, the book’s central theme is the recognitionthat there are complex linkages between ecosystems


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and processes in real landscapes; and since theseecosystems and processes are likely to have theirbeing at different time- and space-scales, a focuson only a single spatial scale (e.g. a plot) or a singletemporal scale (e.g. seasonal) cannot hope tocapture these linkages.

The first half of the book concentrates onremote sensing and the challenges of upscalingand downscaling. In an introductory chapter, thereis an interesting criticism of the IGBP transectsas having been designed too much from a top-downperspective, with emphasis on upscaling frompoint measurements to large regions. It was alsofascinating to me as a geomorphologist to read acritique of the way in which ecology has devel-oped: it was with a deepening sense of déjà vuthat I read of early ecological work (in the 19thcentury and first half of the 20th century) ashaving a landscape-oriented focus, with more recentwork shifting toward an emphasis on mechanismsand processes. The following chapters (includingone group report) were, for me, most useful inproviding an overview of the kinds of data whichare to be expected from the next generation ofremote sensing tools, and of the likely difficultiesof integrating these data into models at a varietyof scales.

It is only from around p. 177 onward that thebook really moves on to interactions betweencomponents of the complex landscape. The intro-ductory group-written chapter to this secondsection quickly brings in notions of linear andnonlinear feedbacks, hierarchy theory, and finallyemergent responses from self-organising complexsystems. A particularly interesting (but too short)section focuses on issues of model predictabilityand limits to model validation for such systems,

including GCMs. (To gain the most from thisdiscussion the reader would need to have somebackground in complex dynamic systems.) This isall excellent stuff, but there is one issue in par-ticular that could have been tackled in a bit moredepth here. Just what is meant by a complexlandscape? In other words, in what circumstanceswill the more ‘traditional’ single-scale approachsuffice, and in what circumstances does the morecomplicated, costly and harder-to-understand multi-scale approach become essential? It seems thatsomething more than ‘I know it when I see it’ (asin art appreciation or pornography) is needed fora definition of complex landscapes, yet that is allthat is really offered here.

Subsequent chapters (including another group-written one) consider separate aspects of landscapefunctioning: hydrology, sediment and nutrienttransport, and landscape fragmentation. The finalgroup-composed chapter attempts to bring all thistogether, and also introduces some interestingideas for applying recent developments in soft-ware engineering to modelling the interactions in acomplex landscape.

Overall, I am left with a feeling that this meetingcould have achieved more, since the group-writtenchapters were almost always richer than the othercontributions but were often too short and insuffi-ciently developed. Taken as a whole, the bookfailed to create a sense of anything really new,either in the way of conclusions or suggestions forthe way forward. Given the difficulty of its self-settask, however, this is hardly surprising. A brave try.

David Favis-Mortlock

School of Geography Queen’s University, Belfast


calling all timid potential modellers

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