When the going gets tough... - Wageningen UR

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sciencePHOTO: GUY ACKERMANSThousands of ecologists the worldover use Cajo ter Braak’s statisticalanalysis model Canoco to processtheir research data. At the end ofJanuary he presented the latestversion of his software: Canoco 5.Even researchers with littleknowledge of statistics can workwith this version.So what does Canoco doexactly? An example. If you want tostudy the negative impact ofpesticides on aquatic life, you willoften be dealing with an ecosystemwith at least 200 species in it. Thatmeans 200 graphs plotting theeffect the poison has on all thelittle water creatures. And that isnot what you want; you want anoverview of the response of all thecreatures at a glance. And you canonly get that with Canoco, saysecotoxicologist Paul van den Brink.He uses the relevant method inCanoco, and indeed helpeddevelop it, as a longstand ingcolleague of Cajo ter Braak’s.Ter Braak, who works at PRIBiometris, laid the foundations forthis software package back in thenineteen nineties. His publicationfrom 1986, in which he combinesseveral methods of statisticalanalysis with the prototype forCanoco, unleashed a revolution inthe processing of research data.Together with Czech researcherPetr Šmilauer, he went on todevelop better and more advancedversions of Canoco. Thousands ofscientists make use of Ter Braak’ssoftware, witness the 4,000licenses sold for it. In the EU,Canoco has become a fixture forthe analysis of certain complexdatasets. And the analysis modelturns up in countless scientificarticles, making Ter Braak, withabout 27,000 citations, the mostcited Wageningen scientist.Nevertheless, previous versions ofCanoco – up to version 4.5 – wereby no means child’s play to use.For the connoisseurs: it was basedon canonical correspondenceanalysis – hence Canoco – whichTer Braak combined with a handfulof other statistical methods.‘You don’t just get that under yourbelt on a Monday morning; it takesyou a week to get to grips with thebasics of Canoco,’ says Van denBrink. ‘But after that you can dosomething other people can’t do.’Van den Brink loses thatadvantage now, because Canoco 5is considerably more user-friendly.Where researchers used to have tocall on Ter Braak to advise them ona regular basis, the Canoco Advisercan do that job now. The digitaladviser evaluates the researchdata, chooses suitable analysismethods and tests the researchoutcomes, complete with areliability check. ‘You no longerneed to be an expert to be able touse the software,’ says Ter Braak.Canoco has come of age, ‘and I amits grandfather.’ In recent years,the programming has been doneby Šmilauer, with Ter Braakchecking his work and helping towrite the new manual.And what is the grandfather ofCanoco doing now? Solving crosswords?No: he has been workingon genetic algorithms for yearswith the aim of extracting informationfrom vast and complex datasets.Using the Markov Chain MonteCarlo version of an algorithm,with the aid of Bayesian theory. Ah,yes of course. ASWhen modern life clashes with traditionin Africa, the number of accusationsof witchcraft increases,suggests research in Sierra Leone.A team of Wageningen developmenteconomists and anthropologistspublished their findings in theJanuary edition of African Affairs.The researchers worked in anarea in which small villages havetraditionally been the fiefdoms ofpolygamous ‘big men’ who alsoowned most of the land. Othermen worked on the land – formerlyas slaves and later as a punishmentor as a service to be rewardedafter about 10 years with marriageto one of the chief’s daughters.The arrival of the market economyoffers these ‘marginal’ men an escaperoute. They become wage labourerson plantations or theygrow cash crops, which leaves thebig men with less free labour attheir disposal.In villages where the marketeconomy clashed with the old patriarchy,there were more accusationsof witchcraft and witch doctorswere consulted more often. Invillages where one set of values wasdominant – whether the traditionalor the market-oriented one –these things happened less often.The study does not offer an explanationof the phenomenon. Inthe literature the researchers encounteredtwo hypotheses: traditionalistsuse old customs to discouragethe pioneers, or these pioneersresort to accusations ofwitchcraft because they feel guiltytowards the community. RRRESOURCE — 31 January 2013
Dolf Weijers is thrilled to bits. Besidesbeing a successful plant scientist, he isalso the best teacher in Wageningenthis year. The jury praised his enthudiscussion
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