Harnessing local ecological knowledge for conservation decision making via Wisdom of Crowds: the case of the Manus green tree snail Papustyla pulcherrima N ATHAN W HITMORE Abstract The shell of the Manus green tree snail Papustyla conservation intervention (e.g. Weitzman, ; Bottrill pulcherrima is renowned for its beauty and is subject to et al., ; Wilson et al., ). Implicit in such methods international protection under CITES, having been har- is an understanding of the level of crisis and the related dri- vested intensively in the past. To determine its threat status, vers affecting the species in question. However, such threat and whether further conservation action is justified, an in- assessments incur costs, and in the case of poorly under- expensive Wisdom of Crowds approach was used to esti- stood or cryptic species, such as invertebrates, the cost of mate the change in relative density of the snail between even a superficial in situ assessment may exceed the funding and . Local men and women were approached available. around the main market on Manus Island, Papua New Species-specific conservation programmes predominantly Guinea, and asked to map the relative abundance of the target vertebrates, with only a small fraction of the available snail on an ordinal scale, based on their personal observa- funding being assigned to invertebrate conservation (Lydeard tions in and (a year of cultural significance). et al., ; Cardoso et al., ). Whereas most vertebrates The spatial abundance data from surveys were analysed have been categorized on the IUCN Red List (IUCN, ), using an information-theoretic approach. A suite of cumu- , .% of all described arthropods and , % of all described lative link models incorporating geographical factors was molluscs have been categorized (Cardoso et al., ). Given used to determine the magnitude of the change and to inves- the scarcity of funding for invertebrate conservation, there is a tigate possible biological influences underpinning the re- need to allocate available funds in a prudent manner. ported pattern. High abundance of the snail was Researchers, especially in fisheries, are recognizing the associated with intact forested areas, high elevation and potential of local ecological knowledge to address knowl- low population density. A slow decline was evident, with edge gaps regarding the status of natural resources and the median percentage of map cells where the snail was ca- their management (e.g. Dulvy & Polunin, ; Sáenz– tegorized as plentiful decreasing by c. % between the Arroyo et al., ; Arlinghaus & Krause, ; Cano & years. On this basis a categorization of Near Threatened Tellería, ). Assessing such knowledge using a Wisdom was advocated for the species. Although it is arguable that of Crowds methodology is one potential way to produce Wisdom of Crowds methods cannot be substituted for in cost-efficient estimates for threat status assignment and tri- situ quantification, the approach appears to have utility as age assessments. Wisdom of Crowds is a mechanism by a preliminary assessment for further conservation expend- which the aggregated knowledge of a large number of indi- iture, and as a tool for determining threat status. viduals is used to generate quantitative estimates. It was de- monstrated over a century ago by Francis Galton (Galton, Keywords Cumulative link model, Data Deficient, decision ), and popularized as a named concept by Surowiecki making, local ecological knowledge, Papustyla pulcherrima, (). By aggregating information from a large sample threat status, triage, Wisdom of Crowds population the idiosyncratic noise of individuals is dimin- ished (Welsh, ). Often the resulting estimate, including those of quantity estimation and spatial reasoning, has been shown to be surprisingly accurate (Galton, ; Surowiecki, Introduction ; Arlinghaus & Krause, ). uring the past decades increasing attention has been Surowiecki () outlined four basic criteria for Wisdom Dgiven to triage methods to prioritize species for of Crowds, which can be summarized as () diversity of opin- ion (i.e. individual interpretations are not censored), () inde- pendence (i.e. the opinion of an individual is not influenced NATHAN WHITMORE Wildlife Conservation Society, Papua New Guinea by others), () decentralization (i.e. individuals are able to Programme, P.O. Box 277, Goroka, Eastern Highlands Province, Papua New Guinea. E-mail [email protected] draw conclusions based on their local knowledge), and () ag- Received November . Revision requested March . gregation (i.e. there is a mechanism for translating private Accepted April . judgements into a collective estimate). Oryx, Page 1 of 9 © 2015 Fauna & Flora International doi:10.1017/S0030605315000526 http://journals.cambridge.org Downloaded: 26 Jan 2016 IP address: 69.74.254.25 2 N. Whitmore Although the application of the methodology is relatively Methods new, Wisdom of Crowds is being investigated in a variety of fields, including politics (e.g. Bosler & Schneider, ), eco- NW and four community facilitators (local Manusian staff nomics (Nofer & Hinz, ), computer science (e.g. trained in community engagement and conservation) sur- Welinder et al., ) and sociology (Lorenz et al., ). veyed adult market-goers, stall holders and local residents Although it has been proposed as a mechanism to assist at random during – September (in a manner in the management of fisheries in data-poor situations accordance with the ethical standards of the British (Arlinghaus & Krause, ), it has yet to become an estab- Sociological Association). The survey began days after lished research method underpinning conservation and Papua New Guinea Independence Day, and market activity natural resource management initiatives. appeared to be typical over the survey period. The Manus green tree snail Papustyla pulcherrima is a Each respondent was given two maps of Manus Island forest-dwelling arboreal snail found only on Manus and adjacent islands, overlain with an indexed grid of Island, a , km densely forested island to the north of , -km map cells marked with village aid posts, town- Papua New Guinea. Its conical, emerald green shell, with ships and roads. Respondents were asked to mark map cells a fine yellow border to the whorl, and a white lip, attains a in which they had observed and were confident of the abun- maximum length of cm and is renowned for its beauty dance of Manus green tree snails, using a five-point ordinal (Pitman, ). After the snail’s existence was popularized scale: () not found, () previously found but now absent, () internationally in the s demand for its shell grew, par- scarce, () moderate numbers, () plentiful. Community fa- ticularly for jewellery, which resulted in the export of large cilitators assisted with interpretation of the map and com- numbers of shells, and concerns about possible extinction of pletion of a form. On one map respondents recorded their the species (Pitman, ). This resulted in the snail being observations of snail distribution and abundance in , the first invertebrate to be listed on the Endangered and on the other they recorded the same information Species Act of (U.S. Government, ). International based on their recollections from (the World Sea trade has been controlled by export permit since under Kayaking Championships were held at Manus Island in CITES Appendix II (UNEP–WCMC, ) but the snail still , and therefore this year had special significance in faces potential threats from overexploitation for legal do- local memory). Only respondents that were years or mestic trade (with the shells used for adornment), and habi- older in were asked to complete the map. Sites tat loss (Shearman et al., , estimated that c. % of the of known extinction were differentiated from sites of natural forest on Manus Island had been cleared or degraded during absence (e.g. because of habitat preference), but for pur- –). As of May the snail was still categorized as poses of modelling between years a single category repre- Data Deficient on the IUCN Red List (Mollusc Specialist senting absence was used. Unless the surveyor understood Group, ), with its extinction risk unclear. the local language of the respondent (there are indigen- The majority of resident Manusians are indigenous and ous languages spoken in Manus Province) interviews were retain a subsistence lifestyle (Hide et al., ), and thus re- conducted in Tok Pisin. present a repository of local ecological knowledge. The ob- Name, age, sex and home village were recorded for each jective of this study was to utilize a Wisdom of Crowds respondent, as well as the name of the snail in their local lan- approach to local ecological knowledge to ascertain tem- guage. All maps were checked for mistakes associated with poral changes in the distribution and relative abundance duplication (for people with the same name), age threshold, of the Manus green tree snail, assess the need for further and form-filling, and indications of influence or interfer- conservation efforts, and explore the utility of the Wisdom ence by a third party. There is no recommended threshold of Crowds technique. for the sample size required for Wisdom of Crowds methods but basic principles suggest that the sample should be suffi- ciently large to diminish idiosyncratic noise. I estimated we would need a minimum sample size of respondents, and Study area aimed to maximize the sample within the constraints of our The study took place in Lorengau, the provincial capital of budget. We conducted