Freshwater fisheries conservation can increase biodiversity

program) matter for the success of this program, suggesting that better targeting of participat- ing villages may further improve its impact. We conclude with three comments. Firstly, we note that these conclusions are based on a matching design, implemented in a relatively data poor environment. Although we don’t disagree with [15] that there is scope for a larger number of randomized control trials in the evaluation of environmental programs, we also suggest that this approach exemplifies the progress that can be made in their absence [27]. That said, the utility of non-experimental approaches will likely be increased if the evaluation of the impact of a project or program is included from its inception. Secondly, this article raises the need to clarify the potentially multiple mechanisms through which conservation may impact on biodiversity, a relatively unexplored area of research [38, 39]. Our data suggests that there is substantial heterogeneity in terms of the rules that are implemented in the process of changing fisheries management. Although we have some guid- ance regarding which design principles may matter (characteristics of the resource, monitor- ing, punishment rules, . . .), building on Ostrom’s Socio-Ecological Systems (SES) approach [40], its inherent complexity makes it exceedingly difficult to identify which ones can be understood as essential, particularly in the context of a participatory approach such as the one that underlies ComFishII. This is a clearly important area of future research, with well under-

stood policy implications if one is to “move beyond panaceas” [41, 42], but one that likely requires a larger sample size than what we have available. Finally, it is perhaps useful to emphasize that, before their wider adoption, FCZ were built on indigenous knowledge of species’ biology and reproduction, the importance of seasonal variation in their habitat and the local importance of spillovers (ie, the increase in fish biomass in areas where fishing is allowed) [11]. Their initial endogenous development likely reflects reliance on local fisheries as a source of protein and micronutrients in the local diet [21, 43, 44]. Such dependency is not unique of Lao PDR, and also characterizes other developing coun- tries [45]. More generally, our analysis provides some encouragement to optimistic views of the relation between poverty reduction and biodiversity conservation [46, 47] that emphasize that the disproportionate reliance of the poor on ecosystem services raises the possibility of synergies between the two objectives [48, 49]. The promise of sustainable development [46, 50] rests on finding ways to identity and achieve such win-win outcomes. That requires to causally establish the links (or lack of) between ecological outcomes, the ecosystem services that potentially flow from them and human outcomes, as they likely drive the continued interest in such conservation initiatives at local level. Even when such analysis is driven by methodological concerns that are similar to those that guide this article, those extra steps bring additional layers of complexity and data

requirements—in our case, from establishing the link from freshwater biodiversity to fishing yield [51] and possibly diet variety, to understanding the overall impact of such changes on resource dependent livelihoods [52]—that may also require better integration between social and physical sciences [53]. Supporting information S1 Appendix. List of fish species & additional results. (PDF) Acknowledgments We thank all respondents for their time, and to Jorge Dresdner Cid, Terry Warren and Agus- tin Perez-Barahona for comments to earlier drafts of this work. PLOS ONE FCZ and biodiversity PLOS ONE | https://doi.org/10.1371/journal.pone.0233775 May 27, 2020 11 / 14