Can systematic reviews facilitate the communication of scientific uncertainty?

Communicating uncertainty is one of the major challenges scientists face when disseminating experimental results, not only to audiences of nonscientists, but also to other scientists. Uncertainty is multifaceted and takes on different meanings in different fields, and its communication operates on the background of complex science–society relationships. However, clear and responsible communication of uncertainty is necessary to adequately present results to the scientific community, for policy making, and for public engagement, which, in turn, may influence policy. “Indeed, the credibility of scientific findings may depend on how uncertainty is depicted, starting at the level of individual research articles.” The natural response of our society to uncertainty is the attempt to wipe it out. However, uncertainty cannot be wiped out; it can only, at times, be minimized. For nonscientists, the most common misunderstanding about science is that scientists aim to prove or disprove hypotheses and, in doing so, find truth. If truth is not found, and we are left with uncertainty, then it seems that scientists have somewhat failed. Therefore, efforts should be made to clearly represent science as an extended process of discovery, based on a making and testing of ever-evolving models or hypotheses, which requires continuous refinement. Although this process underlines the scientist's mind-set, it needs to be spelled out for the nonscientist. Then, uncertainty becomes easily integrated in a research article and could be addressed without compromising credibility. Uncertainty is routinely evaluated in the context of studies that rely on mathematical and statistical models, notably climate change. However, in other fields, it may or may not be weighed and may take on different nuances. In ecotoxicology, uncertainty typically relates to the assessment of chemical risks and is addressed with the use of a conservative approach, based on the so-called “safety” or “uncertainty” factors (Chapman et al. 2009). A more generally applicable approach to uncertainty should take into account not only “how well something is known,” but also “what is known in relation to what we wish to know.” Thus, research articles should provide the appropriate perspective or comprehensive picture of the current status of knowledge, clearly explaining what is known, what is unknown, where the gaps in knowledge are, and what the study adds to the refinement process within that specific context. In many instances, scientists inadequately formulate the research problem, excessively relying on “little is known,” “there is paucity of data,” or comparable phrases, followed by a few pertinent examples. Similarly, the conclusions do not always highlight a clearly defined and continuous discovery–refinement process, and they sometimes contain frivolous overgeneralizations. In view of the staggering number of research papers and the pace at which they are published, providing a complete and clearly defined context while pinpointing the refinements in question may appear, in some cases, daunting. Systematic reviews, followed when appropriate by metaanalyses, might help. They are based on standardized methodologies for aggregating and analyzing studies, and they allow the evaluation of the best available evidence (Haddaway and Bilotta 2016). Systematic reviews have been successfully used for years in medicine and health-related sciences, but although gradually increasing in popularity, they are still sparse in other areas, including ecotoxicology (Attanasio 2017). They are based on a specific research question, problem formulation, or hypothesis, and on a well-defined, structured, and rigorous process that is transparent, accountable, replicable, and updatable. A major aspect of this evidence-based approach is the comprehensiveness of the literature search carried out to identify the primary research articles to be analyzed. The search is expected to rely on multiple databases, include both electronic and print sources, and sometimes articles published in languages other than English. Studies to be included in the review are then selected on the basis of specific criteria, for example, absence of biases, appropriateness of research design and sample size, and data analysis methods. Thus, using the same criteria, each individual study receives a critical appraisal, which should be built on the basis of healthy skepticism. A systematic review includes a thematic synthesis, or qualitative combined analysis of the selected studies, and in many cases also a quantitative analysis (metaanalysis). The thematic synthesis addresses, among other factors, consistency across different studies, reasons for differing results, causes of a given outcome, and limitations of current knowledge. Although systematic reviews and metaanalysis are themselves sampling procedures and therefore subjected to random effects, they tone down the rapid production of predictable results, while encouraging innovative research that is useful to society. Systematic reviews are now being actively solicited in toxicology (Wikoff and Miller 2018), although available frameworks and guidance tailored to evidence-based toxicology are not as extensive as those available for health-related sciences. Analyzable studies in toxicology and ecotoxicology are extremely heterogeneous (e.g., in terms of animal models and in vitro experimental systems). Such heterogeneity poses a challenge to the evidence-based approach because it results in aggregation of studies that are very different. However, once a systematic review is completed, it can be subsequently updated, maintaining the currently published framework, and then used to provide context to many successive studies. Thus, despite some drawbacks due to the complexity of the evidence-based approach, uncertainty communication in toxicology and ecotoxicology is posed to benefit from the advancement of systematic reviews in these fields. Paradoxically, a so-called “evidence-based approach” may lead to an improved representation of uncertainty. It should be pointed out that, as scientists become familiar with the evidence-based framework for the evaluation of data quality and relevance, these elements will be addressed more frequently and comprehensively in primary research articles, therefore providing additional basis for the positioning of uncertainty in their conclusions. Such positioning should also take into consideration the so-called “uncertainty frames,” which are expected to be differentially used to ensure readers are able to perceive uncertainty in the same way that experts intended to communicate it (Guillaume et al. 2017). In the final analysis, the way uncertainty is presented in individual research articles may provide the blueprint for how it will be communicated to audiences of nonscientists, and may therefore modulate decision making. Roberta Attanasio Senior Editor, Integrated Environmental Assessment and Management Georgia State University, Atlanta, Georgia, USA