Quality of meta‐analyses in freshwater ecology: A systematic review

Given the increasing use of systematic reviews and meta‐analyses in ecology, their protocols should be closely followed to ensure quality. Several checklists are available to guide researchers towards a high‐quality meta‐analytic study. Freshwater ecology studies have a tradition of using experimental studies, which provide the ideal data to test hypotheses using meta‐analysis. Here, we evaluated the quality of 114 meta‐analyses in freshwater ecology and 86 meta‐analyses in ecology and evolution for comparative purposes. We found that many studies are still using the term meta‐analysis incorrectly and that this error persisted over time. The quality of the studies that did conduct a formal meta‐analysis has improved. Thus, we speculate that available guidelines are being effective in improving the quality of meta‐analytic studies. Quality was not associated with the impact factor of the journal where the meta‐analyses were published or with the average number of citations. In addition to the incorrect use of the term, we found that many studies failed to: report heterogeneity statistics, evaluate temporal changes in effect size, conduct publication bias analyses, address the collinearity among moderators, and provide the data. In general, meta‐analyses in ecology and evolution have only a slightly better average score than meta‐analyses in freshwater ecology. Although the quality of meta‐analyses in freshwater ecology has improved over time, there is much room for improvement. Authors should not label their studies as meta‐analyses if these methods were not used. Compliance with checklists should be widely fostered as meta‐analyses are increasingly being used to summarise findings in different areas of ecology. Authors, reviewers, and editors should use checklists to improve the quality of meta‐analyses in freshwater ecology.