Mapping literature reviews on coral health: a review map, critical appraisal and bibliometric analysis.
The state of coral reefs has been of great concern, as documented in the growing amount of primary literature. These reports on coral health have accumulated, resulting in reviews of the primary studies (i.e. secondary literature). Recently, such reviews have also accumulated, creating an opportunity to review the secondary literature. Second-order syntheses (reviews of secondary literature) provide an overview of the field, which can be used to guide future research. Based on our previously published protocol, we compiled peer-reviewed secondary literature on coral health from Scopus and Web of Science databases. We synthesised 335 secondary literature papers on coral health, 35 of which underwent critical appraisal and 333 of which also underwent bibliometric analysis. The secondary literature consisted primarily of qualitative reviews (78%). Over 80% of papers stated informing coral conservation as the review's purpose. Climate change (50%) and coral resilience (42%) were the most studied topics, and bioerosion was the least (3.6%). Critically appraised papers scored poorly on Collaboration for Environmental Evidence Synthesis Assessment Tool criteria (studies did not meet standards 55% of the time). The authors of the secondary literature were highly interconnected (with 30% of the authors having more than 15 coauthors within our dataset) and included authors from countries with coral reefs (predominantly in Australia and USA; 79% of papers). The secondary literature on coral health had a median Altmetric score of 5.27. We have revealed key gaps in coral health topics for further review (e.g. coral range shifts and microbial biodiversity), particularly when considering conservation policy. Incorporating research in policy could be improved through greater research accessibility and continuing to gather public interest in coral reefs. We further recommend broadening research collaborations to include even more researchers from countries with coral reefs (e.g. Maldives). Finally, the secondary literature on coral health needs better reporting transparency (e.g. publishing code). Our second-order synthesis is timely, pushing coral health research in a new direction-one which produces research of higher quality, collaboration, and efficiency. As coral reefs decline, we should also aim to rebuild public trust in research and strengthen the evidence base for conservation.