Systematic reviews for environmental science & ecology: Home

A systematic review is just one type of evidence synthesis and typically precedes a meta-analysis.  This form of research is well established in the health sciences, and is gaining traction in ecology and other disciplines. This guide presents an overview of the process.

A systematic review starts with a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the studies that are included in the review. A meta-analysis analyzes and summarizes the results of the studies included in a systematic review.  

In preparing a systematic review, you will:

• Formulate your question in advance.  This will help you determine whether the evidence is relevant to your question.  Ideally, you will use a question framework such as PICO- (Population/People/Problem, Intervention/exposure, Comparison, Outcome).   

• Define your inclusion and exclusion criteria to set parameters for evidence synthesis, e.g. date, geographic location, participants, type of publication, etc.

• Decide which information sources (databases) you will be using, and prepare your full search strategy or search string(s). Save details of your search terms and process to include that as a supplement to your study so others can reproduce it.  

• Plan how you will collect, organize, and manage your references as you gather them.  What citation management software or other tools are being used? 

• Designate who will pre-screen the studies, and who will review studies for eligibility and inclusion in data collection  

• Describe the method of coding and extracting data from the selected studies and process of  obtaining or gathering data from sources or researchers

• If this is a meta-analysis, decide how data will be synthesized, the methods of handling data and combining data from studies, and resolving data consistency issues

These steps will help you develop a protocol.  Read more about protocol development and registries under  >  Develop and register a protocol

Other types of evidence synthesis include scoping reviews and meta-analyses.  Here are a couple additional resources about those,

Koricheva et al. 2013. Handbook of Meta-Analysis in Ecology and Evolution.

Hilary Arksey & Lisa O'Malley (2005) Scoping studies: towards a methodological framework, International Journal of Social Research Methodology, 8:1, 19-32.

Andrea C. Tricco, PhD, MSc, Erin Lillie, MSc, Wasifa Zarin, MPH, et al (2018) PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation, Annals of Internal Medicine, doi.org/10.7326/M18-0850

• Cornell University Library Guide to Evidence Synthesis
• Zotero library of evidence synthesis articles 
• Four principles of good evidence synthesis (Royal Society)
• Campbell Collaboration evidence portals collection of evidence portals in all disciplines

Contact the Cary Institute Library.