This type of evidence is not as strong as the causal demonstration that manipulative experiments can provide, but often a natural experiment is the only feasible approach. Because many questions in environmental science are complex and exist on large scales, they must be addressed with correlative data. As such, environmental scientists cannot always provide black-and-white answers to questions from policymakers and the public.


Nonetheless, good correlative studies can make for very strong science, and they preserve the real-world complexity that manipulative experiments often sacrifice. Whenever possible, scientists try to integrate natural experiments and manipulative experiments to gain the advantages of each. Scientific research takes place within the context of a community of peers. To have impact, a researcher’s work must be published and made accessible to this community. When a researcher’s work is complete and the results are analyzed, he or she writes up the findings and submits them to a journal (a scholarly publication in which scientists share their work).


The journal’s editor asks several other scientists who specialize in the subject area to examine the manuscript, provide comments and criticism (generally anonymously), and judge whether the work merits publication in the journal. This procedure, known as peer review, is an essential part of the scientific process.