When is a wetland a sink and when is a wetland a source?

That is the question an international team of researchers set out to answer in a new study published online March 23 in the Proceedings of the National Academy of Sciences. Ankur Desai, professor of atmospheric and oceanic sciences at the University of Wisconsin-Madison, is one of just a few American scientists involved.

Wetlands both absorb carbon dioxide and emit methane, and scientists have long sought how to balance the two in the global greenhouse gas budget — particularly as humans change these natural ecosystems. The study presents real-world data useful to land managers, policymakers, climate scientists and others interested in the potential for wetlands to increase the effects of climate change or as part of the toolkit to combat it.