Net Carbon Exchange in US Crop Production (IMAGE) DOE/Pacific Northwest National Laboratory Caption Based on US crop production, scientists determined which American regions are carbon sinks, or those that take in more carbon than release it, and carbon sources, or those that release more carbon than they take in. Their calculations showed that the most agriculturally active regions, shown in blue, are carbon sinks while the regions with larger populations, shown in red, are carbon sources. Credit PNNL Usage Restrictions Credit to PNNL License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.