Carbon cycling (IMAGE) Proceedings of the National Academy of Sciences Caption Carbon cycling when land transitioning out of agriculture is reforested (left), or converted to switchgrass cultivation for producing carbon-negative biofuels (right). Credit Image credit: John Field. Usage Restrictions None 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.