South African Savanna (image) North Carolina State University Caption A single global model can't predict savanna tree density as well as continent-specific models, according to research published in Science this week. Photo of a South African savanna courtesy of Dr. William Hoffmann, a co-author of the study. Credit Dr. William Hoffmann, NC State University Usage Restrictions None 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.