Neon Regions (image) University of Washington Share Print E-Mail Caption The study divided the mainland US into the 18 ecological regions shown in this map. The strongest response seen in models was for tree loss in the Pacific Southwest (PS) region, shown in light brown, which covers most of California. Credit National Ecological Observatory Network Usage Restrictions With credit Share Print E-Mail 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.