Final answer:
The characteristic of the western side of the Rift Valley, according to Coppens, is a dry climate with open savanna and few forests.
Step-by-step explanation:
The characteristic of the western side of the Rift Valley, according to Coppens, is a dry climate with open savanna and few forests. The erosion patterns of the highlands in the western side of the Rift Valley have caused a buildup of sediments on the rift valley floor, creating a favorable environment for the preservation of biological remains, including both human and animal remains.