MAB was officially launched by UNESCO in 1970. This network of protected reserves is samples of the world's major ecosystem types, which are devoted to conservation of nature and scientific research. They provide a standard against which man's impact on the environment can be measured. SERS was selected as the Thailand MAB site because it offered the unique opportunity to understand the characteristics of a dry-evergreen forest, a dry-dipterocarp forest and the changes which people have imposed on the natural ecosystems.