It shall be the duty of the Department of Conservation and Natural Resources as to all unused lands owned by the State of Alabama or any institution or department thereof to determine the best use to which said lands may be adapted and, thereafter, at the request of the department or institution having title to or an interest in or charged by law with the management of such lands and with the approval of the Governor, the Commissioner of Conservation and Natural Resources then shall have authority to use such lands for the purpose for which they are suited, and said lands shall be under the exclusive jurisdiction, management and control of the Commissioner of Conservation and Natural Resources; provided, that the lands donated to or purchased by the state to be used as the Fort Morgan Parkway from Fort Morgan to Gulf Shores, now a part of the Dixie Graves Highway, shall not be classified by the Department of Conservation and Natural Resources as unused lands, and the Department of Conservation and Natural Resources shall not, directly or indirectly, lease or sell said lands or any part thereof.